blob: 9a9650f520c0471828168bd4ef90810c180a66e1 [file] [log] [blame]
// Copyright 2011 The Chromium 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 "cc/trees/layer_tree_host_common.h"
#include <algorithm>
#include "base/debug/trace_event.h"
#include "cc/base/math_util.h"
#include "cc/layers/heads_up_display_layer_impl.h"
#include "cc/layers/layer.h"
#include "cc/layers/layer_impl.h"
#include "cc/layers/layer_iterator.h"
#include "cc/layers/render_surface.h"
#include "cc/layers/render_surface_impl.h"
#include "cc/trees/layer_sorter.h"
#include "cc/trees/layer_tree_impl.h"
#include "ui/gfx/geometry/rect_conversions.h"
#include "ui/gfx/geometry/vector2d_conversions.h"
#include "ui/gfx/transform.h"
namespace cc {
: page_scale_delta(1.f), top_controls_delta(0.f) {
ScrollAndScaleSet::~ScrollAndScaleSet() {}
static void SortLayers(LayerList::iterator forst,
LayerList::iterator end,
void* layer_sorter) {
static void SortLayers(LayerImplList::iterator first,
LayerImplList::iterator end,
LayerSorter* layer_sorter) {
TRACE_EVENT0("cc", "LayerTreeHostCommon::SortLayers");
layer_sorter->Sort(first, end);
template <typename LayerType>
static gfx::Vector2dF GetEffectiveScrollDelta(LayerType* layer) {
gfx::Vector2dF scroll_delta = layer->ScrollDelta();
// The scroll parent's scroll delta is the amount we've scrolled on the
// compositor thread since the commit for this layer tree's source frame.
// we last reported to the main thread. I.e., it's the discrepancy between
// a scroll parent's scroll delta and offset, so we must add it here.
if (layer->scroll_parent())
scroll_delta += layer->scroll_parent()->ScrollDelta();
return scroll_delta;
template <typename LayerType>
static gfx::ScrollOffset GetEffectiveTotalScrollOffset(LayerType* layer) {
gfx::ScrollOffset offset = layer->TotalScrollOffset();
// The scroll parent's total scroll offset (scroll offset + scroll delta)
// can't be used because its scroll offset has already been applied to the
// scroll children's positions by the main thread layer positioning code.
if (layer->scroll_parent())
offset += gfx::ScrollOffset(layer->scroll_parent()->ScrollDelta());
return offset;
inline gfx::Rect CalculateVisibleRectWithCachedLayerRect(
const gfx::Rect& target_surface_rect,
const gfx::Rect& layer_bound_rect,
const gfx::Rect& layer_rect_in_target_space,
const gfx::Transform& transform) {
if (layer_rect_in_target_space.IsEmpty())
return gfx::Rect();
// Is this layer fully contained within the target surface?
if (target_surface_rect.Contains(layer_rect_in_target_space))
return layer_bound_rect;
// If the layer doesn't fill up the entire surface, then find the part of
// the surface rect where the layer could be visible. This avoids trying to
// project surface rect points that are behind the projection point.
gfx::Rect minimal_surface_rect = target_surface_rect;
if (minimal_surface_rect.IsEmpty())
return gfx::Rect();
// Project the corners of the target surface rect into the layer space.
// This bounding rectangle may be larger than it needs to be (being
// axis-aligned), but is a reasonable filter on the space to consider.
// Non-invertible transforms will create an empty rect here.
gfx::Transform surface_to_layer(gfx::Transform::kSkipInitialization);
if (!transform.GetInverse(&surface_to_layer)) {
// Because we cannot use the surface bounds to determine what portion of
// the layer is visible, we must conservatively assume the full layer is
// visible.
return layer_bound_rect;
gfx::Rect layer_rect = MathUtil::ProjectEnclosingClippedRect(
surface_to_layer, minimal_surface_rect);
return layer_rect;
gfx::Rect LayerTreeHostCommon::CalculateVisibleRect(
const gfx::Rect& target_surface_rect,
const gfx::Rect& layer_bound_rect,
const gfx::Transform& transform) {
gfx::Rect layer_in_surface_space =
MathUtil::MapEnclosingClippedRect(transform, layer_bound_rect);
return CalculateVisibleRectWithCachedLayerRect(
target_surface_rect, layer_bound_rect, layer_in_surface_space, transform);
template <typename LayerType>
static LayerType* NextTargetSurface(LayerType* layer) {
return layer->parent() ? layer->parent()->render_target() : 0;
// Given two layers, this function finds their respective render targets and,
// computes a change of basis translation. It does this by accumulating the
// translation components of the draw transforms of each target between the
// ancestor and descendant. These transforms must be 2D translations, and this
// requirement is enforced at every step.
template <typename LayerType>
static gfx::Vector2dF ComputeChangeOfBasisTranslation(
const LayerType& ancestor_layer,
const LayerType& descendant_layer) {
const LayerType* descendant_target = descendant_layer.render_target();
const LayerType* ancestor_target = ancestor_layer.render_target();
gfx::Vector2dF translation;
for (const LayerType* target = descendant_target; target != ancestor_target;
target = NextTargetSurface(target)) {
const gfx::Transform& trans = target->render_surface()->draw_transform();
// Ensure that this translation is truly 2d.
DCHECK_EQ(0.f, trans.matrix().get(2, 3));
translation += trans.To2dTranslation();
return translation;
enum TranslateRectDirection {
template <typename LayerType>
static gfx::Rect TranslateRectToTargetSpace(const LayerType& ancestor_layer,
const LayerType& descendant_layer,
const gfx::Rect& rect,
TranslateRectDirection direction) {
gfx::Vector2dF translation = ComputeChangeOfBasisTranslation<LayerType>(
ancestor_layer, descendant_layer);
if (direction == TranslateRectDirectionToDescendant)
return gfx::ToEnclosingRect(
gfx::RectF(rect.origin() + translation, rect.size()));
// Attempts to update the clip rects for the given layer. If the layer has a
// clip_parent, it may not inherit its immediate ancestor's clip.
template <typename LayerType>
static void UpdateClipRectsForClipChild(
const LayerType* layer,
gfx::Rect* clip_rect_in_parent_target_space,
bool* subtree_should_be_clipped) {
// If the layer has no clip_parent, or the ancestor is the same as its actual
// parent, then we don't need special clip rects. Bail now and leave the out
// parameters untouched.
const LayerType* clip_parent = layer->scroll_parent();
if (!clip_parent)
clip_parent = layer->clip_parent();
if (!clip_parent || clip_parent == layer->parent())
// The root layer is never a clip child.
// Grab the cached values.
*clip_rect_in_parent_target_space = clip_parent->clip_rect();
*subtree_should_be_clipped = clip_parent->is_clipped();
// We may have to project the clip rect into our parent's target space. Note,
// it must be our parent's target space, not ours. For one, we haven't
// computed our transforms, so we couldn't put it in our space yet even if we
// wanted to. But more importantly, this matches the expectations of
// CalculateDrawPropertiesInternal. If we, say, create a render surface, these
// clip rects will want to be in its target space, not ours.
if (clip_parent == layer->clip_parent()) {
*clip_rect_in_parent_target_space = TranslateRectToTargetSpace<LayerType>(
} else {
// If we're being clipped by our scroll parent, we must translate through
// our common ancestor. This happens to be our parent, so it is sufficent to
// translate from our clip parent's space to the space of its ancestor (our
// parent).
*clip_rect_in_parent_target_space =
// We collect an accumulated drawable content rect per render surface.
// Typically, a layer will contribute to only one surface, the surface
// associated with its render target. Clip children, however, may affect
// several surfaces since there may be several surfaces between the clip child
// and its parent.
// NB: we accumulate the layer's *clipped* drawable content rect.
template <typename LayerType>
struct AccumulatedSurfaceState {
explicit AccumulatedSurfaceState(LayerType* render_target)
: render_target(render_target) {}
// The accumulated drawable content rect for the surface associated with the
// given |render_target|.
gfx::Rect drawable_content_rect;
// The target owning the surface. (We hang onto the target rather than the
// surface so that we can DCHECK that the surface's draw transform is simply
// a translation when |render_target| reports that it has no unclipped
// descendants).
LayerType* render_target;
template <typename LayerType>
void UpdateAccumulatedSurfaceState(
LayerType* layer,
const gfx::Rect& drawable_content_rect,
accumulated_surface_state) {
if (IsRootLayer(layer))
// We will apply our drawable content rect to the accumulated rects for all
// surfaces between us and |render_target| (inclusive). This is either our
// clip parent's target if we are a clip child, or else simply our parent's
// target. We use our parent's target because we're either the owner of a
// render surface and we'll want to add our rect to our *surface's* target, or
// we're not and our target is the same as our parent's. In both cases, the
// parent's target gives us what we want.
LayerType* render_target = layer->clip_parent()
? layer->clip_parent()->render_target()
: layer->parent()->render_target();
// If the layer owns a surface, then the content rect is in the wrong space.
// Instead, we will use the surface's DrawableContentRect which is in target
// space as required.
gfx::Rect target_rect = drawable_content_rect;
if (layer->render_surface()) {
target_rect =
if (render_target->is_clipped()) {
gfx::Rect clip_rect = render_target->clip_rect();
// If the layer has a clip parent, the clip rect may be in the wrong space,
// so we'll need to transform it before it is applied.
if (layer->clip_parent()) {
clip_rect = TranslateRectToTargetSpace<LayerType>(
// We must have at least one entry in the vector for the root.
