skia2/docs/SkPaint_Reference.bmh

#Topic Paint
#Alias Paint_Reference ##

#Class SkPaint

#Code
#Populate
##

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.

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.

#Method SkPaint()
#Line # constructs with default values ##
Constructs Paint with default values.

#Table
#Legend
# attribute              # default value            ##
#Legend ##
# Anti_Alias             # false                    ##
# Blend_Mode             # SkBlendMode::kSrcOver    ##
# Color                  # SK_ColorBLACK            ##
# Color_Alpha            # 255                      ##
# Color_Filter           # nullptr                  ##
# Dither                 # false                    ##
# Draw_Looper            # nullptr                  ##
# Filter_Quality         # kNone_SkFilterQuality    ##
# Image_Filter           # nullptr                  ##
# Miter_Limit            # 4                        ##
# Mask_Filter            # nullptr                  ##
# Path_Effect            # nullptr                  ##
# Shader                 # nullptr                  ##
# Style                  # kFill_Style              ##
# Stroke_Cap             # kButt_Cap                ##
# Stroke_Join            # kMiter_Join              ##
# Stroke_Width           # 0                        ##
#Table ##

The 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  default initialized Paint ##

#Example
#ToDo mark this as no output ##
#Height 1
###$  $ redefine markup character so preprocessor commands appear normally
#ifndef SkUserConfig_DEFINED
#define SkUserConfig_DEFINED

#define SkPaintDefaults_TextSize   24.f   // double default font size
#define SkPaintDefaults_Hinting    3      // use full hinting
#define SkPaintDefaults_MiterLimit 10.f   // use HTML Canvas miter limit setting

#endif
$$$#  # restore original markup character
##


##

#Method SkPaint(const SkPaint& paint)
#Line # makes a shallow copy ##
#Populate

#Example
#ToDo why is this double-spaced on Fiddle? ##
    SkPaint paint1;
    paint1.setColor(SK_ColorRED);
    SkPaint paint2(paint1);
    paint2.setColor(SK_ColorBLUE);
    SkDebugf("SK_ColorRED %c= paint1.getColor()\n", SK_ColorRED == paint1.getColor() ? '=' : '!');
    SkDebugf("SK_ColorBLUE %c= paint2.getColor()\n", SK_ColorBLUE == paint2.getColor() ? '=' : '!');

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

##

#Method SkPaint(SkPaint&& paint)
#Line # moves paint without copying it ##
#Populate

#Example
        SkPaint paint;
        float intervals[] = { 5, 5 };
        paint.setPathEffect(SkDashPathEffect::Make(intervals, SK_ARRAY_COUNT(intervals), 2.5f));
        SkPaint dashed(std::move(paint));
        SkDebugf("path effect unique: %s\n", dashed.getPathEffect()->unique() ? "true" : "false");

        #StdOut
            path effect unique: true
        ##
    ##

##

# ------------------------------------------------------------------------------

#Method void reset()
#In Constructors
#Line # sets to default values ##
#Populate

#Example
    SkPaint paint1, paint2;
    paint1.setColor(SK_ColorRED);
    paint1.reset();
    SkDebugf("paint1 %c= paint2", paint1 == paint2 ? '=' : '!');

    #StdOut
        paint1 == paint2
    ##
##

##

# ------------------------------------------------------------------------------

#Method ~SkPaint()
#Line # decreases Reference_Count of owned objects ##
#Populate

#NoExample
##

##


# ------------------------------------------------------------------------------

#Subtopic Management
#Line # paint copying, moving, comparing ##
##

#Method SkPaint& operator=(const SkPaint& paint)
#In Management
#Line # makes a shallow copy ##
#Populate

#Example
    SkPaint paint1, paint2;
    paint1.setColor(SK_ColorRED);
    paint2 = paint1;
    SkDebugf("SK_ColorRED %c= paint1.getColor()\n", SK_ColorRED == paint1.getColor() ? '=' : '!');
    SkDebugf("SK_ColorRED %c= paint2.getColor()\n", SK_ColorRED == paint2.getColor() ? '=' : '!');

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

##

# ------------------------------------------------------------------------------

#Method SkPaint& operator=(SkPaint&& paint)
#In Management
#Line # moves paint without copying it ##
#Populate

#Example
    SkPaint paint1, paint2;
    paint1.setColor(SK_ColorRED);
    paint2 = std::move(paint1);
    SkDebugf("SK_ColorRED == paint2.getColor()\n", SK_ColorRED == paint2.getColor() ? '=' : '!');

    #StdOut
        SK_ColorRED == paint2.getColor()
    ##
##

##

# ------------------------------------------------------------------------------

#Method bool operator==(const SkPaint& a, const SkPaint& b)
#Line # compares paints for equality ##
#Populate

#Example
        SkPaint paint1, paint2;
        paint1.setColor(SK_ColorRED);
        paint2.setColor(0xFFFF0000);
        SkDebugf("paint1 %c= paint2\n", paint1 == paint2 ? '=' : '!');
        float intervals[] = { 5, 5 };
        paint1.setPathEffect(SkDashPathEffect::Make(intervals, 2, 2.5f));
        paint2.setPathEffect(SkDashPathEffect::Make(intervals, 2, 2.5f));
        SkDebugf("paint1 %c= paint2\n", paint1 == paint2 ? '=' : '!');

        #StdOut
            paint1 == paint2
            paint1 != paint2
        ##
    ##
#SeeAlso operator!=(const SkPaint& a, const SkPaint& b)
##

# ------------------------------------------------------------------------------

#Method bool operator!=(const SkPaint& a, const SkPaint& b)
#Line # compares paints for inequality ##
#Populate

#Example
    SkPaint paint1, paint2;
    paint1.setColor(SK_ColorRED);
    paint2.setColor(0xFFFF0000);
    SkDebugf("paint1 %c= paint2\n", paint1 == paint2 ? '=' : '!');
    SkDebugf("paint1 %c= paint2\n", paint1 != paint2 ? '!' : '=');

    #StdOut
        paint1 == paint2
        paint1 == paint2
    ##
##
#SeeAlso operator==(const SkPaint& a, const SkPaint& b)
##

# ------------------------------------------------------------------------------

#Method uint32_t getHash() const
#In Management
#Line # returns a shallow hash for equality checks ##
#Populate

#Example
    SkPaint paint1, paint2;
    paint1.setColor(SK_ColorRED);
    paint2.setColor(0xFFFF0000);
    SkDebugf("paint1 %c= paint2\n", paint1 == paint2 ? '=' : '!');
    SkDebugf("paint1.getHash() %c= paint2.getHash()\n",
             paint1.getHash() == paint2.getHash() ? '=' : '!');

    #StdOut
        paint1 == paint2
        paint1.getHash() == paint2.getHash()
    ##
##

##

# ------------------------------------------------------------------------------
#Subtopic Anti_Alias
#Alias Anti_Alias
#Substitute anti-alias
##
#Alias Anti_Aliased
#Substitute anti-aliased
##
#Alias Anti_Aliasing
#Substitute anti-aliasing
##
#In Related_Function
#Line # approximating coverage with transparency ##

Anti_Alias drawing approximates partial pixel coverage with transparency.

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.

#ToDo  add illustration of raster pixels ##

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.

