cc/trees/property_tree.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 <set>
   6 #include <vector>
   7
   8 #include "base/logging.h"
   9 #include "cc/base/math_util.h"
  10 #include "cc/trees/property_tree.h"
  11
  12 namespace cc {
  13
  14 template <typename T>
  15 PropertyTree<T>::PropertyTree()
  16     : needs_update_(false) {
  17   nodes_.push_back(T());
  18   back()->id = 0;
  19   back()->parent_id = -1;
  20 }
  21
  22 template <typename T>
  23 PropertyTree<T>::~PropertyTree() {
  24 }
  25
  26 template <typename T>
  27 int PropertyTree<T>::Insert(const T& tree_node, int parent_id) {
  28   DCHECK_GT(nodes_.size(), 0u);
  29   nodes_.push_back(tree_node);
  30   T& node = nodes_.back();
  31   node.parent_id = parent_id;
  32   node.id = static_cast<int>(nodes_.size()) - 1;
  33   return node.id;
  34 }
  35
  36 template <typename T>
  37 void PropertyTree<T>::clear() {
  38   nodes_.clear();
  39   nodes_.push_back(T());
  40   back()->id = 0;
  41   back()->parent_id = -1;
  42 }
  43
  44 template class PropertyTree<TransformNode>;
  45 template class PropertyTree<ClipNode>;
  46 template class PropertyTree<OpacityNode>;
  47
  48 TransformNodeData::TransformNodeData()
  49     : target_id(-1),
  50       content_target_id(-1),
  51       source_node_id(-1),
  52       needs_local_transform_update(true),
  53       is_invertible(true),
  54       ancestors_are_invertible(true),
  55       is_animated(false),
  56       to_screen_is_animated(false),
  57       flattens_inherited_transform(false),
  58       node_and_ancestors_are_flat(true),
  59       scrolls(false),
  60       needs_sublayer_scale(false),
  61       layer_scale_factor(1.0f),
  62       post_local_scale_factor(1.0f) {
  63 }
  64
  65 TransformNodeData::~TransformNodeData() {
  66 }
  67
  68 void TransformNodeData::update_pre_local_transform(
  69     const gfx::Point3F& transform_origin) {
  70   pre_local.MakeIdentity();
  71   pre_local.Translate3d(-transform_origin.x(), -transform_origin.y(),
  72                         -transform_origin.z());
  73 }
  74
  75 void TransformNodeData::update_post_local_transform(
  76     const gfx::PointF& position,
  77     const gfx::Point3F& transform_origin) {
  78   post_local.MakeIdentity();
  79   post_local.Scale(post_local_scale_factor, post_local_scale_factor);
  80   post_local.Translate3d(
  81       position.x() + source_offset.x() + transform_origin.x(),
  82       position.y() + source_offset.y() + transform_origin.y(),
  83       transform_origin.z());
  84 }
  85
  86 ClipNodeData::ClipNodeData() : transform_id(-1), target_id(-1) {
  87 }
  88
  89 bool TransformTree::ComputeTransform(int source_id,
  90                                      int dest_id,
  91                                      gfx::Transform* transform) const {
  92   transform->MakeIdentity();
  93
  94   if (source_id == dest_id)
  95     return true;
  96
  97   if (source_id > dest_id) {
  98     return CombineTransformsBetween(source_id, dest_id, transform);
  99   }
 100
 101   return CombineInversesBetween(source_id, dest_id, transform);
 102 }
 103
 104 bool TransformTree::ComputeTransformWithDestinationSublayerScale(
 105     int source_id,
 106     int dest_id,
 107     gfx::Transform* transform) const {
 108   bool success = ComputeTransform(source_id, dest_id, transform);
 109
 110   const TransformNode* dest_node = Node(dest_id);
 111   if (!dest_node->data.needs_sublayer_scale)
 112     return success;
 113
 114   transform->matrix().postScale(dest_node->data.sublayer_scale.x(),
 115                                 dest_node->data.sublayer_scale.y(), 1.f);
 116   return success;
 117 }
 118
 119 bool TransformTree::ComputeTransformWithSourceSublayerScale(
 120     int source_id,
 121     int dest_id,
 122     gfx::Transform* transform) const {
 123   bool success = ComputeTransform(source_id, dest_id, transform);
 124
 125   const TransformNode* source_node = Node(source_id);
