impeller::TextContents Class Reference

#include <text_contents.h>

Inheritance diagram for impeller::TextContents:

Public Member Functions
	TextContents ()
	~TextContents ()
void	SetTextFrame (const std::shared_ptr< TextFrame > &frame)
void	SetColor (Color color)
void	SetForceTextColor (bool value)
	Force the text color to apply to the rendered glyphs, even if those glyphs are bitmaps. More...
void	SetTextProperties (Color color, bool stroke, Scalar stroke_width, Cap stroke_cap, Join stroke_join, Scalar stroke_miter)
	Must be set after text frame. More...
Color	GetColor () const
void	SetInheritedOpacity (Scalar opacity) override
	Inherit the provided opacity. More...
void	SetOffset (Vector2 offset)
std::optional< Rect >	GetTextFrameBounds () const
std::optional< Rect >	GetCoverage (const Entity &entity) const override
	Get the area of the render pass that will be affected when this contents is rendered. More...
void	SetScale (Scalar scale)
bool	Render (const ContentContext &renderer, const Entity &entity, RenderPass &pass) const override
Public Member Functions inherited from impeller::Contents
	Contents ()
virtual	~Contents ()
void	SetCoverageHint (std::optional< Rect > coverage_hint)
	Hint that specifies the coverage area of this Contents that will actually be used during rendering. This is for optimization purposes only and can not be relied on as a clip. May optionally affect the result of GetCoverage(). More...
const std::optional< Rect > &	GetCoverageHint () const
virtual bool	IsOpaque (const Matrix &transform) const
	Whether this Contents only emits opaque source colors from the fragment stage. This value does not account for any entity properties (e.g. the blend mode), clips/visibility culling, or inherited opacity. More...
virtual std::optional< Snapshot >	RenderToSnapshot (const ContentContext &renderer, const Entity &entity, std::optional< Rect > coverage_limit=std::nullopt, const std::optional< SamplerDescriptor > &sampler_descriptor=std::nullopt, bool msaa_enabled=true, int32_t mip_count=1, std::string_view label="Snapshot") const
	Render this contents to a snapshot, respecting the entity's transform, path, clip depth, and blend mode. The result texture size is always the size of GetCoverage(entity). More...
std::optional< Size >	GetColorSourceSize () const
	Return the color source's intrinsic size, if available. More...
void	SetColorSourceSize (Size size)
virtual std::optional< Color >	AsBackgroundColor (const Entity &entity, ISize target_size) const
	Returns a color if this Contents will flood the given target_size with a color. This output color is the "Source" color that will be used for the Entity's blend operation. More...
virtual bool	ApplyColorFilter (const ColorFilterProc &color_filter_proc)
	If possible, applies a color filter to this contents inputs on the CPU. More...

Static Public Member Functions
static void	ComputeVertexData (GlyphAtlasPipeline::VertexShader::PerVertexData *vtx_contents, const std::shared_ptr< TextFrame > &frame, Scalar scale, const Matrix &entity_transform, Vector2 offset, std::optional< GlyphProperties > glyph_properties, const std::shared_ptr< GlyphAtlas > &atlas)
Static Public Member Functions inherited from impeller::Contents
static std::shared_ptr< Contents >	MakeAnonymous (RenderProc render_proc, CoverageProc coverage_proc)

Additional Inherited Members
Public Types inherited from impeller::Contents
using	ColorFilterProc = std::function< Color(Color)>
using	RenderProc = std::function< bool(const ContentContext &renderer, const Entity &entity, RenderPass &pass)>
using	CoverageProc = std::function< std::optional< Rect >(const Entity &entity)>

Detailed Description

Definition at line 22 of file text_contents.h.

Constructor & Destructor Documentation

TextContents()

impeller::TextContents::TextContents ( )

default

~TextContents()

impeller::TextContents::~TextContents ( )

default

Member Function Documentation

ComputeVertexData()

void impeller::TextContents::ComputeVertexData ( GlyphAtlasPipeline::VertexShader::PerVertexData *  vtx_contents, const std::shared_ptr< TextFrame > &  frame, Scalar  scale, const Matrix &  entity_transform, Vector2  offset, std::optional< GlyphProperties >  glyph_properties, const std::shared_ptr< GlyphAtlas > &  atlas  )

static

Definition at line 96 of file text_contents.cc.