#Example
    #Width 512
    #Description
        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.
    ##

    void draw(SkCanvas* canvas) {
        SkBitmap bitmap;
        bitmap.allocN32Pixels(50, 50);
        SkCanvas offscreen(bitmap);
        SkPaint paint;
        paint.setStyle(SkPaint::kStroke_Style);
        paint.setStrokeWidth(10);
        for (bool antialias : { false, true }) {
            paint.setColor(antialias ? SK_ColorRED : SK_ColorBLUE);
            paint.setAntiAlias(antialias);
            bitmap.eraseColor(0);
            offscreen.drawLine(5, 5, 15, 30, paint);
            canvas->drawLine(5, 5, 15, 30, paint);
            canvas->save();
            canvas->scale(10, 10);
            canvas->drawBitmap(bitmap, antialias ? 12 : 0, 0);
            canvas->restore();
            canvas->translate(15, 0);
        }
    }
##
#Subtopic Anti_Alias ##

#Method bool isAntiAlias() const
#In Anti_alias
#Line # returns true if Anti_Alias is set ##
#Populate

#Example
    SkPaint paint;
##
##

#Method void setAntiAlias(bool aa)
#In Anti_alias
#Line # sets or clears Anti_Alias ##
#Populate

#Example
    SkPaint paint;
##
##

# ------------------------------------------------------------------------------
#Subtopic Dither
#Line # distributing color error ##

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.

Some platform implementations may ignore dithering. Set #Formula # SK_IGNORE_GPU_DITHER ##
to ignore Dither on GPU_Surface.

#Example
#Description
Dithering in the bottom half more closely approximates the requested color by
alternating nearby colors from pixel to pixel.
##
void draw(SkCanvas* canvas) {
    SkBitmap bm16;
    bm16.allocPixels(SkImageInfo::Make(32, 32, kRGB_565_SkColorType, kOpaque_SkAlphaType));
    SkCanvas c16(bm16);
    SkPaint colorPaint;
    for (auto dither : { false, true } ) {
        colorPaint.setDither(dither);
        for (auto colors : { 0xFF333333, 0xFF666666, 0xFF999999, 0xFFCCCCCC } ) {
            for (auto mask : { 0xFFFF0000, 0xFF00FF00, 0xFF0000FF, 0xFFFFFFFF } ) {
                 colorPaint.setColor(colors & mask);
                 c16.drawRect({0, 0, 8, 4}, colorPaint);
                 c16.translate(8, 0);
            }
            c16.translate(-32, 4);
        }
    }
    canvas->scale(8, 8);
    canvas->drawBitmap(bm16, 0, 0);
}
##

#Example
#Description
Dithering introduces subtle adjustments to color to smooth gradients.
Drawing the gradient repeatedly with SkBlendMode::kPlus exaggerates the
dither, making it easier to see.
##
void draw(SkCanvas* canvas) {
    canvas->clear(0);
    SkBitmap bm32;
    bm32.allocPixels(SkImageInfo::Make(20, 10, kN32_SkColorType, kPremul_SkAlphaType));
    SkCanvas c32(bm32);
    SkPoint points[] = {{0, 0}, {20, 0}};
    SkColor colors[] = {0xFF334455, 0xFF662211 };
    SkPaint paint;
    paint.setShader(SkGradientShader::MakeLinear(
                     points, colors, nullptr, SK_ARRAY_COUNT(colors),
                     SkShader::kClamp_TileMode, 0, nullptr));
    paint.setDither(true);
    c32.drawPaint(paint);
    canvas->scale(12, 12);
    canvas->drawBitmap(bm32, 0, 0);
    paint.setBlendMode(SkBlendMode::kPlus);
    canvas->drawBitmap(bm32, 0, 11, &paint);
    canvas->drawBitmap(bm32, 0, 11, &paint);
    canvas->drawBitmap(bm32, 0, 11, &paint);
}
##
#SeeAlso Gradient kRGB_565_SkColorType
#Subtopic Dither ##

#Method bool isDither() const
#In Dither
#Line # returns true if Dither is set ##
#Populate

#Example
        SkPaint paint;
    ##
##

#Method void setDither(bool dither)
#In Dither
#Line # sets or clears Dither ##
#Populate

#Example
        SkPaint paint;
    ##

    #SeeAlso kRGB_565_SkColorType

##

# ------------------------------------------------------------------------------
#Subtopic Filter_Quality_Methods
#Line # get and set Filter_Quality ##

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
#List
# SkCanvas::drawBitmap ##
# SkCanvas::drawBitmapRect ##
# SkCanvas::drawImage ##
# SkCanvas::drawImageRect ##
  #ToDo probably more... ##
#List ##
and when Paint has a Shader specialization that uses Image or Bitmap.

Filter_Quality is kNone_SkFilterQuality by default.

#Example
#Image 3
void draw(SkCanvas* canvas) {
    SkPaint paint;
    canvas->scale(.2f, .2f);
    for (SkFilterQuality q : { kNone_SkFilterQuality, kLow_SkFilterQuality,
                               kMedium_SkFilterQuality, kHigh_SkFilterQuality } ) {
        paint.setFilterQuality(q);
        canvas->drawImage(image.get(), 0, 0, &paint);
        canvas->translate(550, 0);
        if (kLow_SkFilterQuality == q) canvas->translate(-1100, 550);
    }
}
##
#Subtopic Filter_Quality_Methods ##

#Method SkFilterQuality getFilterQuality() const
#In Filter_Quality_Methods
#Line # returns Filter_Quality, image filtering level ##
#Populate

#Example
    SkPaint paint;
    SkDebugf("kNone_SkFilterQuality %c= paint.getFilterQuality()\n",
            kNone_SkFilterQuality == paint.getFilterQuality() ? '=' : '!');

    #StdOut
        kNone_SkFilterQuality == paint.getFilterQuality()
    ##
##

##


#Method void setFilterQuality(SkFilterQuality quality)
#In Filter_Quality_Methods
#Line # sets Filter_Quality, the image filtering level ##
#Populate

#Example
    SkPaint paint;
    paint.setFilterQuality(kHigh_SkFilterQuality);
    SkDebugf("kHigh_SkFilterQuality %c= paint.getFilterQuality()\n",
            kHigh_SkFilterQuality == paint.getFilterQuality() ? '=' : '!');

    #StdOut
        kHigh_SkFilterQuality == paint.getFilterQuality()
    ##
##

#SeeAlso SkFilterQuality Image_Scaling

##

# ------------------------------------------------------------------------------
#Subtopic Color_Methods
#Line # get and set Color ##

#Table
#Legend
# name                  # description                                          ##
#Legend ##
# getColor              # returns Color_Alpha and RGB, one drawing color ##
# setColor              # sets Color_Alpha and RGB, one drawing color    ##
#Table ##

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.

#Table
#Legend
# bit positions # Color_Alpha # red # blue # green ##
#Legend ##
#               # 31 - 24     # 23 - 16       # 15 - 8         # 7 - 0           ##
#Table ##

#Example
#Height 128
    void draw(SkCanvas* canvas) {
        SkPaint paint;
        paint.setColor(0x8000FF00);  // transparent green
        canvas->drawCircle(50, 50, 40, paint);
        paint.setARGB(128, 255, 0, 0); // transparent red
        canvas->drawCircle(80, 50, 40, paint);
        paint.setColor(SK_ColorBLUE);
        paint.setAlpha(0x80);
        canvas->drawCircle(65, 65, 40, paint);
    }
##
#Subtopic Color_Methods ##

#Method SkColor getColor() const
#In Color_Methods
#Line # returns Color_Alpha and RGB, one drawing color ##
#Populate

#Example
        SkPaint paint;
        paint.setColor(SK_ColorYELLOW);
        SkColor y = paint.getColor();
        SkDebugf("Yellow is %d%% red, %d%% green, and %d%% blue.\n", (int) (SkColorGetR(y) / 2.55f),
                (int) (SkColorGetG(y) / 2.55f), (int) (SkColorGetB(y) / 2.55f));

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

    #SeeAlso getColor4f SkColor

##

#Method SkColor4f getColor4f() const
#In Color_Methods
#Line # returns Color_Alpha and RGB, one drawing color ##
#Populate

