Cary Clark 153e76d4bf deprecate draw text on path in docs

Remove documentation, see also references, and examples
that rely on SkCanvas::drawTextOnPath(HV).

Move example that uses SkDrawTextOnPath into illustrations.
TBR=reed@google.com

Docs-Preview: https://skia.org/?cl=150020
Bug: skia:6898
Change-Id: I1d92f258b75a8a10a6aa89ebf9380871ba7ecac5
Reviewed-on: https://skia-review.googlesource.com/150020
Commit-Queue: Cary Clark <caryclark@skia.org>
Reviewed-by: Cary Clark <caryclark@skia.org>

2018-08-28 16:22:53 +00:00

286 KiB

Raw Blame History

SkPaint Reference

Paint

Class SkPaint

Paint controls options applied when drawing and measuring. Paint collects all options outside of the Canvas Clip and Canvas Matrix.

Various options apply to text, strokes and fills, and images.

Some options may not be implemented on all platforms; in these cases, setting the option has no effect. Some options are conveniences that duplicate Canvas functionality; for instance, text size is identical to matrix scale.

Paint options are rarely exclusive; each option modifies a stage of the drawing pipeline and multiple pipeline stages may be affected by a single Paint.

Paint collects effects and filters that describe single-pass and multiple-pass algorithms that alter the drawing geometry, color, and transparency. For instance, Paint does not directly implement dashing or blur, but contains the objects that do so.

The objects contained by Paint are opaque, and cannot be edited outside of the Paint to affect it. The implementation is free to defer computations associated with the Paint, or ignore them altogether. For instance, some GPU implementations draw all Path geometries with Anti Aliasing, regardless of how SkPaint::kAntiAlias Flag is set in Paint.

Paint describes a single color, a single font, a single image quality, and so on. Multiple colors are drawn either by using multiple paints or with objects like Shader attached to Paint.

Overview

Topic	Description
Constants	enum and enum class, and their const values
Constructors	functions that construct SkPaint
Functions	global and class member functions
Operators	operator overloading methods
Related Functions	similar member functions grouped together
Struct Declarations	embedded struct members

Related Function

SkPaint global, struct, and class related member functions share a topic.

Topic	Description
Alpha Methods	get and set Alpha
Anti Alias	approximating coverage with transparency
Automatic Hinting	always adjust glyph paths
Blend Mode Methods	get and set Blend Mode
Color Filter Methods	get and set Color Filter
Color Methods	get and set Color
Device Text	increase precision of glyph position
Dither	distributing color error
Draw Looper Methods	get and set Draw Looper
Fake Bold	approximate font styles
Fast Bounds	approximate area required by Paint
Fill Path	make Path from Path Effect, stroking
Filter Quality Methods	get and set Filter Quality
Flags	attributes represented by single bits
Font Embedded Bitmaps	custom sized bitmap Glyphs
Font Metrics	common glyph dimensions
Full Hinting Spacing	glyph spacing affected by hinting
Hinting	glyph outline adjustment
Image Filter Methods	get and set Image Filter
Initializers	constructors and initialization
LCD Text	text relying on the order of RGB stripes
Linear Text	selects text rendering as Glyph or Path
Management	paint copying, moving, comparing
Mask Filter Methods	get and set Mask Filter
Measure Text	width, height, bounds of text
Miter Limit	maximum length of stroked corners
Path Effect Methods	get and set Path Effect
Shader Methods	get and set Shader
Stroke Cap	decorations at ends of open strokes
Stroke Join	decoration at corners of strokes
Stroke Width	thickness perpendicular to geometry
Style	geometry filling, stroking
Style Fill	fill and stroke
Style Hairline	lines and curves with minimal width
Style Stroke	lines and curves with width
Subpixel Text	uses pixel transparency to represent fractional offset
Text Align	text placement relative to position
Text Encoding	text encoded as characters or Glyphs
Text Intercepts	advanced underline, strike through
Text Path	geometry of Glyphs
Text Scale X	text horizontal scale
Text Size	overall height in points
Text Skew X	text horizontal slant
Typeface Methods	get and set Typeface
Utility	rarely called management functions
Vertical Text	orient text from top to bottom

Constant

SkPaint related constants are defined by enum, enum class, #define, const, and constexpr.

Topic	Description
Align	glyph locations relative to text position
Cap	start and end geometry on stroked shapes
Flags	values described by bits and masks
Hinting	level of glyph outline adjustment
Join	corner geometry on stroked shapes
Style	stroke, fill, or both
TextEncoding	character or glyph encoded size
kAlignCount	number of different Text Align values defined
kAllFlags	mask of all Flags
kAntiAlias Flag	mask for setting Anti Alias
kAutoHinting Flag	mask for setting Automatic Hinting
kBevel Join	connects outside edges
kButt Cap	no stroke extension
kCapCount	number of different Stroke Cap values defined
kCenter Align	centers line of glyphs by its width or height
kDefault Cap	equivalent to kButt Cap
kDefault Join	equivalent to kMiter Join
kDither Flag	mask for setting Dither
kEmbeddedBitmapText Flag	mask for setting Font Embedded Bitmaps
kFakeBoldText Flag	mask for setting Fake Bold
kFill Style	set to fill geometry
kFull Hinting	modifies glyph outlines for maximum constrast
kGlyphID TextEncoding	uses two byte words to represent glyph indices
kJoinCount	number of different Stroke Join values defined
kLCDRenderText Flag	mask for setting LCD Text
kLast Cap	largest Stroke Cap value
kLast Join	equivalent to the largest value for Stroke Join
kLeft Align	positions glyph by computed font offset
kLinearText Flag	mask for setting Linear Text
kMiter Join	extends to Miter Limit
kNo Hinting	glyph outlines unchanged
kNormal Hinting	glyph outlines modified to improve constrast
kRight Align	moves lines of glyphs by its width or height
kRound Cap	adds circle
kRound Join	adds circle
kSlight Hinting	minimal modification to improve constrast
kSquare Cap	adds square
kStrokeAndFill Style	sets to stroke and fill geometry
kStroke Style	set to stroke geometry
kStyleCount	number of different Style values defined
kSubpixelText Flag	mask for setting Subpixel Text
kUTF16 TextEncoding	uses two byte words to represent most of Unicode
kUTF32 TextEncoding	uses four byte words to represent all of Unicode
kUTF8 TextEncoding	uses bytes to represent UTF-8 or ASCII
kVerticalText Flag	mask for setting Vertical Text

Struct

SkPaint uses C++ structs to declare the public data structures and interfaces.

Topic	Description
FontMetrics	values computed by Font Manager using Typeface

Constructor

SkPaint can be constructed or initialized by these functions, including C++ class constructors.

Topic	Description
SkPaint()	constructs with default values
SkPaint(SkPaint&& paint)	moves paint without copying it
SkPaint(const SkPaint& paint)	makes a shallow copy
~SkPaint()	decreases Reference Count of owned objects

Operator

SkPaint operators inline class member functions with arithmetic equivalents.

Topic	Description
operator!=(const SkPaint& a, const SkPaint& b)	compares paints for inequality
operator=(SkPaint&& paint)	moves paint without copying it
operator=(const SkPaint& paint)	makes a shallow copy
operator==(const SkPaint& a, const SkPaint& b)	compares paints for equality

Member Function

SkPaint member functions read and modify the structure properties.

Topic	Description
breakText	returns text that fits in a width
canComputeFastBounds	returns true if settings allow for fast bounds computation
computeFastBounds	returns fill bounds for quick reject tests
computeFastStrokeBounds	returns stroke bounds for quick reject tests
containsText	returns if all text corresponds to Glyphs
countText	returns number of Glyphs in text
doComputeFastBounds	returns bounds for quick reject tests
getAlpha	returns Color Alpha, color opacity
getBlendMode	returns Blend Mode, how colors combine with Device
getColor	returns Color Alpha and RGB, one drawing color
getColorFilter	returns Color Filter, how colors are altered
getDrawLooper	returns Draw Looper, multiple layers
getFillPath	returns fill path equivalent to stroke
getFilterQuality	returns Filter Quality, image filtering level
getFlags	returns Flags stored in a bit field
getFontBounds	returns union all glyph bounds
getFontMetrics	returns Typeface metrics scaled by text size
getFontSpacing	returns recommended spacing between lines
getHash	returns a shallow hash for equality checks
getHinting	returns Hinting, glyph outline adjustment level
getImageFilter	returns Image Filter, alter pixels; blur
getMaskFilter	returns Mask Filter, alterations to Mask Alpha
getPathEffect	returns Path Effect, modifications to path geometry; dashing
getPosTextHIntercepts	returns where lines intersect horizontally positioned text; underlines
getPosTextIntercepts	returns where lines intersect positioned text; underlines
getPosTextPath	returns Path equivalent to positioned text
getShader	returns Shader, multiple drawing colors; gradients
getStrokeCap	returns Cap, the area drawn at path ends
getStrokeJoin	returns Join, geometry on path corners
getStrokeMiter	returns Miter Limit, angles with sharp corners
getStrokeWidth	returns thickness of the stroke
getStyle	returns Style: stroke, fill, or both
getTextAlign	returns Align: left, center, or right
getTextBlobIntercepts	returns where lines intersect Text Blob; underlines
getTextEncoding	returns character or glyph encoded size
getTextIntercepts	returns where lines intersect text; underlines
getTextPath	returns Path equivalent to text
getTextScaleX	returns the text horizontal scale; condensed text
getTextSize	returns text size in points
getTextSkewX	returns the text horizontal skew; oblique text
getTextWidths	returns advance and bounds for each glyph in text
getTypeface	returns Typeface, font description
glyphsToUnichars	converts Glyphs into text
isAntiAlias	returns true if Anti Alias is set
isAutohinted	returns true if Glyphs are always hinted
isDither	returns true if Dither is set
isEmbeddedBitmapText	returns true if Font Embedded Bitmaps is set
isFakeBoldText	returns true if Fake Bold is set
isLCDRenderText	returns true if LCD Text is set
isLinearText	returns true if text is converted to Path
isSrcOver	returns true if Blend Mode is SkBlendMode::kSrcOver
isSubpixelText	returns true if Subpixel Text is set
isVerticalText	returns true if Vertical Text is set
measureText	returns advance width and bounds of text
nothingToDraw	returns true if Paint prevents all drawing
refColorFilter	references Color Filter, how colors are altered
refDrawLooper	references Draw Looper, multiple layers
refImageFilter	references Image Filter, alter pixels; blur
refMaskFilter	references Mask Filter, alterations to Mask Alpha
refPathEffect	references Path Effect, modifications to path geometry; dashing
refShader	references Shader, multiple drawing colors; gradients
refTypeface	references Typeface, font description
reset	sets to default values
setARGB	sets color by component
setAlpha	sets Color Alpha, color opacity
setAntiAlias	sets or clears Anti Alias
setAutohinted	sets Glyphs to always be hinted
setBlendMode	sets Blend Mode, how colors combine with destination
setColor	sets Color Alpha and RGB, one drawing color
setColorFilter	sets Color Filter, alters color
setDither	sets or clears Dither
setDrawLooper	sets Draw Looper, multiple layers
setEmbeddedBitmapText	sets or clears Font Embedded Bitmaps
setFakeBoldText	sets or clears Fake Bold
setFilterQuality	sets Filter Quality, the image filtering level
setFlags	sets multiple Flags in a bit field
setHinting	sets Hinting, glyph outline adjustment level
setImageFilter	sets Image Filter, alter pixels; blur
setLCDRenderText	sets or clears LCD Text
setLinearText	converts to Path before draw or measure
setMaskFilter	sets Mask Filter, alterations to Mask Alpha
setPathEffect	sets Path Effect, modifications to path geometry; dashing
setShader	sets Shader, multiple drawing colors; gradients
setStrokeCap	sets Cap, the area drawn at path ends
setStrokeJoin	sets Join, geometry on path corners
setStrokeMiter	sets Miter Limit, angles with sharp corners
setStrokeWidth	sets thickness of the stroke
setStyle	sets Style: stroke, fill, or both
setSubpixelText	sets or clears Subpixel Text
setTextAlign	sets Align: left, center, or right
setTextEncoding	sets character or glyph encoded size
setTextScaleX	sets the text horizontal scale; condensed text
setTextSize	sets text size in points
setTextSkewX	sets the text horizontal skew; oblique text
setTypeface	sets Typeface, font description
setVerticalText	sets or clears Vertical Text
textToGlyphs	converts text into glyph indices