DCHECK_LT(0ul, accumulated_surface_state->size());
typedef typename std::vector<AccumulatedSurfaceState<LayerType>>
typedef typename AccumulatedSurfaceStateVector::reverse_iterator
AccumulatedSurfaceStateIterator current_state =
// Add this rect to the accumulated content rect for all surfaces until we
// reach the target surface.
bool found_render_target = false;
for (; current_state != accumulated_surface_state->rend(); ++current_state) {
// If we've reached |render_target| our work is done and we can bail.
if (current_state->render_target == render_target) {
found_render_target = true;
// Transform rect from the current target's space to the next.
LayerType* current_target = current_state->render_target;
const gfx::Transform& current_draw_transform =
// If we have unclipped descendants, the draw transform is a translation.
DCHECK(current_target->num_unclipped_descendants() == 0 ||
target_rect = gfx::ToEnclosingRect(
MathUtil::MapClippedRect(current_draw_transform, target_rect));
// It is an error to not reach |render_target|. If this happens, it means that
// either the clip parent is not an ancestor of the clip child or the surface
// state vector is empty, both of which should be impossible.
template <typename LayerType> static inline bool IsRootLayer(LayerType* layer) {
return !layer->parent();
template <typename LayerType>
static inline bool LayerIsInExisting3DRenderingContext(LayerType* layer) {
return layer->Is3dSorted() && layer->parent() &&
template <typename LayerType>
static bool IsRootLayerOfNewRenderingContext(LayerType* layer) {
if (layer->parent())
return !layer->parent()->Is3dSorted() && layer->Is3dSorted();
return layer->Is3dSorted();
template <typename LayerType>
static bool IsLayerBackFaceVisible(LayerType* layer) {
// The current W3C spec on CSS transforms says that backface visibility should
// be determined differently depending on whether the layer is in a "3d
// rendering context" or not. For Chromium code, we can determine whether we
// are in a 3d rendering context by checking if the parent preserves 3d.
if (LayerIsInExisting3DRenderingContext(layer))
return layer->draw_transform().IsBackFaceVisible();
// In this case, either the layer establishes a new 3d rendering context, or
// is not in a 3d rendering context at all.
return layer->transform().IsBackFaceVisible();
template <typename LayerType>
static bool IsSurfaceBackFaceVisible(LayerType* layer,
const gfx::Transform& draw_transform) {
if (LayerIsInExisting3DRenderingContext(layer))
return draw_transform.IsBackFaceVisible();
if (IsRootLayerOfNewRenderingContext(layer))
return layer->transform().IsBackFaceVisible();
// If the render_surface is not part of a new or existing rendering context,
// then the layers that contribute to this surface will decide back-face
// visibility for themselves.
return false;
template <typename LayerType>
static inline bool LayerClipsSubtree(LayerType* layer) {
return layer->masks_to_bounds() || layer->mask_layer();
template <typename LayerType>
static gfx::Rect CalculateVisibleContentRect(
LayerType* layer,
const gfx::Rect& clip_rect_of_target_surface_in_target_space,
const gfx::Rect& layer_rect_in_target_space) {
// Nothing is visible if the layer bounds are empty.
if (!layer->DrawsContent() || layer->content_bounds().IsEmpty() ||
return gfx::Rect();
// Compute visible bounds in target surface space.
gfx::Rect visible_rect_in_target_surface_space =
if (layer->render_target()->render_surface()->is_clipped()) {
// The |layer| L has a target T which owns a surface Ts. The surface Ts
// has a target TsT.
// In this case the target surface Ts does clip the layer L that contributes
// to it. So, we have to convert the clip rect of Ts from the target space
// of Ts (that is the space of TsT), to the current render target's space
// (that is the space of T). This conversion is done outside this function
// so that it can be cached instead of computing it redundantly for every
// layer.
if (visible_rect_in_target_surface_space.IsEmpty())
return gfx::Rect();
return CalculateVisibleRectWithCachedLayerRect(
static inline bool TransformToParentIsKnown(LayerImpl* layer) { return true; }
static inline bool TransformToParentIsKnown(Layer* layer) {
return !layer->TransformIsAnimating();
static inline bool TransformToScreenIsKnown(LayerImpl* layer) { return true; }
static inline bool TransformToScreenIsKnown(Layer* layer) {
return !layer->screen_space_transform_is_animating();
template <typename LayerType>
static bool LayerShouldBeSkipped(LayerType* layer, bool layer_is_drawn) {
// Layers can be skipped if any of these conditions are met.
// - is not drawn due to it or one of its ancestors being hidden (or having
// no copy requests).
// - does not draw content.
// - is transparent.
// - has empty bounds
// - the layer is not double-sided, but its back face is visible.
// Some additional conditions need to be computed at a later point after the
// recursion is finished.
// - the intersection of render_surface content and layer clip_rect is empty
// - the visible_content_rect is empty
// Note, if the layer should not have been drawn due to being fully
// transparent, we would have skipped the entire subtree and never made it
// into this function, so it is safe to omit this check here.
if (!layer_is_drawn)
return true;
if (!layer->DrawsContent() || layer->bounds().IsEmpty())
return true;
LayerType* backface_test_layer = layer;
if (layer->use_parent_backface_visibility()) {
backface_test_layer = layer->parent();
// The layer should not be drawn if (1) it is not double-sided and (2) the
// back of the layer is known to be facing the screen.
if (!backface_test_layer->double_sided() &&
TransformToScreenIsKnown(backface_test_layer) &&
return true;
return false;
template <typename LayerType>
static bool HasInvertibleOrAnimatedTransform(LayerType* layer) {
return layer->transform_is_invertible() || layer->TransformIsAnimating();
static inline bool SubtreeShouldBeSkipped(LayerImpl* layer,
bool layer_is_drawn) {
// If the layer transform is not invertible, it should not be drawn.
// TODO(ajuma): Correctly process subtrees with singular transform for the
// case where we may animate to a non-singular transform and wish to
// pre-raster.
if (!HasInvertibleOrAnimatedTransform(layer))
return true;
// When we need to do a readback/copy of a layer's output, we can not skip
// it or any of its ancestors.
if (layer->draw_properties().layer_or_descendant_has_copy_request)
return false;
// We cannot skip the the subtree if a descendant has a wheel or touch handler
// or the hit testing code will break (it requires fresh transforms, etc).
if (layer->draw_properties().layer_or_descendant_has_input_handler)
return false;
// If the layer is not drawn, then skip it and its subtree.
if (!layer_is_drawn)
return true;
// If layer is on the pending tree and opacity is being animated then
// this subtree can't be skipped as we need to create, prioritize and
// include tiles for this layer when deciding if tree can be activated.
if (layer->layer_tree_impl()->IsPendingTree() && layer->OpacityIsAnimating())
return false;
// The opacity of a layer always applies to its children (either implicitly
// via a render surface or explicitly if the parent preserves 3D), so the
// entire subtree can be skipped if this layer is fully transparent.
return !layer->opacity();
static inline bool SubtreeShouldBeSkipped(Layer* layer, bool layer_is_drawn) {
// If the layer transform is not invertible, it should not be drawn.
if (!layer->transform_is_invertible() && !layer->TransformIsAnimating())
return true;
// When we need to do a readback/copy of a layer's output, we can not skip
// it or any of its ancestors.
if (layer->draw_properties().layer_or_descendant_has_copy_request)
return false;
// We cannot skip the the subtree if a descendant has a wheel or touch handler
// or the hit testing code will break (it requires fresh transforms, etc).
if (layer->draw_properties().layer_or_descendant_has_input_handler)
return false;
// If the layer is not drawn, then skip it and its subtree.
if (!layer_is_drawn)
return true;
// If the opacity is being animated then the opacity on the main thread is
// unreliable (since the impl thread may be using a different opacity), so it
// should not be trusted.
// In particular, it should not cause the subtree to be skipped.
// Similarly, for layers that might animate opacity using an impl-only
// animation, their subtree should also not be skipped.
return !layer->opacity() && !layer->OpacityIsAnimating() &&
static inline void SavePaintPropertiesLayer(LayerImpl* layer) {}
static inline void SavePaintPropertiesLayer(Layer* layer) {
if (layer->mask_layer())
if (layer->replica_layer() && layer->replica_layer()->mask_layer())
template <typename LayerType>
static bool SubtreeShouldRenderToSeparateSurface(
LayerType* layer,
bool axis_aligned_with_respect_to_parent) {
// A layer and its descendants should render onto a new RenderSurfaceImpl if
// any of these rules hold:
// The root layer owns a render surface, but it never acts as a contributing
// surface to another render target. Compositor features that are applied via
// a contributing surface can not be applied to the root layer. In order to
// use these effects, another child of the root would need to be introduced
// in order to act as a contributing surface to the root layer's surface.
bool is_root = IsRootLayer(layer);
// If the layer uses a mask.
if (layer->mask_layer()) {
return true;
// If the layer has a reflection.
if (layer->replica_layer()) {
return true;
// If the layer uses a CSS filter.
if (!layer->filters().IsEmpty() || !layer->background_filters().IsEmpty()) {
return true;
int num_descendants_that_draw_content =
// If the layer flattens its subtree, but it is treated as a 3D object by its
// parent (i.e. parent participates in a 3D rendering context).
if (LayerIsInExisting3DRenderingContext(layer) &&
layer->should_flatten_transform() &&
num_descendants_that_draw_content > 0) {
"LayerTreeHostCommon::SubtreeShouldRenderToSeparateSurface flattening",
return true;
// If the layer has blending.
