| Flutter Impeller |

Public Types | Public Member Functions | Static Public Member Functions | Protected Member Functions | Static Protected Member Functions | List of all members
impeller::ColorSourceContents Class Reference

`#include <color_source_contents.h>`

Inheritance diagram for impeller::ColorSourceContents:

## Public Types
using | BindFragmentCallback = std::function< bool(RenderPass &pass)>
using | PipelineBuilderCallback = std::function< PipelineRef(ContentContextOptions)>
using | CreateGeometryCallback = std::function< GeometryResult(const ContentContext &renderer, const Entity &entity, RenderPass &pass, const Geometry *geom)>
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)>

## Public Member Functions
| ColorSourceContents ()
| ~ColorSourceContents () override
void | SetGeometry (const Geometry *geometry)
| Set the geometry that this contents will use to render. More...
const Geometry * | GetGeometry () const
| Get the geometry that this contents will use to render. More...
void | SetEffectTransform (Matrix matrix)
| Set the effect transform for this color source. More...
const Matrix & | GetInverseEffectTransform () const
| Set the inverted effect transform for this color source. More...
void | SetOpacityFactor (Scalar opacity)
| Set the opacity factor for this color source. More...
Scalar | GetOpacityFactor () const
| Get the opacity factor for this color source. More...
virtual bool | IsSolidColor () 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 | SetInheritedOpacity (Scalar opacity) override
| Inherit the provided opacity. More...
Public Member Functions inherited from impeller::Contents
| Contents ()
virtual | ~Contents ()
virtual bool | Render (const ContentContext &renderer, const Entity &entity, RenderPass &pass) const =0
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
template<typename VertexShaderT >
static bool | DrawGeometry (const Contents *contents, const Geometry *geometry, const ContentContext &renderer, const Entity &entity, RenderPass &pass, const PipelineBuilderCallback &pipeline_callback, typename VertexShaderT::FrameInfo frame_info, const BindFragmentCallback &bind_fragment_callback, bool force_stencil=false, const CreateGeometryCallback &create_geom_callback=DefaultCreateGeometryCallback)
Static Public Member Functions inherited from impeller::Contents
static std::shared_ptr< Contents > | MakeAnonymous (RenderProc render_proc, CoverageProc coverage_proc)

## Protected Member Functions
bool | AppliesAlphaForStrokeCoverage (const Matrix &transform) const
| Whether the entity should be treated as non-opaque due to stroke geometry requiring alpha for coverage. More...
template<typename VertexShaderT >
bool | DrawGeometry (const ContentContext &renderer, const Entity &entity, RenderPass &pass, const PipelineBuilderCallback &pipeline_callback, typename VertexShaderT::FrameInfo frame_info, const BindFragmentCallback &bind_fragment_callback, bool force_stencil=false, const CreateGeometryCallback &create_geom_callback=DefaultCreateGeometryCallback) const

## Static Protected Member Functions
static GeometryResult | DefaultCreateGeometryCallback (const ContentContext &renderer, const Entity &entity, RenderPass &pass, const Geometry *geom)

## Detailed Description

Color sources are geometry-ignostic `Contents` capable of shading any area defined by an `impeller::Geometry`. Conceptually, `impeller::ColorSourceContents` implement a particular color shading behavior.

This separation of concerns between geometry and color source output allows Impeller to handle most possible draw combinations in a consistent way. For example: There are color sources for handling solid colors, gradients, textures, custom runtime effects, and even 3D scenes.

There are some special rendering exceptions that deviate from this pattern and cross geometry and color source concerns, such as text atlas and image atlas rendering. Special `Contents` exist for rendering these behaviors which don't implement `ColorSourceContents`.

See also
  `impeller::Geometry`

Definition at line 38 of file color_source_contents.h.

## Member Typedef Documentation

## ◆ BindFragmentCallback

using impeller::ColorSourceContents::BindFragmentCallback = std::function<bool(RenderPass& pass)>

Definition at line 40 of file color_source_contents.h.

## ◆ CreateGeometryCallback

using impeller::ColorSourceContents::CreateGeometryCallback = std::function<GeometryResult(const ContentContext& renderer, const Entity& entity, RenderPass& pass, const Geometry* geom)>

Definition at line 43 of file color_source_contents.h.