#Example
        SkPaint paint;
        paint.setColor(SK_ColorYELLOW);
        SkColor4f y = paint.getColor4f();
        SkDebugf("Yellow is %d%% red, %d%% green, and %d%% blue.\n", (int) (y.fR * 100),
                (int) (y.fG * 100), (int) (y.fB * 100));

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

    #SeeAlso getColor SkColor
##


#Method void setColor(SkColor color)
#In Color_Methods
#Line # sets Color_Alpha and RGB, one drawing color ##
#Populate

#Example
        SkPaint green1, green2;
        unsigned a = 255;
        unsigned r = 0;
        unsigned g = 255;
        unsigned b = 0;
        green1.setColor((a << 24) + (r << 16) + (g << 8) + (b << 0));
        green2.setColor(0xFF00FF00);
        SkDebugf("green1 %c= green2\n", green1 == green2 ? '=' : '!');

        #StdOut
            green1 == green2
        ##
    ##

    #SeeAlso SkColor setColor4f setARGB SkColorSetARGB

##

#Method void setColor4f(const SkColor4f& color, SkColorSpace* colorSpace)
#In Color_Methods
#Line # sets Color_Alpha and RGB, one drawing color ##
#Populate

#Example
        SkPaint green1, green2;
        green1.setColor4f({0, 1, 0, 1}, nullptr);  // R=0 G=1 B=0 A=1
        green2.setColor(0xFF00FF00); // A=255 R=0 G=255 B=0
        SkDebugf("green1 %c= green2\n", green1 == green2 ? '=' : '!');

        #StdOut
            green1 == green2
        ##
    ##

    #SeeAlso SkColor setColor setARGB SkColorSetARGB

##

#Subtopic Alpha_Methods
#Line # get and set Alpha ##

Color_Alpha sets the transparency independent of RGB: red, blue, and green.
#Subtopic Alpha_Methods ##

#Method uint8_t getAlpha() const
#In Alpha_Methods
#Line # returns Color_Alpha, color opacity ##
#Populate

#Example
        SkPaint paint;
        SkDebugf("255 %c= paint.getAlpha()\n", 255 == paint.getAlpha() ? '=' : '!');

        #StdOut
            255 == paint.getAlpha()
        ##
    ##

##

#Method float getAlphaf() const
#In Alpha_Methods
#Line # returns Color_Alpha, color opacity ##
#Populate

#Example
    SkPaint paint;
##

##

#Method void setAlpha(U8CPU a)
#In Alpha_Methods
#Line # sets Color_Alpha, color opacity ##
#Populate

#Example
        SkPaint paint;
        paint.setColor(0x00112233);
        paint.setAlpha(0x44);
        SkDebugf("0x44112233 %c= paint.getColor()\n", 0x44112233 == paint.getColor() ? '=' : '!');

        #StdOut
            0x44112233 == paint.getColor()
        ##
    ##

##

#Method void setAlphaf(float a)
#In Alpha_Methods
#Line # sets Color_Alpha, color opacity ##
#Populate

#Example
    SkPaint paint;
##

##

#Method void setARGB(U8CPU a, U8CPU r, U8CPU g, U8CPU b)
#In Color_Methods
#Line # sets color by component ##
#Populate

#Example
        SkPaint transRed1, transRed2;
        transRed1.setARGB(255 / 2, 255, 0, 0);
        transRed2.setColor(SkColorSetARGB(255 / 2, 255, 0, 0));
        SkDebugf("transRed1 %c= transRed2", transRed1 == transRed2 ? '=' : '!');

        #StdOut
            transRed1 == transRed2
        ##
    ##

    #SeeAlso setColor SkColorSetARGB

##

# ------------------------------------------------------------------------------
#Subtopic Style
#Line # geometry filling, stroking ##

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

#Subtopic Fill
Set Style to kFill_Style to fill the shape.
The fill covers the area inside the geometry for most shapes.
#Subtopic Fill ##

#Subtopic Stroke
Set Style to kStroke_Style to stroke the shape.

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.
#Subtopic Stroke ##

As Stroke_Width gets smaller, the drawn path frame is thinner. Stroke_Width less than one
may have gaps, and if antialiasing is on, Color_Alpha will increase to visually decrease coverage.

#SeeAlso Path_Fill_Type Path_Effect Style_Fill Style_Stroke
#Subtopic Style ##

#Subtopic Hairline
Stroke_Width of zero has a special meaning and switches drawing to use Hairline.
Hairline draws the thinnest continuous frame. If antialiasing is off, adjacent pixels
flow horizontally, vertically,or diagonally.

#ToDo  what is the description of Anti_Aliased hairlines? ##

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 antialiasing is on, 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.

#SeeAlso Path_Fill_Type Path_Effect Style_Fill Style_Stroke
#Subtopic Hairline ##

#Enum Style
#Line # stroke, fill, or both ##

#Code
#Populate
##

#Code
#In Constant
#Filter kStyle
#Populate
##

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.

#Const  kFill_Style 0
#Line # set to fill geometry ##
    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.
##

#Const kStroke_Style 1
#Line # set to stroke geometry ##
    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.
##

#Const kStrokeAndFill_Style 2
#Line # sets to stroke and fill geometry ##
    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.
##

#Const kStyleCount 3
#Line # number of different Style values defined ##
May be used to verify that Style is a legal value.
##

#Enum Style ##

#Method Style getStyle() const
#In Style
#Line # returns Style: stroke, fill, or both ##
#Populate

#Example
        SkPaint paint;
        SkDebugf("SkPaint::kFill_Style %c= paint.getStyle()\n",
                SkPaint::kFill_Style == paint.getStyle() ? '=' : '!');

        #StdOut
            SkPaint::kFill_Style == paint.getStyle()
        ##
    ##

#SeeAlso Style setStyle
##

#Method void setStyle(Style style)
#In Style
#Line # sets Style: stroke, fill, or both ##
#Populate

#Example
        void draw(SkCanvas* canvas) {
            SkPaint paint;
            paint.setStrokeWidth(5);
            SkRegion region;
            region.op(140, 10, 160, 30, SkRegion::kUnion_Op);
            region.op(170, 40, 190, 60, SkRegion::kUnion_Op);
            SkBitmap bitmap;
            bitmap.setInfo(SkImageInfo::MakeA8(50, 50), 50);
            uint8_t pixels[50][50];
            for (int x = 0; x < 50; ++x) {
                for (int y = 0; y < 50; ++y) {
                    pixels[y][x] = (x + y) % 5 ? 0xFF : 0x00;
                }
            }
            bitmap.setPixels(pixels);
            for (auto style : { SkPaint::kFill_Style,
                                SkPaint::kStroke_Style,
                                SkPaint::kStrokeAndFill_Style }) {
                paint.setStyle(style);
                canvas->drawLine(10, 10, 60, 60, paint);
                canvas->drawRect({80, 10, 130, 60}, paint);
                canvas->drawRegion(region, paint);
                canvas->drawBitmap(bitmap, 200, 10, &paint);
                canvas->translate(0, 80);
            }
        }
    ##

#SeeAlso Style getStyle
##

# ------------------------------------------------------------------------------
#Subtopic Stroke_Width
#Line # thickness perpendicular to geometry ##

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
#Height 170
    #Platform raster gpu
    #Description
        The pixels hit to represent thin lines vary with the angle of the
        line and the platform implementation.
    ##
    void draw(SkCanvas* canvas) {
        SkPaint paint;
        for (bool antialias : { false, true }) {
            paint.setAntiAlias(antialias);
            for (int width = 0; width <= 4; ++width) {
                SkScalar offset = antialias * 100 + width * 20;
                paint.setStrokeWidth(width * 0.25f);
                canvas->drawLine(10 + offset,  10, 20 + offset,  60, paint);
                canvas->drawLine(10 + offset, 110, 60 + offset, 160, paint);
            }
        }
    }
##