// TODO(rosca): this is temporary, until blending is implemented for other
// types of quads than RenderPassDrawQuad. Layers having descendants that draw
// content will still create a separate rendering surface.
if (!layer->uses_default_blend_mode()) {
"LayerTreeHostCommon::SubtreeShouldRenderToSeparateSurface blending",
return true;
// If the layer clips its descendants but it is not axis-aligned with respect
// to its parent.
bool layer_clips_external_content =
LayerClipsSubtree(layer) || layer->HasDelegatedContent();
if (layer_clips_external_content && !axis_aligned_with_respect_to_parent &&
num_descendants_that_draw_content > 0) {
"LayerTreeHostCommon::SubtreeShouldRenderToSeparateSurface clipping",
return true;
// If the layer has some translucency and does not have a preserves-3d
// transform style. This condition only needs a render surface if two or more
// layers in the subtree overlap. But checking layer overlaps is unnecessarily
// costly so instead we conservatively create a surface whenever at least two
// layers draw content for this subtree.
bool at_least_two_layers_in_subtree_draw_content =
num_descendants_that_draw_content > 0 &&
(layer->DrawsContent() || num_descendants_that_draw_content > 1);
if (layer->opacity() != 1.f && layer->should_flatten_transform() &&
at_least_two_layers_in_subtree_draw_content) {
"LayerTreeHostCommon::SubtreeShouldRenderToSeparateSurface opacity",
return true;
// The root layer should always have a render_surface.
if (is_root)
return true;
// These are allowed on the root surface, as they don't require the surface to
// be used as a contributing surface in order to apply correctly.
// If the layer has isolation.
// TODO(rosca): to be optimized - create separate rendering surface only when
// the blending descendants might have access to the content behind this layer
// (layer has transparent background or descendants overflow).
if (layer->is_root_for_isolated_group()) {
"LayerTreeHostCommon::SubtreeShouldRenderToSeparateSurface isolation",
return true;
// If we force it.
if (layer->force_render_surface())
return true;
// If we'll make a copy of the layer's contents.
if (layer->HasCopyRequest())
return true;
return false;
// This function returns a translation matrix that can be applied on a vector
// that's in the layer's target surface coordinate, while the position offset is
// specified in some ancestor layer's coordinate.
gfx::Transform ComputeSizeDeltaCompensation(
LayerImpl* layer,
LayerImpl* container,
const gfx::Vector2dF& position_offset) {
gfx::Transform result_transform;
// To apply a translate in the container's layer space,
// the following steps need to be done:
// Step 1a. transform from target surface space to the container's target
// surface space
// Step 1b. transform from container's target surface space to the
// container's layer space
// Step 2. apply the compensation
// Step 3. transform back to target surface space
gfx::Transform target_surface_space_to_container_layer_space;
// Calculate step 1a
LayerImpl* container_target_surface = container->render_target();
for (LayerImpl* current_target_surface = NextTargetSurface(layer);
current_target_surface &&
current_target_surface != container_target_surface;
current_target_surface = NextTargetSurface(current_target_surface)) {
// Note: Concat is used here to convert the result coordinate space from
// current render surface to the next render surface.
// Calculate step 1b
gfx::Transform container_layer_space_to_container_target_surface_space =
container->contents_scale_x(), container->contents_scale_y());
gfx::Transform container_target_surface_space_to_container_layer_space;
if (container_layer_space_to_container_target_surface_space.GetInverse(
&container_target_surface_space_to_container_layer_space)) {
// Note: Again, Concat is used to conver the result coordinate space from
// the container render surface to the container layer.
// Apply step 3
gfx::Transform container_layer_space_to_target_surface_space;
if (target_surface_space_to_container_layer_space.GetInverse(
&container_layer_space_to_target_surface_space)) {
} else {
// TODO(shawnsingh): A non-invertible matrix could still make meaningful
// projection. For example ScaleZ(0) is non-invertible but the layer is
// still visible.
return gfx::Transform();
// Apply step 2
result_transform.Translate(position_offset.x(), position_offset.y());
// Apply step 1
return result_transform;
void ApplyPositionAdjustment(
Layer* layer,
Layer* container,
const gfx::Transform& scroll_compensation,
gfx::Transform* combined_transform) {}
void ApplyPositionAdjustment(
LayerImpl* layer,
LayerImpl* container,
const gfx::Transform& scroll_compensation,
gfx::Transform* combined_transform) {
if (!layer->position_constraint().is_fixed_position())
// Special case: this layer is a composited fixed-position layer; we need to
// explicitly compensate for all ancestors' nonzero scroll_deltas to keep
// this layer fixed correctly.
// Note carefully: this is Concat, not Preconcat
// (current_scroll_compensation * combined_transform).
// For right-edge or bottom-edge anchored fixed position layers,
// the layer should relocate itself if the container changes its size.
bool fixed_to_right_edge =
bool fixed_to_bottom_edge =
gfx::Vector2dF position_offset = container->FixedContainerSizeDelta();
position_offset.set_x(fixed_to_right_edge ? position_offset.x() : 0);
position_offset.set_y(fixed_to_bottom_edge ? position_offset.y() : 0);
if (position_offset.IsZero())
// Note: Again, this is Concat. The compensation matrix will be applied on
// the vector in target surface space.
ComputeSizeDeltaCompensation(layer, container, position_offset));
gfx::Transform ComputeScrollCompensationForThisLayer(
LayerImpl* scrolling_layer,
const gfx::Transform& parent_matrix,
const gfx::Vector2dF& scroll_delta) {
// For every layer that has non-zero scroll_delta, we have to compute a
// transform that can undo the scroll_delta translation. In particular, we
// want this matrix to premultiply a fixed-position layer's parent_matrix, so
// we design this transform in three steps as follows. The steps described
// here apply from right-to-left, so Step 1 would be the right-most matrix:
// Step 1. transform from target surface space to the exact space where
// scroll_delta is actually applied.
// -- this is inverse of parent_matrix
// Step 2. undo the scroll_delta
// -- this is just a translation by scroll_delta.
// Step 3. transform back to target surface space.
// -- this transform is the parent_matrix
// These steps create a matrix that both start and end in target surface
// space. So this matrix can pre-multiply any fixed-position layer's
// draw_transform to undo the scroll_deltas -- as long as that fixed position
// layer is fixed onto the same render_target as this scrolling_layer.
gfx::Transform scroll_compensation_for_this_layer = parent_matrix; // Step 3
scroll_delta.y()); // Step 2
gfx::Transform inverse_parent_matrix(gfx::Transform::kSkipInitialization);
if (!parent_matrix.GetInverse(&inverse_parent_matrix)) {
// TODO(shawnsingh): Either we need to handle uninvertible transforms
// here, or DCHECK that the transform is invertible.
inverse_parent_matrix); // Step 1
return scroll_compensation_for_this_layer;
gfx::Transform ComputeScrollCompensationMatrixForChildren(
Layer* current_layer,
const gfx::Transform& current_parent_matrix,
const gfx::Transform& current_scroll_compensation,
const gfx::Vector2dF& scroll_delta) {
// The main thread (i.e. Layer) does not need to worry about scroll
// compensation. So we can just return an identity matrix here.
return gfx::Transform();
gfx::Transform ComputeScrollCompensationMatrixForChildren(
LayerImpl* layer,
const gfx::Transform& parent_matrix,
const gfx::Transform& current_scroll_compensation_matrix,
const gfx::Vector2dF& scroll_delta) {
// "Total scroll compensation" is the transform needed to cancel out all
// scroll_delta translations that occurred since the nearest container layer,
// even if there are render_surfaces in-between.
// There are some edge cases to be aware of, that are not explicit in the
// code:
// - A layer that is both a fixed-position and container should not be its
// own container, instead, that means it is fixed to an ancestor, and is a
// container for any fixed-position descendants.
// - A layer that is a fixed-position container and has a render_surface
// should behave the same as a container without a render_surface, the
// render_surface is irrelevant in that case.
// - A layer that does not have an explicit container is simply fixed to the
// viewport. (i.e. the root render_surface.)
// - If the fixed-position layer has its own render_surface, then the
// render_surface is the one who gets fixed.
// This function needs to be called AFTER layers create their own
// render_surfaces.
// Scroll compensation restarts from identity under two possible conditions:
// - the current layer is a container for fixed-position descendants
// - the current layer is fixed-position itself, so any fixed-position
// descendants are positioned with respect to this layer. Thus, any
// fixed position descendants only need to compensate for scrollDeltas
// that occur below this layer.
bool current_layer_resets_scroll_compensation_for_descendants =
layer->IsContainerForFixedPositionLayers() ||
// Avoid the overheads (including stack allocation and matrix
// initialization/copy) if we know that the scroll compensation doesn't need
// to be reset or adjusted.
if (!current_layer_resets_scroll_compensation_for_descendants &&
scroll_delta.IsZero() && !layer->render_surface())
return current_scroll_compensation_matrix;
// Start as identity matrix.
gfx::Transform next_scroll_compensation_matrix;
// If this layer does not reset scroll compensation, then it inherits the
// existing scroll compensations.
if (!current_layer_resets_scroll_compensation_for_descendants)
next_scroll_compensation_matrix = current_scroll_compensation_matrix;
// If the current layer has a non-zero scroll_delta, then we should compute
// its local scroll compensation and accumulate it to the
// next_scroll_compensation_matrix.
if (!scroll_delta.IsZero()) {
gfx::Transform scroll_compensation_for_this_layer =
layer, parent_matrix, scroll_delta);
// If the layer created its own render_surface, we have to adjust
// next_scroll_compensation_matrix. The adjustment allows us to continue
// using the scroll compensation on the next surface.