 126   if (!source_node->data.needs_sublayer_scale)
 127     return success;
 128
 129   transform->Scale(1.f / source_node->data.sublayer_scale.x(),
 130                    1.f / source_node->data.sublayer_scale.y());
 131   return success;
 132 }
 133
 134 bool TransformTree::Are2DAxisAligned(int source_id, int dest_id) const {
 135   gfx::Transform transform;
 136   return ComputeTransform(source_id, dest_id, &transform) &&
 137          transform.Preserves2dAxisAlignment();
 138 }
 139
 140 void TransformTree::UpdateTransforms(int id) {
 141   TransformNode* node = Node(id);
 142   TransformNode* parent_node = parent(node);
 143   TransformNode* target_node = Node(node->data.target_id);
 144   if (node->data.needs_local_transform_update ||
 145       node->parent_id != node->data.source_node_id)
 146     UpdateLocalTransform(node);
 147   UpdateScreenSpaceTransform(node, parent_node, target_node);
 148   UpdateSublayerScale(node);
 149   UpdateTargetSpaceTransform(node, target_node);
 150   UpdateIsAnimated(node, parent_node);
 151   UpdateSnapping(node);
 152 }
 153
 154 bool TransformTree::IsDescendant(int desc_id, int source_id) const {
 155   while (desc_id != source_id) {
 156     if (desc_id < 0)
 157       return false;
 158     desc_id = Node(desc_id)->parent_id;
 159   }
 160   return true;
 161 }
 162
 163 bool TransformTree::CombineTransformsBetween(int source_id,
 164                                              int dest_id,
 165                                              gfx::Transform* transform) const {
 166   DCHECK(source_id > dest_id);
 167   const TransformNode* current = Node(source_id);
 168   const TransformNode* dest = Node(dest_id);
 169   // Combine transforms to and from the screen when possible. Since flattening
 170   // is a non-linear operation, we cannot use this approach when there is
 171   // non-trivial flattening between the source and destination nodes. For
 172   // example, consider the tree R->A->B->C, where B flattens its inherited
 173   // transform, and A has a non-flat transform. Suppose C is the source and A is
 174   // the destination. The expected result is C * B. But C's to_screen
 175   // transform is C * B * flattened(A * R), and A's from_screen transform is
 176   // R^{-1} * A^{-1}. If at least one of A and R isn't flat, the inverse of
 177   // flattened(A * R) won't be R^{-1} * A{-1}, so multiplying C's to_screen and
 178   // A's from_screen will not produce the correct result.
 179   if (!dest || (dest->data.ancestors_are_invertible &&
 180                 dest->data.node_and_ancestors_are_flat)) {
 181     transform->ConcatTransform(current->data.to_screen);
 182     if (dest)
 183       transform->ConcatTransform(dest->data.from_screen);
 184     return true;
 185   }
 186
 187   // Flattening is defined in a way that requires it to be applied while
 188   // traversing downward in the tree. We first identify nodes that are on the
 189   // path from the source to the destination (this is traversing upward), and
 190   // then we visit these nodes in reverse order, flattening as needed. We
 191   // early-out if we get to a node whose target node is the destination, since
 192   // we can then re-use the target space transform stored at that node.
 193   std::vector<int> source_to_destination;
 194   source_to_destination.push_back(current->id);
 195   current = parent(current);
 196   for (; current && current->id > dest_id; current = parent(current)) {
 197     if (current->data.target_id == dest_id &&
 198         current->data.content_target_id == dest_id)
 199       break;
 200     source_to_destination.push_back(current->id);
 201   }
 202
 203   gfx::Transform combined_transform;
 204   if (current->id > dest_id) {
 205     combined_transform = current->data.to_target;
 206     // The stored target space transform has sublayer scale baked in, but we
 207     // need the unscaled transform.