## ◆ PipelineBuilderCallback

using impeller::ColorSourceContents::PipelineBuilderCallback = std::function<PipelineRef(ContentContextOptions)>

Definition at line 41 of file color_source_contents.h.

## Constructor & Destructor Documentation

## ◆ ColorSourceContents()

impeller::ColorSourceContents::ColorSourceContents | ( |  | ) |
| default

## ◆ ~ColorSourceContents()

impeller::ColorSourceContents::~ColorSourceContents | ( |  | ) |
| override default

## Member Function Documentation

## ◆ AppliesAlphaForStrokeCoverage()

bool impeller::ColorSourceContents::AppliesAlphaForStrokeCoverage | ( | const Matrix & | transform | ) | const
| protected

Whether the entity should be treated as non-opaque due to stroke geometry requiring alpha for coverage.

Definition at line 53 of file color_source_contents.cc.

54 {
55 return GetGeometry() && GetGeometry()->ComputeAlphaCoverage(transform) < 1.0;
56 }
impeller::ColorSourceContents::GetGeometry
const Geometry * GetGeometry() const
Get the geometry that this contents will use to render.
Definition: color_source_contents.cc:20
impeller::Geometry::ComputeAlphaCoverage
virtual Scalar ComputeAlphaCoverage(const Matrix &transform) const
Definition: geometry.h:118
transform
Matrix transform
Definition: gaussian_blur_filter_contents.cc:214

References impeller::Geometry::ComputeAlphaCoverage(), GetGeometry(), and transform.

Referenced by impeller::LinearGradientContents::IsOpaque(), impeller::RadialGradientContents::IsOpaque(), impeller::SolidColorContents::IsOpaque(), impeller::SweepGradientContents::IsOpaque(), and impeller::TiledTextureContents::IsOpaque().

## ◆ DefaultCreateGeometryCallback()

static GeometryResult impeller::ColorSourceContents::DefaultCreateGeometryCallback | ( | const ContentContext & | renderer,
|  | const Entity & | entity,
|  | RenderPass & | pass,
|  | const Geometry * | geom
| ) |  |
| inline static protected

Definition at line 259 of file color_source_contents.h.

263 {
264 return geom->GetPositionBuffer(renderer, entity, pass);
265 }

References impeller::Geometry::GetPositionBuffer().

## ◆ DrawGeometry() [1/2]

template<typename VertexShaderT >

bool impeller::ColorSourceContents::DrawGeometry | ( | const ContentContext & | renderer,
|  | const Entity & | entity,
|  | RenderPass & | pass,
|  | const PipelineBuilderCallback & | pipeline_callback,
|  | typename VertexShaderT::FrameInfo | frame_info,
|  | const BindFragmentCallback & | bind_fragment_callback,
|  | bool | force_stencil = `false`,
|  | const CreateGeometryCallback & | create_geom_callback = `DefaultCreateGeometryCallback`
| ) |  | const
| inline protected

Definition at line 272 of file color_source_contents.h.

280 {
281 //
282 return DrawGeometry<VertexShaderT>(this, //
283 GetGeometry(), //
284 renderer, //
285 entity, //
286 pass, //
287 pipeline_callback, //
288 frame_info, //
289 bind_fragment_callback, //
290 force_stencil, //
291 create_geom_callback);
292 }

References GetGeometry().

## ◆ DrawGeometry() [2/2]

template<typename VertexShaderT >

static bool impeller::ColorSourceContents::DrawGeometry | ( | const Contents * | contents,
|  | const Geometry * | geometry,
|  | const ContentContext & | renderer,
|  | const Entity & | entity,
|  | RenderPass & | pass,
|  | const PipelineBuilderCallback & | pipeline_callback,
|  | typename VertexShaderT::FrameInfo | frame_info,
|  | const BindFragmentCallback & | bind_fragment_callback,
|  | bool | force_stencil = `false`,
|  | const CreateGeometryCallback & | create_geom_callback = `DefaultCreateGeometryCallback`
| ) |  |
| inline static

Stencil preparation draw.

Cover draw.

Definition at line 113 of file color_source_contents.h.