// Step 1 (right-most in the math): transform from the new surface to the
// original ancestor surface
// Step 2: apply the scroll compensation
// Step 3: transform back to the new surface.
if (layer->render_surface() &&
!next_scroll_compensation_matrix.IsIdentity()) {
gfx::Transform inverse_surface_draw_transform(
if (!layer->render_surface()->draw_transform().GetInverse(
&inverse_surface_draw_transform)) {
// TODO(shawnsingh): Either we need to handle uninvertible transforms
// here, or DCHECK that the transform is invertible.
next_scroll_compensation_matrix =
inverse_surface_draw_transform * next_scroll_compensation_matrix *
return next_scroll_compensation_matrix;
template <typename LayerType>
static inline void UpdateLayerScaleDrawProperties(
LayerType* layer,
float ideal_contents_scale,
float maximum_animation_contents_scale,
float page_scale_factor,
float device_scale_factor) {
layer->draw_properties().ideal_contents_scale = ideal_contents_scale;
layer->draw_properties().maximum_animation_contents_scale =
layer->draw_properties().page_scale_factor = page_scale_factor;
layer->draw_properties().device_scale_factor = device_scale_factor;
static inline void CalculateContentsScale(LayerImpl* layer,
float contents_scale) {
// LayerImpl has all of its content scales and bounds pushed from the Main
// thread during commit and just uses those values as-is.
static inline void CalculateContentsScale(Layer* layer, float contents_scale) {
Layer* mask_layer = layer->mask_layer();
if (mask_layer) {
Layer* replica_mask_layer =
layer->replica_layer() ? layer->replica_layer()->mask_layer() : NULL;
if (replica_mask_layer) {
static inline void UpdateLayerContentsScale(
LayerImpl* layer,
bool can_adjust_raster_scale,
float ideal_contents_scale,
float device_scale_factor,
float page_scale_factor,
bool animating_transform_to_screen) {
CalculateContentsScale(layer, ideal_contents_scale);
static inline void UpdateLayerContentsScale(
Layer* layer,
bool can_adjust_raster_scale,
float ideal_contents_scale,
float device_scale_factor,
float page_scale_factor,
bool animating_transform_to_screen) {
if (can_adjust_raster_scale) {
float ideal_raster_scale =
ideal_contents_scale / (device_scale_factor * page_scale_factor);
bool need_to_set_raster_scale = layer->raster_scale_is_unknown();
// If we've previously saved a raster_scale but the ideal changes, things
// are unpredictable and we should just use 1.
if (!need_to_set_raster_scale && layer->raster_scale() != 1.f &&
ideal_raster_scale != layer->raster_scale()) {
ideal_raster_scale = 1.f;
need_to_set_raster_scale = true;
if (need_to_set_raster_scale) {
bool use_and_save_ideal_scale =
ideal_raster_scale >= 1.f && !animating_transform_to_screen;
if (use_and_save_ideal_scale)
float raster_scale = 1.f;
if (!layer->raster_scale_is_unknown())
raster_scale = layer->raster_scale();
gfx::Size old_content_bounds = layer->content_bounds();
float old_contents_scale_x = layer->contents_scale_x();
float old_contents_scale_y = layer->contents_scale_y();
float contents_scale = raster_scale * device_scale_factor * page_scale_factor;
CalculateContentsScale(layer, contents_scale);
if (layer->content_bounds() != old_content_bounds ||
layer->contents_scale_x() != old_contents_scale_x ||
layer->contents_scale_y() != old_contents_scale_y)
static inline void CalculateAnimationContentsScale(
Layer* layer,
bool ancestor_is_animating_scale,
float ancestor_maximum_animation_contents_scale,
const gfx::Transform& parent_transform,
const gfx::Transform& combined_transform,
bool* combined_is_animating_scale,
float* combined_maximum_animation_contents_scale) {
*combined_is_animating_scale = false;
*combined_maximum_animation_contents_scale = 0.f;
static inline void CalculateAnimationContentsScale(
LayerImpl* layer,
bool ancestor_is_animating_scale,
float ancestor_maximum_animation_contents_scale,
const gfx::Transform& ancestor_transform,
const gfx::Transform& combined_transform,
bool* combined_is_animating_scale,
float* combined_maximum_animation_contents_scale) {
if (ancestor_is_animating_scale &&
ancestor_maximum_animation_contents_scale == 0.f) {
// We've already failed to compute a maximum animated scale at an
// ancestor, so we'll continue to fail.
*combined_maximum_animation_contents_scale = 0.f;
*combined_is_animating_scale = true;
if (!combined_transform.IsScaleOrTranslation()) {
// Computing maximum animated scale in the presence of
// non-scale/translation transforms isn't supported.
*combined_maximum_animation_contents_scale = 0.f;
*combined_is_animating_scale = true;
// We currently only support computing maximum scale for combinations of
// scales and translations. We treat all non-translations as potentially
// affecting scale. Animations that include non-translation/scale components
// will cause the computation of MaximumScale below to fail.
bool layer_is_animating_scale =
if (!layer_is_animating_scale && !ancestor_is_animating_scale) {
*combined_maximum_animation_contents_scale = 0.f;
*combined_is_animating_scale = false;
// We don't attempt to accumulate animation scale from multiple nodes,
// because of the risk of significant overestimation. For example, one node
// may be increasing scale from 1 to 10 at the same time as a descendant is
// decreasing scale from 10 to 1. Naively combining these scales would produce
// a scale of 100.
if (layer_is_animating_scale && ancestor_is_animating_scale) {
*combined_maximum_animation_contents_scale = 0.f;
*combined_is_animating_scale = true;
// At this point, we know either the layer or an ancestor, but not both,
// is animating scale.
*combined_is_animating_scale = true;
if (!layer_is_animating_scale) {
gfx::Vector2dF layer_transform_scales =
MathUtil::ComputeTransform2dScaleComponents(layer->transform(), 0.f);
*combined_maximum_animation_contents_scale =
ancestor_maximum_animation_contents_scale *
std::max(layer_transform_scales.x(), layer_transform_scales.y());
float layer_maximum_animated_scale = 0.f;
if (!layer->layer_animation_controller()->MaximumTargetScale(
&layer_maximum_animated_scale)) {
*combined_maximum_animation_contents_scale = 0.f;
gfx::Vector2dF ancestor_transform_scales =
MathUtil::ComputeTransform2dScaleComponents(ancestor_transform, 0.f);
*combined_maximum_animation_contents_scale =
layer_maximum_animated_scale *
std::max(ancestor_transform_scales.x(), ancestor_transform_scales.y());
template <typename LayerType>
static inline typename LayerType::RenderSurfaceType* CreateOrReuseRenderSurface(
LayerType* layer) {
if (!layer->render_surface()) {
return layer->render_surface();
return layer->render_surface();
template <typename LayerTypePtr>
static inline void MarkLayerWithRenderSurfaceLayerListId(
LayerTypePtr layer,
int current_render_surface_layer_list_id) {
layer->draw_properties().last_drawn_render_surface_layer_list_id =
template <typename LayerTypePtr>
static inline void MarkMasksWithRenderSurfaceLayerListId(
LayerTypePtr layer,
int current_render_surface_layer_list_id) {
if (layer->mask_layer()) {
if (layer->replica_layer() && layer->replica_layer()->mask_layer()) {
template <typename LayerListType>
static inline void MarkLayerListWithRenderSurfaceLayerListId(
LayerListType* layer_list,
int current_render_surface_layer_list_id) {
for (typename LayerListType::iterator it = layer_list->begin();
it != layer_list->end();
++it) {
template <typename LayerType>
static inline void RemoveSurfaceForEarlyExit(
LayerType* layer_to_remove,
typename LayerType::RenderSurfaceListType* render_surface_layer_list) {
// Technically, we know that the layer we want to remove should be
// at the back of the render_surface_layer_list. However, we have had
// bugs before that added unnecessary layers here
// (, but that causes
// things to crash. So here we proactively remove any additional
// layers from the end of the list.
while (render_surface_layer_list->back() != layer_to_remove) {
&render_surface_layer_list->back()->render_surface()->layer_list(), 0);
MarkLayerWithRenderSurfaceLayerListId(render_surface_layer_list->back(), 0);
DCHECK_EQ(render_surface_layer_list->back(), layer_to_remove);
&layer_to_remove->render_surface()->layer_list(), 0);
MarkLayerWithRenderSurfaceLayerListId(layer_to_remove, 0);
struct PreCalculateMetaInformationRecursiveData {
bool layer_or_descendant_has_copy_request;
bool layer_or_descendant_has_input_handler;
int num_unclipped_descendants;
: layer_or_descendant_has_copy_request(false),
num_unclipped_descendants(0) {}
void Merge(const PreCalculateMetaInformationRecursiveData& data) {
layer_or_descendant_has_copy_request |=
layer_or_descendant_has_input_handler |=
num_unclipped_descendants +=
// Recursively walks the layer tree to compute any information that is needed
// before doing the main recursion.
template <typename LayerType>
static void PreCalculateMetaInformation(
LayerType* layer,
PreCalculateMetaInformationRecursiveData* recursive_data) {
layer->draw_properties().sorted_for_recursion = false;
layer->draw_properties().has_child_with_a_scroll_parent = false;
if (!HasInvertibleOrAnimatedTransform(layer)) {
// Layers with singular transforms should not be drawn, the whole subtree
// can be skipped.
