flutter::TransformLayer Class Reference

#include <transform_layer.h>

Inheritance diagram for flutter::TransformLayer:

Public Member Functions
	TransformLayer (const SkMatrix &transform)
	TransformLayer (const SkM44 &transform)
void	Diff (DiffContext *context, const Layer *old_layer) override
void	Preroll (PrerollContext *context) override
void	Paint (PaintContext &context) const override
Public Member Functions inherited from flutter::ContainerLayer
	ContainerLayer ()
void	PreservePaintRegion (DiffContext *context) override
virtual void	Add (std::shared_ptr< Layer > layer)
const std::vector< std::shared_ptr< Layer > > &	layers () const
virtual void	DiffChildren (DiffContext *context, const ContainerLayer *old_layer)
void	PaintChildren (PaintContext &context) const override
const ContainerLayer *	as_container_layer () const override
const SkRect &	child_paint_bounds () const
void	set_child_paint_bounds (const SkRect &bounds)
int	children_renderable_state_flags () const
void	set_children_renderable_state_flags (int flags)
Public Member Functions inherited from flutter::Layer
	Layer ()
virtual	~Layer ()
void	AssignOldLayer (Layer *old_layer)
virtual bool	IsReplacing (DiffContext *context, const Layer *old_layer) const
bool	subtree_has_platform_view () const
void	set_subtree_has_platform_view (bool value)
const SkRect &	paint_bounds () const
void	set_paint_bounds (const SkRect &paint_bounds)
bool	is_empty () const
bool	needs_painting (PaintContext &context) const
uint64_t	original_layer_id () const
uint64_t	unique_id () const
virtual RasterCacheKeyID	caching_key_id () const
virtual const DisplayListLayer *	as_display_list_layer () const
virtual const TextureLayer *	as_texture_layer () const
virtual const PerformanceOverlayLayer *	as_performance_overlay_layer () const
virtual const testing::MockLayer *	as_mock_layer () const

Additional Inherited Members
Static Public Attributes inherited from flutter::Layer
static constexpr int	kSaveLayerRenderFlags
static constexpr int	kRasterCacheRenderFlags
Protected Member Functions inherited from flutter::ContainerLayer
void	PrerollChildren (PrerollContext *context, SkRect *child_paint_bounds)

Detailed Description

Definition at line 14 of file transform_layer.h.

Constructor & Destructor Documentation

TransformLayer() [1/2]

flutter::TransformLayer::TransformLayer ( const SkMatrix &  transform )

inlineexplicit

Definition at line 16 of file transform_layer.h.

      : TransformLayer(SkM44(transform)) {}

TransformLayer() [2/2]

flutter::TransformLayer::TransformLayer ( const SkM44 &  transform )

explicit

Definition at line 11 of file transform_layer.cc.

                                                     : transform_(transform) {
  // Checks (in some degree) that SkM44 transform_ is valid and initialized.
  //
  // If transform_ is uninitialized, this assert may look flaky as it doesn't
  // fail all the time, and some rerun may make it pass. But don't ignore it and
  // just rerun the test if this is triggered, since even a flaky failure here
  // may signify a potentially big problem in the code.
  //
  // We have to write this flaky test because there is no reliable way to test
  // whether a variable is initialized or not in C++.
  FML_DCHECK(transform_.isFinite());
  if (!transform_.isFinite()) {
    FML_LOG(ERROR) << "TransformLayer is constructed with an invalid matrix.";
    transform_.setIdentity();
  }
}

Member Function Documentation

Diff()

void flutter::TransformLayer::Diff ( DiffContext *  context, const Layer *  old_layer  )

overridevirtual

Reimplemented from flutter::ContainerLayer.

Definition at line 28 of file transform_layer.cc.

                                                                      {
  DiffContext::AutoSubtreeRestore subtree(context);
  auto* prev = static_cast<const TransformLayer*>(old_layer);
  if (!context->IsSubtreeDirty()) {
    FML_DCHECK(prev);
    if (transform_ != prev->transform_) {
      context->MarkSubtreeDirty(context->GetOldLayerPaintRegion(old_layer));
    }
  }
  context->PushTransform(transform_);
  DiffChildren(context, prev);
  context->SetLayerPaintRegion(this, context->CurrentSubtreeRegion());
}

Paint()

void flutter::TransformLayer::Paint ( PaintContext &  context ) const

overridevirtual

Reimplemented from flutter::ContainerLayer.

Definition at line 68 of file transform_layer.cc.

                                                      {
  FML_DCHECK(needs_painting(context));
 
  auto mutator = context.state_stack.save();
  mutator.transform(transform_);
 
  PaintChildren(context);
}

Preroll()

void flutter::TransformLayer::Preroll ( PrerollContext *  context )

overridevirtual

Reimplemented from flutter::ContainerLayer.

Definition at line 42 of file transform_layer.cc.

                                                    {
  auto mutator = context->state_stack.save();
  mutator.transform(transform_);
 
  SkRect child_paint_bounds = SkRect::MakeEmpty();
  PrerollChildren(context, &child_paint_bounds);
 
  // We convert to a 3x3 matrix here primarily because the SkM44 object
  // does not support a mapRect operation.
  // https://bugs.chromium.org/p/skia/issues/detail?id=11720&q=mapRect&can=2
  //
  // All geometry is X,Y only which means the 3rd row of the 4x4 matrix
  // is ignored and the output of the 3rd column is also ignored.
  // So we can transform the rectangle using just the 3x3 SkMatrix
  // equivalent without any loss of information.
  //
  // Performance consideration:
  // Skia has an internal mapRect for their SkM44 object that is faster
  // than what SkMatrix does when it has perspective elements. But SkMatrix
  // is otherwise optimal for non-perspective matrices. If SkM44 ever exposes
  // a mapRect operation, or if SkMatrix ever optimizes its handling of
  // the perspective elements, this issue will become moot.
  transform_.asM33().mapRect(&child_paint_bounds);
  set_paint_bounds(child_paint_bounds);
}

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

• flow/layers/transform_layer.h
• flow/layers/transform_layer.cc