#Method SkScalar getStrokeWidth() const

#In Stroke_Width
#Line # returns thickness of the stroke ##
#Populate

#Example
        SkPaint paint;
        SkDebugf("0 %c= paint.getStrokeWidth()\n", 0 == paint.getStrokeWidth() ? '=' : '!');

        #StdOut
            0 == paint.getStrokeWidth()
        ##
    ##

##

#Method void setStrokeWidth(SkScalar width)

#In Stroke_Width
#Line # sets thickness of the stroke ##
#Populate

#Example
        SkPaint paint;
        paint.setStrokeWidth(5);
        paint.setStrokeWidth(-1);
        SkDebugf("5 %c= paint.getStrokeWidth()\n", 5 == paint.getStrokeWidth() ? '=' : '!');

        #StdOut
            5 == paint.getStrokeWidth()
        ##
    ##

##

#Subtopic Stroke_Width ##
# ------------------------------------------------------------------------------
#Subtopic Miter_Limit
#Line # maximum length of stroked corners ##

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 using:
#Formula # 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.
#Table
#Legend
    # miter limit    # angle in degrees ##
#Legend ##
    # 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              ##
#Table ##

#Example
    #Height 170
    #Width 384
    #Description
        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.
    ##
    void draw(SkCanvas* canvas) {
        SkPoint pts[] = {{ 10, 50 }, { 110, 80 }, { 10, 110 }};
        SkVector v[] = { pts[0] - pts[1], pts[2] - pts[1] };
        SkScalar angle1 = SkScalarATan2(v[0].fY, v[0].fX);
        SkScalar angle2 = SkScalarATan2(v[1].fY, v[1].fX);
        const SkScalar strokeWidth = 20;
        SkScalar miterLimit = 1 / SkScalarSin((angle2 - angle1) / 2);
        SkScalar miterLength = strokeWidth * miterLimit;
        SkPath path;
        path.moveTo(pts[0]);
        path.lineTo(pts[1]);
        path.lineTo(pts[2]);
        SkPaint paint;  // set to default kMiter_Join
        paint.setAntiAlias(true);
        paint.setStyle(SkPaint::kStroke_Style);
        paint.setStrokeMiter(miterLimit);
        paint.setStrokeWidth(strokeWidth);
        canvas->drawPath(path, paint);
        paint.setStrokeWidth(1);
        canvas->drawLine(pts[1].fX - miterLength / 2, pts[1].fY + 50,
                         pts[1].fX + miterLength / 2, pts[1].fY + 50, paint);
        canvas->translate(200, 0);
        miterLimit *= 0.99f;
        paint.setStrokeMiter(miterLimit);
        paint.setStrokeWidth(strokeWidth);
        canvas->drawPath(path, paint);
        paint.setStrokeWidth(1);
        canvas->drawLine(pts[1].fX - miterLength / 2, pts[1].fY + 50,
                         pts[1].fX + miterLength / 2, pts[1].fY + 50, paint);
    }
##

#Method SkScalar getStrokeMiter() const

#In Miter_Limit
#Line # returns Miter_Limit, angles with sharp corners ##
#Populate

#Example
        SkPaint paint;
        SkDebugf("default miter limit == %g\n", paint.getStrokeMiter());

        #StdOut
        default miter limit == 4
        ##
    ##

    #SeeAlso Miter_Limit setStrokeMiter Join

##

#Method void setStrokeMiter(SkScalar miter)

#In Miter_Limit
#Line # sets Miter_Limit, angles with sharp corners ##
#Populate

#Example
        SkPaint paint;
        paint.setStrokeMiter(8);
        paint.setStrokeMiter(-1);
        SkDebugf("default miter limit == %g\n", paint.getStrokeMiter());

        #StdOut
        default miter limit == 8
        ##
    ##

    #SeeAlso Miter_Limit getStrokeMiter Join

##

#Subtopic Miter_Limit ##
# ------------------------------------------------------------------------------
#Subtopic Stroke_Cap
#Line # decorations at ends of open strokes ##
#Subtopic Stroke_Cap ##

#Enum Cap
#Line # start and end geometry on stroked shapes ##

#Code
#Populate
##

#Code
#In Constant
#Filter kCap
#Populate
##

Stroke_Cap draws at the beginning and end of an open Path_Contour.

    #Const kButt_Cap 0
    #Line # no stroke extension ##
        Does not extend the stroke past the beginning or the end.
    ##
    #Const kRound_Cap 1
    #Line # adds circle ##
        Adds a circle with a diameter equal to Stroke_Width at the beginning
        and end.
    ##
    #Const kSquare_Cap 2
    #Line # adds square ##
        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.
    ##
    #Const kLast_Cap 2
    #Line # largest Stroke_Cap value ##
        Equivalent to the largest value for Stroke_Cap.
    ##
    #Const kDefault_Cap 0
    #Line # equivalent to kButt_Cap ##
        Stroke_Cap is set to kButt_Cap by default.
    ##

    #Const kCapCount 3
    #Line # number of different Stroke_Cap values defined ##
        May be used to verify that Stroke_Cap is a legal value.
    ##
#Enum ##

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
#Height 200
    SkPaint paint;
    paint.setStyle(SkPaint::kStroke_Style);
    paint.setStrokeWidth(20);
    SkPath path;
    path.moveTo(30, 30);
    path.lineTo(30, 30);
    path.moveTo(70, 30);
    path.lineTo(90, 40);
    for (SkPaint::Cap c : { SkPaint::kButt_Cap, SkPaint::kRound_Cap, SkPaint::kSquare_Cap } ) {
        paint.setStrokeCap(c);
        canvas->drawPath(path, paint);
        canvas->translate(0, 70);
    }
##

#Method Cap getStrokeCap() const

#In Stroke_Cap
#Line # returns Cap, the area drawn at path ends ##
#Populate

#Example
        SkPaint paint;
        SkDebugf("kButt_Cap %c= default stroke cap\n",
                SkPaint::kButt_Cap == paint.getStrokeCap() ? '=' : '!');

        #StdOut
            kButt_Cap == default stroke cap
        ##
    ##

    #SeeAlso Stroke_Cap setStrokeCap
##

#Method void setStrokeCap(Cap cap)

#In Stroke_Cap
#Line # sets Cap, the area drawn at path ends ##
#Populate

#Example
        SkPaint paint;
        paint.setStrokeCap(SkPaint::kRound_Cap);
        paint.setStrokeCap((SkPaint::Cap) SkPaint::kCapCount);
        SkDebugf("kRound_Cap %c= paint.getStrokeCap()\n",
                SkPaint::kRound_Cap == paint.getStrokeCap() ? '=' : '!');

        #StdOut
            kRound_Cap == paint.getStrokeCap()
        ##
    ##

    #SeeAlso Stroke_Cap getStrokeCap
##

# ------------------------------------------------------------------------------
#Subtopic Stroke_Join
#Line # decoration at corners of strokes ##
#Subtopic 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
#Height 200
    SkPaint paint;
    paint.setStyle(SkPaint::kStroke_Style);
    paint.setStrokeWidth(20);
    SkPath path;
    path.moveTo(30, 20);
    path.lineTo(40, 40);
    path.conicTo(70, 20, 100, 20, .707f);
    for (SkPaint::Join j : { SkPaint::kMiter_Join, SkPaint::kRound_Join, SkPaint::kBevel_Join } ) {
        paint.setStrokeJoin(j);
        canvas->drawPath(path, paint);
        canvas->translate(0, 70);
    }
##

#Enum Join
#Line # corner geometry on stroked shapes ##
#Code
#Populate
##

#Code
#In Constant
#Filter kJoin
#Populate
##

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.

