| Flutter Impeller |

Public Member Functions | List of all members
impeller::ClipContents Class Referencefinal

`#include <clip_contents.h>`

Inheritance diagram for impeller::ClipContents:

## Public Member Functions
| ClipContents ()
| ~ClipContents ()
void | SetGeometry (const Geometry *geometry)
void | SetClipOperation (Entity::ClipOperation clip_op)
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...
ClipCoverage | GetClipCoverage (const Entity &entity, const std::optional< Rect > &current_clip_coverage) const override
| Given the current pass space bounding rectangle of the clip buffer, return the expected clip coverage after this draw call. This should only be implemented for contents that may write to the clip buffer. More...
bool | Render (const ContentContext &renderer, const Entity &entity, RenderPass &pass) const override
void | SetInheritedOpacity (Scalar opacity) override
| Inherit the provided opacity. More...
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, const std::string &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 const FilterContents * | AsFilter () const
| Cast to a filter. Returns `nullptr` if this Contents is not a filter. More...
virtual bool | ApplyColorFilter (const ColorFilterProc &color_filter_proc)
| If possible, applies a color filter to this contents inputs on the CPU. More...

## 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)>
Static Public Member Functions inherited from impeller::Contents
static std::shared_ptr< Contents > | MakeAnonymous (RenderProc render_proc, CoverageProc coverage_proc)

## Detailed Description

Definition at line 14 of file clip_contents.h.

## Constructor & Destructor Documentation

## ◆ ClipContents()

impeller::ClipContents::ClipContents | ( |  | ) |
| default

## ◆ ~ClipContents()

impeller::ClipContents::~ClipContents | ( |  | ) |
| default

## Member Function Documentation

## ◆ GetClipCoverage()

Contents::ClipCoverage impeller::ClipContents::GetClipCoverage | ( | const Entity & | entity,
|  | const std::optional< Rect > & | current_clip_coverage
| ) |  | const
| override virtual

Given the current pass space bounding rectangle of the clip buffer, return the expected clip coverage after this draw call. This should only be implemented for contents that may write to the clip buffer.

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

Reimplemented from impeller::Contents.

Definition at line 47 of file clip_contents.cc.

49 {
50 if (!current_clip_coverage.has_value()) {
51 return {.type = ClipCoverage::Type::kAppend, .coverage = std::nullopt};
52 }
53 switch (clip_op_) {
54 case Entity::ClipOperation::kDifference:
55 // This can be optimized further by considering cases when the bounds of
56 // the current stencil will shrink.
57 return {
58 .type = ClipCoverage::Type::kAppend, //
59 .is_difference_or_non_square = true, //
60 .coverage = current_clip_coverage //
61 };
62 case Entity::ClipOperation::kIntersect:
63 if (!geometry_) {
64 return {.type = ClipCoverage::Type::kAppend, .coverage = std::nullopt};
65 }
66 auto coverage = geometry_->GetCoverage(entity.GetTransform());
67 if (!coverage.has_value() || !current_clip_coverage.has_value()) {
68 return {.type = ClipCoverage::Type::kAppend, .coverage = std::nullopt};
69 }
70 return {
71 .type = ClipCoverage::Type::kAppend, //
72 .is_difference_or_non_square = !geometry_->IsAxisAlignedRect(), //
73 .coverage = current_clip_coverage->Intersection(coverage.value()), //
74 };
75 }
76 FML_UNREACHABLE();
77 }

References impeller::Geometry::GetCoverage(), impeller::Entity::GetTransform(), impeller::Geometry::IsAxisAlignedRect(), impeller::Entity::kDifference, impeller::Entity::kIntersect, and impeller::Contents::ClipCoverage::type.

## ◆ GetCoverage()

std::optional< Rect > impeller::ClipContents::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.

Definition at line 43 of file clip_contents.cc.

43 {
44 return std::nullopt;
45 };

## ◆ Render()

bool impeller::ClipContents::Render | ( | const ContentContext & | renderer,
|  | const Entity & | entity,
|  | RenderPass & | pass
| ) |  | const
| override virtual

Stencil preparation draw.