123 {
124 auto options = OptionsFromPassAndEntity(pass, entity);
125
126 GeometryResult::Mode geometry_mode = geometry->GetResultMode();
127 bool do_cover_draw = false;
128 Rect cover_area = {};
129
130 bool is_stencil_then_cover =
131 geometry_mode == GeometryResult::Mode::kNonZero ||
132 geometry_mode == GeometryResult::Mode::kEvenOdd;
133 if (!is_stencil_then_cover && force_stencil) {
134 geometry_mode = GeometryResult::Mode::kNonZero;
135 is_stencil_then_cover = true;
136 }
137
138 if (is_stencil_then_cover) {
139 pass.SetStencilReference(0);
140
141 /// Stencil preparation draw.
142
143 GeometryResult stencil_geometry_result =
144 geometry->GetPositionBuffer(renderer, entity, pass);
145 if (stencil_geometry_result.vertex_buffer.vertex_count == 0u) {
146 return true;
147 }
148 pass.SetVertexBuffer(std::move(stencil_geometry_result.vertex_buffer));
149 options.primitive_type = stencil_geometry_result.type;
150
151 options.blend_mode = BlendMode::kDst;
152 switch (stencil_geometry_result.mode) {
153 case GeometryResult::Mode::kNonZero:
154 pass.SetCommandLabel("Stencil preparation (NonZero)");
155 options.stencil_mode =
156 ContentContextOptions::StencilMode::kStencilNonZeroFill;
157 break;
158 case GeometryResult::Mode::kEvenOdd:
159 pass.SetCommandLabel("Stencil preparation (EvenOdd)");
160 options.stencil_mode =
161 ContentContextOptions::StencilMode::kStencilEvenOddFill;
162 break;
163 default:
164 if (force_stencil) {
165 pass.SetCommandLabel("Stencil preparation (NonZero)");
166 options.stencil_mode =
167 ContentContextOptions::StencilMode::kStencilNonZeroFill;
168 break;
169 }
170 FML_UNREACHABLE();
171 }
172 pass.SetPipeline(renderer.GetClipPipeline(options));
173 ClipPipeline::VertexShader::FrameInfo clip_frame_info;
174 clip_frame_info.depth = entity.GetShaderClipDepth();
175 clip_frame_info.mvp = stencil_geometry_result.transform;
176 ClipPipeline::VertexShader::BindFrameInfo(
177 pass, renderer.GetTransientsBuffer().EmplaceUniform(clip_frame_info));
178
179 if (!pass.Draw().ok()) {
180 return false;
181 }
182
183 /// Cover draw.
184
185 options.blend_mode = entity.GetBlendMode();
186 options.stencil_mode = ContentContextOptions::StencilMode::kCoverCompare;
187 std::optional<Rect> maybe_cover_area = geometry->GetCoverage({});
188 if (!maybe_cover_area.has_value()) {
189 return true;
190 }
191 do_cover_draw = true;
192 cover_area = maybe_cover_area.value();
193 }
194
195 GeometryResult geometry_result;
196 if (do_cover_draw) {
197 RectGeometry geom(cover_area);
198 geometry_result = create_geom_callback(renderer, entity, pass, &geom);
199 } else {
200 geometry_result = create_geom_callback(renderer, entity, pass, geometry);
201 }
202
203 if (geometry_result.vertex_buffer.vertex_count == 0u) {
204 return true;
205 }
206 pass.SetVertexBuffer(std::move(geometry_result.vertex_buffer));
207 options.primitive_type = geometry_result.type;
208
209 // Enable depth writing for all opaque entities in order to allow
210 // reordering. Opaque entities are coerced to source blending by
211 // `EntityPass::AddEntity`.
212 options.depth_write_enabled = options.blend_mode == BlendMode::kSrc;
213
214 // Take the pre-populated vertex shader uniform struct and set managed
215 // values.
216 frame_info.mvp = geometry_result.transform;
217
218 // If overdraw prevention is enabled (like when drawing stroke paths), we
219 // increment the stencil buffer as we draw, preventing overlapping fragments
220 // from drawing. Afterwards, we need to append another draw call to clean up
221 // the stencil buffer (happens below in this method). This can be skipped
222 // for draws that are fully opaque or use src blend mode.
223 if (geometry_result.mode == GeometryResult::Mode::kPreventOverdraw &&
224 options.blend_mode != BlendMode::kSrc) {
225 options.stencil_mode =
226 ContentContextOptions::StencilMode::kOverdrawPreventionIncrement;
227 }
228 pass.SetStencilReference(0);
229
230 VertexShaderT::BindFrameInfo(
231 pass, renderer.GetTransientsBuffer().EmplaceUniform(frame_info));
232
233 // The reason we need to have a callback mechanism here is that this routine
234 // may insert draw calls before the main draw call below. For example, for
235 // sufficiently complex paths we may opt to use stencil-then-cover to avoid
236 // tessellation.
237 if (!bind_fragment_callback(pass)) {
238 return false;
239 }
240
241 pass.SetPipeline(pipeline_callback(options));
242
243 if (!pass.Draw().ok()) {
244 return false;
245 }
246
247 // If we performed overdraw prevention, a subsection of the clip heightmap
248 // was incremented by 1 in order to self-clip. So simply append a clip
249 // restore to clean it up.
250 if (geometry_result.mode == GeometryResult::Mode::kPreventOverdraw &&
251 options.blend_mode != BlendMode::kSrc) {
252 return RenderClipRestore(renderer, pass, entity.GetClipDepth(),
253 contents->GetCoverage(entity));
254 }
255 return true;
256 }
impeller::Rect
TRect< Scalar > Rect
Definition: rect.h:792
impeller::RenderClipRestore
bool RenderClipRestore(const ContentContext &renderer, RenderPass &pass, uint32_t clip_depth, std::optional< Rect > restore_coverage)
Render a restore clip.
Definition: clip_contents.cc:153
impeller::BlendMode::kDst
@ kDst
impeller::BlendMode::kSrc
@ kSrc
impeller::OptionsFromPassAndEntity
ContentContextOptions OptionsFromPassAndEntity(const RenderPass &pass, const Entity &entity)
Definition: contents.cc:34
impeller::ContentContextOptions::StencilMode::kStencilEvenOddFill
@ kStencilEvenOddFill
impeller::ContentContextOptions::StencilMode::kOverdrawPreventionIncrement
@ kOverdrawPreventionIncrement
impeller::ContentContextOptions::StencilMode::kStencilNonZeroFill
@ kStencilNonZeroFill
impeller::ContentContextOptions::StencilMode::kCoverCompare
@ kCoverCompare
impeller::GeometryResult::Mode
Mode
Definition: geometry.h:22
impeller::GeometryResult::Mode::kEvenOdd
@ kEvenOdd
impeller::GeometryResult::Mode::kPreventOverdraw
@ kPreventOverdraw
impeller::GeometryResult::Mode::kNonZero
@ kNonZero