                                            {
  // Common vertex information for all glyphs.
  // All glyphs are given the same vertex information in the form of a
  // unit-sized quad. The size of the glyph is specified in per instance data
  // and the vertex shader uses this to size the glyph correctly. The
  // interpolated vertex information is also used in the fragment shader to
  // sample from the glyph atlas.
 
  constexpr std::array<Point, 4> unit_points = {Point{0, 0}, Point{1, 0},
                                                Point{0, 1}, Point{1, 1}};
 
  ISize atlas_size = atlas->GetTexture()->GetSize();
  bool is_translation_scale = entity_transform.IsTranslationScaleOnly();
  Matrix basis_transform = entity_transform.Basis();
 
  VS::PerVertexData vtx;
  size_t i = 0u;
  size_t bounds_offset = 0u;
  Rational rounded_scale = frame->GetScale();
  Scalar inverted_rounded_scale = static_cast<Scalar>(rounded_scale.Invert());
  Matrix unscaled_basis =
      basis_transform *
      Matrix::MakeScale({inverted_rounded_scale, inverted_rounded_scale, 1});
 
  // In typical scales < 48x these values should be -1 or 1. We round to
  // those to avoid inaccuracies.
  unscaled_basis.m[0] = AttractToOne(unscaled_basis.m[0]);
  unscaled_basis.m[5] = AttractToOne(unscaled_basis.m[5]);
 
  for (const TextRun& run : frame->GetRuns()) {
    const Font& font = run.GetFont();
    const Matrix transform = frame->GetOffsetTransform();
    FontGlyphAtlas* font_atlas = nullptr;
 
    // Adjust glyph position based on the subpixel rounding
    // used by the font.
    Point subpixel_adjustment(0.5, 0.5);
    switch (font.GetAxisAlignment()) {
      case AxisAlignment::kNone:
        break;
      case AxisAlignment::kX:
        subpixel_adjustment.x = 0.125;
        break;
      case AxisAlignment::kY:
        subpixel_adjustment.y = 0.125;
        break;
      case AxisAlignment::kAll:
        subpixel_adjustment.x = 0.125;
        subpixel_adjustment.y = 0.125;
        break;
    }
 
    Point screen_offset = (entity_transform * Point(0, 0));
    for (const TextRun::GlyphPosition& glyph_position :
         run.GetGlyphPositions()) {
      const FrameBounds& frame_bounds = frame->GetFrameBounds(bounds_offset);
      bounds_offset++;
      auto atlas_glyph_bounds = frame_bounds.atlas_bounds;
      auto glyph_bounds = frame_bounds.glyph_bounds;
 
      // If frame_bounds.is_placeholder is true, this is the first frame
      // the glyph has been rendered and so its atlas position was not
      // known when the glyph was recorded. Perform a slow lookup into the
      // glyph atlas hash table.
      if (frame_bounds.is_placeholder) {
        if (!font_atlas) {
          font_atlas =
              atlas->GetOrCreateFontGlyphAtlas(ScaledFont{font, rounded_scale});
        }
 
        if (!font_atlas) {
          VALIDATION_LOG << "Could not find font in the atlas.";
          continue;
        }
        SubpixelPosition subpixel = TextFrame::ComputeSubpixelPosition(
            glyph_position, font.GetAxisAlignment(), transform);
 
        std::optional<FrameBounds> maybe_atlas_glyph_bounds =
            font_atlas->FindGlyphBounds(SubpixelGlyph{
                glyph_position.glyph,  //
                subpixel,              //
                glyph_properties       //
            });
        if (!maybe_atlas_glyph_bounds.has_value()) {
          VALIDATION_LOG << "Could not find glyph position in the atlas.";
          continue;
        }
        atlas_glyph_bounds = maybe_atlas_glyph_bounds.value().atlas_bounds;
      }
 