Write depth.

Implements impeller::Contents.

Definition at line 81 of file clip_contents.cc.

83 {
84 if (!geometry_) {
85 return true;
86 }
87
88 using VS = ClipPipeline::VertexShader;
89
90 VS::FrameInfo info;
91 info.depth = GetShaderClipDepth(entity);
92
93 auto geometry_result = geometry_->GetPositionBuffer(renderer, entity, pass);
94 auto options = OptionsFromPass(pass);
95 options.blend_mode = BlendMode::kDestination;
96
97 pass.SetStencilReference(0);
98
99 /// Stencil preparation draw.
100
101 options.depth_write_enabled = false;
102 options.primitive_type = geometry_result.type;
103 pass.SetVertexBuffer(std::move(geometry_result.vertex_buffer));
104 switch (geometry_result.mode) {
105 case GeometryResult::Mode::kNonZero:
106 pass.SetCommandLabel("Clip stencil preparation (NonZero)");
107 options.stencil_mode =
108 ContentContextOptions::StencilMode::kStencilNonZeroFill;
109 break;
110 case GeometryResult::Mode::kEvenOdd:
111 pass.SetCommandLabel("Clip stencil preparation (EvenOdd)");
112 options.stencil_mode =
113 ContentContextOptions::StencilMode::kStencilEvenOddFill;
114 break;
115 case GeometryResult::Mode::kNormal:
116 case GeometryResult::Mode::kPreventOverdraw:
117 pass.SetCommandLabel("Clip stencil preparation (Increment)");
118 options.stencil_mode =
119 ContentContextOptions::StencilMode::kOverdrawPreventionIncrement;
120 break;
121 }
122 pass.SetPipeline(renderer.GetClipPipeline(options));
123
124 info.mvp = geometry_result.transform;
125 VS::BindFrameInfo(pass, renderer.GetTransientsBuffer().EmplaceUniform(info));
126
127 if (!pass.Draw().ok()) {
128 return false;
129 }
130
131 /// Write depth.
132
133 options.depth_write_enabled = true;
134 options.primitive_type = PrimitiveType::kTriangleStrip;
135 Rect cover_area;
136 switch (clip_op_) {
137 case Entity::ClipOperation::kIntersect:
138 pass.SetCommandLabel("Intersect Clip");
139 options.stencil_mode =
140 ContentContextOptions::StencilMode::kCoverCompareInverted;
141 cover_area = Rect::MakeSize(pass.GetRenderTargetSize());
142 break;
143 case Entity::ClipOperation::kDifference:
144 pass.SetCommandLabel("Difference Clip");
145 options.stencil_mode = ContentContextOptions::StencilMode::kCoverCompare;
146 std::optional<Rect> maybe_cover_area =
147 geometry_->GetCoverage(entity.GetTransform());
148 if (!maybe_cover_area.has_value()) {
149 return true;
150 }
151 cover_area = maybe_cover_area.value();
152 break;
153 }
154 auto points = cover_area.GetPoints();
155 pass.SetVertexBuffer(
156 CreateVertexBuffer(points, renderer.GetTransientsBuffer()));
157
158 pass.SetPipeline(renderer.GetClipPipeline(options));
159
160 info.mvp = pass.GetOrthographicTransform();
161 VS::BindFrameInfo(pass, renderer.GetTransientsBuffer().EmplaceUniform(info));
162
163 return pass.Draw().ok();
164 }