if (layer->clip_parent())
for (size_t i = 0; i < layer->children().size(); ++i) {
LayerType* child_layer =
LayerTreeHostCommon::get_layer_as_raw_ptr(layer->children(), i);
PreCalculateMetaInformationRecursiveData data_for_child;
PreCalculateMetaInformation(child_layer, &data_for_child);
if (child_layer->scroll_parent())
layer->draw_properties().has_child_with_a_scroll_parent = true;
if (layer->clip_children()) {
int num_clip_children = layer->clip_children()->size();
DCHECK_GE(recursive_data->num_unclipped_descendants, num_clip_children);
recursive_data->num_unclipped_descendants -= num_clip_children;
if (layer->HasCopyRequest())
recursive_data->layer_or_descendant_has_copy_request = true;
if (!layer->touch_event_handler_region().IsEmpty() ||
recursive_data->layer_or_descendant_has_input_handler = true;
layer->draw_properties().num_unclipped_descendants =
layer->draw_properties().layer_or_descendant_has_copy_request =
layer->draw_properties().layer_or_descendant_has_input_handler =
static void RoundTranslationComponents(gfx::Transform* transform) {
transform->matrix().set(0, 3, MathUtil::Round(transform->matrix().get(0, 3)));
transform->matrix().set(1, 3, MathUtil::Round(transform->matrix().get(1, 3)));
template <typename LayerType>
struct SubtreeGlobals {
LayerSorter* layer_sorter;
int max_texture_size;
float device_scale_factor;
float page_scale_factor;
const LayerType* page_scale_application_layer;
gfx::Vector2dF elastic_overscroll;
const LayerType* elastic_overscroll_application_layer;
bool can_adjust_raster_scales;
bool can_render_to_separate_surface;
bool layers_always_allowed_lcd_text;
template<typename LayerType>
struct DataForRecursion {
// The accumulated sequence of transforms a layer will use to determine its
// own draw transform.
gfx::Transform parent_matrix;
// The accumulated sequence of transforms a layer will use to determine its
// own screen-space transform.
gfx::Transform full_hierarchy_matrix;
// The transform that removes all scrolling that may have occurred between a
// fixed-position layer and its container, so that the layer actually does
// remain fixed.
gfx::Transform scroll_compensation_matrix;
// The ancestor that would be the container for any fixed-position / sticky
// layers.
LayerType* fixed_container;
// This is the normal clip rect that is propagated from parent to child.
gfx::Rect clip_rect_in_target_space;
// When the layer's children want to compute their visible content rect, they
// want to know what their target surface's clip rect will be. BUT - they
// want to know this clip rect represented in their own target space. This
// requires inverse-projecting the surface's clip rect from the surface's
// render target space down to the surface's own space. Instead of computing
// this value redundantly for each child layer, it is computed only once
// while dealing with the parent layer, and then this precomputed value is
// passed down the recursion to the children that actually use it.
gfx::Rect clip_rect_of_target_surface_in_target_space;
// The maximum amount by which this layer will be scaled during the lifetime
// of currently running animations.
float maximum_animation_contents_scale;
bool ancestor_is_animating_scale;
bool ancestor_clips_subtree;
typename LayerType::RenderSurfaceType*
bool in_subtree_of_page_scale_application_layer;
bool subtree_can_use_lcd_text;
bool subtree_is_visible_from_ancestor;
template <typename LayerType>
static LayerType* GetChildContainingLayer(const LayerType& parent,
LayerType* layer) {
for (LayerType* ancestor = layer; ancestor; ancestor = ancestor->parent()) {
if (ancestor->parent() == &parent)
return ancestor;
return 0;
template <typename LayerType>
static void AddScrollParentChain(std::vector<LayerType*>* out,
const LayerType& parent,
LayerType* layer) {
// At a high level, this function walks up the chain of scroll parents
// recursively, and once we reach the end of the chain, we add the child
// of |parent| containing each scroll ancestor as we unwind. The result is
// an ordering of parent's children that ensures that scroll parents are
// visited before their descendants.
// Take for example this layer tree:
// + stacking_context
// + scroll_child (1)
// + scroll_parent_graphics_layer (*)
// | + scroll_parent_scrolling_layer
// | + scroll_parent_scrolling_content_layer (2)
// + scroll_grandparent_graphics_layer (**)
// + scroll_grandparent_scrolling_layer
// + scroll_grandparent_scrolling_content_layer (3)
// The scroll child is (1), its scroll parent is (2) and its scroll
// grandparent is (3). Note, this doesn't mean that (2)'s scroll parent is
// (3), it means that (*)'s scroll parent is (3). We don't want our list to
// look like [ (3), (2), (1) ], even though that does have the ancestor chain
// in the right order. Instead, we want [ (**), (*), (1) ]. That is, only want
// (1)'s siblings in the list, but we want them to appear in such an order
// that the scroll ancestors get visited in the correct order.
// So our first task at this step of the recursion is to determine the layer
// that we will potentionally add to the list. That is, the child of parent
// containing |layer|.
LayerType* child = GetChildContainingLayer(parent, layer);
if (child->draw_properties().sorted_for_recursion)
if (LayerType* scroll_parent = child->scroll_parent())
AddScrollParentChain(out, parent, scroll_parent);
child->draw_properties().sorted_for_recursion = true;
template <typename LayerType>
static bool SortChildrenForRecursion(std::vector<LayerType*>* out,
const LayerType& parent) {
bool order_changed = false;
for (size_t i = 0; i < parent.children().size(); ++i) {
LayerType* current =
LayerTreeHostCommon::get_layer_as_raw_ptr(parent.children(), i);
if (current->draw_properties().sorted_for_recursion) {
order_changed = true;
AddScrollParentChain(out, parent, current);
DCHECK_EQ(parent.children().size(), out->size());
return order_changed;
template <typename LayerType>
static void GetNewDescendantsStartIndexAndCount(LayerType* layer,
size_t* start_index,
size_t* count) {
*start_index = layer->draw_properties().index_of_first_descendants_addition;
*count = layer->draw_properties().num_descendants_added;
template <typename LayerType>
static void GetNewRenderSurfacesStartIndexAndCount(LayerType* layer,
size_t* start_index,
size_t* count) {
*start_index = layer->draw_properties()
*count = layer->draw_properties().num_render_surfaces_added;
// We need to extract a list from the the two flavors of RenderSurfaceListType
// for use in the sorting function below.
static LayerList* GetLayerListForSorting(RenderSurfaceLayerList* rsll) {
return &rsll->AsLayerList();
static LayerImplList* GetLayerListForSorting(LayerImplList* layer_list) {
return layer_list;
static inline gfx::Vector2d BoundsDelta(Layer* layer) {
return gfx::Vector2d();
static inline gfx::Vector2d BoundsDelta(LayerImpl* layer) {
return gfx::ToCeiledVector2d(layer->bounds_delta());
template <typename LayerType, typename GetIndexAndCountType>
static void SortLayerListContributions(
const LayerType& parent,
typename LayerType::LayerListType* unsorted,
size_t start_index_for_all_contributions,
GetIndexAndCountType get_index_and_count) {
typename LayerType::LayerListType buffer;
for (size_t i = 0; i < parent.children().size(); ++i) {
LayerType* child =
LayerTreeHostCommon::get_layer_as_raw_ptr(parent.children(), i);
size_t start_index = 0;
size_t count = 0;
get_index_and_count(child, &start_index, &count);
for (size_t j = start_index; j < start_index + count; ++j)
unsorted->size() - start_index_for_all_contributions);
for (size_t i = 0; i < buffer.size(); ++i)
(*unsorted)[i + start_index_for_all_contributions] = buffer[i];
// Recursively walks the layer tree starting at the given node and computes all
// the necessary transformations, clip rects, render surfaces, etc.
template <typename LayerType>
static void CalculateDrawPropertiesInternal(
LayerType* layer,
const SubtreeGlobals<LayerType>& globals,
const DataForRecursion<LayerType>& data_from_ancestor,
typename LayerType::RenderSurfaceListType* render_surface_layer_list,
typename LayerType::LayerListType* layer_list,
std::vector<AccumulatedSurfaceState<LayerType>>* accumulated_surface_state,
int current_render_surface_layer_list_id) {
// This function computes the new matrix transformations recursively for this
// layer and all its descendants. It also computes the appropriate render
// surfaces.
// Some important points to remember:
// 0. Here, transforms are notated in Matrix x Vector order, and in words we
// describe what the transform does from left to right.
// 1. In our terminology, the "layer origin" refers to the top-left corner of
// a layer, and the positive Y-axis points downwards. This interpretation is
// valid because the orthographic projection applied at draw time flips the Y
// axis appropriately.
// 2. The anchor point, when given as a PointF object, is specified in "unit
// layer space", where the bounds of the layer map to [0, 1]. However, as a
// Transform object, the transform to the anchor point is specified in "layer
// space", where the bounds of the layer map to [bounds.width(),
// bounds.height()].
// 3. Definition of various transforms used:
// M[parent] is the parent matrix, with respect to the nearest render
// surface, passed down recursively.
// M[root] is the full hierarchy, with respect to the root, passed down
// recursively.
// Tr[origin] is the translation matrix from the parent's origin to
// this layer's origin.
// Tr[origin2anchor] is the translation from the layer's origin to its
// anchor point
// Tr[origin2center] is the translation from the layer's origin to its
// center
// M[layer] is the layer's matrix (applied at the anchor point)
// S[layer2content] is the ratio of a layer's content_bounds() to its
// Bounds().
// Some composite transforms can help in understanding the sequence of
// transforms:
// composite_layer_transform = Tr[origin2anchor] * M[layer] *
// Tr[origin2anchor].inverse()
// 4. When a layer (or render surface) is drawn, it is drawn into a "target
// render surface". Therefore the draw transform does not necessarily
// transform from screen space to local layer space. Instead, the draw
// transform is the transform between the "target render surface space" and
// local layer space. Note that render surfaces, except for the root, also
// draw themselves into a different target render surface, and so their draw
// transform and origin transforms are also described with respect to the
// target.
// Using these definitions, then:
// The draw transform for the layer is:
// M[draw] = M[parent] * Tr[origin] * composite_layer_transform *
// S[layer2content] = M[parent] * Tr[layer->position() + anchor] *
// M[layer] * Tr[anchor2origin] * S[layer2content]
// Interpreting the math left-to-right, this transforms from the
// layer's render surface to the origin of the layer in content space.