 208     combined_transform.Scale(1.0f / dest->data.sublayer_scale.x(),
 209                              1.0f / dest->data.sublayer_scale.y());
 210   } else if (current->id < dest_id) {
 211     // We have reached the lowest common ancestor of the source and destination
 212     // nodes. This case can occur when we are transforming between a node
 213     // corresponding to a fixed-position layer (or its descendant) and the node
 214     // corresponding to the layer's render target. For example, consider the
 215     // layer tree R->T->S->F where F is fixed-position, S owns a render surface,
 216     // and T has a significant transform. This will yield the following
 217     // transform tree:
 218     //    R
 219     //    |
 220     //    T
 221     //   /|
 222     //  S F
 223     // In this example, T will have id 2, S will have id 3, and F will have id
 224     // 4. When walking up the ancestor chain from F, the first node with a
 225     // smaller id than S will be T, the lowest common ancestor of these nodes.
 226     // We compute the transform from T to S here, and then from F to T in the
 227     // loop below.
 228     DCHECK(IsDescendant(dest_id, current->id));
 229     CombineInversesBetween(current->id, dest_id, &combined_transform);
 230     DCHECK(combined_transform.IsApproximatelyIdentityOrTranslation(
 231         SkDoubleToMScalar(1e-4)));
 232   }
 233
 234   for (int i = source_to_destination.size() - 1; i >= 0; i--) {
 235     const TransformNode* node = Node(source_to_destination[i]);
 236     if (node->data.flattens_inherited_transform)
 237       combined_transform.FlattenTo2d();
 238     combined_transform.PreconcatTransform(node->data.to_parent);
 239   }
 240
 241   transform->ConcatTransform(combined_transform);
 242   return true;
 243 }
 244
 245 bool TransformTree::CombineInversesBetween(int source_id,
 246                                            int dest_id,
 247                                            gfx::Transform* transform) const {
 248   DCHECK(source_id < dest_id);
 249   const TransformNode* current = Node(dest_id);
 250   const TransformNode* dest = Node(source_id);
 251   // Just as in CombineTransformsBetween, we can use screen space transforms in
 252   // this computation only when there isn't any non-trivial flattening
 253   // involved.
 254   if (current->data.ancestors_are_invertible &&
 255       current->data.node_and_ancestors_are_flat) {
 256     transform->PreconcatTransform(current->data.from_screen);
 257     if (dest)
 258       transform->PreconcatTransform(dest->data.to_screen);
 259     return true;
 260   }
 261
 262   // Inverting a flattening is not equivalent to flattening an inverse. This
 263   // means we cannot, for example, use the inverse of each node's to_parent
 264   // transform, flattening where needed. Instead, we must compute the transform
 265   // from the destination to the source, with flattening, and then invert the
 266   // result.
 267   gfx::Transform dest_to_source;
 268   CombineTransformsBetween(dest_id, source_id, &dest_to_source);
 269   gfx::Transform source_to_dest;
 270   bool all_are_invertible = dest_to_source.GetInverse(&source_to_dest);
 271   transform->PreconcatTransform(source_to_dest);
 272   return all_are_invertible;
 273 }
 274
 275 void TransformTree::UpdateLocalTransform(TransformNode* node) {
 276   gfx::Transform transform = node->data.post_local;
 277   gfx::Vector2dF source_to_parent;
 278   if (node->parent_id != node->data.source_node_id) {
 279     gfx::Transform to_parent;
 280     ComputeTransform(node->data.source_node_id, node->parent_id, &to_parent);
 281     source_to_parent = to_parent.To2dTranslation();
 282   }
 283   transform.Translate(source_to_parent.x() - node->data.scroll_offset.x(),
 284                       source_to_parent.y() - node->data.scroll_offset.y());
 285   transform.PreconcatTransform(node->data.local);
 286   transform.PreconcatTransform(node->data.pre_local);
 287   node->data.set_to_parent(transform);
 288   node->data.needs_local_transform_update = false;
 289 }
 290
 291 void TransformTree::UpdateScreenSpaceTransform(TransformNode* node,
 292                                                TransformNode* parent_node,
 293                                                TransformNode* target_node) {
 294   if (!parent_node) {
 295     node->data.to_screen = node->data.to_parent;
 296     node->data.ancestors_are_invertible = true;
 297     node->data.to_screen_is_animated = false;
 298     node->data.node_and_ancestors_are_flat = node->data.to_parent.IsFlat();
 299   } else {
 300     node->data.to_screen = parent_node->data.to_screen;
 301     if (node->data.flattens_inherited_transform)
 302       node->data.to_screen.FlattenTo2d();
 303     node->data.to_screen.PreconcatTransform(node->data.to_parent);
 304     node->data.ancestors_are_invertible =
 305         parent_node->data.ancestors_are_invertible;
 306     node->data.node_and_ancestors_are_flat =
 307         parent_node->data.node_and_ancestors_are_flat &&
 308         node->data.to_parent.IsFlat();
 309   }
 310
 311   if (!node->data.to_screen.GetInverse(&node->data.from_screen))
 312     node->data.ancestors_are_invertible = false;
 313 }
 314
 315 void TransformTree::UpdateSublayerScale(TransformNode* node) {
 316   // The sublayer scale depends on the screen space transform, so update it too.
