| Flutter Impeller |

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

`#include <clip_contents.h>`

## Public Member Functions
| ClipContents (Rect coverage_rect, bool is_axis_aligned_rect)
| ~ClipContents ()
void | SetGeometry (GeometryResult geometry)
| Set the pre-tessellated clip geometry. More...
void | SetClipOperation (Entity::ClipOperation clip_op)
ClipCoverage | GetClipCoverage (const std::optional< Rect > &current_clip_coverage) const
| 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, RenderPass &pass, uint32_t clip_depth) const

## Detailed Description

Definition at line 29 of file clip_contents.h.

## Constructor & Destructor Documentation

## ◆ ClipContents()

impeller::ClipContents::ClipContents | ( | Rect | coverage_rect,
|  | bool | is_axis_aligned_rect
| ) |  |

Definition at line 31 of file clip_contents.cc.

32 : coverage_rect_(coverage_rect),
33 is_axis_aligned_rect_(is_axis_aligned_rect) {}

## ◆ ~ClipContents()

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

## Member Function Documentation

## ◆ GetClipCoverage()

ClipCoverage impeller::ClipContents::GetClipCoverage | ( | const std::optional< Rect > & | current_clip_coverage | ) | const

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.

Definition at line 45 of file clip_contents.cc.

46 {
47 if (!current_clip_coverage.has_value()) {
48 return ClipCoverage{.coverage = std::nullopt};
49 }
50 switch (clip_op_) {
51 case Entity::ClipOperation::kDifference:
52 // This can be optimized further by considering cases when the bounds of
53 // the current stencil will shrink.
54 return {
55 .is_difference_or_non_square = true, //
56 .coverage = current_clip_coverage //
57 };
58 case Entity::ClipOperation::kIntersect:
59 if (coverage_rect_.IsEmpty() || !current_clip_coverage.has_value()) {
60 return ClipCoverage{.coverage = std::nullopt};
61 }
62 return {
63 .is_difference_or_non_square = !is_axis_aligned_rect_, //
64 .coverage = current_clip_coverage->Intersection(coverage_rect_), //
65 };
66 }
67 FML_UNREACHABLE();
68 }
impeller::Entity::ClipOperation::kIntersect
@ kIntersect
impeller::Entity::ClipOperation::kDifference
@ kDifference
impeller::TRect::IsEmpty
constexpr bool IsEmpty() const
Returns true if either of the width or height are 0, negative, or NaN.
Definition: rect.h:297

References impeller::ClipCoverage::coverage, impeller::TRect< T >::IsEmpty(), impeller::Entity::kDifference, and impeller::Entity::kIntersect.

Referenced by impeller::EntityPassClipStack::RecordClip().

## ◆ Render()

bool impeller::ClipContents::Render | ( | const ContentContext & | renderer,
|  | RenderPass & | pass,
|  | uint32_t | clip_depth
| ) |  | const

Stencil preparation draw.

Write depth.

Definition at line 70 of file clip_contents.cc.

