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// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "flutter/flow/layers/opacity_layer.h"
#include "flutter/flow/layers/cacheable_layer.h"
#include "third_party/skia/include/core/SkPaint.h"
namespace flutter {
// the opacity_layer couldn't cache itself, so the cache_threshold is the
// max_int
OpacityLayer::OpacityLayer(SkAlpha alpha, const SkPoint& offset)
: CacheableContainerLayer(std::numeric_limits<int>::max(), true),
alpha_(alpha),
offset_(offset),
children_can_accept_opacity_(false) {}
void OpacityLayer::Diff(DiffContext* context, const Layer* old_layer) {
DiffContext::AutoSubtreeRestore subtree(context);
auto* prev = static_cast<const OpacityLayer*>(old_layer);
if (!context->IsSubtreeDirty()) {
FML_DCHECK(prev);
if (alpha_ != prev->alpha_ || offset_ != prev->offset_) {
context->MarkSubtreeDirty(context->GetOldLayerPaintRegion(old_layer));
}
}
context->PushTransform(SkMatrix::Translate(offset_.fX, offset_.fY));
DiffChildren(context, prev);
context->SetLayerPaintRegion(this, context->CurrentSubtreeRegion());
}
void OpacityLayer::Preroll(PrerollContext* context, const SkMatrix& matrix) {
TRACE_EVENT0("flutter", "OpacityLayer::Preroll");
FML_DCHECK(!layers().empty()); // We can't be a leaf.
SkMatrix child_matrix = matrix;
child_matrix.preTranslate(offset_.fX, offset_.fY);
// Similar to what's done in TransformLayer::Preroll, we have to apply the
// reverse transformation to the cull rect to properly cull child layers.
context->cull_rect = context->cull_rect.makeOffset(-offset_.fX, -offset_.fY);
context->mutators_stack.PushTransform(
SkMatrix::Translate(offset_.fX, offset_.fY));
context->mutators_stack.PushOpacity(alpha_);
AutoCache auto_cache =
AutoCache(layer_raster_cache_item_.get(), context, matrix);
Layer::AutoPrerollSaveLayerState save =
Layer::AutoPrerollSaveLayerState::Create(context);
// Collect inheritance information on our children in Preroll so that
// we can decide whether or not to use a saveLayer in Paint.
context->subtree_can_inherit_opacity = true;
// ContainerLayer will turn the flag off if any children are
// incompatible or if they overlap
ContainerLayer::Preroll(context, child_matrix);
// We store the inheritance ability of our children for |Paint|
set_children_can_accept_opacity(context->subtree_can_inherit_opacity);
// Now we let our parent layers know that we, too, can inherit opacity
// regardless of what our children are capable of
context->subtree_can_inherit_opacity = true;
context->mutators_stack.Pop();
context->mutators_stack.Pop();
set_paint_bounds(paint_bounds().makeOffset(offset_.fX, offset_.fY));
if (children_can_accept_opacity()) {
// For opacity layer, we can use raster_cache children only when the
// children can't accept opacity so if the children_can_accept_opacity we
// should tell the AutoCache object don't do raster_cache.
auto_cache.ShouldNotBeCached();
}
// Restore cull_rect
context->cull_rect = context->cull_rect.makeOffset(offset_.fX, offset_.fY);
}
void OpacityLayer::Paint(PaintContext& context) const {
TRACE_EVENT0("flutter", "OpacityLayer::Paint");
FML_DCHECK(needs_painting(context));
SkAutoCanvasRestore save(context.internal_nodes_canvas, true);
context.internal_nodes_canvas->translate(offset_.fX, offset_.fY);
SkScalar inherited_opacity = context.inherited_opacity;
SkScalar subtree_opacity = opacity() * inherited_opacity;
if (children_can_accept_opacity()) {
context.inherited_opacity = subtree_opacity;
PaintChildren(context);
context.inherited_opacity = inherited_opacity;
return;
}
SkPaint paint;
paint.setAlphaf(subtree_opacity);
if (layer_raster_cache_item_->Draw(context, &paint)) {
return;
}
// Skia may clip the content with saveLayerBounds (although it's not a
// guaranteed clip). So we have to provide a big enough saveLayerBounds. To do
// so, we first remove the offset from paint bounds since it's already in the
// matrix. Then we round out the bounds.
//
// Note that the following lines are only accessible when the raster cache is
// not available (e.g., when we're using the software backend in golden
// tests).
SkRect saveLayerBounds;
paint_bounds()
.makeOffset(-offset_.fX, -offset_.fY)
.roundOut(&saveLayerBounds);
Layer::AutoSaveLayer save_layer =
Layer::AutoSaveLayer::Create(context, saveLayerBounds, &paint);
context.inherited_opacity = SK_Scalar1;
PaintChildren(context);
context.inherited_opacity = inherited_opacity;
}
} // namespace flutter