References impeller::RenderPass::Draw(), impeller::HostBuffer::EmplaceUniform(), impeller::Entity::GetBlendMode(), impeller::Entity::GetClipDepth(), impeller::ContentContext::GetClipPipeline(), impeller::Contents::GetCoverage(), impeller::Geometry::GetCoverage(), impeller::Geometry::GetPositionBuffer(), impeller::Geometry::GetResultMode(), impeller::Entity::GetShaderClipDepth(), impeller::ContentContext::GetTransientsBuffer(), impeller::ContentContextOptions::kCoverCompare, impeller::kDst, impeller::GeometryResult::kEvenOdd, impeller::GeometryResult::kNonZero, impeller::ContentContextOptions::kOverdrawPreventionIncrement, impeller::GeometryResult::kPreventOverdraw, impeller::kSrc, impeller::ContentContextOptions::kStencilEvenOddFill, impeller::ContentContextOptions::kStencilNonZeroFill, impeller::GeometryResult::mode, impeller::OptionsFromPassAndEntity(), impeller::RenderClipRestore(), impeller::RenderPass::SetCommandLabel(), impeller::RenderPass::SetPipeline(), impeller::RenderPass::SetStencilReference(), impeller::RenderPass::SetVertexBuffer(), impeller::GeometryResult::transform, impeller::GeometryResult::type, impeller::GeometryResult::vertex_buffer, and impeller::VertexBuffer::vertex_count.

## ◆ GetCoverage()

std::optional< Rect > impeller::ColorSourceContents::GetCoverage | ( | const Entity & | entity | ) | const
| override virtual

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.

Reimplemented in impeller::SolidColorContents.

Definition at line 44 of file color_source_contents.cc.

45 {
46 return geometry_->GetCoverage(entity.GetTransform());
47 };
impeller::Geometry::GetCoverage
virtual std::optional< Rect > GetCoverage(const Matrix &transform) const =0

References impeller::Geometry::GetCoverage(), and impeller::Entity::GetTransform().