#Const kMiter_Join 0
#Line # extends to Miter_Limit ##
    Extends the outside corner to the extent allowed by Miter_Limit.
    If the extension exceeds Miter_Limit, kBevel_Join is used instead.
##

#Const kRound_Join 1
#Line # adds circle ##
    Adds a circle with a diameter of Stroke_Width at the sharp corner.
##

#Const kBevel_Join 2
#Line # connects outside edges ##
    Connects the outside edges of the sharp corner.
##

#Const kLast_Join 2
#Line # equivalent to the largest value for Stroke_Join ##
##

#Const kDefault_Join 1
#Line # equivalent to kMiter_Join ##
    Stroke_Join is set to kMiter_Join by default.
##

#Const kJoinCount 3
#Line # number of different Stroke_Join values defined ##
    May be used to verify that Stroke_Join is a legal value.
##

#Example
#Width 462
void draw(SkCanvas* canvas) {
    SkPath path;
    path.moveTo(10, 50);
    path.quadTo(35, 110, 60, 210);
    path.quadTo(105, 110, 130, 10);
    SkPaint paint;  // set to default kMiter_Join
    paint.setAntiAlias(true);
    paint.setStyle(SkPaint::kStroke_Style);
    paint.setStrokeWidth(20);
    canvas->drawPath(path, paint);
    canvas->translate(150, 0);
    paint.setStrokeJoin(SkPaint::kBevel_Join);
    canvas->drawPath(path, paint);
    canvas->translate(150, 0);
    paint.setStrokeJoin(SkPaint::kRound_Join);
    canvas->drawPath(path, paint);
}
##

#SeeAlso setStrokeJoin getStrokeJoin setStrokeMiter getStrokeMiter

#Enum ##

#Method Join getStrokeJoin() const

#In Stroke_Join
#Line # returns Join, geometry on path corners ##
#Populate

#Example
        SkPaint paint;
        SkDebugf("kMiter_Join %c= default stroke join\n",
                SkPaint::kMiter_Join == paint.getStrokeJoin() ? '=' : '!');

        #StdOut
            kMiter_Join == default stroke join
        ##
    ##

    #SeeAlso Stroke_Join setStrokeJoin
##

#Method void setStrokeJoin(Join join)

#In Stroke_Join
#Line # sets Join, geometry on path corners ##
#Populate

#Example
        SkPaint paint;
        paint.setStrokeJoin(SkPaint::kMiter_Join);
        paint.setStrokeJoin((SkPaint::Join) SkPaint::kJoinCount);
        SkDebugf("kMiter_Join %c= paint.getStrokeJoin()\n",
                SkPaint::kMiter_Join == paint.getStrokeJoin() ? '=' : '!');

        #StdOut
            kMiter_Join == paint.getStrokeJoin()
        ##
    ##

    #SeeAlso Stroke_Join getStrokeJoin
##

#SeeAlso Miter_Limit

# ------------------------------------------------------------------------------
#Subtopic Fill_Path
#Line # make Path from Path_Effect, stroking ##

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.

#SeeAlso Style_Stroke Stroke_Width Path_Effect

#Subtopic Fill_Path ##

#Method bool getFillPath(const SkPath& src, SkPath* dst, const SkRect* cullRect,
                     SkScalar resScale = 1) const
#In Fill_Path
#Line # returns fill path equivalent to stroke ##
#Populate

#Example
    #Height 192
    #Description
    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.
    ##
        void draw(SkCanvas* canvas) {
            SkPaint strokePaint;
            strokePaint.setAntiAlias(true);
            strokePaint.setStyle(SkPaint::kStroke_Style);
            strokePaint.setStrokeWidth(.1f);
            SkPath strokePath;
            strokePath.moveTo(.08f, .08f);
            strokePath.quadTo(.09f, .08f, .17f, .17f);
            SkPath fillPath;
            SkPaint outlinePaint(strokePaint);
            outlinePaint.setStrokeWidth(2);
            SkMatrix scale = SkMatrix::MakeScale(300, 300);
            for (SkScalar precision : { 0.01f, .1f, 1.f, 10.f, 100.f } ) {
                strokePaint.getFillPath(strokePath, &fillPath, nullptr, precision);
                fillPath.transform(scale);
                canvas->drawPath(fillPath, outlinePaint);
                canvas->translate(60, 0);
                if (1.f == precision) canvas->translate(-180, 100);
            }
            strokePath.transform(scale);
            strokePaint.setStrokeWidth(30);
            canvas->drawPath(strokePath, strokePaint);
        }
    ##

##

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

#In Fill_Path
#Populate

#Example
    #Height 128
        void draw(SkCanvas* canvas) {
            SkPaint paint;
            paint.setStyle(SkPaint::kStroke_Style);
            paint.setStrokeWidth(10);
            SkPath strokePath;
            strokePath.moveTo(20, 20);
            strokePath.lineTo(100, 100);
            canvas->drawPath(strokePath, paint);
            SkPath fillPath;
            paint.getFillPath(strokePath, &fillPath);
            paint.setStrokeWidth(2);
            canvas->translate(40, 0);
            canvas->drawPath(fillPath, paint);
        }
    ##

##

# ------------------------------------------------------------------------------
#Subtopic Shader_Methods
#Line # get and set Shader ##

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
void draw(SkCanvas* canvas) {
   SkPaint paint;
   SkPoint center = { 50, 50 };
   SkScalar radius = 50;
   const SkColor colors[] = { 0xFFFFFFFF, 0xFF000000 };
   paint.setShader(SkGradientShader::MakeRadial(center, radius, colors,
        nullptr, SK_ARRAY_COUNT(colors), SkShader::kClamp_TileMode));
   for (SkScalar a : { 0.3f, 0.6f, 1.0f } ) {
       paint.setAlpha((int) (a * 255));
       canvas->drawCircle(center.fX, center.fY, radius, paint);
       canvas->translate(70, 70);
   }
}
##

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

#Example
void draw(SkCanvas* canvas) {
   SkPaint paint;
   SkBitmap bitmap;
   bitmap.setInfo(SkImageInfo::MakeA8(5, 1), 5);  // bitmap only contains alpha
   uint8_t pixels[5] = { 0x22, 0x55, 0x88, 0xBB, 0xFF };
   bitmap.setPixels(pixels);
   paint.setShader(SkShader::MakeBitmapShader(bitmap,
            SkShader::kMirror_TileMode, SkShader::kMirror_TileMode));
   for (SkColor c : { SK_ColorRED, SK_ColorBLUE, SK_ColorGREEN } ) {
       paint.setColor(c);  // all components in color affect shader
       canvas->drawCircle(50, 50, 50, paint);
       canvas->translate(70, 70);
   }
}
##

#Method SkShader* getShader() const

#In Shader_Methods
#Line # returns Shader, multiple drawing colors; gradients ##
#Populate

#Example
        void draw(SkCanvas* canvas) {
           SkPaint paint;
           SkDebugf("nullptr %c= shader\n", paint.getShader() ? '!' : '=');
           paint.setShader(SkShader::MakeEmptyShader());
           SkDebugf("nullptr %c= shader\n", paint.getShader() ? '!' : '=');
        }

        #StdOut
            nullptr == shader
            nullptr != shader
        ##
    ##

##

#Method sk_sp<SkShader> refShader() const

#In Shader_Methods
#Line # references Shader, multiple drawing colors; gradients ##
#Populate

