docs/SkTextBlobBuilder_Reference.bmh

#Topic Text_Blob_Builder
#Alias Text_Blob_Builder_Reference ##

#Class SkTextBlobBuilder

#Code
#Populate
##

Helper class for constructing SkTextBlob.

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

#Struct RunBuffer
#Line # storage for Glyphs and Glyph positions ##

#Code
    struct RunBuffer {
        SkGlyphID* glyphs;
        SkScalar* pos;
        char* utf8text;
        uint32_t* clusters;
    };
##

RunBuffer supplies storage for Glyphs and positions within a run.

A run is a sequence of Glyphs sharing Paint_Font_Metrics and positioning.
Each run may position its Glyphs in one of three ways:
by specifying where the first Glyph is drawn, and allowing Paint_Font_Metrics to
determine the advance to subsequent Glyphs; by specifying a baseline, and
the position on that baseline for each Glyph in run; or by providing Point
array, one per Glyph.

#Member SkGlyphID* glyphs
#Line # storage for Glyphs in run ##
    glyphs points to memory for one or more Glyphs. glyphs memory must be
    written to by the caller.
##

#Member SkScalar* pos
#Line # storage for positions in run ##
    pos points to memory for Glyph positions. Depending on how RunBuffer
    is allocated, pos may point to zero bytes per Glyph, one Scalar per Glyph,
    or one Point per Glyph.
##

#Member char* utf8text
#Line # reserved for future use ##
    Reserved for future use. utf8text should not be read or written.
##

#Member uint32_t* clusters
#Line # reserved for future use ##
    Reserved for future use. clusters should not be read or written.
##

#SeeAlso allocRun allocRunPos allocRunPosH

#Struct RunBuffer ##

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

#Method SkTextBlobBuilder()
#In Constructors
#Line # constructs with default values ##

Constructs empty Text_Blob_Builder. By default, Text_Blob_Builder has no runs.

#Return empty Text_Blob_Builder ##

#Example
    SkTextBlobBuilder builder;
    sk_sp<SkTextBlob> blob = builder.make();
    SkDebugf("blob " "%s" " nullptr", blob == nullptr ? "equals" : "does not equal");
#StdOut
blob equals nullptr
##
##

#SeeAlso make SkTextBlob::MakeFromText

#Method ##

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

#Method ~SkTextBlobBuilder()
#In Constructors
#Line # deletes storage ##
Deletes data allocated internally by Text_Blob_Builder.

#NoExample
##

#SeeAlso SkTextBlobBuilder()

#Method ##

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

#Method sk_sp<SkTextBlob> make()
#In Constructors
#Line # constructs Text_Blob from bulider ##

Returns Text_Blob built from runs of Glyphs added by builder. Returned
Text_Blob is immutable; it may be copied, but its contents may not be altered.
Returns nullptr if no runs of Glyphs were added by builder.

Resets Text_Blob_Builder to its initial empty state, allowing it to be
reused to build a new set of runs.

#Return Text_Blob or nullptr ##

#Example
    SkTextBlobBuilder builder;
    sk_sp<SkTextBlob> blob = builder.make();
    SkDebugf("blob " "%s" " nullptr\n", blob == nullptr ? "equals" : "does not equal");
    SkPaint paint;
    paint.setTextEncoding(SkPaint::kGlyphID_TextEncoding);
    paint.textToGlyphs("x", 1, builder.allocRun(paint, 1, 20, 20).glyphs);
    blob = builder.make();
    SkDebugf("blob " "%s" " nullptr\n", blob == nullptr ? "equals" : "does not equal");
    blob = builder.make();
    SkDebugf("blob " "%s" " nullptr\n", blob == nullptr ? "equals" : "does not equal");
#StdOut
blob equals nullptr
blob does not equal nullptr
blob equals nullptr
##
##

#SeeAlso SkTextBlob::MakeFromText

#Method ##

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

#Method const RunBuffer& allocRun(const SkPaint& font, int count, SkScalar x, SkScalar y,
                              const SkRect* bounds = nullptr)
#In Allocator
#Line # returns writable glyph buffer at Point ##

Returns run with storage for Glyphs. Caller must write count Glyphs to
RunBuffer.glyphs before next call to FontBlobBuilder.

RunBuffer.utf8text, and RunBuffer.clusters should be ignored.

Glyphs share Paint_Font_Metrics in font, including: #paint_font_metrics#.

Glyphs are positioned on a baseline at (x, y), using font Paint_Font_Metrics to
determine their relative placement.

bounds defines an optional bounding box, used to suppress drawing when Text_Blob
bounds does not intersect Surface bounds. If bounds is nullptr, Text_Blob bounds
is computed from (x, y) and RunBuffer.glyphs Paint_Font_Metrics.

