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d117ac979c
* Remove erroneous ChildView opacity * Wire frame metrics through contexts * Maintain layer stack inside of SceneBuilder * Remove EnsureSingleChild * Centralize system-composite and elevation logic * Wire up OpacityLayer to Scenic
50 lines
1.8 KiB
C++
50 lines
1.8 KiB
C++
// Copyright 2013 The Flutter Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "flutter/flow/layers/elevated_container_layer.h"
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namespace flutter {
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namespace {
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float ClampElevation(float elevation,
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float parent_elevation,
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float max_elevation) {
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// TODO(mklim): Deal with bounds overflow more elegantly. We'd like to be
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// able to have developers specify the behavior here to alternatives besides
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// clamping, like normalization on some arbitrary curve.
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float clamped_elevation = elevation;
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if (max_elevation > -1 && (parent_elevation + elevation) > max_elevation) {
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// Clamp the local z coordinate at our max bound. Take into account the
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// parent z position here to fix clamping in cases where the child is
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// overflowing because of its parents.
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clamped_elevation = max_elevation - parent_elevation;
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}
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return clamped_elevation;
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}
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} // namespace
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ElevatedContainerLayer::ElevatedContainerLayer(float elevation)
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: elevation_(elevation), clamped_elevation_(elevation) {}
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void ElevatedContainerLayer::Preroll(PrerollContext* context,
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const SkMatrix& matrix) {
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TRACE_EVENT0("flutter", "ElevatedContainerLayer::Preroll");
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// Track total elevation as we walk the tree, in order to deal with bounds
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// overflow in z.
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parent_elevation_ = context->total_elevation;
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clamped_elevation_ = ClampElevation(elevation_, parent_elevation_,
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context->frame_physical_depth);
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context->total_elevation += clamped_elevation_;
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ContainerLayer::Preroll(context, matrix);
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// Restore the elevation for our parent.
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context->total_elevation = parent_elevation_;
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}
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} // namespace flutter
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