72 {
73 if (!clip_geometry_.vertex_buffer) {
74 return true;
75 }
76
77 using VS = ClipPipeline::VertexShader;
78
79 VS::FrameInfo info;
80 info.depth = GetShaderClipDepth(clip_depth);
81
82 auto options = OptionsFromPass(pass);
83 options.blend_mode = BlendMode::kDst;
84
85 pass.SetStencilReference(0);
86
87 /// Stencil preparation draw.
88
89 options.depth_write_enabled = false;
90 options.primitive_type = clip_geometry_.type;
91 pass.SetVertexBuffer(clip_geometry_.vertex_buffer);
92 switch (clip_geometry_.mode) {
93 case GeometryResult::Mode::kNonZero:
94 pass.SetCommandLabel("Clip stencil preparation (NonZero)");
95 options.stencil_mode =
96 ContentContextOptions::StencilMode::kStencilNonZeroFill;
97 break;
98 case GeometryResult::Mode::kEvenOdd:
99 pass.SetCommandLabel("Clip stencil preparation (EvenOdd)");
100 options.stencil_mode =
101 ContentContextOptions::StencilMode::kStencilEvenOddFill;
102 break;
103 case GeometryResult::Mode::kNormal:
104 case GeometryResult::Mode::kPreventOverdraw:
105 pass.SetCommandLabel("Clip stencil preparation (Increment)");
106 options.stencil_mode =
107 ContentContextOptions::StencilMode::kOverdrawPreventionIncrement;
108 break;
109 }
110 pass.SetPipeline(renderer.GetClipPipeline(options));
111
112 info.mvp = clip_geometry_.transform;
113 VS::BindFrameInfo(pass,
114 renderer.GetTransientsDataBuffer().EmplaceUniform(info));
115
116 if (!pass.Draw().ok()) {
117 return false;
118 }
119
120 /// Write depth.
121
122 options.depth_write_enabled = true;
123 options.primitive_type = PrimitiveType::kTriangleStrip;
124 Rect cover_area;
125 switch (clip_op_) {
126 case Entity::ClipOperation::kIntersect:
127 pass.SetCommandLabel("Intersect Clip");
128 options.stencil_mode =
129 ContentContextOptions::StencilMode::kCoverCompareInverted;
130 cover_area = Rect::MakeSize(pass.GetRenderTargetSize());
131 break;
132 case Entity::ClipOperation::kDifference:
133 pass.SetCommandLabel("Difference Clip");
134 options.stencil_mode = ContentContextOptions::StencilMode::kCoverCompare;
135 cover_area = coverage_rect_;
136 break;
137 }
138 auto points = cover_area.GetPoints();
139 pass.SetVertexBuffer(
140 CreateVertexBuffer(points, renderer.GetTransientsDataBuffer()));
141
142 pass.SetPipeline(renderer.GetClipPipeline(options));
143
144 info.mvp = pass.GetOrthographicTransform();
145 VS::BindFrameInfo(pass,
146 renderer.GetTransientsDataBuffer().EmplaceUniform(info));
147
148 return pass.Draw().ok();
149 }
impeller::RenderPipelineHandle::VertexShader
VertexShader_ VertexShader
Definition: pipeline.h:163
impeller::PrimitiveType::kTriangleStrip
@ kTriangleStrip
impeller::GetShaderClipDepth
static Scalar GetShaderClipDepth(uint32_t clip_depth)
Definition: clip_contents.cc:20
impeller::Rect
TRect< Scalar > Rect
Definition: rect.h:788
impeller::CreateVertexBuffer
VertexBuffer CreateVertexBuffer(std::array< VertexType, size > input, HostBuffer &data_host_buffer)
Create an index-less vertex buffer from a fixed size array.
Definition: vertex_buffer_builder.h:24
impeller::BlendMode::kDst
@ kDst
impeller::VS
LinePipeline::VertexShader VS
Definition: line_contents.cc:13
impeller::OptionsFromPass
ContentContextOptions OptionsFromPass(const RenderPass &pass)
Definition: contents.cc:19
impeller::ContentContextOptions::StencilMode::kStencilEvenOddFill
@ kStencilEvenOddFill
impeller::ContentContextOptions::StencilMode::kOverdrawPreventionIncrement
@ kOverdrawPreventionIncrement
impeller::ContentContextOptions::StencilMode::kCoverCompareInverted
@ kCoverCompareInverted
impeller::ContentContextOptions::StencilMode::kStencilNonZeroFill
@ kStencilNonZeroFill
impeller::ContentContextOptions::StencilMode::kCoverCompare
@ kCoverCompare
impeller::GeometryResult::type
PrimitiveType type
Definition: geometry.h:37
impeller::GeometryResult::Mode::kNormal
@ kNormal
The geometry has no overlapping triangles.
impeller::GeometryResult::Mode::kEvenOdd
@ kEvenOdd
impeller::GeometryResult::Mode::kPreventOverdraw
@ kPreventOverdraw
impeller::GeometryResult::Mode::kNonZero
@ kNonZero
impeller::GeometryResult::transform
Matrix transform
Definition: geometry.h:39
impeller::GeometryResult::vertex_buffer
VertexBuffer vertex_buffer
Definition: geometry.h:38
impeller::GeometryResult::mode
Mode mode
Definition: geometry.h:40
impeller::TRect< Scalar >::MakeSize
constexpr static TRect MakeSize(const TSize< U > &size)
Definition: rect.h:150
points
std::vector< Point > points
Definition: tessellator_libtess.cc:76

References impeller::CreateVertexBuffer(), impeller::RenderPass::Draw(), impeller::HostBuffer::EmplaceUniform(), impeller::ContentContext::GetClipPipeline(), impeller::RenderPass::GetOrthographicTransform(), impeller::TRect< T >::GetPoints(), impeller::RenderPass::GetRenderTargetSize(), impeller::GetShaderClipDepth(), impeller::ContentContext::GetTransientsDataBuffer(), impeller::ContentContextOptions::kCoverCompare, impeller::ContentContextOptions::kCoverCompareInverted, impeller::Entity::kDifference, impeller::kDst, 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::GeometryResult::mode, impeller::OptionsFromPass(), points, impeller::RenderPass::SetCommandLabel(), impeller::RenderPass::SetPipeline(), impeller::RenderPass::SetStencilReference(), impeller::RenderPass::SetVertexBuffer(), impeller::GeometryResult::transform, impeller::GeometryResult::type, and impeller::GeometryResult::vertex_buffer.

Referenced by impeller::Canvas::ClipGeometry().

## ◆ SetClipOperation()

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

Definition at line 41 of file clip_contents.cc.

41 {
42 clip_op_ = clip_op;
43 }

Referenced by impeller::Canvas::ClipGeometry().

## ◆ SetGeometry()

void impeller::ClipContents::SetGeometry | ( | GeometryResult | geometry | ) |

Set the pre-tessellated clip geometry.

Definition at line 37 of file clip_contents.cc.

37 {
38 clip_geometry_ = std::move(clip_geometry);
39 }

Referenced by impeller::Canvas::ClipGeometry().

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

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