#Example
        void draw(SkCanvas* canvas) {
           SkPaint paint1, paint2;
           paint1.setShader(SkShader::MakeEmptyShader());
           SkDebugf("shader unique: %s\n", paint1.getShader()->unique() ? "true" : "false");
           paint2.setShader(paint1.refShader());
           SkDebugf("shader unique: %s\n", paint1.getShader()->unique() ? "true" : "false");
        }

        #StdOut
            shader unique: true
            shader unique: false
        ##
    ##

##

#Method void setShader(sk_sp<SkShader> shader)

#In Shader_Methods
#Line # sets Shader, multiple drawing colors; gradients ##
#Populate

#Example
    #Height 64
        void draw(SkCanvas* canvas) {
            SkPaint paint;
            paint.setColor(SK_ColorBLUE);
            paint.setShader(SkShader::MakeColorShader(SK_ColorRED));
            canvas->drawRect(SkRect::MakeWH(40, 40), paint);
            paint.setShader(nullptr);
            canvas->translate(50, 0);
            canvas->drawRect(SkRect::MakeWH(40, 40), paint);
        }
    ##

##

#Subtopic Shader_Methods ##
# ------------------------------------------------------------------------------
#Subtopic Color_Filter_Methods
#Line # get and set Color_Filter ##

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
#Height 128
void draw(SkCanvas* canvas) {
    SkPaint paint;
    paint.setColorFilter(SkColorMatrixFilter::MakeLightingFilter(0xFFFFFF, 0xFF0000));
    for (SkColor c : { SK_ColorBLACK, SK_ColorGREEN } ) {
        paint.setColor(c);
        canvas->drawRect(SkRect::MakeXYWH(10, 10, 50, 50), paint);
        paint.setAlpha(0x80);
        canvas->drawRect(SkRect::MakeXYWH(60, 60, 50, 50), paint);
        canvas->translate(100, 0);
    }
}
##

#Method SkColorFilter* getColorFilter() const

#In Color_Filter_Methods
#Line # returns Color_Filter, how colors are altered ##
#Populate

#Example
        void draw(SkCanvas* canvas) {
           SkPaint paint;
           SkDebugf("nullptr %c= color filter\n", paint.getColorFilter() ? '!' : '=');
           paint.setColorFilter(SkColorFilter::MakeModeFilter(SK_ColorLTGRAY, SkBlendMode::kSrcIn));
           SkDebugf("nullptr %c= color filter\n", paint.getColorFilter() ? '!' : '=');
        }

        #StdOut
            nullptr == color filter
            nullptr != color filter
        ##
    ##
##

#Method sk_sp<SkColorFilter> refColorFilter() const

#In Color_Filter_Methods
#Line # references Color_Filter, how colors are altered ##
#Populate

#Example
    void draw(SkCanvas* canvas) {
        SkPaint paint1, paint2;
        paint1.setColorFilter(SkColorFilter::MakeModeFilter(0xFFFF0000, SkBlendMode::kSrcATop));
        SkDebugf("color filter unique: %s\n", paint1.getColorFilter()->unique() ? "true" : "false");
        paint2.setColorFilter(paint1.refColorFilter());
        SkDebugf("color filter unique: %s\n", paint1.getColorFilter()->unique() ? "true" : "false");
    }

        #StdOut
            color filter unique: true
            color filter unique: false
        ##
    ##
##

#Method void setColorFilter(sk_sp<SkColorFilter> colorFilter)

#In Color_Filter_Methods
#Line # sets Color_Filter, alters color ##
#Populate

#Example
    #Height 64
        void draw(SkCanvas* canvas) {
           SkPaint paint;
           paint.setColorFilter(SkColorFilter::MakeModeFilter(SK_ColorLTGRAY, SkBlendMode::kSrcIn));
           canvas->drawRect(SkRect::MakeWH(50, 50), paint);
           paint.setColorFilter(nullptr);
           canvas->translate(70, 0);
           canvas->drawRect(SkRect::MakeWH(50, 50), paint);
        }
    ##

##

#Subtopic Color_Filter_Methods ##
# ------------------------------------------------------------------------------
#Subtopic Blend_Mode_Methods
#Line # get and set Blend_Mode ##

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

#Example
void draw(SkCanvas* canvas) {
    SkPaint normal, blender;
    normal.setColor(0xFF58a889);
    blender.setColor(0xFF8958a8);
    canvas->clear(0);
    for (SkBlendMode m : { SkBlendMode::kSrcOver, SkBlendMode::kSrcIn, SkBlendMode::kSrcOut } ) {
        normal.setBlendMode(SkBlendMode::kSrcOver);
        canvas->drawOval(SkRect::MakeXYWH(30, 30, 30, 80), normal);
        blender.setBlendMode(m);
        canvas->drawOval(SkRect::MakeXYWH(10, 50, 80, 30), blender);
        canvas->translate(70, 70);
    }
}
##

#SeeAlso Blend_Mode

#Method SkBlendMode getBlendMode() const

#In Blend_Mode_Methods
#Line # returns Blend_Mode, how colors combine with Device ##
#Populate

#Example
        void draw(SkCanvas* canvas) {
           SkPaint paint;
           SkDebugf("kSrcOver %c= getBlendMode\n",
                    SkBlendMode::kSrcOver == paint.getBlendMode() ? '=' : '!');
           paint.setBlendMode(SkBlendMode::kSrc);
           SkDebugf("kSrcOver %c= getBlendMode\n",
                    SkBlendMode::kSrcOver == paint.getBlendMode() ? '=' : '!');
        }

        #StdOut
            kSrcOver == getBlendMode
            kSrcOver != getBlendMode
        ##
    ##

##

#Method bool isSrcOver() const

#In Blend_Mode_Methods
#Line # returns true if Blend_Mode is SkBlendMode::kSrcOver ##
#Populate

#Example
        void draw(SkCanvas* canvas) {
           SkPaint paint;
           SkDebugf("isSrcOver %c= true\n", paint.isSrcOver() ? '=' : '!');
           paint.setBlendMode(SkBlendMode::kSrc);
           SkDebugf("isSrcOver %c= true\n", paint.isSrcOver() ? '=' : '!');
        }

        #StdOut
            isSrcOver == true
            isSrcOver != true
        ##
    ##

##

#Method void setBlendMode(SkBlendMode mode)

#In Blend_Mode_Methods
#Line # sets Blend_Mode, how colors combine with destination ##
#Populate

#Example
        void draw(SkCanvas* canvas) {
           SkPaint paint;
           SkDebugf("isSrcOver %c= true\n", paint.isSrcOver() ? '=' : '!');
           paint.setBlendMode(SkBlendMode::kSrc);
           SkDebugf("isSrcOver %c= true\n", paint.isSrcOver() ? '=' : '!');
        }

        #StdOut
            isSrcOver == true
            isSrcOver != true
        ##
    ##

##

#Subtopic Blend_Mode_Methods ##
# ------------------------------------------------------------------------------
#Subtopic Path_Effect_Methods
#Line # get and set Path_Effect ##

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
#Height 160
        void draw(SkCanvas* canvas) {
            SkPaint paint;
            paint.setStyle(SkPaint::kStroke_Style);
            paint.setStrokeWidth(16);
            SkScalar intervals[] = {30, 10};
            paint.setPathEffect(SkDashPathEffect::Make(intervals, SK_ARRAY_COUNT(intervals), 1));
            canvas->drawRoundRect({20, 20, 120, 120}, 20, 20, paint);
        }
##

#SeeAlso Path_Effect

#Method SkPathEffect* getPathEffect() const

#In Path_Effect_Methods
#Line # returns Path_Effect, modifications to path geometry; dashing ##
#Populate

#Example
        void draw(SkCanvas* canvas) {
           SkPaint paint;
           SkDebugf("nullptr %c= path effect\n", paint.getPathEffect() ? '!' : '=');
           paint.setPathEffect(SkCornerPathEffect::Make(10));
           SkDebugf("nullptr %c= path effect\n", paint.getPathEffect() ? '!' : '=');
        }

