skia2/docs/SkTextBlob_Reference.bmh

#Topic Text_Blob
#Alias Text_Blob_Reference ##

#PhraseDef paint_font_metrics
Typeface, Paint_Text_Size, Paint_Text_Scale_X,
Paint_Text_Skew_X, Paint_Text_Align, Paint_Hinting, Anti_Alias, Paint_Fake_Bold,
Font_Embedded_Bitmaps, Full_Hinting_Spacing, LCD_Text, Linear_Text,
and Subpixel_Text
##

Text_Blob holds one or more runs of text. Each run associates a string of Glyphs
with a position and Paint. Each Paint contains attributes used
to define the run text: #paint_font_metrics#.

Text_Blob runs of text use Glyph_ID encoding; each run Paint must set
Paint_Text_Encoding to SkPaint::kGlyphID_TextEncoding.

Text_Blob is constructed with SkTextBlob::MakeFromText or Text_Blob_Builder.
Once created, Text_Blob can not be modified.

#Subtopic Overview
#Populate
##

#Subtopic Constructor
#Populate
##

#Subtopic Member_Function
#Populate
##

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

#Class SkTextBlob

SkTextBlob combines multiple text runs into an immutable container. Each text
run consists of Glyphs, Paint, and position. Only parts of Paint related to
fonts and text rendering are used by run.

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

#Method const SkRect& bounds() const
#In Property
#Line # returns conservative bounding box ##

Returns conservative bounding box. Uses Paint associated with each glyph to
determine glyph bounds, and unions all bounds. Returned bounds may be
larger than the bounds of all Glyphs in runs. 

#Return conservative bounding box ##

#Example
#Height 70
    SkTextBlobBuilder textBlobBuilder;
    const char bunny[] = "/(^x^)\\";
    const int len = sizeof(bunny) - 1;
    uint16_t glyphs[len];
    SkPaint paint;
    paint.textToGlyphs(bunny, len, glyphs);
    paint.setTextEncoding(SkPaint::kGlyphID_TextEncoding);
    int runs[] = { 3, 1, 3 };
    SkPoint textPos = { 20, 50 };
    int glyphIndex = 0;
    for (auto runLen : runs) {
        paint.setTextSize(1 == runLen ? 20 : 50);
        const SkTextBlobBuilder::RunBuffer& run =
                textBlobBuilder.allocRun(paint, runLen, textPos.fX, textPos.fY);
        memcpy(run.glyphs, &glyphs[glyphIndex], sizeof(glyphs[0]) * runLen);
        textPos.fX += paint.measureText(&glyphs[glyphIndex], sizeof(glyphs[0]) * runLen, nullptr);
        glyphIndex += runLen;
    }
    sk_sp<const SkTextBlob> blob = textBlobBuilder.make();
    paint.reset();
    canvas->drawTextBlob(blob.get(), 0, 0, paint);
    paint.setStyle(SkPaint::kStroke_Style);
    canvas->drawRect(blob->bounds(), paint);
##

#SeeAlso SkPath::getBounds

#Method ##

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

#Method uint32_t uniqueID() const
#In Property
#Line # returns identifier for Text_Blob ##

Returns a non-zero value unique among all text blobs.

#Return identifier for Text_Blob ##

#Example
for (int index = 0; index < 2; ++index) {
    SkTextBlobBuilder textBlobBuilder;
    const char bunny[] = "/(^x^)\\";
    const int len = sizeof(bunny) - 1;
    uint16_t glyphs[len];
    SkPaint paint;
    paint.textToGlyphs(bunny, len, glyphs);
    paint.setTextEncoding(SkPaint::kGlyphID_TextEncoding);
    paint.setTextScaleX(0.5);
    int runs[] = { 3, 1, 3 };
    SkPoint textPos = { 20, 50 };
    int glyphIndex = 0;
    for (auto runLen : runs) {
        paint.setTextSize(1 == runLen ? 20 : 50);
        const SkTextBlobBuilder::RunBuffer& run =
                textBlobBuilder.allocRun(paint, runLen, textPos.fX, textPos.fY);
        memcpy(run.glyphs, &glyphs[glyphIndex], sizeof(glyphs[0]) * runLen);
        textPos.fX += paint.measureText(&glyphs[glyphIndex], sizeof(glyphs[0]) * runLen, nullptr);
        glyphIndex += runLen;
    }
    sk_sp<const SkTextBlob> blob = textBlobBuilder.make();
    paint.reset();
    canvas->drawTextBlob(blob.get(), 0, 0, paint);
    std::string id = "unique ID:" + std::to_string(blob->uniqueID());
    canvas->drawString(id.c_str(), 30, blob->bounds().fBottom + 15, paint);
    canvas->translate(blob->bounds().fRight + 10, 0);
}
##