      Rect scaled_bounds = glyph_bounds.Scale(inverted_rounded_scale);
      // For each glyph, we compute two rectangles. One for the vertex
      // positions and one for the texture coordinates (UVs). The atlas
      // glyph bounds are used to compute UVs in cases where the
      // destination and source sizes may differ due to clamping the sizes
      // of large glyphs.
      Point uv_origin = atlas_glyph_bounds.GetLeftTop() / atlas_size;
      Point uv_size = SizeToPoint(atlas_glyph_bounds.GetSize()) / atlas_size;
 
      Point unrounded_glyph_position =
          // This is for RTL text.
          unscaled_basis * glyph_bounds.GetLeftTop() +
          (basis_transform * glyph_position.position);
 
      Point screen_glyph_position =
          (screen_offset + unrounded_glyph_position + subpixel_adjustment)
              .Floor();
      for (const Point& point : unit_points) {
        Point position;
        if (is_translation_scale) {
          position = (screen_glyph_position +
                      (unscaled_basis * point * glyph_bounds.GetSize()))
                         .Round();
        } else {
          position = entity_transform *
                     (glyph_position.position + scaled_bounds.GetLeftTop() +
                      point * scaled_bounds.GetSize());
        }
        vtx.uv = uv_origin + (uv_size * point);
        vtx.position = position;
        vtx_contents[i++] = vtx;
      }
    }
  }
}

References impeller::FrameBounds::atlas_bounds, impeller::Matrix::Basis(), impeller::TextFrame::ComputeSubpixelPosition(), impeller::FontGlyphAtlas::FindGlyphBounds(), impeller::Font::GetAxisAlignment(), impeller::TRect< T >::GetLeftTop(), impeller::TRect< T >::GetSize(), impeller::SubpixelGlyph::glyph, impeller::FrameBounds::glyph_bounds, impeller::Rational::Invert(), impeller::FrameBounds::is_placeholder, impeller::Matrix::IsTranslationScaleOnly(), impeller::kAll, impeller::kNone, impeller::kX, impeller::kY, impeller::Matrix::m, impeller::Matrix::MakeScale(), impeller::TPoint< T >::Round(), impeller::TRect< T >::Scale(), impeller::SizeToPoint(), transform, VALIDATION_LOG, vtx, impeller::TPoint< T >::x, and impeller::TPoint< T >::y.

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

GetColor()

Color impeller::TextContents::GetColor

(

)

const

Definition at line 40 of file text_contents.cc.

                                   {
  return color_.WithAlpha(color_.alpha * inherited_opacity_);
}

References impeller::Color::alpha, and impeller::Color::WithAlpha().

Referenced by Render().

GetCoverage()

std::optional< Rect > impeller::TextContents::GetCoverage ( const Entity &  entity ) const

overridevirtual

Get the area of the render pass that will be affected when this contents is rendered.

During rendering, coverage coordinates count pixels from the top left corner of the framebuffer.

Returns

The coverage rectangle. An std::nullopt result means that rendering this contents has no effect on the output color.

Implements impeller::Contents.

Definition at line 56 of file text_contents.cc.

                                                                      {
  return frame_->GetBounds().TransformBounds(entity.GetTransform());
}

References impeller::Entity::GetTransform().

GetTextFrameBounds()

std::optional<Rect> impeller::TextContents::GetTextFrameBounds

(

)

const

Render()

bool impeller::TextContents::Render ( const ContentContext &  renderer, const Entity &  entity, RenderPass &  pass  ) const

overridevirtual

Implements impeller::Contents.

Definition at line 229 of file text_contents.cc.

                                                  {
  Color color = GetColor();
  if (color.IsTransparent()) {
    return true;
  }
 
  GlyphAtlas::Type type = frame_->GetAtlasType();
  const std::shared_ptr<GlyphAtlas>& atlas =
      renderer.GetLazyGlyphAtlas()->CreateOrGetGlyphAtlas(
          *renderer.GetContext(), renderer.GetTransientsBuffer(), type);
 
  if (!atlas || !atlas->IsValid()) {
    VALIDATION_LOG << "Cannot render glyphs without prepared atlas.";
    return false;
  }
  if (!frame_->IsFrameComplete()) {
    VALIDATION_LOG << "Failed to find font glyph bounds.";
    return false;
  }
 