        #StdOut
            nullptr == path effect
            nullptr != path effect
        ##
    ##

##


#Method sk_sp<SkPathEffect> refPathEffect() const

#In Path_Effect_Methods
#Line # references Path_Effect, modifications to path geometry; dashing ##
#Populate

#Example
    void draw(SkCanvas* canvas) {
        SkPaint paint1, paint2;
        SkScalar intervals[] = {1, 2};
        paint1.setPathEffect(SkDashPathEffect::Make(intervals, SK_ARRAY_COUNT(intervals), 10));
        SkDebugf("path effect unique: %s\n", paint1.getPathEffect()->unique() ? "true" : "false");
        paint2.setPathEffect(paint1.refPathEffect());
        SkDebugf("path effect unique: %s\n", paint1.getPathEffect()->unique() ? "true" : "false");
    }

        #StdOut
            path effect unique: true
            path effect unique: false
        ##
    ##

##


#Method void setPathEffect(sk_sp<SkPathEffect> pathEffect)

#In Path_Effect_Methods
#Line # sets Path_Effect, modifications to path geometry; dashing ##
#Populate

#Example
        void draw(SkCanvas* canvas) {
            SkPaint paint;
            paint.setPathEffect(SkDiscretePathEffect::Make(3, 5));
            canvas->drawRect(SkRect::MakeXYWH(40, 40, 175, 175), paint);
        }
    ##

##

#Subtopic Path_Effect_Methods ##
# ------------------------------------------------------------------------------
#Subtopic Mask_Filter_Methods
#Line # get and set Mask_Filter ##

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
    void draw(SkCanvas* canvas) {
        SkPaint paint;
        paint.setMaskFilter(SkMaskFilter::MakeBlur(kSolid_SkBlurStyle, 3));
        canvas->drawRect(SkRect::MakeXYWH(40, 40, 175, 175), paint);
    }
##

#Method SkMaskFilter* getMaskFilter() const

#In Mask_Filter_Methods
#Line # returns Mask_Filter, alterations to Mask_Alpha ##
#Populate

#Example
        void draw(SkCanvas* canvas) {
           SkPaint paint;
           SkDebugf("nullptr %c= mask filter\n", paint.getMaskFilter() ? '!' : '=');
           paint.setMaskFilter(SkMaskFilter::MakeBlur(kOuter_SkBlurStyle, 3));
           SkDebugf("nullptr %c= mask filter\n", paint.getMaskFilter() ? '!' : '=');
        }

        #StdOut
            nullptr == mask filter
            nullptr != mask filter
        ##
    ##

##

#Method sk_sp<SkMaskFilter> refMaskFilter() const

#In Mask_Filter_Methods
#Line # references Mask_Filter, alterations to Mask_Alpha ##
#Populate

#Example
    void draw(SkCanvas* canvas) {
        SkPaint paint1, paint2;
        paint1.setMaskFilter(SkMaskFilter::MakeBlur(kNormal_SkBlurStyle, 1));
        SkDebugf("mask filter unique: %s\n", paint1.getMaskFilter()->unique() ? "true" : "false");
        paint2.setMaskFilter(paint1.refMaskFilter());
        SkDebugf("mask filter unique: %s\n", paint1.getMaskFilter()->unique() ? "true" : "false");
    }

        #StdOut
            mask filter unique: true
            mask filter unique: false
        ##
    ##

##

#Method void setMaskFilter(sk_sp<SkMaskFilter> maskFilter)

#In Mask_Filter_Methods
#Line # sets Mask_Filter, alterations to Mask_Alpha ##
#Populate

#Example
        void draw(SkCanvas* canvas) {
            SkPaint paint;
            paint.setStyle(SkPaint::kStroke_Style);
            paint.setStrokeWidth(10);
            paint.setMaskFilter(SkMaskFilter::MakeBlur(kNormal_SkBlurStyle, 10));
            canvas->drawRect(SkRect::MakeXYWH(40, 40, 175, 175), paint);
        }
    ##

##

#Subtopic Mask_Filter_Methods ##
# ------------------------------------------------------------------------------
#Subtopic Typeface_Methods
#Line # get and set Typeface ##

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
#Height 100
    void draw(SkCanvas* canvas) {
        SkPaint paint;
        paint.setTypeface(SkTypeface::MakeFromName(nullptr, SkFontStyle()));
        SkFont font(nullptr, 36);
        canvas->drawString("A Big Hello!", 10, 40, font, paint);
        paint.setTypeface(nullptr);
        paint.setFakeBoldText(true);
        canvas->drawString("A Big Hello!", 10, 80, font, paint);
    }
##

#Subtopic Typeface_Methods ##
# ------------------------------------------------------------------------------
#Subtopic Image_Filter_Methods
#Line # get and set Image_Filter ##

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
    #ToDo explain why the two draws are so different ##
    #Function
    ###$
    #include "SkBlurImageFilter.h"
    $$$#
    ##
    void draw(SkCanvas* canvas) {
        SkPaint paint;
        paint.setStyle(SkPaint::kStroke_Style);
        paint.setStrokeWidth(2);
        SkRegion region;
        region.op( 10, 10, 50, 50, SkRegion::kUnion_Op);
        region.op( 10, 50, 90, 90, SkRegion::kUnion_Op);
        paint.setImageFilter(SkBlurImageFilter::Make(5.0f, 5.0f, nullptr));
        canvas->drawRegion(region, paint);
        paint.setImageFilter(nullptr);
        paint.setMaskFilter(SkMaskFilter::MakeBlur(kNormal_SkBlurStyle, 5));
        canvas->translate(100, 100);
        canvas->drawRegion(region, paint);
    }
##

#Method SkImageFilter* getImageFilter() const

#In Image_Filter_Methods
#Line # returns Image_Filter, alter pixels; blur ##
#Populate

#Example
        #Function
        ###$
        #include "SkBlurImageFilter.h"
        $$$#
        ##
        void draw(SkCanvas* canvas) {
           SkPaint paint;
           SkDebugf("nullptr %c= image filter\n", paint.getImageFilter() ? '!' : '=');
           paint.setImageFilter(SkBlurImageFilter::Make(kOuter_SkBlurStyle, 3, nullptr, nullptr));
           SkDebugf("nullptr %c= image filter\n", paint.getImageFilter() ? '!' : '=');
        }

        #StdOut
            nullptr == image filter
            nullptr != image filter
        ##
    ##

##

#Method sk_sp<SkImageFilter> refImageFilter() const

#In Image_Filter_Methods
#Line # references Image_Filter, alter pixels; blur ##
#Populate

#Example
    void draw(SkCanvas* canvas) {
        SkPaint paint1, paint2;
        paint1.setImageFilter(SkOffsetImageFilter::Make(25, 25, nullptr));
        SkDebugf("image filter unique: %s\n", paint1.getImageFilter()->unique() ? "true" : "false");
        paint2.setImageFilter(paint1.refImageFilter());
        SkDebugf("image filter unique: %s\n", paint1.getImageFilter()->unique() ? "true" : "false");
    }

        #StdOut
            image filter unique: true
            image filter unique: false
        ##
    ##

##

#Method void setImageFilter(sk_sp<SkImageFilter> imageFilter)

#In Image_Filter_Methods
#Line # sets Image_Filter, alter pixels; blur ##
#Populate