Initializers

SkPaint

SkPaint()

Constructs Paint with default values.

attribute	default value
Anti Alias	false
Blend Mode	SkBlendMode::kSrcOver
Color	SK ColorBLACK
Color Alpha	255
Color Filter	nullptr
Dither	false
Draw Looper	nullptr
Fake Bold	false
Filter Quality	kNone_SkFilterQuality
Font Embedded Bitmaps	false
Automatic Hinting	false
Full Hinting Spacing	false
Hinting	kNormal Hinting
Image Filter	nullptr
LCD Text	false
Linear Text	false
Miter Limit	4
Mask Filter	nullptr
Path Effect	nullptr
Shader	nullptr
Style	kFill Style
Text Align	kLeft Align
Text Encoding	kUTF8 TextEncoding
Text Scale X	1
Text Size	12
Text Skew X	0
Typeface	nullptr
Stroke Cap	kButt Cap
Stroke Join	kMiter Join
Stroke Width	0
Subpixel Text	false
Vertical Text	false

The flags, text size, hinting, and miter limit may be overridden at compile time by defining paint default values. The overrides may be included in "SkUserConfig.h" or predefined by the build system.

Return Value

default initialized Paint

Example

SkPaint

SkPaint(const SkPaint& paint)

The referenced objects Path Effect, Shader, Mask Filter, Color Filter, Draw Looper, and Image Filter cannot be modified after they are created. This prevents objects with Reference Count from being modified once Paint refers to them.

Parameters

paint original to copy

Return Value

shallow copy of paint

Example

Example Output

SK_ColorRED == paint1.getColor()
SK_ColorBLUE == paint2.getColor()

SkPaint

SkPaint(SkPaint&& paint)

Implements a move constructor to avoid increasing the reference counts of objects referenced by the paint.

After the call, paint is undefined, and can be safely destructed.

Parameters

paint original to move

Return Value

content of paint

Example

Example Output

path effect unique: true

reset

void reset()

Sets all Paint contents to their initial values. This is equivalent to replacing Paint with the result of SkPaint().

Example

Example Output

paint1 == paint2

~SkPaint

~SkPaint()

Decreases Paint Reference Count of owned objects: Typeface, Path Effect, Shader, Mask Filter, Color Filter, Draw Looper, and Image Filter. If the objects containing Reference Count go to zero, they are deleted.

Management

operator=

SkPaint& operator=(const SkPaint& paint)

Makes a shallow copy of Paint. Typeface, Path Effect, Shader, Mask Filter, Color Filter, Draw Looper, and Image Filter are shared between the original paint and the copy. Objects containing Reference Count in the prior destination are decreased by one, and the referenced objects are deleted if the resulting count is zero. Objects containing Reference Count in the parameter paint are increased by one. paint is unmodified.

Parameters

paint original to copy

Return Value

content of paint

Example

Example Output

SK_ColorRED == paint1.getColor()
SK_ColorRED == paint2.getColor()

operator=

SkPaint& operator=(SkPaint&& paint)

Moves the paint to avoid increasing the reference counts of objects referenced by the paint parameter. Objects containing Reference Count in the prior destination are decreased by one; those objects are deleted if the resulting count is zero.

After the call, paint is undefined, and can be safely destructed.

Parameters

paint original to move

Return Value

content of paint

Example

Example Output

SK_ColorRED == paint2.getColor()

operator==

bool operator==(const SkPaint& a, const SkPaint& b)

Compares a and b, and returns true if a and b are equivalent. May return false if Typeface, Path Effect, Shader, Mask Filter, Color Filter, Draw Looper, or Image Filter have identical contents but different pointers.

Parameters

`a`	Paint to compare
`b`	Paint to compare

Return Value

true if Paint pair are equivalent

Example

Example Output

paint1 == paint2
paint1 != paint2

operator!=

bool operator!=(const SkPaint& a, const SkPaint& b)

Compares a and b, and returns true if a and b are not equivalent. May return true if Typeface, Path Effect, Shader, Mask Filter, Color Filter, Draw Looper, or Image Filter have identical contents but different pointers.

Parameters

`a`	Paint to compare
`b`	Paint to compare

Return Value

true if Paint pair are not equivalent

Example

Example Output

paint1 == paint2
paint1 == paint2

getHash

uint32_t getHash() const

Returns a hash generated from Paint values and pointers. Identical hashes guarantee that the paints are equivalent, but differing hashes do not guarantee that the paints have differing contents.

If operator==(const SkPaint& a, const SkPaint& b) returns true for two paints, their hashes are also equal.

The hash returned is platform and implementation specific.

Return Value

a shallow hash

Example

Example Output

paint1 == paint2
paint1.getHash() == paint2.getHash()

Hinting

Enum SkPaint::Hinting

    enum Hinting {
        kNo Hinting            = 0,
        kSlight Hinting        = 1,
        kNormal Hinting        = 2,
        kFull Hinting          = 3,
    };

Hinting adjusts the glyph outlines so that the shape provides a uniform look at a given point size on font engines that support it. Hinting may have a muted effect or no effect at all depending on the platform.

The four levels roughly control corresponding features on platforms that use FreeType as the Font Engine.

Constants

Const	Value	Description
`SkPaint::kNo_Hinting`	0	Leaves glyph outlines unchanged from their native representation. With FreeType, this is equivalent to the FT_LOAD_NO_HINTING bit-field constant supplied to FT_Load_Glyph, which indicates that the vector outline being loaded should not be fitted to the pixel grid but simply scaled to 26.6 fractional pixels.
`SkPaint::kSlight_Hinting`	1	Modifies glyph outlines minimally to improve constrast. With FreeType, this is equivalent in spirit to the FT_LOAD_TARGET_LIGHT value supplied to FT_Load_Glyph. It chooses a lighter hinting algorithm for non-monochrome modes. Generated Glyphs may be fuzzy but better resemble their original shape.
`SkPaint::kNormal_Hinting`	2	Modifies glyph outlines to improve constrast. This is the default. With FreeType, this supplies FT_LOAD_TARGET_NORMAL to FT_Load_Glyph, choosing the default hinting algorithm, which is optimized for standard gray-level rendering.
`SkPaint::kFull_Hinting`	3	Modifies glyph outlines for maximum constrast. With FreeType, this selects FT_LOAD_TARGET_LCD or FT_LOAD_TARGET_LCD_V if kLCDRenderText Flag is set. FT_LOAD_TARGET_LCD is a variant of FT_LOAD_TARGET_NORMAL optimized for horizontally decimated LCD displays; FT_LOAD_TARGET_LCD_V is a variant of FT_LOAD_TARGET_NORMAL optimized for vertically decimated LCD displays.

On OS X and iOS, hinting controls whether Core Graphics dilates the font outlines to account for LCD text. No hinting uses Core Text Grayscale output. Normal hinting uses Core Text LCD output. If kLCDRenderText Flag is clear, the LCD output is reduced to a single Grayscale channel.

On Windows with DirectWrite, Hinting has no effect.

Hinting defaults to kNormal Hinting. Set SkPaintDefaults Hinting at compile time to change the default setting.

getHinting

Hinting getHinting() const

Returns level of glyph outline adjustment.

Return Value

one of: kNo Hinting, kSlight Hinting, kNormal Hinting, kFull Hinting

Example

Example Output

SkPaint::kNormal_Hinting == paint.getHinting()

setHinting

void setHinting(Hinting hintingLevel)

Sets level of glyph outline adjustment. Does not check for valid values of hintingLevel.

Hinting	value	effect on generated glyph outlines
kNo Hinting	0	leaves glyph outlines unchanged from their native representation
kSlight Hinting	1	modifies glyph outlines minimally to improve contrast
kNormal Hinting	2	modifies glyph outlines to improve contrast
kFull Hinting	3	modifies glyph outlines for maximum contrast

Parameters

hintingLevel one of: kNo Hinting, kSlight Hinting, kNormal Hinting, kFull Hinting

Example

Example Output

paint1 == paint2

Flags

Enum SkPaint::Flags

    enum Flags {
        kAntiAlias Flag       = 0x01,
        kDither Flag          = 0x04,
        kFakeBoldText Flag    = 0x20,
        kLinearText Flag      = 0x40,
        kSubpixelText Flag    = 0x80,
        kLCDRenderText Flag   = 0x200,
        kEmbeddedBitmapText Flag = 0x400,
        kAutoHinting Flag     = 0x800,
        kVerticalText Flag    = 0x1000,

        kAllFlags = 0xFFFF,
    };

The bit values stored in Flags. The default value for Flags, normally zero, can be changed at compile time with a custom definition of SkPaintDefaults Flags. All flags can be read and written explicitly; Flags allows manipulating multiple settings at once.

Constants

Flags default to all flags clear, disabling the associated feature.

Const	Value	Description
`SkPaint::kAntiAlias_Flag`	0x0001	mask for setting Anti_Alias
`SkPaint::kDither_Flag`	0x0004	mask for setting Dither
`SkPaint::kFakeBoldText_Flag`	0x0020	mask for setting Fake_Bold
`SkPaint::kLinearText_Flag`	0x0040	mask for setting Linear_Text
`SkPaint::kSubpixelText_Flag`	0x0080	mask for setting Subpixel_Text
`SkPaint::kLCDRenderText_Flag`	0x0200	mask for setting LCD_Text
`SkPaint::kEmbeddedBitmapText_Flag`	0x0400	mask for setting Font_Embedded_Bitmaps
`SkPaint::kAutoHinting_Flag`	0x0800	mask for setting Automatic_Hinting
`SkPaint::kVerticalText_Flag`	0x1000	mask for setting Vertical_Text
`SkPaint::kAllFlags`	0xFFFF	mask of all Flags, including private flags and flags reserved for future use

Enum SkPaint::ReserveFlags

Deprecated.

soonOnly valid for Android framework.

    enum ReserveFlags {
        kUnderlineText ReserveFlag   = 0x08,
        kStrikeThruText ReserveFlag  = 0x10,
    };

Constants

Const	Value	Description
`SkPaint::kUnderlineText_ReserveFlag`	0x0008	Deprecated. soon
`SkPaint::kStrikeThruText_ReserveFlag`	0x0010	Deprecated. soon

getFlags

uint32_t getFlags() const

Returns paint settings described by Flags. Each setting uses one bit, and can be tested with Flags members.

Return Value

zero, one, or more bits described by Flags

Example

Example Output

(SkPaint::kAntiAlias_Flag & paint.getFlags()) != 0

setFlags

void setFlags(uint32_t flags)

Replaces Flags with flags, the union of the Flags members. All Flags members may be cleared, or one or more may be set.