References impeller::CreateVertexBuffer(), impeller::RenderPass::Draw(), impeller::HostBuffer::EmplaceUniform(), impeller::ContentContext::GetClipPipeline(), impeller::Geometry::GetCoverage(), impeller::RenderPass::GetOrthographicTransform(), impeller::TRect< T >::GetPoints(), impeller::Geometry::GetPositionBuffer(), impeller::RenderPass::GetRenderTargetSize(), impeller::GetShaderClipDepth(), impeller::Entity::GetTransform(), impeller::ContentContext::GetTransientsBuffer(), impeller::ContentContextOptions::kCoverCompare, impeller::ContentContextOptions::kCoverCompareInverted, impeller::kDestination, impeller::Entity::kDifference, impeller::GeometryResult::kEvenOdd, impeller::Entity::kIntersect, impeller::GeometryResult::kNonZero, impeller::GeometryResult::kNormal, impeller::ContentContextOptions::kOverdrawPreventionIncrement, impeller::GeometryResult::kPreventOverdraw, impeller::ContentContextOptions::kStencilEvenOddFill, impeller::ContentContextOptions::kStencilNonZeroFill, impeller::kTriangleStrip, impeller::TRect< Scalar >::MakeSize(), impeller::OptionsFromPass(), impeller::RenderPass::SetCommandLabel(), impeller::RenderPass::SetPipeline(), impeller::RenderPass::SetStencilReference(), and impeller::RenderPass::SetVertexBuffer().

## ◆ SetClipOperation()

void impeller::ClipContents::SetClipOperation | ( | Entity::ClipOperation | clip_op | ) |

Definition at line 39 of file clip_contents.cc.

39 {
40 clip_op_ = clip_op;
41 }

## ◆ SetGeometry()

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

Definition at line 35 of file clip_contents.cc.

35 {
36 geometry_ = geometry;
37 }

## ◆ SetInheritedOpacity()

void impeller::ClipContents::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 79 of file clip_contents.cc.

79 {}

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

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

impeller::GeometryResult::Mode::kNormal
@ kNormal
The geometry has no overlapping triangles.
impeller::Entity::ClipOperation::kIntersect
@ kIntersect
impeller::OptionsFromPass
ContentContextOptions OptionsFromPass(const RenderPass &pass)
Definition: contents.cc:19
impeller::Entity::ClipOperation::kDifference
@ kDifference
impeller::ContentContextOptions::StencilMode::kOverdrawPreventionIncrement
@ kOverdrawPreventionIncrement
impeller::Geometry::GetCoverage
virtual std::optional< Rect > GetCoverage(const Matrix &transform) const =0
impeller::BlendMode::kDestination
@ kDestination
impeller::Geometry::IsAxisAlignedRect
virtual bool IsAxisAlignedRect() const
Definition: geometry.cc:124
impeller::ContentContextOptions::StencilMode::kStencilEvenOddFill
@ kStencilEvenOddFill
impeller::GeometryResult::Mode::kEvenOdd
@ kEvenOdd
impeller::GetShaderClipDepth
static Scalar GetShaderClipDepth(const Entity &entity)
Definition: clip_contents.cc:19
impeller::VS
SolidFillVertexShader VS
Definition: stroke_path_geometry.cc:16
impeller::PrimitiveType::kTriangleStrip
@ kTriangleStrip
impeller::Geometry::GetPositionBuffer
virtual GeometryResult GetPositionBuffer(const ContentContext &renderer, const Entity &entity, RenderPass &pass) const =0
impeller::CreateVertexBuffer
VertexBuffer CreateVertexBuffer(std::array< VertexType, size > input, HostBuffer &host_buffer)
Create an index-less vertex buffer from a fixed size array.
Definition: vertex_buffer_builder.h:24
impeller::ContentContextOptions::StencilMode::kStencilNonZeroFill
@ kStencilNonZeroFill
impeller::RenderPipelineHandle::VertexShader
VertexShader_ VertexShader
Definition: pipeline.h:106
impeller::Rect
TRect< Scalar > Rect
Definition: rect.h:776
impeller::TRect< Scalar >::MakeSize
constexpr static TRect MakeSize(const TSize< U > &size)
Definition: rect.h:150
impeller::GeometryResult::Mode::kPreventOverdraw
@ kPreventOverdraw
impeller::ContentContextOptions::StencilMode::kCoverCompareInverted
@ kCoverCompareInverted
impeller::ContentContextOptions::StencilMode::kCoverCompare
@ kCoverCompare
impeller::GeometryResult::Mode::kNonZero
@ kNonZero