// The screen space transform is:
// M[screenspace] = M[root] * Tr[origin] * composite_layer_transform *
// S[layer2content]
// = M[root] * Tr[layer->position() + anchor] * M[layer]
// * Tr[anchor2origin] * S[layer2content]
// Interpreting the math left-to-right, this transforms from the root
// render surface's content space to the origin of the layer in content
// space.
// The transform hierarchy that is passed on to children (i.e. the child's
// parent_matrix) is:
// M[parent]_for_child = M[parent] * Tr[origin] *
// composite_layer_transform
// = M[parent] * Tr[layer->position() + anchor] *
// M[layer] * Tr[anchor2origin]
// and a similar matrix for the full hierarchy with respect to the
// root.
// Finally, note that the final matrix used by the shader for the layer is P *
// M[draw] * S . This final product is computed in drawTexturedQuad(), where:
// P is the projection matrix
// S is the scale adjustment (to scale up a canonical quad to the
// layer's size)
// When a render surface has a replica layer, that layer's transform is used
// to draw a second copy of the surface. gfx::Transforms named here are
// relative to the surface, unless they specify they are relative to the
// replica layer.
// We will denote a scale by device scale S[deviceScale]
// The render surface draw transform to its target surface origin is:
// M[surfaceDraw] = M[owningLayer->Draw]
// The render surface origin transform to its the root (screen space) origin
// is:
// M[surface2root] = M[owningLayer->screenspace] *
// S[deviceScale].inverse()
// The replica draw transform to its target surface origin is:
// M[replicaDraw] = S[deviceScale] * M[surfaceDraw] *
// Tr[replica->position() + replica->anchor()] * Tr[replica] *
// Tr[origin2anchor].inverse() * S[contents_scale].inverse()
// The replica draw transform to the root (screen space) origin is:
// M[replica2root] = M[surface2root] * Tr[replica->position()] *
// Tr[replica] * Tr[origin2anchor].inverse()
// It makes no sense to have a non-unit page_scale_factor without specifying
// which layer roots the subtree the scale is applied to.
DCHECK(globals.page_scale_application_layer ||
(globals.page_scale_factor == 1.f));
DataForRecursion<LayerType> data_for_children;
typename LayerType::RenderSurfaceType*
nearest_occlusion_immune_ancestor_surface =
data_for_children.in_subtree_of_page_scale_application_layer =
data_for_children.subtree_can_use_lcd_text =
// Layers that are marked as hidden will hide themselves and their subtree.
// Exception: Layers with copy requests, whether hidden or not, must be drawn
// anyway. In this case, we will inform their subtree they are visible to get
// the right results.
const bool layer_is_visible =
data_from_ancestor.subtree_is_visible_from_ancestor &&
const bool layer_is_drawn = layer_is_visible || layer->HasCopyRequest();
// The root layer cannot skip CalcDrawProperties.
if (!IsRootLayer(layer) && SubtreeShouldBeSkipped(layer, layer_is_drawn)) {
if (layer->render_surface())
// We need to circumvent the normal recursive flow of information for clip
// children (they don't inherit their direct ancestor's clip information).
// This is unfortunate, and would be unnecessary if we were to formally
// separate the clipping hierarchy from the layer hierarchy.
bool ancestor_clips_subtree = data_from_ancestor.ancestor_clips_subtree;
gfx::Rect ancestor_clip_rect_in_target_space =
// Update our clipping state. If we have a clip parent we will need to pull
// from the clip state cache rather than using the clip state passed from our
// immediate ancestor.
layer, &ancestor_clip_rect_in_target_space, &ancestor_clips_subtree);
// As this function proceeds, these are the properties for the current
// layer that actually get computed. To avoid unnecessary copies
// (particularly for matrices), we do computations directly on these values
// when possible.
DrawProperties<LayerType>& layer_draw_properties = layer->draw_properties();
gfx::Rect clip_rect_in_target_space;
bool layer_or_ancestor_clips_descendants = false;
// This value is cached on the stack so that we don't have to inverse-project
// the surface's clip rect redundantly for every layer. This value is the
// same as the target surface's clip rect, except that instead of being
// described in the target surface's target's space, it is described in the
// current render target's space.
gfx::Rect clip_rect_of_target_surface_in_target_space;
float accumulated_draw_opacity = layer->opacity();
bool animating_opacity_to_target = layer->OpacityIsAnimating();
bool animating_opacity_to_screen = animating_opacity_to_target;
if (layer->parent()) {
accumulated_draw_opacity *= layer->parent()->draw_opacity();
animating_opacity_to_target |= layer->parent()->draw_opacity_is_animating();
animating_opacity_to_screen |=
bool animating_transform_to_target = layer->TransformIsAnimating();
bool animating_transform_to_screen = animating_transform_to_target;
if (layer->parent()) {
animating_transform_to_target |=
animating_transform_to_screen |=
gfx::Point3F transform_origin = layer->transform_origin();
gfx::ScrollOffset scroll_offset = GetEffectiveTotalScrollOffset(layer);
gfx::PointF position =
layer->position() - ScrollOffsetToVector2dF(scroll_offset);
gfx::Transform combined_transform = data_from_ancestor.parent_matrix;
if (!layer->transform().IsIdentity()) {
// LT = Tr[origin] * Tr[origin2transformOrigin]
combined_transform.Translate3d(position.x() + transform_origin.x(),
position.y() + transform_origin.y(),
// LT = Tr[origin] * Tr[origin2origin] * M[layer]
// LT = Tr[origin] * Tr[origin2origin] * M[layer] *
// Tr[transformOrigin2origin]
-transform_origin.x(), -transform_origin.y(), -transform_origin.z());
} else {
combined_transform.Translate(position.x(), position.y());
gfx::Vector2dF effective_scroll_delta = GetEffectiveScrollDelta(layer);
if (!animating_transform_to_target && layer->scrollable() &&
combined_transform.IsScaleOrTranslation()) {
// Align the scrollable layer's position to screen space pixels to avoid
// blurriness. To avoid side-effects, do this only if the transform is
// simple.
gfx::Vector2dF previous_translation = combined_transform.To2dTranslation();
gfx::Vector2dF current_translation = combined_transform.To2dTranslation();
// This rounding changes the scroll delta, and so must be included
// in the scroll compensation matrix. The scaling converts from physical
// coordinates to the scroll delta's CSS coordinates (using the parent
// matrix instead of combined transform since scrolling is applied before
// the layer's transform). For example, if we have a total scale factor of
// 3.0, then 1 physical pixel is only 1/3 of a CSS pixel.
gfx::Vector2dF parent_scales = MathUtil::ComputeTransform2dScaleComponents(
data_from_ancestor.parent_matrix, 1.f);
effective_scroll_delta -=
gfx::ScaleVector2d(current_translation - previous_translation,
1.f / parent_scales.x(),
1.f / parent_scales.y());
// Apply adjustment from position constraints.
ApplyPositionAdjustment(layer, data_from_ancestor.fixed_container,
data_from_ancestor.scroll_compensation_matrix, &combined_transform);
bool combined_is_animating_scale = false;
float combined_maximum_animation_contents_scale = 0.f;
if (globals.can_adjust_raster_scales) {
data_for_children.ancestor_is_animating_scale = combined_is_animating_scale;
data_for_children.maximum_animation_contents_scale =
// Compute the 2d scale components of the transform hierarchy up to the target
// surface. From there, we can decide on a contents scale for the layer.
float layer_scale_factors = globals.device_scale_factor;
if (data_from_ancestor.in_subtree_of_page_scale_application_layer)
layer_scale_factors *= globals.page_scale_factor;
gfx::Vector2dF combined_transform_scales =
float ideal_contents_scale =
? std::max(combined_transform_scales.x(),
: layer_scale_factors;
? globals.page_scale_factor
: 1.f,
? globals.page_scale_factor
: 1.f,
LayerType* mask_layer = layer->mask_layer();
if (mask_layer) {
? globals.page_scale_factor
: 1.f,
LayerType* replica_mask_layer =
layer->replica_layer() ? layer->replica_layer()->mask_layer() : NULL;
if (replica_mask_layer) {
? globals.page_scale_factor
: 1.f,
// The draw_transform that gets computed below is effectively the layer's
// draw_transform, unless the layer itself creates a render_surface. In that
// case, the render_surface re-parents the transforms.
layer_draw_properties.target_space_transform = combined_transform;
// M[draw] = M[parent] * LT * S[layer2content]
SK_MScalar1 / layer->contents_scale_x(),
SK_MScalar1 / layer->contents_scale_y());
// The layer's screen_space_transform represents the transform between root
// layer's "screen space" and local content space.
layer_draw_properties.screen_space_transform =
if (layer->should_flatten_transform())
// Adjusting text AA method during animation may cause repaints, which in-turn
// causes jank.
bool adjust_text_aa =
!animating_opacity_to_screen && !animating_transform_to_screen;
bool layer_can_use_lcd_text = true;
bool subtree_can_use_lcd_text = true;
if (!globals.layers_always_allowed_lcd_text) {
// To avoid color fringing, LCD text should only be used on opaque layers
// with just integral translation.
subtree_can_use_lcd_text = data_from_ancestor.subtree_can_use_lcd_text &&
accumulated_draw_opacity == 1.f &&
// Also disable LCD text locally for non-opaque content.
layer_can_use_lcd_text = subtree_can_use_lcd_text &&
// full_hierarchy_matrix is the matrix that transforms objects between screen
// space (except projection matrix) and the most recent RenderSurfaceImpl's
// space. next_hierarchy_matrix will only change if this layer uses a new
// RenderSurfaceImpl, otherwise remains the same.
data_for_children.full_hierarchy_matrix =
// If the subtree will scale layer contents by the transform hierarchy, then
// we should scale things into the render surface by the transform hierarchy
// to take advantage of that.
gfx::Vector2dF render_surface_sublayer_scale =
? combined_transform_scales
: gfx::Vector2dF(layer_scale_factors, layer_scale_factors);
bool render_to_separate_surface;
if (globals.can_render_to_separate_surface) {
render_to_separate_surface = SubtreeShouldRenderToSeparateSurface(
layer, combined_transform.Preserves2dAxisAlignment());
} else {
render_to_separate_surface = IsRootLayer(layer);
if (render_to_separate_surface) {
// Check back-face visibility before continuing with this surface and its
// subtree
if (!layer->double_sided() && TransformToParentIsKnown(layer) &&
IsSurfaceBackFaceVisible(layer, combined_transform)) {
typename LayerType::RenderSurfaceType* render_surface =
if (IsRootLayer(layer)) {
// The root layer's render surface size is predetermined and so the root
// layer can't directly support non-identity transforms. It should just
// forward top-level transforms to the rest of the tree.
data_for_children.parent_matrix = combined_transform;
// The root surface does not contribute to any other surface, it has no
// target.