#SeeAlso SkRefCnt

#Method ##

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

#Method static sk_sp<SkTextBlob> MakeFromText(
            const void* text, size_t byteLength, const SkPaint& paint)
#In Constructor
#Line # constructs Text_Blob with one run ##

Creates Text_Blob with a single run. text meaning depends on Paint_Text_Encoding;
by default, text is encoded as UTF-8.

paint contains attributes used to define the run text: #paint_font_metrics#.

#Param text character code points or Glyphs drawn ##
#Param  byteLength   byte length of text array ##
#Param  paint    text size, typeface, text scale, and so on, used to draw ##

#Return Text_Blob constructed from one run ##

#Example
#Height 24
    SkPaint blobPaint;
    blobPaint.setColor(SK_ColorRED); // ignored
    blobPaint.setTextSize(24);  // respected
    blobPaint.setAntiAlias(true); // ignored
    SkPaint canvasPaint = blobPaint;
    canvasPaint.setColor(SK_ColorBLUE); // respected
    canvasPaint.setTextSize(2); // ignored
    sk_sp<SkTextBlob> blob = SkTextBlob::MakeFromText("Hello World", 11, blobPaint);
    canvas->drawTextBlob(blob, 20, 20, canvasPaint);
##

#SeeAlso MakeFromString TextBlobBuilder

##

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

#Method static sk_sp<SkTextBlob> MakeFromString(const char* string, const SkPaint& paint)
#In Constructor
#Line # constructs Text_Blob with one run ##

Creates Text_Blob with a single run. string meaning depends on Paint_Text_Encoding;
by default, string is encoded as UTF-8.

paint contains Paint_Font_Metrics used to define the run text: #paint_font_metrics#.

#Param string character code points or Glyphs drawn ##
#Param  paint    text size, typeface, text scale, and so on, used to draw ##

#Return Text_Blob constructed from one run ##

#Example
#Height 24
    SkPaint blobPaint;
    blobPaint.setColor(SK_ColorRED); // ignored
    blobPaint.setTextSize(24);  // respected
    blobPaint.setAntiAlias(true); // ignored
    SkPaint canvasPaint = blobPaint;
    canvasPaint.setColor(SK_ColorBLUE); // respected
    canvasPaint.setTextSize(2); // ignored
    sk_sp<SkTextBlob> blob = SkTextBlob::MakeFromString("Hello World", blobPaint);
    canvas->drawTextBlob(blob, 20, 20, canvasPaint);
##

#SeeAlso MakeFromText TextBlobBuilder

##

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

#Method size_t serialize(const SkSerialProcs& procs, void* memory, size_t memory_size) const
#In Utility
#Line # writes Text_Blob to memory ##

Writes data to allow later reconstruction of Text_Blob. memory points to storage
to receive the encoded data, and memory_size describes the size of storage. 
Returns bytes used if provided storage is large enough to hold all data;
otherwise, returns zero.

procs.fTypefaceProc permits supplying a custom function to encode Typeface.
If procs.fTypefaceProc is nullptr, default encoding is used. procs.fTypefaceCtx
may be used to provide user context to procs.fTypefaceProc; procs.fTypefaceProc
is called with a pointer to Typeface and user context.