Parameters

flags union of Flags for Paint

Example

Example Output

paint.isAntiAlias()
paint.isDither()

Anti Alias

Anti Alias drawing approximates partial pixel coverage with transparency. If kAntiAlias Flag is clear, pixel centers contained by the shape edge are drawn opaque. If kAntiAlias Flag is set, pixels are drawn with Color Alpha equal to their coverage.

The rule for Aliased pixels is inconsistent across platforms. A shape edge passing through the pixel center may, but is not required to, draw the pixel.

Raster Engine draws Aliased pixels whose centers are on or to the right of the start of an active Path edge, and whose center is to the left of the end of the active Path edge.

A platform may only support Anti Aliased drawing. Some GPU-backed platforms use Supersampling to Anti Alias all drawing, and have no mechanism to selectively Alias.

The amount of coverage computed for Anti Aliased pixels also varies across platforms.

Anti Alias is disabled by default. Anti Alias can be enabled by default by setting SkPaintDefaults Flags to kAntiAlias Flag at compile time.

Example

A red line is drawn with transparency on the edges to make it look smoother. A blue line draws only where the pixel centers are contained. The lines are drawn into Bitmap, then drawn magnified to make the Aliasing easier to see.

isAntiAlias

bool isAntiAlias() const

Returns true if pixels on the active edges of Path may be drawn with partial transparency.

Equivalent to getFlags masked with kAntiAlias Flag.

Return Value

kAntiAlias Flag state

Example

Example Output

paint.isAntiAlias() == !!(paint.getFlags() & SkPaint::kAntiAlias_Flag)
paint.isAntiAlias() == !!(paint.getFlags() & SkPaint::kAntiAlias_Flag)

setAntiAlias

void setAntiAlias(bool aa)

Requests, but does not require, that Path edge pixels draw opaque or with partial transparency.

Sets kAntiAlias Flag if aa is true. Clears kAntiAlias Flag if aa is false.

Parameters

`aa`	setting for kAntiAlias Flag

Example

Example Output

paint1 == paint2

Dither

Dither increases fidelity by adjusting the color of adjacent pixels. This can help to smooth color transitions and reducing banding in gradients. Dithering lessens visible banding from kRGB_565_SkColorType and kRGBA_8888_SkColorType gradients, and improves rendering into a kRGB_565_SkColorType Surface.

Dithering is always enabled for linear gradients drawing into kRGB_565_SkColorType Surface and kRGBA_8888_SkColorType Surface. Dither cannot be enabled for kAlpha_8_SkColorType Surface and kRGBA_F16_SkColorType Surface.

Dither is disabled by default. Dither can be enabled by default by setting SkPaintDefaults Flags to kDither Flag at compile time.

Some platform implementations may ignore dithering. SetSK_IGNORE_GPU_DITHERto ignore Dither on GPU Surface.

Example

Dithering in the bottom half more closely approximates the requested color by alternating nearby colors from pixel to pixel.

Example

Dithering introduces subtle adjustments to color to smooth gradients. Drawing the gradient repeatedly with SkBlendMode::kPlus exaggerates the dither, making it easier to see.

isDither

bool isDither() const

Returns true if color error may be distributed to smooth color transition.

Equivalent to getFlags masked with kDither Flag.

Return Value

kDither Flag state

Example

Example Output

paint.isDither() == !!(paint.getFlags() & SkPaint::kDither_Flag)
paint.isDither() == !!(paint.getFlags() & SkPaint::kDither_Flag)

setDither

void setDither(bool dither)

Requests, but does not require, to distribute color error.

Sets kDither Flag if dither is true. Clears kDither Flag if dither is false.

Parameters

dither setting for kDither Flag

Example

Example Output

paint1 == paint2

Device Text

LCD Text and Subpixel Text increase the precision of glyph position.

When set, Flags kLCDRenderText Flag takes advantage of the organization of RGB stripes that create a color, and relies on the small size of the stripe and visual perception to make the color fringing imperceptible. LCD Text can be enabled on devices that orient stripes horizontally or vertically, and that order the color components as RGB or BGR.

Flags kSubpixelText Flag uses the pixel transparency to represent a fractional offset. As the opaqueness of the color increases, the edge of the glyph appears to move towards the outside of the pixel.

Either or both techniques can be enabled. kLCDRenderText Flag and kSubpixelText Flag are clear by default. LCD Text or Subpixel Text can be enabled by default by setting SkPaintDefaults Flags to kLCDRenderText Flag or kSubpixelText Flag (or both) at compile time.

Example

Four commas are drawn normally and with combinations of LCD Text and Subpixel Text. When Subpixel Text is disabled, the comma Glyphs are identical, but not evenly spaced. When Subpixel Text is enabled, the comma Glyphs are unique, but appear evenly spaced.

Linear Text

Linear Text selects whether text is rendered as a Glyph or as a Path. If kLinearText Flag is set, it has the same effect as setting Hinting to kNormal Hinting. If kLinearText Flag is clear, it is the same as setting Hinting to kNo Hinting.

isLinearText

bool isLinearText() const

Returns true if text is converted to Path before drawing and measuring.

Equivalent to getFlags masked with kLinearText Flag.

Return Value

kLinearText Flag state

Example

setLinearText

void setLinearText(bool linearText)

Returns true if text is converted to Path before drawing and measuring. By default, kLinearText Flag is clear.

Sets kLinearText Flag if linearText is true. Clears kLinearText Flag if linearText is false.

Parameters

linearText setting for kLinearText Flag

Example

Subpixel Text

isSubpixelText

bool isSubpixelText() const

Returns true if Glyphs at different sub-pixel positions may differ on pixel edge coverage.

Equivalent to getFlags masked with kSubpixelText Flag.

Return Value

kSubpixelText Flag state

Example

Example Output

paint.isSubpixelText() == !!(paint.getFlags() & SkPaint::kSubpixelText_Flag)
paint.isSubpixelText() == !!(paint.getFlags() & SkPaint::kSubpixelText_Flag)

setSubpixelText

void setSubpixelText(bool subpixelText)

Requests, but does not require, that Glyphs respect sub-pixel positioning.

Sets kSubpixelText Flag if subpixelText is true. Clears kSubpixelText Flag if subpixelText is false.

Parameters

subpixelText setting for kSubpixelText Flag

Example

Example Output

paint1 == paint2

LCD Text

isLCDRenderText

bool isLCDRenderText() const

Returns true if Glyphs may use LCD striping to improve glyph edges.

Returns true if Flags kLCDRenderText Flag is set.

Return Value

kLCDRenderText Flag state

Example

Example Output

paint.isLCDRenderText() == !!(paint.getFlags() & SkPaint::kLCDRenderText_Flag)
paint.isLCDRenderText() == !!(paint.getFlags() & SkPaint::kLCDRenderText_Flag)

setLCDRenderText

void setLCDRenderText(bool lcdText)

Requests, but does not require, that Glyphs use LCD striping for glyph edges.

Sets kLCDRenderText Flag if lcdText is true. Clears kLCDRenderText Flag if lcdText is false.

Parameters

lcdText setting for kLCDRenderText Flag

Example

Example Output

paint1 == paint2

Font Embedded Bitmaps

Font Embedded Bitmaps allows selecting custom sized bitmap Glyphs. Flags kEmbeddedBitmapText Flag when set chooses an embedded bitmap glyph over an outline contained in a font if the platform supports this option.

FreeType selects the bitmap glyph if available when kEmbeddedBitmapText Flag is set, and selects the outline glyph if kEmbeddedBitmapText Flag is clear. Windows may select the bitmap glyph but is not required to do so. OS X and iOS do not support this option.

Font Embedded Bitmaps is disabled by default. Font Embedded Bitmaps can be enabled by default by setting SkPaintDefaults Flags to kEmbeddedBitmapText Flag at compile time.

Example

The "hintgasp" TrueType font in the Skia resources/fonts directory
        includes an embedded bitmap Glyph at odd font sizes. This example works
        on platforms that use FreeType as their Font_Engine.
        Windows may, but is not required to, return a bitmap glyph if
        kEmbeddedBitmapText_Flag is set.SkBitmap bitmap;
    bitmap.allocN32Pixels(30, 15);
    bitmap.eraseColor(0);
    SkCanvas offscreen(bitmap);
    SkPaint paint;
    paint.setAntiAlias(true);
    paint.setTextSize(13);
    paint.setTypeface(MakeResourceAsTypeface("fonts/hintgasp.ttf"));
    for (bool embedded : { false, true}) {
        paint.setEmbeddedBitmapText(embedded);
        offscreen.drawString("A", embedded ? 5 : 15, 15, paint);
    }
    canvas->drawBitmap(bitmap, 0, 0);
    canvas->scale(10, 10);
    canvas->drawBitmap(bitmap, -2, 1);

isEmbeddedBitmapText

bool isEmbeddedBitmapText() const

Returns true if Font Engine may return Glyphs from font bitmaps instead of from outlines.

Equivalent to getFlags masked with kEmbeddedBitmapText Flag.

Return Value

kEmbeddedBitmapText Flag state

Example

Example Output

paint.isEmbeddedBitmapText() == !!(paint.getFlags() & SkPaint::kEmbeddedBitmapText_Flag)
paint.isEmbeddedBitmapText() == !!(paint.getFlags() & SkPaint::kEmbeddedBitmapText_Flag)

setEmbeddedBitmapText

void setEmbeddedBitmapText(bool useEmbeddedBitmapText)

Requests, but does not require, to use bitmaps in fonts instead of outlines.

Sets kEmbeddedBitmapText Flag if useEmbeddedBitmapText is true. Clears kEmbeddedBitmapText Flag if useEmbeddedBitmapText is false.

Parameters

useEmbeddedBitmapText setting for kEmbeddedBitmapText Flag

Example

Example Output

paint1 == paint2

Automatic Hinting

If Hinting is set to kNormal Hinting or kFull Hinting, Automatic Hinting instructs the Font Manager to always hint Glyphs. Automatic Hinting has no effect if Hinting is set to kNo Hinting or kSlight Hinting.

Automatic Hinting only affects platforms that use FreeType as the Font Manager.

isAutohinted

bool isAutohinted() const

Returns true if Hinting is set to kNormal Hinting or kFull Hinting, and if platform uses FreeType as the Font Manager. If true, instructs the Font Manager to always hint Glyphs.

Equivalent to getFlags masked with kAutoHinting Flag.

Return Value

kAutoHinting Flag state

Example

Example Output

paint.isAutohinted() == !!(paint.getFlags() & SkPaint::kAutoHinting_Flag)
paint.isAutohinted() == !!(paint.getFlags() & SkPaint::kAutoHinting_Flag)

setAutohinted

void setAutohinted(bool useAutohinter)

Sets whether to always hint Glyphs. If Hinting is set to kNormal Hinting or kFull Hinting and useAutohinter is set, instructs the Font Manager to always hint Glyphs. Automatic Hinting has no effect if Hinting is set to kNo Hinting or kSlight Hinting.

Only affects platforms that use FreeType as the Font Manager.

Sets kAutoHinting Flag if useAutohinter is true. Clears kAutoHinting Flag if useAutohinter is false.

Parameters

useAutohinter setting for kAutoHinting Flag

Example

Vertical Text

Text may be drawn by positioning each glyph, or by positioning the first glyph and using Font Advance to position subsequent Glyphs. By default, each successive glyph is positioned to the right of the preceding glyph. Vertical Text sets successive Glyphs to position below the preceding glyph.

