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