#Example
    #Height 160
    void draw(SkCanvas* canvas) {
        SkBitmap bitmap;
        bitmap.allocN32Pixels(100, 100);
        SkCanvas offscreen(bitmap);
        SkPaint paint;
        paint.setAntiAlias(true);
        paint.setColor(SK_ColorWHITE);
        SkFont font(nullptr, 96);
        offscreen.clear(0);
        offscreen.drawString("e", 20, 70, font, paint);
        paint.setImageFilter(
               SkLightingImageFilter::MakePointLitDiffuse(SkPoint3::Make(80, 100, 10),
               SK_ColorWHITE, 1, 2, nullptr, nullptr));
        canvas->drawBitmap(bitmap, 0, 0, &paint);
    }
    ##

##

#Subtopic Image_Filter_Methods ##
# ------------------------------------------------------------------------------
#Subtopic Draw_Looper_Methods
#Line # get and set Draw_Looper ##

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
#Height 128
    void draw(SkCanvas* canvas) {
        SkLayerDrawLooper::LayerInfo info;
        info.fPaintBits = (SkLayerDrawLooper::BitFlags) SkLayerDrawLooper::kColorFilter_Bit;
        info.fColorMode = SkBlendMode::kSrc;
        SkLayerDrawLooper::Builder looperBuilder;
        SkPaint* loopPaint = looperBuilder.addLayer(info);
        loopPaint->setColor(SK_ColorRED);
        info.fOffset.set(20, 20);
        loopPaint = looperBuilder.addLayer(info);
        loopPaint->setColor(SK_ColorBLUE);
        SkPaint paint;
        paint.setDrawLooper(looperBuilder.detach());
        canvas->drawCircle(50, 50, 50, paint);
    }

##

#Method SkDrawLooper* getDrawLooper() const

#In Draw_Looper_Methods
#Line # returns Draw_Looper, multiple layers ##
#Populate

#Example
        void draw(SkCanvas* canvas) {
           SkPaint paint;
           SkDebugf("nullptr %c= draw looper\n", paint.getDrawLooper() ? '!' : '=');
           SkLayerDrawLooper::Builder looperBuilder;
           paint.setDrawLooper(looperBuilder.detach());
           SkDebugf("nullptr %c= draw looper\n", paint.getDrawLooper() ? '!' : '=');
        }

        #StdOut
            nullptr == draw looper
            nullptr != draw looper
        ##
    ##

##

#Method sk_sp<SkDrawLooper> refDrawLooper() const

#In Draw_Looper_Methods
#Line # references Draw_Looper, multiple layers ##
#Populate

#Example
    void draw(SkCanvas* canvas) {
        SkPaint paint1, paint2;
        SkLayerDrawLooper::Builder looperBuilder;
        paint1.setDrawLooper(looperBuilder.detach());
        SkDebugf("draw looper unique: %s\n", paint1.getDrawLooper()->unique() ? "true" : "false");
        paint2.setDrawLooper(paint1.refDrawLooper());
        SkDebugf("draw looper unique: %s\n", paint1.getDrawLooper()->unique() ? "true" : "false");
    }

        #StdOut
            draw looper unique: true
            draw looper unique: false
        ##
    ##

##

#Method void setDrawLooper(sk_sp<SkDrawLooper> drawLooper)
#In Draw_Looper_Methods
#Line # sets Draw_Looper, multiple layers ##
#Populate

#Example
    #Height 128
        void draw(SkCanvas* canvas) {
            SkPaint paint;
            paint.setDrawLooper(SkBlurDrawLooper::Make(0x7FFF0000, 4, -5, -10));
            paint.setStyle(SkPaint::kStroke_Style);
            paint.setStrokeWidth(10);
            paint.setAntiAlias(true);
            paint.setColor(0x7f0000ff);
            canvas->drawCircle(70, 70, 50, paint);
        }
    ##

##

#Subtopic Draw_Looper_Methods ##

#Subtopic Text_Size
#Line # overall height in points ##

Text_Size adjusts the overall text size in points.
Text_Size can be set to any positive value or zero.
Text_Size defaults to 12.
Set SkPaintDefaults_TextSize at compile time to change the default setting.

#Example
#Height 135
    void draw(SkCanvas* canvas) {
        SkPaint paint;
        SkFont font;
        canvas->drawString("12 point", 10, 20, font, paint);
        font.setSize(24);
        canvas->drawString("24 point", 10, 60, font, paint);
        font.setSize(48);
        canvas->drawString("48 point", 10, 120, paint);
    }
##

#Subtopic Text_Size ##
# ------------------------------------------------------------------------------
#Subtopic Text_Scale_X
#Line # text horizontal scale ##

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
#Height 128
    void draw(SkCanvas* canvas) {
        SkPaint paint;
        SkFont font(nullptr, 24);
        font.setScaleX(.8f);
        canvas->drawString("narrow", 10, 20, font, paint);
        font.setScaleX(1);
        canvas->drawString("normal", 10, 60, font, paint);
        font.setScaleX(1.2f);
        canvas->drawString("wide", 10, 100, font, paint);
    }
##

#Subtopic Text_Scale_X ##

#Subtopic Text_Skew_X
#Line # text horizontal slant ##


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
#Height 128
    void draw(SkCanvas* canvas) {
        SkPaint paint;
        SkFont font(nullptr, 24);
        font.setSkewX(-.25f);
        canvas->drawString("right-leaning", 10, 100, font, paint);
        font.setSkewX(0);
        canvas->drawString("normal", 10, 60, font, paint);
        font.setSkewX(.25f);
        canvas->drawString("left-leaning", 10, 20, font, paint);
    }
##

#Subtopic Text_Skew_X ##

# ------------------------------------------------------------------------------
#Subtopic Text_Encoding
#Line # text encoded as characters or Glyphs ##

#Example
#Height 128
#Description
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.
##
void draw(SkCanvas* canvas) {
    SkPaint paint;
    const char hello8[] = "Hello" "\xE2" "\x98" "\xBA";
    const uint16_t hello16[] = { 'H', 'e', 'l', 'l', 'o', 0x263A };
    const uint32_t hello32[] = { 'H', 'e', 'l', 'l', 'o', 0x263A };
    SkFont font(nullptr, 24);
    canvas->drawSimpleText(hello8, sizeof(hello8) - 1, SkTextEncoding::kUTF8, 10, 30, font, paint);
    canvas->drawSimpleText(hello16, sizeof(hello16), SkTextEncoding::kUTF16, 10, 60, font, paint);
    canvas->drawSimpleText(hello32, sizeof(hello32), SkTextEncoding::kUTF32, 10, 90, font, paint);
    uint16_t glyphs[SK_ARRAY_COUNT(hello32)];
    font.textToGlyphs(hello32, sizeof(hello32), SkTextEncoding::kUTF32,
            glyphs, SK_ARRAY_COUNT(hello32));
    canvas->drawSimpleText(glyphs, sizeof(glyphs), kGlyphID_SkTextEncoding, 10, 120, font, paint);
}
##

#Subtopic Text_Encoding ##

# ------------------------------------------------------------------------------

#Method bool nothingToDraw() const
#In Utility
#Line # returns true if Paint prevents all drawing ##
#Populate

#Example
        void draw(SkCanvas* canvas) {
            auto debugster = [](const char* prefix, const SkPaint& p) -> void {
                SkDebugf("%s nothing to draw: %s\n", prefix,
                         p.nothingToDraw() ? "true" : "false");
            };
            SkPaint paint;
            debugster("initial", paint);
            paint.setBlendMode(SkBlendMode::kDst);
            debugster("blend dst", paint);
            paint.setBlendMode(SkBlendMode::kSrcOver);
            debugster("blend src over", paint);
            paint.setAlpha(0);
            debugster("alpha 0", paint);
        }

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

##

# ------------------------------------------------------------------------------
#Subtopic Utility
#Line # rarely called management functions ##
##

# ------------------------------------------------------------------------------

#Class SkPaint ##

#Topic Paint ##