} else {
// The owning layer's draw transform has a scale from content to layer
// space which we do not want; so here we use the combined_transform
// instead of the draw_transform. However, we do need to add a different
// scale factor that accounts for the surface's pixel dimensions.
combined_transform.Scale(1.0 / render_surface_sublayer_scale.x(),
1.0 / render_surface_sublayer_scale.y());
// The owning layer's transform was re-parented by the surface, so the
// layer's new draw_transform only needs to scale the layer to surface
// space.
Scale(render_surface_sublayer_scale.x() / layer->contents_scale_x(),
render_surface_sublayer_scale.y() / layer->contents_scale_y());
// Inside the surface's subtree, we scale everything to the owning layer's
// scale. The sublayer matrix transforms layer rects into target surface
// content space. Conceptually, all layers in the subtree inherit the
// scale at the point of the render surface in the transform hierarchy,
// but we apply it explicitly to the owning layer and the remainder of the
// subtree independently.
// Even if the |layer_is_drawn|, it only contributes to a drawn surface
// when the |layer_is_visible|.
// The opacity value is moved from the layer to its surface, so that the
// entire subtree properly inherits opacity.
animating_opacity_to_target = false;
layer_draw_properties.opacity = 1.f;
layer_draw_properties.blend_mode = SkXfermode::kSrcOver_Mode;
layer_draw_properties.opacity_is_animating = animating_opacity_to_target;
layer_draw_properties.screen_space_opacity_is_animating =
animating_transform_to_target = false;
layer_draw_properties.target_space_transform_is_animating =
layer_draw_properties.screen_space_transform_is_animating =
// Update the aggregate hierarchy matrix to include the transform of the
// newly created RenderSurfaceImpl.
if (layer->mask_layer()) {
DrawProperties<LayerType>& mask_layer_draw_properties =
mask_layer_draw_properties.render_target = layer;
mask_layer_draw_properties.visible_content_rect =
if (layer->replica_layer() && layer->replica_layer()->mask_layer()) {
DrawProperties<LayerType>& replica_mask_draw_properties =
replica_mask_draw_properties.render_target = layer;
replica_mask_draw_properties.visible_content_rect =
// Ignore occlusion from outside the surface when surface contents need to
// be fully drawn. Layers with copy-request need to be complete.
// We could be smarter about layers with replica and exclude regions
// where both layer and the replica are occluded, but this seems like an
// overkill. The same is true for layers with filters that move pixels.
// TODO(senorblanco): make this smarter for the SkImageFilter case (check
// for pixel-moving filters)
if (layer->HasCopyRequest() ||
layer->has_replica() ||
layer->filters().HasReferenceFilter() ||
layer->filters().HasFilterThatMovesPixels()) {
nearest_occlusion_immune_ancestor_surface = render_surface;
layer_or_ancestor_clips_descendants = false;
bool subtree_is_clipped_by_surface_bounds = false;
if (ancestor_clips_subtree) {
// It may be the layer or the surface doing the clipping of the subtree,
// but in either case, we'll be clipping to the projected clip rect of our
// ancestor.
gfx::Transform inverse_surface_draw_transform(
if (!render_surface->draw_transform().GetInverse(
&inverse_surface_draw_transform)) {
// TODO(shawnsingh): Either we need to handle uninvertible transforms
// here, or DCHECK that the transform is invertible.
gfx::Rect surface_clip_rect_in_target_space = gfx::IntersectRects(
gfx::Rect projected_surface_rect = MathUtil::ProjectEnclosingClippedRect(
inverse_surface_draw_transform, surface_clip_rect_in_target_space);
if (layer_draw_properties.num_unclipped_descendants > 0) {
// If we have unclipped descendants, we cannot count on the render
// surface's bounds clipping our subtree: the unclipped descendants
// could cause us to expand our bounds. In this case, we must rely on
// layer clipping for correctess. NB: since we can only encounter
// translations between a clip child and its clip parent, clipping is
// guaranteed to be exact in this case.
layer_or_ancestor_clips_descendants = true;
clip_rect_in_target_space = projected_surface_rect;
} else {
// The new render_surface here will correctly clip the entire subtree.
// So, we do not need to continue propagating the clipping state further
// down the tree. This way, we can avoid transforming clip rects from
// ancestor target surface space to current target surface space that
// could cause more w < 0 headaches. The render surface clip rect is
// expressed in the space where this surface draws, i.e. the same space
// as clip_rect_from_ancestor_in_ancestor_target_space.
clip_rect_of_target_surface_in_target_space = projected_surface_rect;
subtree_is_clipped_by_surface_bounds = true;
DCHECK(!layer->parent() || layer->parent()->render_target() ==
if (!subtree_is_clipped_by_surface_bounds) {
clip_rect_of_target_surface_in_target_space =
// If the new render surface is drawn translucent or with a non-integral
// translation then the subtree that gets drawn on this render surface
// cannot use LCD text.
data_for_children.subtree_can_use_lcd_text = subtree_can_use_lcd_text;
} else {
// Note: layer_draw_properties.target_space_transform is computed above,
// before this if-else statement.
layer_draw_properties.target_space_transform_is_animating =
layer_draw_properties.screen_space_transform_is_animating =
layer_draw_properties.opacity = accumulated_draw_opacity;
layer_draw_properties.blend_mode = layer->blend_mode();
layer_draw_properties.opacity_is_animating = animating_opacity_to_target;
layer_draw_properties.screen_space_opacity_is_animating =
data_for_children.parent_matrix = combined_transform;
// Layers without render_surfaces directly inherit the ancestor's clip
// status.
layer_or_ancestor_clips_descendants = ancestor_clips_subtree;
if (ancestor_clips_subtree) {
clip_rect_in_target_space =
// The surface's cached clip rect value propagates regardless of what
// clipping goes on between layers here.
clip_rect_of_target_surface_in_target_space =
// Layers that are not their own render_target will render into the target
// of their nearest ancestor.
layer_draw_properties.render_target = layer->parent()->render_target();
if (adjust_text_aa)
layer_draw_properties.can_use_lcd_text = layer_can_use_lcd_text;
gfx::Size content_size_affected_by_delta(layer->content_bounds());
// Non-zero BoundsDelta imply the contents_scale of 1.0
// because BoundsDela is only set on Android where
// ContentScalingLayer is never used.
(layer->contents_scale_x() == 1.0 &&
layer->contents_scale_y() == 1.0));
// Thus we can omit contents scale in the following calculation.
gfx::Vector2d bounds_delta = BoundsDelta(layer);
content_size_affected_by_delta.Enlarge(bounds_delta.x(), bounds_delta.y());
gfx::Rect rect_in_target_space = MathUtil::MapEnclosingClippedRect(
if (LayerClipsSubtree(layer)) {
layer_or_ancestor_clips_descendants = true;
if (ancestor_clips_subtree && !layer->render_surface()) {
// A layer without render surface shares the same target as its ancestor.
clip_rect_in_target_space =
} else {
clip_rect_in_target_space = rect_in_target_space;
// Tell the layer the rect that it's clipped by. In theory we could use a
// tighter clip rect here (drawable_content_rect), but that actually does not
// reduce how much would be drawn, and instead it would create unnecessary
// changes to scissor state affecting GPU performance. Our clip information
// is used in the recursion below, so we must set it beforehand.
layer_draw_properties.is_clipped = layer_or_ancestor_clips_descendants;
if (layer_or_ancestor_clips_descendants) {
layer_draw_properties.clip_rect = clip_rect_in_target_space;
} else {
// Initialize the clip rect to a safe value that will not clip the
// layer, just in case clipping is still accidentally used.
layer_draw_properties.clip_rect = rect_in_target_space;
typename LayerType::LayerListType& descendants =
(layer->render_surface() ? layer->render_surface()->layer_list()
: *layer_list);
// Any layers that are appended after this point are in the layer's subtree
// and should be included in the sorting process.
size_t sorting_start_index = descendants.size();
if (!LayerShouldBeSkipped(layer, layer_is_drawn)) {
// Any layers that are appended after this point may need to be sorted if we
// visit the children out of order.
size_t render_surface_layer_list_child_sorting_start_index =
size_t layer_list_child_sorting_start_index = descendants.size();
if (!layer->children().empty()) {
if (layer == globals.page_scale_application_layer) {
data_for_children.in_subtree_of_page_scale_application_layer = true;
if (layer == globals.elastic_overscroll_application_layer) {
// Flatten to 2D if the layer doesn't preserve 3D.
if (layer->should_flatten_transform())
data_for_children.scroll_compensation_matrix =
data_for_children.fixed_container =
layer->IsContainerForFixedPositionLayers() ?
layer : data_from_ancestor.fixed_container;
data_for_children.clip_rect_in_target_space = clip_rect_in_target_space;
data_for_children.clip_rect_of_target_surface_in_target_space =
data_for_children.ancestor_clips_subtree =
data_for_children.nearest_occlusion_immune_ancestor_surface =
data_for_children.subtree_is_visible_from_ancestor = layer_is_drawn;
std::vector<LayerType*> sorted_children;
bool child_order_changed = false;
if (layer_draw_properties.has_child_with_a_scroll_parent)
child_order_changed = SortChildrenForRecursion(&sorted_children, *layer);
for (size_t i = 0; i < layer->children().size(); ++i) {
// If one of layer's children has a scroll parent, then we may have to
// visit the children out of order. The new order is stored in
// sorted_children. Otherwise, we'll grab the child directly from the
// layer's list of children.