Skia can translate text character codes as a series of Glyphs, but does not implement font substitution, textual substitution, line layout, or contextual spacing like Kerning pairs. Use a text shaping engine like HarfBuzz to translate text runs into glyph series.

Vertical Text is clear if text is drawn left to right or set if drawn from top to bottom.

Flags kVerticalText Flag if clear draws text left to right. Flags kVerticalText Flag if set draws text top to bottom.

Vertical Text is clear by default. Vertical Text can be set by default by setting SkPaintDefaults Flags to kVerticalText Flag at compile time.

Example

isVerticalText

bool isVerticalText() const

Returns true if Glyphs are drawn top to bottom instead of left to right.

Equivalent to getFlags masked with kVerticalText Flag.

Return Value

kVerticalText Flag state

Example

Example Output

paint.isVerticalText() == !!(paint.getFlags() & SkPaint::kVerticalText_Flag)
paint.isVerticalText() == !!(paint.getFlags() & SkPaint::kVerticalText_Flag)

setVerticalText

void setVerticalText(bool verticalText)

Returns true if text advance positions the next glyph below the previous glyph instead of to the right of previous glyph.

Sets kVerticalText Flag if vertical is true. Clears kVerticalText Flag if vertical is false.

Parameters

verticalText setting for kVerticalText Flag

Example

Example Output

paint1 == paint2

Fake Bold

Fake Bold approximates the bold font style accompanying a normal font when a bold font face is not available. Skia does not provide font substitution; it is up to the client to find the bold font face using the platform Font Manager.

Use Text Skew X to approximate an italic font style when the italic font face is not available.

A FreeType based port may define SK_USE_FREETYPE_EMBOLDEN at compile time to direct the font engine to create the bold Glyphs. Otherwise, the extra bold is computed by increasing the stroke width and setting the Style to kStrokeAndFill Style as needed.

Fake Bold is disabled by default.

Example

isFakeBoldText

bool isFakeBoldText() const

Returns true if approximate bold by increasing the stroke width when creating glyph bitmaps from outlines.

Equivalent to getFlags masked with kFakeBoldText Flag.

Return Value

kFakeBoldText Flag state

Example

Example Output

paint.isFakeBoldText() == !!(paint.getFlags() & SkPaint::kFakeBoldText_Flag)
paint.isFakeBoldText() == !!(paint.getFlags() & SkPaint::kFakeBoldText_Flag)

setFakeBoldText

void setFakeBoldText(bool fakeBoldText)

Increases stroke width when creating glyph bitmaps to approximate a bold typeface.

Sets kFakeBoldText Flag if fakeBoldText is true. Clears kFakeBoldText Flag if fakeBoldText is false.

Parameters

fakeBoldText setting for kFakeBoldText Flag

Example

Example Output

paint1 == paint2

Full Hinting Spacing

if Hinting is set to kFull Hinting, Full Hinting Spacing adjusts the character spacing by the difference of the hinted and Unhinted Left Side Bearing and Right Side Bearing. Full Hinting Spacing only applies to platforms that use FreeType as their Font Engine.

Full Hinting Spacing is not related to text Kerning, where the space between a specific pair of characters is adjusted using data in the font Kerning tables.

isDevKernText

bool isDevKernText() const

Deprecated.

setDevKernText

void setDevKernText(bool)

Deprecated.

Filter Quality Methods

Filter Quality trades speed for image filtering when the image is scaled. A lower Filter Quality draws faster, but has less fidelity. A higher Filter Quality draws slower, but looks better. If the image is drawn without scaling, the Filter Quality choice will not result in a noticeable difference.

Filter Quality is used in Paint passed as a parameter to

SkCanvas::drawBitmap

SkCanvas::drawBitmapRect

SkCanvas::drawImage

SkCanvas::drawImageRect

and when Paint has a Shader specialization that uses Image or Bitmap.

Filter Quality is kNone_SkFilterQuality by default.

Example

getFilterQuality

SkFilterQuality getFilterQuality() const

Returns Filter Quality, the image filtering level. A lower setting draws faster; a higher setting looks better when the image is scaled.

Return Value

one of: kNone_SkFilterQuality, kLow_SkFilterQuality, kMedium_SkFilterQuality, kHigh_SkFilterQuality

Example

Example Output

kNone_SkFilterQuality == paint.getFilterQuality()

setFilterQuality

void setFilterQuality(SkFilterQuality quality)

Sets Filter Quality, the image filtering level. A lower setting draws faster; a higher setting looks better when the image is scaled. Does not check to see if quality is valid.

Parameters

quality one of: kNone_SkFilterQuality, kLow_SkFilterQuality, kMedium_SkFilterQuality, kHigh_SkFilterQuality

Example

Example Output

kHigh_SkFilterQuality == paint.getFilterQuality()

Color Methods

name	description
getColor	returns Color Alpha and RGB, one drawing color
setColor	sets Color Alpha and RGB, one drawing color

Color specifies the red, blue, green, and Color Alpha values used to draw a filled or stroked shape in a 32-bit value. Each component occupies 8-bits, ranging from zero: no contribution; to 255: full intensity. All values in any combination are valid.

Color is not Premultiplied; Color Alpha sets the transparency independent of RGB: red, blue, and green.

The bit positions of Color Alpha and RGB are independent of the bit positions on the output device, which may have more or fewer bits, and may have a different arrangement.

bit positions	Color Alpha	red	blue	green
	31 - 24	23 - 16	15 - 8	7 - 0

Example

getColor

SkColor getColor() const

Retrieves Alpha and RGB, Unpremultiplied, packed into 32 bits. Use helpers SkColorGetA, SkColorGetR, SkColorGetG, and SkColorGetB to extract a color component.

Return Value

Unpremultiplied ARGB

Example

Example Output

Yellow is 100% red, 100% green, and 0% blue.

setColor

void setColor(SkColor color)

Sets Alpha and RGB used when stroking and filling. The color is a 32-bit value, Unpremultiplied, packing 8-bit components for Alpha, red, blue, and green.

Parameters

color Unpremultiplied ARGB

Example

Example Output

green1 == green2

Alpha Methods

Color Alpha sets the transparency independent of RGB: red, blue, and green.

getAlpha

uint8_t getAlpha() const

Retrieves Alpha from the Color used when stroking and filling.

Return Value

Alpha ranging from zero, fully transparent, to 255, fully opaque

Example

Example Output

255 == paint.getAlpha()

setAlpha

void setAlpha(U8CPU a)

Replaces Alpha, leaving RGB unchanged. An out of range value triggers an assert in the debug build. a is a value from zero to 255. a set to zero makes Color fully transparent; a set to 255 makes Color fully opaque.

Parameters

`a`	Alpha component of Color

Example

Example Output

0x44112233 == paint.getColor()

setARGB

void setARGB(U8CPU a, U8CPU r, U8CPU g, U8CPU b)

Sets Color used when drawing solid fills. The color components range from 0 to 255. The color is Unpremultiplied; Alpha sets the transparency independent of RGB.

Parameters

`a`	amount of Color Alpha, from fully transparent (0) to fully opaque (255)
`r`	amount of red, from no red (0) to full red (255)
`g`	amount of green, from no green (0) to full green (255)
`b`	amount of blue, from no blue (0) to full blue (255)

Example

Example Output

transRed1 == transRed2

Style

Style specifies if the geometry is filled, stroked, or both filled and stroked. Some shapes ignore Style and are always drawn filled or stroked.

Set Style to kFill Style to fill the shape. The fill covers the area inside the geometry for most shapes.

Set Style to kStroke Style to stroke the shape.

Style Fill

Style Stroke

The stroke covers the area described by following the shape edge with a pen or brush of Stroke Width. The area covered where the shape starts and stops is described by Stroke Cap. The area covered where the shape turns a corner is described by Stroke Join. The stroke is centered on the shape; it extends equally on either side of the shape edge.

As Stroke Width gets smaller, the drawn path frame is thinner. Stroke Width less than one may have gaps, and if kAntiAlias Flag is set, Color Alpha will increase to visually decrease coverage.

Style Hairline

Stroke Width of zero has a special meaning and switches drawing to use Hairline. Hairline draws the thinnest continuous frame. If kAntiAlias Flag is clear, adjacent pixels flow horizontally, vertically,or diagonally.

Path drawing with Hairline may hit the same pixel more than once. For instance, Path containing two lines in one Path Contour will draw the corner point once, but may both lines may draw the adjacent pixel. If kAntiAlias Flag is set, transparency is applied twice, resulting in a darker pixel. Some GPU-backed implementations apply transparency at a later drawing stage, avoiding double hit pixels while stroking.

Enum SkPaint::Style

    enum Style {
        kFill Style,
        kStroke Style,
        kStrokeAndFill Style,
    };

    static constexpr int kStyleCount = kStrokeAndFill Style + 1;

Set Style to fill, stroke, or both fill and stroke geometry. The stroke and fill share all paint attributes; for instance, they are drawn with the same color.

Use kStrokeAndFill Style to avoid hitting the same pixels twice with a stroke draw and a fill draw.

Constants

Const	Value	Description
`SkPaint::kFill_Style`	0	Applies to Rect, Region, Round Rect, Circles, Ovals, Path, and Text. Bitmap, Image, Patches, Region, Sprites, and Vertices are painted as if kFill Style is set, and ignore the set Style. The Path Fill Type specifies additional rules to fill the area outside the path edge, and to create an unfilled hole inside the shape. Style is set to kFill Style by default.
`SkPaint::kStroke_Style`	1	Applies to Rect, Region, Round Rect, Arcs, Circles, Ovals, Path, and Text. Arcs, Lines, and points, are always drawn as if kStroke Style is set, and ignore the set Style. The stroke construction is unaffected by the Path Fill Type.
`SkPaint::kStrokeAndFill_Style`	2	Applies to Rect, Region, Round Rect, Circles, Ovals, Path, and Text. Path is treated as if it is set to SkPath::kWinding FillType, and the set Path Fill Type is ignored.
`SkPaint::kStyleCount`	3	May be used to verify that Style is a legal value.

getStyle

Style getStyle() const

Returns whether the geometry is filled, stroked, or filled and stroked.

Return Value

one of:kFill Style, kStroke Style, kStrokeAndFill Style

Example

Example Output

SkPaint::kFill_Style == paint.getStyle()

setStyle

void setStyle(Style style)

Sets whether the geometry is filled, stroked, or filled and stroked. Has no effect if style is not a legal Style value.

Parameters

style one of: kFill Style, kStroke Style, kStrokeAndFill Style

Example

Stroke Width

Stroke Width sets the width for stroking. The width is the thickness of the stroke perpendicular to the path direction when the paint style is set to kStroke Style or kStrokeAndFill Style.

When width is greater than zero, the stroke encompasses as many pixels partially or fully as needed. When the width equals zero, the paint enables hairlines; the stroke is always one pixel wide.

The stroke dimensions are scaled by the canvas matrix, but Hairline stroke remains one pixel wide regardless of scaling.

The default width for the paint is zero.

Example

The pixels hit to represent thin lines vary with the angle of the line and the platform implementation.

getStrokeWidth

SkScalar getStrokeWidth() const

Returns the thickness of the pen used by Paint to outline the shape.

Return Value

zero for Hairline, greater than zero for pen thickness

Example

Example Output

0 == paint.getStrokeWidth()

setStrokeWidth

void setStrokeWidth(SkScalar width)

Sets the thickness of the pen used by the paint to outline the shape. Has no effect if width is less than zero.

Parameters

width zero thickness for Hairline; greater than zero for pen thickness

Example

Example Output

5 == paint.getStrokeWidth()

Miter Limit

Miter Limit specifies the maximum miter length, relative to the stroke width.