#Param procs  custom serial data encoders; may be nullptr ##
#Param memory  storage for data ##
#Param size  size of storage ##

#Return bytes written, or zero if required storage is larger than memory_size ##

#Example
#Height 64
###$
$Function
#include "SkSerialProcs.h"
$$
$$$#
    SkPaint blobPaint;
    blobPaint.setTextSize(24);
    sk_sp<SkTextBlob> blob = SkTextBlob::MakeAsDrawText("Hello World", 11, blobPaint);
    char storage[2048];
    size_t used = blob->serialize(SkSerialProcs(), storage, sizeof(storage));
    sk_sp<SkTextBlob> copy = SkTextBlob::Deserialize(storage, used, SkDeserialProcs());
    canvas->drawTextBlob(copy, 20, 20, SkPaint());
    std::string usage = "size=" + std::to_string(sizeof(storage)) + " used=" + std::to_string(used);
    canvas->drawString(usage.c_str(), 20, 40, SkPaint());
##

#SeeAlso Deserialize SkSerialProcs

#Method ##

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

#Method sk_sp<SkData> serialize(const SkSerialProcs& procs) const
#In Utility
#Line # writes Text_Blob to Data ##
Returns storage containing Data describing Text_Blob, using optional custom
encoders.

procs.fTypefaceProc permits supplying a custom function to encode Typeface.
If procs.fTypefaceProc is nullptr, default encoding is used. procs.fTypefaceCtx
may be used to provide user context to procs.fTypefaceProc; procs.fTypefaceProc
is called with a pointer to Typeface and user context.

#Param procs  custom serial data encoders; may be nullptr ##

#Return storage containing serialized Text_Blob ##

#Example
#Height 24
###$
$Function
#include "SkSerialProcs.h"
$$
$$$#
    SkPaint blobPaint;
    blobPaint.setTextSize(24);
    sk_sp<SkTextBlob> blob = SkTextBlob::MakeAsDrawText("Hello World", 11, blobPaint);
    sk_sp<SkData> data = blob->serialize(SkSerialProcs());
    sk_sp<SkTextBlob> copy = SkTextBlob::Deserialize(data->data(), data->size(), SkDeserialProcs());
    canvas->drawTextBlob(copy, 20, 20, SkPaint());
##

#SeeAlso Deserialize SkData SkSerialProcs

#Method ##

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

#Method static sk_sp<SkTextBlob> Deserialize(const void* data, size_t size, const SkDeserialProcs& procs)
#In Constructor
#Line # constructs Text_Blob from memory ##

Recreates Text_Blob that was serialized into data. Returns constructed Text_Blob
if successful; otherwise, returns nullptr. Fails if size is smaller than
required data length, or if data does not permit constructing valid Text_Blob.

procs.fTypefaceProc permits supplying a custom function to decode Typeface.
If procs.fTypefaceProc is nullptr, default decoding is used. procs.fTypefaceCtx
may be used to provide user context to procs.fTypefaceProc; procs.fTypefaceProc
is called with a pointer to Typeface data, data byte length, and user context.

#Param data  pointer for serial data ##
#Param size  size of data ##
#Param procs  custom serial data decoders; may be nullptr ##

#Return Text_Blob constructed from data in memory ##

#Example
#Height 24
#Description
Text "Hacker" replaces "World!", but does not update its metrics.
When drawn, "Hacker" uses the spacing computed for "World!".
##
###$
$Function
#include "SkSerialProcs.h"
$$
$$$#
    SkPaint blobPaint;
    blobPaint.setTextSize(24);
    sk_sp<SkTextBlob> blob = SkTextBlob::MakeAsDrawText("Hello World!", 12, blobPaint);
    sk_sp<SkData> data = blob->serialize(SkSerialProcs());
    uint16_t glyphs[6];
    blobPaint.textToGlyphs("Hacker", 6, glyphs);
    memcpy((char*)data->writable_data() + 0x54, glyphs, sizeof(glyphs));
    sk_sp<SkTextBlob> copy = SkTextBlob::Deserialize(data->data(), data->size(), SkDeserialProcs());
    canvas->drawTextBlob(copy, 20, 20, SkPaint());
##

#SeeAlso serialize SkDeserialProcs

#Method ##

#Class SkTextBlob ##

#Topic Text_Blob ##