impeller::TextFrame Class Reference

Represents a collection of shaped text runs. More...

#include <text_frame.h>

Public Member Functions
	TextFrame ()
	TextFrame (std::vector< TextRun > &runs, Rect bounds, bool has_color)
	~TextFrame ()
void	CollectUniqueFontGlyphPairs (FontGlyphMap &glyph_map, Scalar scale, Point offset, const GlyphProperties &properties) const
Rect	GetBounds () const
	The conservative bounding box for this text frame. More...
size_t	GetRunCount () const
	The number of runs in this text frame. More...
const std::vector< TextRun > &	GetRuns () const
	Returns a reference to all the text runs in this frame. More...
bool	HasColor () const
	Returns the paint color this text frame was recorded with. More...
GlyphAtlas::Type	GetAtlasType () const
	The type of atlas this run should be emplaced in. More...
TextFrame &	operator= (TextFrame &&other)=default
	TextFrame (const TextFrame &other)=default

Static Public Member Functions
static Point	ComputeSubpixelPosition (const TextRun::GlyphPosition &glyph_position, AxisAlignment alignment, Point offset, Scalar scale)
static Scalar	RoundScaledFontSize (Scalar scale, Scalar point_size)

Detailed Description

Represents a collection of shaped text runs.

        This object is typically the entrypoint in the Impeller type
        rendering subsystem.

Definition at line 19 of file text_frame.h.

Constructor & Destructor Documentation

TextFrame() [1/3]

impeller::TextFrame::TextFrame ( )

default

TextFrame() [2/3]

impeller::TextFrame::TextFrame	(	std::vector< TextRun > &	runs,
		Rect	bounds,
		bool	has_color
	)

Definition at line 13 of file text_frame.cc.

    : runs_(std::move(runs)), bounds_(bounds), has_color_(has_color) {}

~TextFrame()

impeller::TextFrame::~TextFrame ( )

default

TextFrame() [3/3]

impeller::TextFrame::TextFrame ( const TextFrame &  other )

default

Member Function Documentation

CollectUniqueFontGlyphPairs()

void impeller::TextFrame::CollectUniqueFontGlyphPairs	(	FontGlyphMap &	glyph_map,
		Scalar	scale,
		Point	offset,
		const GlyphProperties &	properties
	)		const

Definition at line 87 of file text_frame.cc.

                                             {
  std::optional<GlyphProperties> lookup =
      (properties.stroke || HasColor())
          ? std::optional<GlyphProperties>(properties)
          : std::nullopt;
  for (const TextRun& run : GetRuns()) {
    const Font& font = run.GetFont();
    auto rounded_scale =
        RoundScaledFontSize(scale, font.GetMetrics().point_size);
    auto& set = glyph_map[ScaledFont{font, rounded_scale}];
    for (const TextRun::GlyphPosition& glyph_position :
         run.GetGlyphPositions()) {
      Point subpixel = ComputeSubpixelPosition(
          glyph_position, font.GetAxisAlignment(), offset, scale);
      set.emplace(glyph_position.glyph, subpixel, lookup);
    }
  }
}

References ComputeSubpixelPosition(), impeller::Font::GetAxisAlignment(), impeller::Font::GetMetrics(), GetRuns(), HasColor(), offset, impeller::Font::Metrics::point_size, RoundScaledFontSize(), scale, and impeller::GlyphProperties::stroke.

Referenced by impeller::LazyGlyphAtlas::AddTextFrame(), and impeller::testing::CreateGlyphAtlas().

ComputeSubpixelPosition()

Point impeller::TextFrame::ComputeSubpixelPosition ( const TextRun::GlyphPosition &  glyph_position, AxisAlignment  alignment, Point  offset, Scalar  scale  )

static

Definition at line 68 of file text_frame.cc.

                  {
  Point pos = glyph_position.position + offset;
  switch (alignment) {
    case AxisAlignment::kNone:
      return Point(0, 0);
    case AxisAlignment::kX:
      return Point(ComputeFractionalPosition(pos.x * scale), 0);
    case AxisAlignment::kY:
      return Point(0, ComputeFractionalPosition(pos.y * scale));
    case AxisAlignment::kAll:
      return Point(ComputeFractionalPosition(pos.x * scale),
                   ComputeFractionalPosition(pos.y * scale));
  }
}

References impeller::ComputeFractionalPosition(), impeller::kAll, impeller::kNone, impeller::kX, impeller::kY, offset, impeller::TextRun::GlyphPosition::position, scale, impeller::TPoint< T >::x, and impeller::TPoint< T >::y.

Referenced by CollectUniqueFontGlyphPairs(), and impeller::TextContents::Render().

GetAtlasType()

GlyphAtlas::Type impeller::TextFrame::GetAtlasType

(

)

const

The type of atlas this run should be emplaced in.

Definition at line 30 of file text_frame.cc.

                                             {
  return has_color_ ? GlyphAtlas::Type::kColorBitmap
                    : GlyphAtlas::Type::kAlphaBitmap;
}

References impeller::GlyphAtlas::kAlphaBitmap, and impeller::GlyphAtlas::kColorBitmap.

Referenced by impeller::LazyGlyphAtlas::AddTextFrame().

GetBounds()

Rect impeller::TextFrame::GetBounds

(

)

const

The conservative bounding box for this text frame.

Returns

The bounds rectangle. If there are no glyphs in this text frame and empty Rectangle is returned instead.

Definition at line 18 of file text_frame.cc.

                                {
  return bounds_;
}

GetRunCount()

size_t impeller::TextFrame::GetRunCount

(

)

const

The number of runs in this text frame.

Returns

The run count.

Definition at line 22 of file text_frame.cc.

                                    {
  return runs_.size();
}

GetRuns()

const std::vector< TextRun > & impeller::TextFrame::GetRuns

(

)

const

Returns a reference to all the text runs in this frame.

Returns

The runs in this frame.

Definition at line 26 of file text_frame.cc.

                                                   {
  return runs_;
}

Referenced by CollectUniqueFontGlyphPairs().

HasColor()

bool impeller::TextFrame::HasColor

(

)

const

Returns the paint color this text frame was recorded with.

        Non-bitmap/COLR fonts always use a black text color here, but
        COLR fonts can potentially use the paint color in the glyph
        atlas, so this color must be considered as part of the cache
        key. 

Definition at line 35 of file text_frame.cc.

                               {
  return has_color_;
}

Referenced by CollectUniqueFontGlyphPairs().

operator=()

TextFrame& impeller::TextFrame::operator= ( TextFrame &&  other )

default

RoundScaledFontSize()

Scalar impeller::TextFrame::RoundScaledFontSize ( Scalar  scale, Scalar  point_size  )

static

Definition at line 40 of file text_frame.cc.

                                                                     {
  // An arbitrarily chosen maximum text scale to ensure that regardless of the
  // CTM, a glyph will fit in the atlas. If we clamp significantly, this may
  // reduce fidelity but is preferable to the alternative of failing to render.
  constexpr Scalar kMaximumTextScale = 48;
  Scalar result = std::round(scale * 100) / 100;
  return std::clamp(result, 0.0f, kMaximumTextScale);
}

References scale.

Referenced by CollectUniqueFontGlyphPairs(), impeller::TextContents::Render(), and impeller::testing::TEST_P().

---

The documentation for this class was generated from the following files:

• impeller/typographer/text_frame.h
• impeller/typographer/text_frame.cc