cc/layers/layer_utils.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "cc/layers/layer_utils.h"
   6
   7 #include "cc/layers/layer_impl.h"
   8 #include "cc/trees/layer_tree_host_common.h"
   9 #include "ui/gfx/geometry/box_f.h"
  10
  11 namespace cc {
  12
  13 namespace {
  14
  15 bool HasAnimationThatInflatesBounds(const LayerImpl& layer) {
  16   return layer.HasAnimationThatInflatesBounds();
  17 }
  18
  19 bool HasFilterAnimationThatInflatesBounds(const LayerImpl& layer) {
  20   return layer.HasFilterAnimationThatInflatesBounds();
  21 }
  22
  23 bool HasTransformAnimationThatInflatesBounds(const LayerImpl& layer) {
  24   return layer.HasTransformAnimationThatInflatesBounds();
  25 }
  26
  27 inline bool HasAncestorTransformAnimation(const LayerImpl& layer) {
  28   return layer.screen_space_transform_is_animating();
  29 }
  30
  31 inline bool HasAncestorFilterAnimation(const LayerImpl& layer) {
  32   for (const LayerImpl* current = &layer; current;
  33        current = current->parent()) {
  34     if (HasFilterAnimationThatInflatesBounds(*current))
  35         return true;
  36   }
  37
  38   return false;
  39 }
  40
  41 }  // namespace
  42
  43 bool LayerUtils::GetAnimationBounds(const LayerImpl& layer_in, gfx::BoxF* out) {
  44   // We don't care about animated bounds for invisible layers.
  45   if (!layer_in.DrawsContent())
  46     return false;
  47
  48   // We also don't care for layers that are not animated or a child of an
  49   // animated layer.
  50   if (!HasAncestorTransformAnimation(layer_in) &&
  51       !HasAncestorFilterAnimation(layer_in))
  52     return false;
  53
  54   // To compute the inflated bounds for a layer, we start by taking its bounds
  55   // and converting it to a 3d box, and then we transform or inflate it
  56   // repeatedly as we walk up the layer tree to the root.
  57   //
  58   // At each layer we apply the following transformations to the box:
  59   //   1) We translate so that the anchor point is the origin.
  60   //   2) We either apply the layer's transform or inflate if the layer's
  61   //      transform is animated.
  62   //   3) We undo the translation from step 1 and apply a second translation
  63   //      to account for the layer's position.
  64   //
  65   gfx::BoxF box(layer_in.bounds().width(), layer_in.bounds().height(), 0.f);
  66
  67   // We want to inflate/transform the box as few times as possible. Each time
  68   // we do this, we have to make the box axis aligned again, so if we make many
  69   // small adjustments to the box by transforming it repeatedly rather than
  70   // once by the product of all these matrices, we will accumulate a bunch of
  71   // unnecessary inflation because of the the many axis-alignment fixes. This
  72   // matrix stores said product.
  73   gfx::Transform coalesced_transform;
  74
  75   for (const LayerImpl* layer = &layer_in; layer; layer = layer->parent()) {
  76     int transform_origin_x = layer->transform_origin().x();
  77     int transform_origin_y = layer->transform_origin().y();
  78     int transform_origin_z = layer->transform_origin().z();
  79
  80     gfx::PointF position = layer->position();
  81     if (layer->parent() && !HasAnimationThatInflatesBounds(*layer)) {
  82       // |composite_layer_transform| contains 1 - 4 mentioned above. We compute
  83       // it separately and apply afterwards because it's a bit more efficient
  84       // because post-multiplication appears a bit more expensive, so we want
  85       // to do it only once.
  86       gfx::Transform composite_layer_transform;
  87
  88       composite_layer_transform.Translate3d(transform_origin_x + position.x(),
  89                                             transform_origin_y + position.y(),
  90                                             transform_origin_z);
  91       composite_layer_transform.PreconcatTransform(layer->transform());
  92       composite_layer_transform.Translate3d(
  93           -transform_origin_x, -transform_origin_y, -transform_origin_z);
  94
  95       // Add this layer's contributions to the |coalesced_transform|.
  96       coalesced_transform.ConcatTransform(composite_layer_transform);
  97       continue;
  98     }
  99
 100     // First, apply coalesced transform we've been building and reset it.
 101     coalesced_transform.TransformBox(&box);
 102     coalesced_transform.MakeIdentity();
 103
 104     // We need to apply the inflation about the layer's anchor point. Rather
 105     // than doing this via transforms, we'll just shift the box directly.
 106     box.set_origin(box.origin() + gfx::Vector3dF(-transform_origin_x,
 107                                                  -transform_origin_y,
 108                                                  -transform_origin_z));
 109
 110     // Perform the inflation
 111     if (HasFilterAnimationThatInflatesBounds(*layer)) {
 112       gfx::BoxF inflated;
 113       if (!layer->FilterAnimationBoundsForBox(box, &inflated))
 114         return false;
 115       box = inflated;
 116     }
 117
 118     if (HasTransformAnimationThatInflatesBounds(*layer)) {
 119       gfx::BoxF inflated;
 120       if (!layer->TransformAnimationBoundsForBox(box, &inflated))
 121         return false;
 122       box = inflated;
 123     }
 124
 125     // Apply step 3) mentioned above.
 126     box.set_origin(box.origin() +
 127                    gfx::Vector3dF(transform_origin_x + position.x(),
 128                                   transform_origin_y + position.y(),
 129                                   transform_origin_z));
 130   }
 131
 132   // If we've got an unapplied coalesced transform at this point, it must still
 133   // be applied.
 134   if (!coalesced_transform.IsIdentity())
 135     coalesced_transform.TransformBox(&box);
 136
 137   *out = box;
 138
 139   return true;
 140 }
 141
 142 }  // namespace cc