LayerType* child =
? sorted_children[i]
: LayerTreeHostCommon::get_layer_as_raw_ptr(layer->children(), i);
child->draw_properties().index_of_first_descendants_addition =
child->draw_properties().index_of_first_render_surface_layer_list_addition =
if (child->render_surface() &&
!child->render_surface()->layer_list().empty() &&
!child->render_surface()->content_rect().IsEmpty()) {
// This child will contribute its render surface, which means
// we need to mark just the mask layer (and replica mask layer)
// with the id.
child, current_render_surface_layer_list_id);
child->draw_properties().num_descendants_added =
descendants.size() -
child->draw_properties().num_render_surfaces_added =
render_surface_layer_list->size() -
// Add the unsorted layer list contributions, if necessary.
if (child_order_changed) {
// Compute the total drawable_content_rect for this subtree (the rect is in
// target surface space).
gfx::Rect local_drawable_content_rect_of_subtree =
if (layer->render_surface()) {
DCHECK(accumulated_surface_state->back().render_target == layer);
if (layer->render_surface() && !IsRootLayer(layer) &&
layer->render_surface()->layer_list().empty()) {
RemoveSurfaceForEarlyExit(layer, render_surface_layer_list);
// Compute the layer's drawable content rect (the rect is in target surface
// space).
layer_draw_properties.drawable_content_rect = rect_in_target_space;
if (layer_or_ancestor_clips_descendants) {
if (layer->DrawsContent()) {
// Compute the layer's visible content rect (the rect is in content space).
layer_draw_properties.visible_content_rect = CalculateVisibleContentRect(
layer, clip_rect_of_target_surface_in_target_space, rect_in_target_space);
// Compute the remaining properties for the render surface, if the layer has
// one.
if (IsRootLayer(layer)) {
// The root layer's surface's content_rect is always the entire viewport.
} else if (layer->render_surface()) {
typename LayerType::RenderSurfaceType* render_surface =
gfx::Rect clipped_content_rect = local_drawable_content_rect_of_subtree;
// Don't clip if the layer is reflected as the reflection shouldn't be
// clipped. If the layer is animating, then the surface's transform to
// its target is not known on the main thread, and we should not use it
// to clip.
if (!layer->replica_layer() && TransformToParentIsKnown(layer)) {
// Note, it is correct to use data_from_ancestor.ancestor_clips_subtree
// here, because we are looking at this layer's render_surface, not the
// layer itself.
if (render_surface->is_clipped() && !clipped_content_rect.IsEmpty()) {
gfx::Rect surface_clip_rect = LayerTreeHostCommon::CalculateVisibleRect(
// The RenderSurfaceImpl backing texture cannot exceed the maximum supported
// texture size.
std::min(clipped_content_rect.width(), globals.max_texture_size));
std::min(clipped_content_rect.height(), globals.max_texture_size));
if (clipped_content_rect.IsEmpty()) {
RemoveSurfaceForEarlyExit(layer, render_surface_layer_list);
// Layers having a non-default blend mode will blend with the content
// inside its parent's render target. This render target should be
// either root_for_isolated_group, or the root of the layer tree.
// Otherwise, this layer will use an incomplete backdrop, limited to its
// render target and the blending result will be incorrect.
DCHECK(layer->uses_default_blend_mode() || IsRootLayer(layer) ||
!layer->parent()->render_target() ||
IsRootLayer(layer->parent()->render_target()) ||
// The owning layer's screen_space_transform has a scale from content to
// layer space which we need to undo and replace with a scale from the
// surface's subtree into layer space.
gfx::Transform screen_space_transform = layer->screen_space_transform();
layer->contents_scale_x() / render_surface_sublayer_scale.x(),
layer->contents_scale_y() / render_surface_sublayer_scale.y());
if (layer->replica_layer()) {
gfx::Transform surface_origin_to_replica_origin_transform;
render_surface_sublayer_scale.x(), render_surface_sublayer_scale.y());
layer->replica_layer()->position().x() +
layer->replica_layer()->position().y() +
1.0 / render_surface_sublayer_scale.x(),
1.0 / render_surface_sublayer_scale.y());
// Compute the replica's "originTransform" that maps from the replica's
// origin space to the target surface origin space.
gfx::Transform replica_origin_transform =
layer->render_surface()->draw_transform() *
// Compute the replica's "screen_space_transform" that maps from the
// replica's origin space to the screen's origin space.
gfx::Transform replica_screen_space_transform =
layer->render_surface()->screen_space_transform() *
// If neither this layer nor any of its children were added, early out.
if (sorting_start_index == descendants.size()) {
DCHECK(!layer->render_surface() || IsRootLayer(layer));
// If preserves-3d then sort all the descendants in 3D so that they can be
// drawn from back to front. If the preserves-3d property is also set on the
// parent then skip the sorting as the parent will sort all the descendants
// anyway.
if (globals.layer_sorter && descendants.size() && layer->Is3dSorted() &&
!LayerIsInExisting3DRenderingContext(layer)) {
SortLayers(descendants.begin() + sorting_start_index,
layer, local_drawable_content_rect_of_subtree, accumulated_surface_state);
if (layer->HasContributingDelegatedRenderPasses()) {
} // NOLINT(readability/fn_size)
template <typename LayerType, typename RenderSurfaceLayerListType>
static void ProcessCalcDrawPropsInputs(
const LayerTreeHostCommon::CalcDrawPropsInputs<LayerType,
SubtreeGlobals<LayerType>* globals,
DataForRecursion<LayerType>* data_for_recursion) {
gfx::Transform identity_matrix;
// The root layer's render_surface should receive the device viewport as the
// initial clip rect.
gfx::Rect device_viewport_rect(inputs.device_viewport_size);
gfx::Vector2dF device_transform_scale_components =
MathUtil::ComputeTransform2dScaleComponents(inputs.device_transform, 1.f);
// Not handling the rare case of different x and y device scale.
float device_transform_scale =
gfx::Transform scaled_device_transform = inputs.device_transform;
globals->layer_sorter = NULL;
globals->max_texture_size = inputs.max_texture_size;
globals->device_scale_factor =
inputs.device_scale_factor * device_transform_scale;
globals->page_scale_factor = inputs.page_scale_factor;
globals->page_scale_application_layer = inputs.page_scale_application_layer;
globals->elastic_overscroll = inputs.elastic_overscroll;
globals->elastic_overscroll_application_layer =
globals->can_render_to_separate_surface =
globals->can_adjust_raster_scales = inputs.can_adjust_raster_scales;
globals->layers_always_allowed_lcd_text =
data_for_recursion->parent_matrix = scaled_device_transform;
data_for_recursion->full_hierarchy_matrix = identity_matrix;
data_for_recursion->scroll_compensation_matrix = identity_matrix;
data_for_recursion->fixed_container = inputs.root_layer;
data_for_recursion->clip_rect_in_target_space = device_viewport_rect;
data_for_recursion->clip_rect_of_target_surface_in_target_space =
data_for_recursion->maximum_animation_contents_scale = 0.f;
data_for_recursion->ancestor_is_animating_scale = false;
data_for_recursion->ancestor_clips_subtree = true;
data_for_recursion->nearest_occlusion_immune_ancestor_surface = NULL;
data_for_recursion->in_subtree_of_page_scale_application_layer = false;
data_for_recursion->subtree_can_use_lcd_text = inputs.can_use_lcd_text;
data_for_recursion->subtree_is_visible_from_ancestor = true;
void LayerTreeHostCommon::CalculateDrawProperties(
CalcDrawPropsMainInputs* inputs) {
LayerList dummy_layer_list;
SubtreeGlobals<Layer> globals;
DataForRecursion<Layer> data_for_recursion;
ProcessCalcDrawPropsInputs(*inputs, &globals, &data_for_recursion);
PreCalculateMetaInformationRecursiveData recursive_data;
PreCalculateMetaInformation(inputs->root_layer, &recursive_data);
std::vector<AccumulatedSurfaceState<Layer>> accumulated_surface_state;
// The dummy layer list should not have been used.
DCHECK_EQ(0u, dummy_layer_list.size());
// A root layer render_surface should always exist after
// CalculateDrawProperties.
void LayerTreeHostCommon::CalculateDrawProperties(
CalcDrawPropsImplInputs* inputs) {
LayerImplList dummy_layer_list;
SubtreeGlobals<LayerImpl> globals;
DataForRecursion<LayerImpl> data_for_recursion;
ProcessCalcDrawPropsInputs(*inputs, &globals, &data_for_recursion);
LayerSorter layer_sorter;
globals.layer_sorter = &layer_sorter;
PreCalculateMetaInformationRecursiveData recursive_data;
PreCalculateMetaInformation(inputs->root_layer, &recursive_data);
std::vector<AccumulatedSurfaceState<LayerImpl>> accumulated_surface_state;
// The dummy layer list should not have been used.
DCHECK_EQ(0u, dummy_layer_list.size());
// A root layer render_surface should always exist after
// CalculateDrawProperties.
} // namespace cc