Miter Limit is used when the Stroke Join is set to kMiter Join, and the Style is either kStroke Style or kStrokeAndFill Style.

If the miter at a corner exceeds this limit, kMiter Join is replaced with kBevel Join.

Miter Limit can be computed from the corner angle:

miter limit = 1 / sin ( angle / 2 )Miter Limit default value is 4. The default may be changed at compile time by setting SkPaintDefaults MiterLimit in "SkUserConfig.h" or as a define supplied by the build environment.

Here are some miter limits and the angles that triggers them.

miter limit	angle in degrees
10	11.48
9	12.76
8	14.36
7	16.43
6	19.19
5	23.07
4	28.96
3	38.94
2	60
1	180

Example

This example draws a stroked corner and the miter length beneath. When the miter limit is decreased slightly, the miter join is replaced by a bevel join.

getStrokeMiter

SkScalar getStrokeMiter() const

Returns the limit at which a sharp corner is drawn beveled.

Return Value

zero and greater Miter Limit

Example

Example Output

default miter limit == 4

setStrokeMiter

void setStrokeMiter(SkScalar miter)

Sets the limit at which a sharp corner is drawn beveled. Valid values are zero and greater. Has no effect if miter is less than zero.

Parameters

miter zero and greater Miter Limit

Example

Example Output

default miter limit == 8

Stroke Cap

Enum SkPaint::Cap

    enum Cap {
        kButt Cap,
        kRound Cap,
        kSquare Cap,

        kLast Cap = kSquare Cap,
        kDefault Cap = kButt Cap,
    };

    static constexpr int kCapCount = kLast Cap + 1;

Stroke Cap draws at the beginning and end of an open Path Contour.

Constants

Const	Value	Description
`SkPaint::kButt_Cap`	0	Does not extend the stroke past the beginning or the end.
`SkPaint::kRound_Cap`	1	Adds a circle with a diameter equal to Stroke Width at the beginning and end.
`SkPaint::kSquare_Cap`	2	Adds a square with sides equal to Stroke Width at the beginning and end. The square sides are parallel to the initial and final direction of the stroke.
`SkPaint::kLast_Cap`	2	Equivalent to the largest value for Stroke Cap.
`SkPaint::kDefault_Cap`	0	Stroke Cap is set to kButt Cap by default.
`SkPaint::kCapCount`	3	May be used to verify that Stroke Cap is a legal value.

Stroke describes the area covered by a pen of Stroke Width as it follows the Path Contour, moving parallel to the contour direction.

If the Path Contour is not terminated by SkPath::kClose Verb, the contour has a visible beginning and end.

Path Contour may start and end at the same point; defining Zero Length Contour.

kButt Cap and Zero Length Contour is not drawn. kRound Cap and Zero Length Contour draws a circle of diameter Stroke Width at the contour point. kSquare Cap and Zero Length Contour draws an upright square with a side of Stroke Width at the contour point.

Stroke Cap is kButt Cap by default.

Example

getStrokeCap

Cap getStrokeCap() const

Returns the geometry drawn at the beginning and end of strokes.

Return Value

one of: kButt Cap, kRound Cap, kSquare Cap

Example

Example Output

kButt_Cap == default stroke cap

setStrokeCap

void setStrokeCap(Cap cap)

Sets the geometry drawn at the beginning and end of strokes.

Parameters

cap one of: kButt Cap, kRound Cap, kSquare Cap; has no effect if cap is not valid

Example

Example Output

kRound_Cap == paint.getStrokeCap()

Stroke Join

Stroke Join draws at the sharp corners of an open or closed Path Contour.

Stroke describes the area covered by a pen of Stroke Width as it follows the Path Contour, moving parallel to the contour direction.

If the contour direction changes abruptly, because the tangent direction leading to the end of a curve within the contour does not match the tangent direction of the following curve, the pair of curves meet at Stroke Join.

Example

Enum SkPaint::Join

    enum Join {
        kMiter Join,
        kRound Join,
        kBevel Join,

        kLast Join = kBevel Join,
        kDefault Join = kMiter Join,
    };

    static constexpr int kJoinCount = kLast Join + 1;

Join specifies how corners are drawn when a shape is stroked. Join affects the four corners of a stroked rectangle, and the connected segments in a stroked path.

Choose miter join to draw sharp corners. Choose round join to draw a circle with a radius equal to the stroke width on top of the corner. Choose bevel join to minimally connect the thick strokes.

The fill path constructed to describe the stroked path respects the join setting but may not contain the actual join. For instance, a fill path constructed with round joins does not necessarily include circles at each connected segment.

Constants

Const	Value	Description
`SkPaint::kMiter_Join`	0	Extends the outside corner to the extent allowed by Miter Limit. If the extension exceeds Miter Limit, kBevel Join is used instead.
`SkPaint::kRound_Join`	1	Adds a circle with a diameter of Stroke Width at the sharp corner.
`SkPaint::kBevel_Join`	2	Connects the outside edges of the sharp corner.
`SkPaint::kLast_Join`	2	equivalent to the largest value for Stroke_Join
`SkPaint::kDefault_Join`	1	Stroke Join is set to kMiter Join by default.
`SkPaint::kJoinCount`	3	May be used to verify that Stroke Join is a legal value.

Example

getStrokeJoin

Join getStrokeJoin() const

Returns the geometry drawn at the corners of strokes.

Return Value

one of: kMiter Join, kRound Join, kBevel Join

Example

Example Output

kMiter_Join == default stroke join

setStrokeJoin

void setStrokeJoin(Join join)

Sets the geometry drawn at the corners of strokes.

Parameters

join one of: kMiter Join, kRound Join, kBevel Join; otherwise, has no effect

Example

Example Output

kMiter_Join == paint.getStrokeJoin()

Fill Path

Fill Path creates a Path by applying the Path Effect, followed by the Style Stroke.

If Paint contains Path Effect, Path Effect operates on the source Path; the result replaces the destination Path. Otherwise, the source Path is replaces the destination Path.

Fill Path can request the Path Effect to restrict to a culling rectangle, but the Path Effect is not required to do so.

If Style is kStroke Style or kStrokeAndFill Style, and Stroke Width is greater than zero, the Stroke Width, Stroke Cap, Stroke Join, and Miter Limit operate on the destination Path, replacing it.

Fill Path can specify the precision used by Stroke Width to approximate the stroke geometry.

If the Style is kStroke Style and the Stroke Width is zero, getFillPath returns false since Hairline has no filled equivalent.

getFillPath

bool getFillPath(const SkPath& src, SkPath* dst, const SkRect* cullRect, SkScalar resScale = 1) const

Returns the filled equivalent of the stroked path.

Parameters

`src`	Path read to create a filled version
`dst`	resulting Path; may be the same as src, but may not be nullptr
`cullRect`	optional limit passed to Path Effect
`resScale`	if > 1, increase precision, else if (0 < res < 1) reduce precision to favor speed and size

Return Value

true if the path represents Style Fill, or false if it represents Hairline

Example

A very small Quad stroke is turned into a filled path with increasing levels of precision. At the lowest precision, the Quad stroke is approximated by a rectangle. At the highest precision, the filled path has high fidelity compared to the original stroke.

bool getFillPath(const SkPath& src, SkPath* dst) const

Returns the filled equivalent of the stroked path.

Replaces dst with the src path modified by Path Effect and Style Stroke. Path Effect, if any, is not culled. Stroke Width is created with default precision.

Parameters

`src`	Path read to create a filled version
`dst`	resulting Path dst may be the same as src, but may not be nullptr

Return Value

true if the path represents Style Fill, or false if it represents Hairline

Example

Shader Methods

Shader defines the colors used when drawing a shape. Shader may be an image, a gradient, or a computed fill. If Paint has no Shader, then Color fills the shape.

Shader is modulated by Color Alpha component of Color. If Shader object defines only Color Alpha, then Color modulated by Color Alpha describes the fill.

The drawn transparency can be modified without altering Shader, by changing Color Alpha.

Example

If Shader generates only Color Alpha then all components of Color modulate the output.

Example

getShader

SkShader* getShader() const

Returns optional colors used when filling a path, such as a gradient.

Does not alter Shader Reference Count.

Return Value

Shader if previously set, nullptr otherwise

Example

Example Output

nullptr == shader
nullptr != shader

refShader

sk sp<SkShader> refShader() const

Returns optional colors used when filling a path, such as a gradient.

Increases Shader Reference Count by one.

Return Value

Shader if previously set, nullptr otherwise

Example

Example Output

shader unique: true
shader unique: false

setShader

void setShader(sk sp<SkShader> shader)

Sets optional colors used when filling a path, such as a gradient.

Sets Shader to shader, decreasing Reference Count of the previous Shader. Increments shader Reference Count by one.

Parameters

shader how geometry is filled with color; if nullptr, Color is used instead

Example

Color Filter Methods

Color Filter alters the color used when drawing a shape. Color Filter may apply Blend Mode, transform the color through a matrix, or composite multiple filters. If Paint has no Color Filter, the color is unaltered.

The drawn transparency can be modified without altering Color Filter, by changing Color Alpha.

Example

getColorFilter

SkColorFilter* getColorFilter() const

Returns Color Filter if set, or nullptr. Does not alter Color Filter Reference Count.

Return Value

Color Filter if previously set, nullptr otherwise

Example

Example Output

nullptr == color filter
nullptr != color filter

refColorFilter

sk sp<SkColorFilter> refColorFilter() const

Returns Color Filter if set, or nullptr. Increases Color Filter Reference Count by one.

Return Value

Color Filter if set, or nullptr

Example

Example Output

color filter unique: true
color filter unique: false

setColorFilter

void setColorFilter(sk sp<SkColorFilter> colorFilter)

Sets Color Filter to filter, decreasing Reference Count of the previous Color Filter. Pass nullptr to clear Color Filter.

Increments filter Reference Count by one.

Parameters

colorFilter Color Filter to apply to subsequent draw

Example

Blend Mode Methods

Blend Mode describes how Color combines with the destination color. The default setting, SkBlendMode::kSrcOver, draws the source color over the destination color.

Example

getBlendMode

SkBlendMode getBlendMode() const

Returns Blend Mode. By default, returns SkBlendMode::kSrcOver.

Return Value

mode used to combine source color with destination color

Example

Example Output

kSrcOver == getBlendMode
kSrcOver != getBlendMode

isSrcOver

bool isSrcOver() const

Returns true if Blend Mode is SkBlendMode::kSrcOver, the default.

Return Value

true if Blend Mode is SkBlendMode::kSrcOver

Example

Example Output

isSrcOver == true
isSrcOver != true

setBlendMode

void setBlendMode(SkBlendMode mode)

Sets Blend Mode to mode. Does not check for valid input.

Parameters

mode SkBlendMode used to combine source color and destination

Example

Example Output

isSrcOver == true
isSrcOver != true

Path Effect Methods

Path Effect modifies the path geometry before drawing it. Path Effect may implement dashing, custom fill effects and custom stroke effects. If Paint has no Path Effect, the path geometry is unaltered when filled or stroked.

Example

getPathEffect

SkPathEffect* getPathEffect() const

Returns Path Effect if set, or nullptr. Does not alter Path Effect Reference Count.

Return Value

Path Effect if previously set, nullptr otherwise

Example

Example Output

nullptr == path effect
nullptr != path effect

refPathEffect

sk sp<SkPathEffect> refPathEffect() const

Returns Path Effect if set, or nullptr. Increases Path Effect Reference Count by one.