#Param font  Paint used for this run ##
#Param count  number of glyphs ##
#Param x  horizontal offset within the blob ##
#Param y  vertical offset within the blob ##
#Param bounds  optional run bounding box ##

#Return writable glyph buffer ##

#Example
#Height 60
    SkTextBlobBuilder builder;
    SkPaint paint, glyphPaint;
    glyphPaint.setTextEncoding(SkPaint::kGlyphID_TextEncoding);
    const SkTextBlobBuilder::RunBuffer& run = builder.allocRun(glyphPaint, 5, 20, 20);
    paint.textToGlyphs("hello", 5, run.glyphs);
    canvas->drawRect({20, 20, 30, 30}, paint);
    canvas->drawTextBlob(builder.make(), 20, 20, paint);    
##

#SeeAlso allocRunPosH allocRunPos

#Method ##

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

#Method const RunBuffer& allocRunPosH(const SkPaint& font, int count, SkScalar y,
                                  const SkRect* bounds = nullptr)
#In Allocator
#Line # returns writable glyph and x-axis position buffers ##

Returns run with storage for Glyphs and positions along baseline. Caller must
write count Glyphs to RunBuffer.glyphs, and count Scalars to RunBuffer.pos;
before next call to FontBlobBuilder.

RunBuffer.utf8text, and RunBuffer.clusters should be ignored.

Glyphs share Paint_Font_Metrics in font, including: #paint_font_metrics#.

Glyphs are positioned on a baseline at y, using x-axis positions written by
caller to RunBuffer.pos.

bounds defines an optional bounding box, used to suppress drawing when Text_Blob
bounds does not intersect Surface bounds. If bounds is nullptr, Text_Blob bounds
is computed from y, RunBuffer.pos, and RunBuffer.glyphs Paint_Font_Metrics.

#Param font  Paint used for this run ##
#Param count  number of Glyphs ##
#Param y  vertical offset within the blob ##
#Param bounds  optional run bounding box ##

#Return writable glyph buffer and x-axis position buffer ##

#Example
#Height 60
    SkTextBlobBuilder builder;
    SkPaint paint, glyphPaint;
    glyphPaint.setTextEncoding(SkPaint::kGlyphID_TextEncoding);
    const SkTextBlobBuilder::RunBuffer& run = builder.allocRunPosH(glyphPaint, 5, 20);
    paint.textToGlyphs("hello", 5, run.glyphs);
    SkScalar positions[] = {0, 10, 20, 40, 80};
    memcpy(run.pos, positions, sizeof(positions));
    canvas->drawTextBlob(builder.make(), 20, 20, paint);    
##

#SeeAlso allocRunPos allocRun

#Method ##

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

#Method const RunBuffer& allocRunPos(const SkPaint& font, int count,
                                 const SkRect* bounds = nullptr)
#In Allocator
#Line # returns writable glyph and Point buffers ##

Returns run with storage for Glyphs and Point positions. Caller must
write count Glyphs to RunBuffer.glyphs, and count Points to RunBuffer.pos;
before next call to FontBlobBuilder.

RunBuffer.utf8text, and RunBuffer.clusters should be ignored.

Glyphs share Paint_Font_Metrics in font, including: #paint_font_metrics#.

Glyphs are positioned using Points written by caller to RunBuffer.pos, using
two Scalar values for each Point.

bounds defines an optional bounding box, used to suppress drawing when Text_Blob
bounds does not intersect Surface bounds. If bounds is nullptr, Text_Blob bounds
is computed from RunBuffer.pos, and RunBuffer.glyphs Paint_Font_Metrics.

#Param font  Paint used for this run ##
#Param count  number of Glyphs ##
#Param bounds  optional run bounding box ##

#Return writable glyph buffer and Point buffer ##

#Example
#Height 90
    SkTextBlobBuilder builder;
    SkPaint paint, glyphPaint;
    glyphPaint.setTextEncoding(SkPaint::kGlyphID_TextEncoding);
    const SkTextBlobBuilder::RunBuffer& run = builder.allocRunPos(glyphPaint, 5);
    paint.textToGlyphs("hello", 5, run.glyphs);
    SkPoint positions[] = {{0, 0}, {10, 10}, {20, 20}, {40, 40}, {80, 80}};
    memcpy(run.pos, positions, sizeof(positions));
    canvas->drawTextBlob(builder.make(), 20, 20, paint);    
##

#SeeAlso allocRunPosH allocRun

#Method ##

#Class SkTextBlobBuilder ##

#Topic Text_Blob_Builder ##