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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/container_layer.h"
#include <optional>
namespace flutter {
ContainerLayer::ContainerLayer() : child_paint_bounds_(SkRect::MakeEmpty()) {}
void ContainerLayer::Diff(DiffContext* context, const Layer* old_layer) {
auto old_container = static_cast<const ContainerLayer*>(old_layer);
DiffContext::AutoSubtreeRestore subtree(context);
DiffChildren(context, old_container);
context->SetLayerPaintRegion(this, context->CurrentSubtreeRegion());
}
void ContainerLayer::PreservePaintRegion(DiffContext* context) {
Layer::PreservePaintRegion(context);
for (auto& layer : layers_) {
layer->PreservePaintRegion(context);
}
}
void ContainerLayer::DiffChildren(DiffContext* context,
const ContainerLayer* old_layer) {
if (context->IsSubtreeDirty()) {
for (auto& layer : layers_) {
layer->Diff(context, nullptr);
}
return;
}
FML_DCHECK(old_layer);
const auto& prev_layers = old_layer->layers_;
// first mismatched element
int new_children_top = 0;
int old_children_top = 0;
// last mismatched element
int new_children_bottom = layers_.size() - 1;
int old_children_bottom = prev_layers.size() - 1;
while ((old_children_top <= old_children_bottom) &&
(new_children_top <= new_children_bottom)) {
if (!layers_[new_children_top]->IsReplacing(
context, prev_layers[old_children_top].get())) {
break;
}
++new_children_top;
++old_children_top;
}
while ((old_children_top <= old_children_bottom) &&
(new_children_top <= new_children_bottom)) {
if (!layers_[new_children_bottom]->IsReplacing(
context, prev_layers[old_children_bottom].get())) {
break;
}
--new_children_bottom;
--old_children_bottom;
}
// old layers that don't match
for (int i = old_children_top; i <= old_children_bottom; ++i) {
auto layer = prev_layers[i];
context->AddDamage(context->GetOldLayerPaintRegion(layer.get()));
}
for (int i = 0; i < static_cast<int>(layers_.size()); ++i) {
if (i < new_children_top || i > new_children_bottom) {
int i_prev =
i < new_children_top ? i : prev_layers.size() - (layers_.size() - i);
auto layer = layers_[i];
auto prev_layer = prev_layers[i_prev];
auto paint_region = context->GetOldLayerPaintRegion(prev_layer.get());
if (layer == prev_layer && !paint_region.has_readback() &&
!paint_region.has_texture()) {
// for retained layers, stop processing the subtree and add existing
// region; We know current subtree is not dirty (every ancestor up to
// here matches) so the retained subtree will render identically to
// previous frame; We can only do this if there is no readback in the
// subtree. Layers that do readback must be able to register readback
// inside Diff
context->AddExistingPaintRegion(paint_region);
// While we don't need to diff retained layers, we still need to
// associate their paint region with current layer tree so that we can
// retrieve it in next frame diff
layer->PreservePaintRegion(context);
} else {
layer->Diff(context, prev_layer.get());
}
} else {
DiffContext::AutoSubtreeRestore subtree(context);
context->MarkSubtreeDirty();
auto layer = layers_[i];
layer->Diff(context, nullptr);
}
}
}
void ContainerLayer::Add(std::shared_ptr<Layer> layer) {
layers_.emplace_back(std::move(layer));
}
void ContainerLayer::Preroll(PrerollContext* context) {
SkRect child_paint_bounds = SkRect::MakeEmpty();
PrerollChildren(context, &child_paint_bounds);
set_paint_bounds(child_paint_bounds);
}
void ContainerLayer::Paint(PaintContext& context) const {
FML_DCHECK(needs_painting(context));
PaintChildren(context);
}
static bool safe_intersection_test(const SkRect* rect1, const SkRect& rect2) {
if (rect1->isEmpty() || rect2.isEmpty()) {
return false;
}
return rect1->intersects(rect2);
}
void ContainerLayer::PrerollChildren(PrerollContext* context,
SkRect* child_paint_bounds) {
// Platform views have no children, so context->has_platform_view should
// always be false.
FML_DCHECK(!context->has_platform_view);
FML_DCHECK(!context->has_texture_layer);
bool child_has_platform_view = false;
bool child_has_texture_layer = false;
bool all_renderable_state_flags = LayerStateStack::kCallerCanApplyAnything;
for (auto& layer : layers_) {
// Reset context->has_platform_view and context->has_texture_layer to false
// so that layers aren't treated as if they have a platform view or texture
// layer based on one being previously found in a sibling tree.
context->has_platform_view = false;
context->has_texture_layer = false;
// Initialize the renderable state flags to false to force the layer to
// opt-in to applying state attributes during its |Preroll|
context->renderable_state_flags = 0;
layer->Preroll(context);
all_renderable_state_flags &= context->renderable_state_flags;
if (safe_intersection_test(child_paint_bounds, layer->paint_bounds())) {
// This will allow inheritance by a linear sequence of non-overlapping
// children, but will fail with a grid or other arbitrary 2D layout.
// See https://github.com/flutter/flutter/issues/93899
all_renderable_state_flags = 0;
}
child_paint_bounds->join(layer->paint_bounds());
child_has_platform_view =
child_has_platform_view || context->has_platform_view;
child_has_texture_layer =
child_has_texture_layer || context->has_texture_layer;
}
context->has_platform_view = child_has_platform_view;
context->has_texture_layer = child_has_texture_layer;
context->renderable_state_flags = all_renderable_state_flags;
set_subtree_has_platform_view(child_has_platform_view);
set_children_renderable_state_flags(all_renderable_state_flags);
set_child_paint_bounds(*child_paint_bounds);
}
void ContainerLayer::PaintChildren(PaintContext& context) const {
// We can no longer call FML_DCHECK here on the needs_painting(context)
// condition as that test is only valid for the PaintContext that
// is initially handed to a layer's Paint() method. By the time the
// layer calls PaintChildren(), though, it may have modified the
// PaintContext so the test doesn't work in this "context".
// Apply any outstanding state that the children cannot individually
// and collectively handle.
auto restore = context.state_stack.applyState(
child_paint_bounds(), children_renderable_state_flags());
// Intentionally not tracing here as there should be no self-time
// and the trace event on this common function has a small overhead.
for (auto& layer : layers_) {
if (layer->needs_painting(context)) {
layer->Paint(context);
}
}
}
} // namespace flutter