Return Value

Path Effect if previously set, nullptr otherwise

Example

Example Output

path effect unique: true
path effect unique: false

setPathEffect

void setPathEffect(sk sp<SkPathEffect> pathEffect)

Sets Path Effect to pathEffect, decreasing Reference Count of the previous Path Effect. Pass nullptr to leave the path geometry unaltered.

Increments pathEffect Reference Count by one.

Parameters

pathEffect replace Path with a modification when drawn

Example

Mask Filter Methods

Mask Filter uses coverage of the shape drawn to create Mask Alpha. Mask Filter takes a Mask, and returns a Mask.

Mask Filter may change the geometry and transparency of the shape, such as creating a blur effect. Set Mask Filter to nullptr to prevent Mask Filter from modifying the draw.

Example

getMaskFilter

SkMaskFilter* getMaskFilter() const

Returns Mask Filter if set, or nullptr. Does not alter Mask Filter Reference Count.

Return Value

Mask Filter if previously set, nullptr otherwise

Example

Example Output

nullptr == mask filter
nullptr != mask filter

refMaskFilter

sk sp<SkMaskFilter> refMaskFilter() const

Returns Mask Filter if set, or nullptr.

Increases Mask Filter Reference Count by one.

Return Value

Mask Filter if previously set, nullptr otherwise

Example

Example Output

mask filter unique: true
mask filter unique: false

setMaskFilter

void setMaskFilter(sk sp<SkMaskFilter> maskFilter)

Sets Mask Filter to maskFilter, decreasing Reference Count of the previous Mask Filter. Pass nullptr to clear Mask Filter and leave Mask Filter effect on Mask Alpha unaltered.

Increments maskFilter Reference Count by one.

Parameters

maskFilter modifies clipping mask generated from drawn geometry

Example

Typeface Methods

Typeface identifies the font used when drawing and measuring text. Typeface may be specified by name, from a file, or from a data stream. The default Typeface defers to the platform-specific default font implementation.

Example

getTypeface

SkTypeface* getTypeface() const

Returns Typeface if set, or nullptr. Does not alter Typeface Reference Count.

Return Value

Typeface if previously set, nullptr otherwise

Example

Example Output

nullptr == typeface
nullptr != typeface

refTypeface

sk sp<SkTypeface> refTypeface() const

Increases Typeface Reference Count by one.

Return Value

Typeface if previously set, nullptr otherwise

Example

Example Output

typeface1 != typeface2
typeface1 == typeface2

setTypeface

void setTypeface(sk sp<SkTypeface> typeface)

Sets Typeface to typeface, decreasing Reference Count of the previous Typeface. Pass nullptr to clear Typeface and use the default typeface. Increments typeface Reference Count by one.

Parameters

typeface font and style used to draw text

Example

Image Filter Methods

Image Filter operates on the pixel representation of the shape, as modified by Paint with Blend Mode set to SkBlendMode::kSrcOver. Image Filter creates a new bitmap, which is drawn to the device using the set Blend Mode.

Image Filter is higher level than Mask Filter; for instance, an Image Filter can operate on all channels of Color, while Mask Filter generates Alpha only. Image Filter operates independently of and can be used in combination with Mask Filter.

Example

getImageFilter

SkImageFilter* getImageFilter() const

Returns Image Filter if set, or nullptr. Does not alter Image Filter Reference Count.

Return Value

Image Filter if previously set, nullptr otherwise

Example

Example Output

nullptr == image filter
nullptr != image filter

refImageFilter

sk sp<SkImageFilter> refImageFilter() const

Returns Image Filter if set, or nullptr. Increases Image Filter Reference Count by one.

Return Value

Image Filter if previously set, nullptr otherwise

Example

Example Output

image filter unique: true
image filter unique: false

setImageFilter

void setImageFilter(sk sp<SkImageFilter> imageFilter)

Sets Image Filter to imageFilter, decreasing Reference Count of the previous Image Filter. Pass nullptr to clear Image Filter, and remove Image Filter effect on drawing.

Increments imageFilter Reference Count by one.

Parameters

imageFilter how Image is sampled when transformed

Example

Draw Looper Methods

Draw Looper sets a modifier that communicates state from one Draw Layer to another to construct the draw.

Draw Looper draws one or more times, modifying the canvas and paint each time. Draw Looper may be used to draw multiple colors or create a colored shadow. Set Draw Looper to nullptr to prevent Draw Looper from modifying the draw.

Example

getDrawLooper

SkDrawLooper* getDrawLooper() const

Returns Draw Looper if set, or nullptr. Does not alter Draw Looper Reference Count.

Return Value

Draw Looper if previously set, nullptr otherwise

Example

Example Output

nullptr == draw looper
nullptr != draw looper

refDrawLooper

sk sp<SkDrawLooper> refDrawLooper() const

Returns Draw Looper if set, or nullptr. Increases Draw Looper Reference Count by one.

Return Value

Draw Looper if previously set, nullptr otherwise

Example

Example Output

draw looper unique: true
draw looper unique: false

getLooper

SkDrawLooper* getLooper() const

Deprecated.

setDrawLooper

void setDrawLooper(sk sp<SkDrawLooper> drawLooper)

Sets Draw Looper to drawLooper, decreasing Reference Count of the previous drawLooper. Pass nullptr to clear Draw Looper and leave Draw Looper effect on drawing unaltered.

Increments drawLooper Reference Count by one.

Parameters

drawLooper iterates through drawing one or more time, altering Paint

Example

setLooper

void setLooper(sk sp<SkDrawLooper> drawLooper)

Deprecated.

Text Align

Enum SkPaint::Align

    enum Align {
        kLeft Align,
        kCenter Align,
        kRight Align,
    };

    static constexpr int kAlignCount = 3;

Align adjusts the text relative to the text position. Align affects Glyphs drawn with: SkCanvas::drawText, SkCanvas::drawPosText, SkCanvas::drawPosTextH, SkCanvas::drawTextRSXform, SkCanvas::drawTextBlob, and SkCanvas::drawString; as well as calls that place text Glyphs like getTextWidths and getTextPath.

The text position is set by the font for both horizontal and vertical text. Typically, for horizontal text, the position is to the left side of the glyph on the base line; and for vertical text, the position is the horizontal center of the glyph at the caps height.

Align adjusts the glyph position to center it or move it to abut the position using the metrics returned by the font.

Align defaults to kLeft Align.

Constants

Const	Value	Description
`SkPaint::kLeft_Align`	0	Leaves the glyph at the position computed by the font offset by the text position.
`SkPaint::kCenter_Align`	1	Moves the glyph half its width if Flags has kVerticalText Flag clear, and half its height if Flags has kVerticalText Flag set.
`SkPaint::kRight_Align`	2	Moves the glyph by its width if Flags has kVerticalText Flag clear, and by its height if Flags has kVerticalText Flag set.
`SkPaint::kAlignCount`	3	May be used to verify that Align is a legal value.

Example

Each position separately moves the glyph in drawPosText.

Example

Vertical Text treats kLeft Align as top align, and kRight Align as bottom align.

getTextAlign

Align getTextAlign() const

Returns Text Align. Returns kLeft Align if Text Align has not been set.

Return Value

text placement relative to position

Example

Example Output

kLeft_Align == default

setTextAlign

void    setTextAlign(Align align)

Sets Text Align to align. Has no effect if align is an invalid value.

Parameters

align text placement relative to position

Example

Text is left-aligned by default, and then set to center. Setting the alignment out of range has no effect.

getTextSize

SkScalar getTextSize() const

Returns Text Size in points.

Return Value

typographic height of text

Example

setTextSize

void setTextSize(SkScalar textSize)

Sets Text Size in points. Has no effect if textSize is not greater than or equal to zero.

Parameters

textSize typographic height of text

Example

Text Scale X

Text Scale X adjusts the text horizontal scale. Text scaling approximates condensed and expanded type faces when the actual face is not available. Text Scale X can be set to any value. Text Scale X defaults to 1.

Example

getTextScaleX

SkScalar getTextScaleX() const

Returns Text Scale X. Default value is 1.

Return Value

text horizontal scale

Example

setTextScaleX

void setTextScaleX(SkScalar scaleX)

Sets Text Scale X. Default value is 1.

Parameters

scaleX text horizontal scale

Example

Text Skew X

Text Skew X adjusts the text horizontal slant. Text skewing approximates italic and oblique type faces when the actual face is not available. Text Skew X can be set to any value. Text Skew X defaults to 0.

Example

getTextSkewX

SkScalar getTextSkewX() const

Returns Text Skew X. Default value is zero.

Return Value

additional shear in x-axis relative to y-axis

Example

setTextSkewX

void setTextSkewX(SkScalar skewX)

Sets Text Skew X. Default value is zero.

Parameters

skewX additional shear in x-axis relative to y-axis

Example

Text Encoding

Enum SkPaint::TextEncoding

    enum TextEncoding {
        kUTF8 TextEncoding,
        kUTF16 TextEncoding,
        kUTF32 TextEncoding,
        kGlyphID TextEncoding,
    };

TextEncoding determines whether text specifies character codes and their encoded size, or glyph indices. Characters are encoded as specified by the Unicode standard .

Character codes encoded size are specified by UTF-8, UTF-16, or UTF-32. All character code formats are able to represent all of Unicode, differing only in the total storage required.

UTF-8 (RFC 3629) encodes each character as one or more 8-bit bytes.

UTF-16 (RFC 2781) encodes each character as one or two 16-bit words.

UTF-32 encodes each character as one 32-bit word.

Font Manager uses font data to convert character code points into glyph indices. A glyph index is a 16-bit word.

TextEncoding is set to kUTF8 TextEncoding by default.

Constants

Const	Value	Description
`SkPaint::kUTF8_TextEncoding`	0	uses bytes to represent UTF-8 or ASCII
`SkPaint::kUTF16_TextEncoding`	1	uses two byte words to represent most of Unicode
`SkPaint::kUTF32_TextEncoding`	2	uses four byte words to represent all of Unicode
`SkPaint::kGlyphID_TextEncoding`	3	uses two byte words to represent glyph indices

Example

First line is encoded in UTF-8. Second line is encoded in UTF-16. Third line is encoded in UTF-32. Fourth line has 16-bit glyph indices.

getTextEncoding

TextEncoding getTextEncoding() const

Returns Text Encoding. Text Encoding determines how character code points are mapped to font glyph indices.

Return Value

one of: kUTF8 TextEncoding, kUTF16 TextEncoding, kUTF32 TextEncoding, or kGlyphID TextEncoding

Example

Example Output

kUTF8_TextEncoding == text encoding
kGlyphID_TextEncoding == text encoding

setTextEncoding

void setTextEncoding(TextEncoding encoding)

Sets Text Encoding to encoding. Text Encoding determines how character code points are mapped to font glyph indices. Invalid values for encoding are ignored.

Parameters

encoding one of: kUTF8 TextEncoding, kUTF16 TextEncoding, kUTF32 TextEncoding, or kGlyphID TextEncoding

Example

Example Output

4 != text encoding

Font Metrics

Font Metrics describe dimensions common to the Glyphs in Typeface. The dimensions are computed by Font Manager from font data and do not take Paint settings other than Text Size into account.

Font dimensions specify the anchor to the left of the glyph at baseline as the origin. X-axis values to the left of the glyph are negative, and to the right of the left glyph edge are positive. Y-axis values above the baseline are negative, and below the baseline are positive.

Example

Struct SkPaint::FontMetrics

Constant

SkPaint::FontMetrics related constants are defined by enum, enum class, #define, const, and constexpr.