 317   node->data.sublayer_scale =
 318       node->data.needs_sublayer_scale
 319           ? MathUtil::ComputeTransform2dScaleComponents(
 320                 node->data.to_screen, node->data.layer_scale_factor)
 321           : gfx::Vector2dF(1.0f, 1.0f);
 322 }
 323
 324 void TransformTree::UpdateTargetSpaceTransform(TransformNode* node,
 325                                                TransformNode* target_node) {
 326   if (node->data.needs_sublayer_scale) {
 327     node->data.to_target.MakeIdentity();
 328     node->data.to_target.Scale(node->data.sublayer_scale.x(),
 329                                node->data.sublayer_scale.y());
 330   } else {
 331     const bool target_is_root_surface = target_node->id == 1;
 332     // In order to include the root transform for the root surface, we walk up
 333     // to the root of the transform tree in ComputeTransform.
 334     int target_id = target_is_root_surface ? 0 : target_node->id;
 335     ComputeTransformWithDestinationSublayerScale(node->id, target_id,
 336                                                  &node->data.to_target);
 337   }
 338
 339   if (!node->data.to_target.GetInverse(&node->data.from_target))
 340     node->data.ancestors_are_invertible = false;
 341 }
 342
 343 void TransformTree::UpdateIsAnimated(TransformNode* node,
 344                                      TransformNode* parent_node) {
 345   if (parent_node) {
 346     node->data.to_screen_is_animated =
 347         node->data.is_animated || parent_node->data.to_screen_is_animated;
 348   }
 349 }
 350
 351 void TransformTree::UpdateSnapping(TransformNode* node) {
 352   if (!node->data.scrolls || node->data.to_screen_is_animated ||
 353       !node->data.to_target.IsScaleOrTranslation()) {
 354     return;
 355   }
 356
 357   // Scroll snapping must be done in target space (the pixels we care about).
 358   // This means we effectively snap the target space transform. If TT is the
 359   // target space transform and TT' is TT with its translation components
 360   // rounded, then what we're after is the scroll delta X, where TT * X = TT'.
 361   // I.e., we want a transform that will realize our scroll snap. It follows
 362   // that X = TT^-1 * TT'. We cache TT and TT^-1 to make this more efficient.
 363   gfx::Transform rounded = node->data.to_target;
 364   rounded.RoundTranslationComponents();
 365   gfx::Transform delta = node->data.from_target;
 366   delta *= rounded;
 367
 368   DCHECK(delta.IsApproximatelyIdentityOrTranslation(SkDoubleToMScalar(1e-4)))
 369       << delta.ToString();
 370
 371   gfx::Vector2dF translation = delta.To2dTranslation();
 372
 373   // Now that we have our scroll delta, we must apply it to each of our
 374   // combined, to/from matrices.
 375   node->data.to_parent.Translate(translation.x(), translation.y());
 376   node->data.to_target.Translate(translation.x(), translation.y());
 377   node->data.from_target.matrix().postTranslate(-translation.x(),
 378                                                 -translation.y(), 0);
 379   node->data.to_screen.Translate(translation.x(), translation.y());
 380   node->data.from_screen.matrix().postTranslate(-translation.x(),
 381                                                 -translation.y(), 0);
 382
 383   node->data.scroll_snap = translation;
 384 }
 385
 386 PropertyTrees::PropertyTrees() : needs_rebuild(true), sequence_number(0) {
 387 }
 388
 389 }  // namespace cc