Referenced by impeller::TiledTextureContents::RenderToSnapshot().

## ◆ GetGeometry()

const Geometry * impeller::ColorSourceContents::GetGeometry | ( |  | ) | const

Get the geometry that this contents will use to render.

Definition at line 20 of file color_source_contents.cc.

20 {
21 return geometry_;
22 }

Referenced by AppliesAlphaForStrokeCoverage(), impeller::SolidColorContents::AsBackgroundColor(), DrawGeometry(), impeller::SolidColorContents::GetCoverage(), impeller::SolidColorContents::Render(), impeller::TiledTextureContents::Render(), and impeller::TiledTextureContents::RenderToSnapshot().

## ◆ GetInverseEffectTransform()

const Matrix & impeller::ColorSourceContents::GetInverseEffectTransform | ( |  | ) | const

Set the inverted effect transform for this color source.

         When the effect transform is set via `SetEffectTransform`, the
         value is inverted upon storage. The reason for this is that most
         color sources internally use the inverted transform.

Returns
  The inverse of the transform set by `SetEffectTransform`.

See also
  `SetEffectTransform`

Definition at line 36 of file color_source_contents.cc.

36 {
37 return inverse_matrix_;
38 }

Referenced by impeller::TiledTextureContents::Render(), and impeller::TiledTextureContents::RenderToSnapshot().

## ◆ GetOpacityFactor()

Scalar impeller::ColorSourceContents::GetOpacityFactor | ( |  | ) | const

Get the opacity factor for this color source.

        This value is is factored into the output of the color source in
        addition to opacity information that may be supplied any other
        inputs.

Note
  If set, the output of this method factors factors in the inherited opacity of this `Contents`.

Definition at line 28 of file color_source_contents.cc.

28 {
29 return opacity_ * inherited_opacity_;
30 }

Referenced by impeller::SolidColorContents::GetColor(), impeller::LinearGradientContents::IsOpaque(), impeller::RadialGradientContents::IsOpaque(), impeller::SweepGradientContents::IsOpaque(), impeller::TiledTextureContents::IsOpaque(), impeller::TiledTextureContents::Render(), and impeller::TiledTextureContents::RenderToSnapshot().

## ◆ IsSolidColor()

bool impeller::ColorSourceContents::IsSolidColor | ( |  | ) | const
| virtual

Reimplemented in impeller::SolidColorContents.

Definition at line 40 of file color_source_contents.cc.

40 {
41 return false;
42 }

## ◆ SetEffectTransform()

void impeller::ColorSourceContents::SetEffectTransform | ( | Matrix | matrix | ) |

Set the effect transform for this color source.

        The effect transform is a transform matrix that is applied to
        the shaded color output and does not impact geometry in any way.

        For example: With repeat tiling, any gradient or
        `TiledTextureContents` could be used with an effect transform to
        inexpensively draw an infinite scrolling background pattern.

Definition at line 32 of file color_source_contents.cc.

32 {
33 inverse_matrix_ = matrix.Invert();
34 }
impeller::Matrix::Invert
Matrix Invert() const
Definition: matrix.cc:97

References impeller::Matrix::Invert().

## ◆ SetGeometry()

void impeller::ColorSourceContents::SetGeometry | ( | const Geometry * | geometry | ) |

Set the geometry that this contents will use to render.

Definition at line 16 of file color_source_contents.cc.

16 {
17 geometry_ = geometry;
18 }

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

## ◆ SetInheritedOpacity()

void impeller::ColorSourceContents::SetInheritedOpacity | ( | Scalar | opacity | ) |
| override virtual

Inherit the provided opacity.

       Use of this method is invalid if CanAcceptOpacity returns false.

Reimplemented from impeller::Contents.

Definition at line 49 of file color_source_contents.cc.

49 {
50 inherited_opacity_ = opacity;
51 }

## ◆ SetOpacityFactor()

void impeller::ColorSourceContents::SetOpacityFactor | ( | Scalar | opacity | ) |

Set the opacity factor for this color source.

Definition at line 24 of file color_source_contents.cc.

24 {
25 opacity_ = alpha;
26 }

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

- impeller/entity/contents/color_source_contents.h
- impeller/entity/contents/color_source_contents.cc