Topic	Description
FontMetricsFlags	valid Font Metrics
kStrikeoutPositionIsValid Flag	set if fStrikeoutPosition is valid
kStrikeoutThicknessIsValid Flag	set if fStrikeoutThickness is valid
kUnderlinePositionIsValid Flag	set if fUnderlinePosition is valid
kUnderlineThicknessIsValid Flag	set if fUnderlineThickness is valid

Member_Function

SkPaint::FontMetrics member functions read and modify the structure properties.

Topic	Description
hasStrikeoutPosition	returns strikeout position if set
hasStrikeoutThickness	returns strikeout thickness if set
hasUnderlinePosition	returns underline position if set
hasUnderlineThickness	returns underline thickness if set

Member

SkPaint::FontMetrics members may be read and written directly without using a member function.

Topic	Description
fAscent	distance to reserve above baseline
fAvgCharWidth	average character width
fBottom	extent below baseline
fCapHeight	height of an upper-case letter
fDescent	distance to reserve below baseline
fFlags	is set to FontMetricsFlags when metrics are valid
fLeading	distance to add between lines
fMaxCharWidth	maximum character width
fStrikeoutPosition	strikeout position relative to baseline
fStrikeoutThickness	strikeout thickness
fTop	extent above baseline
fUnderlinePosition	underline position relative to baseline
fUnderlineThickness	underline thickness
fXHeight	height of lower-case 'x'
fXMax	maximum x
fXMin	minimum x

    struct FontMetrics {
        enum FontMetricsFlags {
            kUnderlineThicknessIsValid Flag = 1 << 0,
            kUnderlinePositionIsValid Flag = 1 << 1,
            kStrikeoutThicknessIsValid Flag = 1 << 2,
            kStrikeoutPositionIsValid Flag = 1 << 3,
        };

        uint32_t    fFlags;
        SkScalar    fTop;
        SkScalar    fAscent;
        SkScalar    fDescent;
        SkScalar    fBottom;
        SkScalar    fLeading;
        SkScalar    fAvgCharWidth;
        SkScalar    fMaxCharWidth;
        SkScalar    fXMin;
        SkScalar    fXMax;
        SkScalar    fXHeight;
        SkScalar    fCapHeight;
        SkScalar    fUnderlineThickness;
        SkScalar    fUnderlinePosition;
        SkScalar    fStrikeoutThickness;
        SkScalar    fStrikeoutPosition;

        bool hasUnderlineThickness(SkScalar* thickness) const;
        bool hasUnderlinePosition(SkScalar* position) const;
        bool hasStrikeoutThickness(SkScalar* thickness) const;
        bool hasStrikeoutPosition(SkScalar* position) const;
    };

FontMetrics is filled out by getFontMetrics. FontMetrics contents reflect the values computed by Font Manager using Typeface. Values are set to zero if they are not available.

All vertical values are relative to the baseline, on a y-axis pointing down. Zero is on the baseline, negative values are above the baseline, and positive values are below the baseline.

fUnderlineThickness and fUnderlinePosition have a bit set in fFlags if their values are valid, since their value may be zero.

fStrikeoutThickness and fStrikeoutPosition have a bit set in fFlags if their values are valid, since their value may be zero.

Enum SkPaint::FontMetrics::FontMetricsFlags

        enum FontMetricsFlags {
            kUnderlineThicknessIsValid Flag = 1 << 0,
            kUnderlinePositionIsValid Flag = 1 << 1,
            kStrikeoutThicknessIsValid Flag = 1 << 2,
            kStrikeoutPositionIsValid Flag = 1 << 3,
        };

FontMetricsFlags are set in fFlags when underline and strikeout metrics are valid; the underline or strikeout metric may be valid and zero. Fonts with embedded bitmaps may not have valid underline or strikeout metrics.

Constants

Const	Value	Description
`SkPaint::FontMetrics::kUnderlineThicknessIsValid_Flag`	0x0001	set if fUnderlineThickness is valid
`SkPaint::FontMetrics::kUnderlinePositionIsValid_Flag`	0x0002	set if fUnderlinePosition is valid
`SkPaint::FontMetrics::kStrikeoutThicknessIsValid_Flag`	0x0004	set if fStrikeoutThickness is valid
`SkPaint::FontMetrics::kStrikeoutPositionIsValid_Flag`	0x0008	set if fStrikeoutPosition is valid

Members

Type	Name	Description
uint32_t	`fFlags`	is set to FontMetricsFlags when metrics are valid
SkScalar	`fTop`	Greatest extent above the baseline for any glyph. Typically less than zero.
SkScalar	`fAscent`	Recommended distance above the baseline to reserve for a line of text. Typically less than zero.
SkScalar	`fDescent`	Recommended distance below the baseline to reserve for a line of text. Typically greater than zero.
SkScalar	`fBottom`	Greatest extent below the baseline for any glyph. Typically greater than zero.
SkScalar	`fLeading`	Recommended distance to add between lines of text. Typically greater than or equal to zero.
SkScalar	`fAvgCharWidth`	Average character width, if it is available. Zero if no average width is stored in the font.
SkScalar	`fMaxCharWidth`	maximum character width
SkScalar	`fXMin`	Minimum bounding box x-axis value for all Glyphs. Typically less than zero.
SkScalar	`fXMax`	Maximum bounding box x-axis value for all Glyphs. Typically greater than zero.
SkScalar	`fXHeight`	May be zero if no lower-case height is stored in the font.
SkScalar	`fCapHeight`	May be zero if no upper-case height is stored in the font.
SkScalar	`fUnderlineThickness`	If the metric is valid, the kUnderlineThicknessIsValid Flag is set in fFlags. If kUnderlineThicknessIsValid Flag is clear, fUnderlineThickness is zero.
SkScalar	`fUnderlinePosition`	Position of the top of the underline stroke relative to the baseline. Typically positive when valid. If the metric is valid, the kUnderlinePositionIsValid Flag is set in fFlags. If kUnderlinePositionIsValid Flag is clear, fUnderlinePosition is zero.
SkScalar	`fStrikeoutThickness`	If the metric is valid, the kStrikeoutThicknessIsValid Flag is set in fFlags. If kStrikeoutThicknessIsValid Flag is clear, fStrikeoutThickness is zero.
SkScalar	`fStrikeoutPosition`	Position of the bottom of the strikeout stroke relative to the baseline. Typically negative when valid. If the metric is valid, the kStrikeoutPositionIsValid Flag is set in fFlags. If kStrikeoutPositionIsValid Flag is clear, fStrikeoutPosition is zero.

hasUnderlineThickness

bool hasUnderlineThickness(SkScalar* thickness) const

Returns true if Font Metrics has a valid underline thickness, and sets thickness to that value. If the underline thickness is not valid, return false, and ignore thickness.

Parameters

thickness storage for underline width

Return Value

true if font specifies underline width

hasUnderlinePosition

bool hasUnderlinePosition(SkScalar* position) const

Returns true if Font Metrics has a valid underline position, and sets position to that value. If the underline position is not valid, return false, and ignore position.

Parameters

position storage for underline position

Return Value

true if font specifies underline position

hasStrikeoutThickness

bool hasStrikeoutThickness(SkScalar* thickness) const

Returns true if Font Metrics has a valid strikeout thickness, and sets thickness to that value. If the underline thickness is not valid, return false, and ignore thickness.

Parameters

thickness storage for strikeout width

Return Value

true if font specifies strikeout width

hasStrikeoutPosition

bool hasStrikeoutPosition(SkScalar* position) const

Returns true if Font Metrics has a valid strikeout position, and sets position to that value. If the underline position is not valid, return false, and ignore position.

Parameters

position storage for strikeout position

Return Value

true if font specifies strikeout position

getFontMetrics

SkScalar getFontMetrics(FontMetrics* metrics, SkScalar scale = 0) const

Returns Font Metrics associated with Typeface. The return value is the recommended spacing between lines: the sum of metrics descent, ascent, and leading. If metrics is not nullptr, Font Metrics is copied to metrics. Results are scaled by Text Size but does not take into account dimensions required by Text Scale X, Text Skew X, Fake Bold, Style Stroke, and Path Effect. Results can be additionally scaled by scale; a scale of zero is ignored.

Parameters

`metrics`	storage for Font Metrics from Typeface; may be nullptr
`scale`	additional multiplier for returned values

Return Value

recommended spacing between lines

Example

getFontSpacing

SkScalar getFontSpacing() const

Returns the recommended spacing between lines: the sum of metrics descent, ascent, and leading. Result is scaled by Text Size but does not take into account dimensions required by stroking and Path Effect. Returns the same result as getFontMetrics.

Return Value

recommended spacing between lines

Example

Example Output

textSize: 12 fontSpacing: 13.9688
textSize: 18 fontSpacing: 20.9531
textSize: 24 fontSpacing: 27.9375
textSize: 32 fontSpacing: 37.25

getFontBounds

SkRect getFontBounds() const

Returns the union of bounds of all Glyphs. Returned dimensions are computed by Font Manager from font data, ignoring Hinting. Includes Text Size, Text Scale X, and Text Skew X, but not Fake Bold or Path Effect.

If Text Size is large, Text Scale X is one, and Text Skew X is zero, returns the same bounds as Font Metrics { FontMetrics::fXMin, FontMetrics::fTop, FontMetrics::fXMax, FontMetrics::fBottom }.

Return Value

union of bounds of all Glyphs

Example

Example Output

metrics bounds = { -12.2461, -14.7891, 21.5215, 5.55469 }
font bounds    = { -12.2461, -14.7891, 21.5215, 5.55469 }

textToGlyphs

int textToGlyphs(const void* text, size_t byteLength, SkGlyphID glyphs[]) const

Converts text into glyph indices. Returns the number of glyph indices represented by text. Text Encoding specifies how text represents characters or glyphs. glyphs may be nullptr, to compute the glyph count.

Does not check text for valid character codes or valid glyph indices.

If byteLength equals zero, returns zero. If byteLength includes a partial character, the partial character is ignored.

If Text Encoding is kUTF8 TextEncoding and text contains an invalid UTF-8 sequence, zero is returned.

Parameters

`text`	character storage encoded with Text Encoding
`byteLength`	length of character storage in bytes
`glyphs`	storage for glyph indices; may be nullptr

Return Value

number of glyphs represented by text of length byteLength

Example

countText

int countText(const void* text, size_t byteLength) const

Returns the number of Glyphs in text. Uses Text Encoding to count the Glyphs. Returns the same result as textToGlyphs.

Parameters

`text`	character storage encoded with Text Encoding
`byteLength`	length of character storage in bytes

Return Value

number of Glyphs represented by text of length byteLength

Example

Example Output

count = 5

containsText

bool containsText(const void* text, size_t byteLength) const

Returns true if all text corresponds to a non-zero glyph index. Returns false if any characters in text are not supported in Typeface.

If Text Encoding is kGlyphID TextEncoding, returns true if all glyph indices in text are non-zero; does not check to see if text contains valid glyph indices for Typeface.

Returns true if byteLength is zero.

Parameters

`text`	array of characters or Glyphs
`byteLength`	number of bytes in text array

Return Value

true if all text corresponds to a non-zero glyph index

containsText succeeds for degree symbol, but cannot find a glyph index corresponding to the Unicode surrogate code point.

Example Output

0x00b0 == has char
0xd800 != has char

Example

containsText returns true that glyph index is greater than zero, not that it corresponds to an entry in Typeface.