  // Information shared by all glyph draw calls.
  pass.SetCommandLabel("TextFrame");
  auto opts = OptionsFromPassAndEntity(pass, entity);
  opts.primitive_type = PrimitiveType::kTriangle;
  pass.SetPipeline(renderer.GetGlyphAtlasPipeline(opts));
 
  // Common vertex uniforms for all glyphs.
  VS::FrameInfo frame_info;
  frame_info.mvp =
      Entity::GetShaderTransform(entity.GetShaderClipDepth(), pass, Matrix());
  bool is_translation_scale = entity.GetTransform().IsTranslationScaleOnly();
  Matrix entity_transform = entity.GetTransform();
 
  VS::BindFrameInfo(pass,
                    renderer.GetTransientsBuffer().EmplaceUniform(frame_info));
 
  FS::FragInfo frag_info;
  frag_info.use_text_color = force_text_color_ ? 1.0 : 0.0;
  frag_info.text_color = ToVector(color.Premultiply());
  frag_info.is_color_glyph = type == GlyphAtlas::Type::kColorBitmap;
 
  FS::BindFragInfo(pass,
                   renderer.GetTransientsBuffer().EmplaceUniform(frag_info));
 
  SamplerDescriptor sampler_desc;
  if (is_translation_scale) {
    sampler_desc.min_filter = MinMagFilter::kNearest;
    sampler_desc.mag_filter = MinMagFilter::kNearest;
  } else {
    // Currently, we only propagate the scale of the transform to the atlas
    // renderer, so if the transform has more than just a translation, we turn
    // on linear sampling to prevent crunchiness caused by the pixel grid not
    // being perfectly aligned.
    // The downside is that this slightly over-blurs rotated/skewed text.
    sampler_desc.min_filter = MinMagFilter::kLinear;
    sampler_desc.mag_filter = MinMagFilter::kLinear;
  }
 
  // No mipmaps for glyph atlas (glyphs are generated at exact scales).
  sampler_desc.mip_filter = MipFilter::kBase;
 
  FS::BindGlyphAtlasSampler(
      pass,                 // command
      atlas->GetTexture(),  // texture
      renderer.GetContext()->GetSamplerLibrary()->GetSampler(
          sampler_desc)  // sampler
  );
 
  HostBuffer& host_buffer = renderer.GetTransientsBuffer();
  size_t glyph_count = 0;
  for (const auto& run : frame_->GetRuns()) {
    glyph_count += run.GetGlyphPositions().size();
  }
  size_t vertex_count = glyph_count * 4;
  size_t index_count = glyph_count * 6;
 
  BufferView buffer_view = host_buffer.Emplace(
      vertex_count * sizeof(VS::PerVertexData), alignof(VS::PerVertexData),
      [&](uint8_t* data) {
        VS::PerVertexData* vtx_contents =
            reinterpret_cast<VS::PerVertexData*>(data);
        ComputeVertexData(/*vtx_contents=*/vtx_contents,
                          /*frame=*/frame_,
                          /*scale=*/scale_,
                          /*entity_transform=*/entity_transform,
                          /*offset=*/offset_,
                          /*glyph_properties=*/GetGlyphProperties(),
                          /*atlas=*/atlas);
      });
  BufferView index_buffer_view = host_buffer.Emplace(
      index_count * sizeof(uint16_t), alignof(uint16_t), [&](uint8_t* data) {
        uint16_t* indices = reinterpret_cast<uint16_t*>(data);
        size_t j = 0;
        for (auto i = 0u; i < glyph_count; i++) {
          size_t base = i * 4;
          indices[j++] = base + 0;
          indices[j++] = base + 1;
          indices[j++] = base + 2;
          indices[j++] = base + 1;
          indices[j++] = base + 2;
          indices[j++] = base + 3;
        }
      });
 
  pass.SetVertexBuffer(std::move(buffer_view));
  pass.SetIndexBuffer(index_buffer_view, IndexType::k16bit);
  pass.SetElementCount(index_count);
 