Example Output

0x01ff == has glyph
0x0000 != has glyph
0xffff == has glyph

glyphsToUnichars

void glyphsToUnichars(const SkGlyphID glyphs[], int count, SkUnichar text[]) const

Converts glyphs into text if possible. Glyph values without direct Unicode equivalents are mapped to zero. Uses the Typeface, but is unaffected by Text Encoding; the text values returned are equivalent to kUTF32 TextEncoding.

Only supported on platforms that use FreeType as the Font Engine.

Parameters

`glyphs`	array of indices into font
`count`	length of glyph array
`text`	storage for character codes, one per glyph

Example

Convert UTF-8 text to glyphs; then convert glyphs to Unichar code points.

Measure Text

measureText

SkScalar measureText(const void* text, size_t length, SkRect* bounds) const

Returns the advance width of text if kVerticalText Flag is clear, and the height of text if kVerticalText Flag is set. The advance is the normal distance to move before drawing additional text. Uses Text Encoding to decode text, Typeface to get the font metrics, and Text Size, Text Scale X, Text Skew X, Stroke Width, and Path Effect to scale the metrics and bounds. Returns the bounding box of text if bounds is not nullptr. The bounding box is computed as if the text was drawn at the origin.

Parameters

`text`	character codes or glyph indices to be measured
`length`	number of bytes of text to measure
`bounds`	returns bounding box relative to (0, 0) if not nullptr

Return Value

advance width or height

Example

SkScalar measureText(const void* text, size_t length) const

Returns the advance width of text if kVerticalText Flag is clear, and the height of text if kVerticalText Flag is set. The advance is the normal distance to move before drawing additional text. Uses Text Encoding to decode text, Typeface to get the font metrics, and Text Size to scale the metrics. Does not scale the advance or bounds by Fake Bold or Path Effect.

Parameters

`text`	character codes or glyph indices to be measured
`length`	number of bytes of text to measure

Return Value

advance width or height

Example

Example Output

default width = 5
double width = 10

breakText

size_t breakText(const void* text, size_t length, SkScalar maxWidth,
                 SkScalar* measuredWidth = nullptr) const

Returns the bytes of text that fit within maxWidth. If kVerticalText Flag is clear, the text fragment fits if its advance width is less than or equal to maxWidth. If kVerticalText Flag is set, the text fragment fits if its advance height is less than or equal to maxWidth. Measures only while the advance is less than or equal to maxWidth. Returns the advance or the text fragment in measuredWidth if it not nullptr. Uses Text Encoding to decode text, Typeface to get the font metrics, and Text Size to scale the metrics. Does not scale the advance or bounds by Fake Bold or Path Effect.

Parameters

`text`	character codes or glyph indices to be measured
`length`	number of bytes of text to measure
`maxWidth`	advance limit; text is measured while advance is less than maxWidth
`measuredWidth`	returns the width of the text less than or equal to maxWidth

Return Value

bytes of text that fit, always less than or equal to length

Example

Line under "" shows desired width, shorter than available characters. Line under "" shows measured width after breaking text.

getTextWidths

int getTextWidths(const void* text, size_t byteLength, SkScalar widths[], SkRect bounds[] = nullptr) const

Retrieves the advance and bounds for each glyph in text, and returns the glyph count in text. Both widths and bounds may be nullptr. If widths is not nullptr, widths must be an array of glyph count entries. if bounds is not nullptr, bounds must be an array of glyph count entries. If kVerticalText Flag is clear, widths returns the horizontal advance. If kVerticalText Flag is set, widths returns the vertical advance. Uses Text Encoding to decode text, Typeface to get the font metrics, and Text Size to scale the widths and bounds. Does not scale the advance by Fake Bold or Path Effect. Does include Fake Bold and Path Effect in the bounds.

Parameters

`text`	character codes or glyph indices to be measured
`byteLength`	number of bytes of text to measure
`widths`	returns text advances for each glyph; may be nullptr
`bounds`	returns bounds for each glyph relative to (0, 0); may be nullptr

Return Value

glyph count in text

Example

Bounds of Glyphs increase for stroked text, but text advance remains the same. The underlines show the text advance, spaced to keep them distinct.

Text Path

Text Path describes the geometry of Glyphs used to draw text.

getTextPath

void getTextPath(const void* text, size_t length, SkScalar x, SkScalar y, SkPath* path) const

Returns the geometry as Path equivalent to the drawn text. Uses Text Encoding to decode text, Typeface to get the glyph paths, and Text Size, Fake Bold, and Path Effect to scale and modify the glyph paths. All of the glyph paths are stored in path. Uses x, y, and Text Align to position path.

Parameters

`text`	character codes or glyph indices
`length`	number of bytes of text
`x`	x-axis value of the origin of the text
`y`	y-axis value of the origin of the text
`path`	geometry of the Glyphs

Example

Text is added to Path, offset, and subtracted from Path, then added at the offset location. The result is rendered with one draw call.

getPosTextPath

void getPosTextPath(const void* text, size_t length, const SkPoint pos[], SkPath* path) const

Parameters

`text`	character codes or glyph indices
`length`	number of bytes of text
`pos`	positions of each glyph
`path`	geometry of the Glyphs

Example

Simplifies three Glyphs to eliminate overlaps, and strokes the result.

Text Intercepts

Text Intercepts describe the intersection of drawn text Glyphs with a pair of lines parallel to the text advance. Text Intercepts permits creating a underline that skips Descenders.

getTextIntercepts

int getTextIntercepts(const void* text, size_t length, SkScalar x, SkScalar y,
                      const SkScalar bounds[2], SkScalar* intervals) const

Returns the number of intervals that intersect bounds. bounds describes a pair of lines parallel to the text advance. The return count is zero or a multiple of two, and is at most twice the number of Glyphs in the string. Uses Text Encoding to decode text, Typeface to get the glyph paths, and Text Size, Fake Bold, and Path Effect to scale and modify the glyph paths. Uses x, y, and Text Align to position intervals.

Pass nullptr for intervals to determine the size of the interval array.

intervals are cached to improve performance for multiple calls.

Parameters

`text`	character codes or glyph indices
`length`	number of bytes of text
`x`	x-axis value of the origin of the text
`y`	y-axis value of the origin of the text
`bounds`	lower and upper line parallel to the advance
`intervals`	returned intersections; may be nullptr

Return Value

number of intersections; may be zero

Example

Underline uses intercepts to draw on either side of the glyph Descender.

getPosTextIntercepts

int getPosTextIntercepts(const void* text, size_t length, const SkPoint pos[],
                         const SkScalar bounds[2], SkScalar* intervals) const

Pass nullptr for intervals to determine the size of the interval array.

intervals are cached to improve performance for multiple calls.

Parameters

`text`	character codes or glyph indices
`length`	number of bytes of text
`pos`	positions of each glyph
`bounds`	lower and upper line parallel to the advance
`intervals`	returned intersections; may be nullptr

Return Value

number of intersections; may be zero

Example

Text intercepts draw on either side of, but not inside, Glyphs in a run.

getPosTextHIntercepts

int getPosTextHIntercepts(const void* text, size_t length, const SkScalar xpos[], SkScalar constY,
                          const SkScalar bounds[2], SkScalar* intervals) const

Pass nullptr for intervals to determine the size of the interval array.

intervals are cached to improve performance for multiple calls.

Parameters

`text`	character codes or glyph indices
`length`	number of bytes of text
`xpos`	positions of each glyph in x
`constY`	position of each glyph in y
`bounds`	lower and upper line parallel to the advance
`intervals`	returned intersections; may be nullptr

Return Value

number of intersections; may be zero

Example

Text intercepts do not take stroke thickness into consideration.

getTextBlobIntercepts

int getTextBlobIntercepts(const SkTextBlob* blob, const SkScalar bounds[2], SkScalar* intervals) const

Returns the number of intervals that intersect bounds. bounds describes a pair of lines parallel to the text advance. The return count is zero or a multiple of two, and is at most twice the number of Glyphs in the string. Uses Typeface to get the glyph paths, and Text Size, Fake Bold, and Path Effect to scale and modify the glyph paths. Uses run array and Text Align to position intervals.

Text Encoding must be set to SkPaint::kGlyphID TextEncoding.

Pass nullptr for intervals to determine the size of the interval array.

intervals are cached to improve performance for multiple calls.

Parameters

`blob`	Glyphs, positions, and text paint attributes
`bounds`	lower and upper line parallel to the advance
`intervals`	returned intersections; may be nullptr

Return Value

number of intersections; may be zero

Example

nothingToDraw

bool nothingToDraw() const

Returns true if Paint prevents all drawing; otherwise, the Paint may or may not allow drawing.

Returns true if, for example, Blend Mode combined with Color Alpha computes a new Alpha of zero.

Return Value

true if Paint prevents all drawing

Example

Example Output

initial nothing to draw: false
blend dst nothing to draw: true
blend src over nothing to draw: false
alpha 0 nothing to draw: true

Fast Bounds

Fast Bounds functions conservatively outset a drawing bounds by additional area Paint may draw to.

canComputeFastBounds

bool canComputeFastBounds() const

Returns true if Paint does not include elements requiring extensive computation to compute Device bounds of drawn geometry. For instance, Paint with Path Effect always returns false.

Return Value

true if Paint allows for fast computation of bounds

computeFastBounds

const SkRect& computeFastBounds(const SkRect& orig, SkRect* storage) const

Only call this if canComputeFastBounds returned true. This takes a raw rectangle (the raw bounds of a shape), and adjusts it for stylistic effects in the paint (e.g. stroking). If needed, it uses the storage parameter. It returns the adjusted bounds that can then be used for SkCanvas::quickReject tests.

The returned Rect will either be orig or storage, thus the caller should not rely on storage being set to the result, but should always use the returned value. It is legal for orig and storage to be the same Rect.

Parameters

`orig`	geometry modified by Paint when drawn
`storage`	computed bounds of geometry; may not be nullptr

Return Value

fast computed bounds

computeFastStrokeBounds

const SkRect& computeFastStrokeBounds(const SkRect& orig, SkRect* storage) const

Parameters

`orig`	geometry modified by Paint when drawn
`storage`	computed bounds of geometry

Return Value

fast computed bounds

doComputeFastBounds

const SkRect& doComputeFastBounds(const SkRect& orig, SkRect* storage, Style style) const

Computes the bounds, overriding the Paint Style. This can be used to account for additional width required by stroking orig, without altering Style set to fill.

Parameters

`orig`	geometry modified by Paint when drawn
`storage`	computed bounds of geometry
`style`	overrides Style

Return Value

fast computed bounds

Utility

Topic	Description
containsText	returns if all text corresponds to Glyphs
countText	returns number of Glyphs in text
glyphsToUnichars	converts Glyphs into text
nothingToDraw	returns true if Paint prevents all drawing
textToGlyphs	converts text into glyph indices

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SkPaint Reference

Overview

SkPaint

Return Value

Example

SkPaint

Parameters

Return Value

Example

Example Output

SkPaint

Parameters

Return Value

Example

Example Output

reset

Example

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~SkPaint

operator=

Parameters

Return Value

Example

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operator=

Parameters

Return Value

Example

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operator==

Parameters

Return Value

Example

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See Also

operator!=

Parameters

Return Value

Example

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See Also

getHash

Return Value

Example

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Constants

getHinting

Return Value

Example

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setHinting

Parameters

Example

Example Output

Constants

Constants

getFlags

Return Value

Example

Example Output

setFlags

Parameters

Example

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Example

isAntiAlias

Return Value

Example

Example Output

setAntiAlias

Parameters

Example

Example Output

Example

Example

isDither

Return Value

Example

Example Output

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