  return pass.Draw().ok();
}

References buffer_view, ComputeVertexData(), data, impeller::RenderPass::Draw(), impeller::HostBuffer::Emplace(), impeller::HostBuffer::EmplaceUniform(), GetColor(), impeller::ContentContext::GetContext(), impeller::ContentContext::GetGlyphAtlasPipeline(), impeller::ContentContext::GetLazyGlyphAtlas(), impeller::Entity::GetShaderClipDepth(), impeller::Entity::GetShaderTransform(), impeller::Entity::GetTransform(), impeller::ContentContext::GetTransientsBuffer(), impeller::Matrix::IsTranslationScaleOnly(), impeller::Color::IsTransparent(), impeller::k16bit, impeller::kBase, impeller::GlyphAtlas::kColorBitmap, impeller::kLinear, impeller::kNearest, impeller::kTriangle, impeller::SamplerDescriptor::mag_filter, impeller::SamplerDescriptor::min_filter, impeller::SamplerDescriptor::mip_filter, impeller::OptionsFromPassAndEntity(), impeller::Color::Premultiply(), impeller::RenderPass::SetCommandLabel(), impeller::RenderPass::SetElementCount(), impeller::RenderPass::SetIndexBuffer(), impeller::RenderPass::SetPipeline(), impeller::RenderPass::SetVertexBuffer(), impeller::ToVector(), type, and VALIDATION_LOG.

Referenced by impeller::testing::TEST_P().

SetColor()

void impeller::TextContents::SetColor

(

Color

color

)

Definition at line 36 of file text_contents.cc.

                                       {
  color_ = color;
}

Referenced by impeller::testing::TEST_P().

SetForceTextColor()

void impeller::TextContents::SetForceTextColor

(

bool

value

)

Force the text color to apply to the rendered glyphs, even if those glyphs are bitmaps.

This is used to ensure that mask blurs work correctly on emoji.

Definition at line 52 of file text_contents.cc.

                                               {
  force_text_color_ = value;
}

References value.

SetInheritedOpacity()

void impeller::TextContents::SetInheritedOpacity ( Scalar  opacity )

overridevirtual

Inherit the provided opacity.

   Use of this method is invalid if CanAcceptOpacity returns false.

Reimplemented from impeller::Contents.

Definition at line 44 of file text_contents.cc.

                                                     {
  inherited_opacity_ = opacity;
}

SetOffset()

void impeller::TextContents::SetOffset

(

Vector2

offset

)

Definition at line 48 of file text_contents.cc.

                                           {
  offset_ = offset;
}

References offset.

Referenced by impeller::testing::TEST_P().

SetScale()

void impeller::TextContents::SetScale ( Scalar  scale )

inline

Definition at line 59 of file text_contents.h.

{ scale_ = scale; }

References scale.

Referenced by impeller::testing::TEST_P().

SetTextFrame()

void impeller::TextContents::SetTextFrame

(

const std::shared_ptr< TextFrame > &

frame

)

Definition at line 32 of file text_contents.cc.

                                                                     {
  frame_ = frame;
}

Referenced by impeller::testing::TEST_P().

SetTextProperties()

void impeller::TextContents::SetTextProperties	(	Color	color,
		bool	stroke,
		Scalar	stroke_width,
		Cap	stroke_cap,
		Join	stroke_join,
		Scalar	stroke_miter
	)

Must be set after text frame.

Definition at line 60 of file text_contents.cc.

                                                          {
  if (frame_->HasColor()) {
    // Alpha is always applied when rendering, remove it here so
    // we do not double-apply the alpha.
    properties_.color = color.WithAlpha(1.0);
  }
  if (stroke) {
    properties_.stroke = true;
    properties_.stroke_width = stroke_width;
    properties_.stroke_cap = stroke_cap;
    properties_.stroke_join = stroke_join;
    properties_.stroke_miter = stroke_miter;
  }
}

References impeller::GlyphProperties::color, impeller::GlyphProperties::stroke, impeller::GlyphProperties::stroke_cap, impeller::GlyphProperties::stroke_join, impeller::GlyphProperties::stroke_miter, stroke_width, impeller::GlyphProperties::stroke_width, and impeller::Color::WithAlpha().

---

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

• impeller/entity/contents/text_contents.h
• impeller/entity/contents/text_contents.cc