Mozart: Improve internal scene graph representation.

services/gfx/compositor/graph/scene_def.cc

Index: services/gfx/compositor/graph/scene_def.cc
diff --git a/services/gfx/compositor/graph/scene_def.cc b/services/gfx/compositor/graph/scene_def.cc
index a23c1088a2376bb4d1a43442fe92e1a62f808248..649c43e8a76ee6362758014d5682353dbe847602 100644
--- a/services/gfx/compositor/graph/scene_def.cc
+++ b/services/gfx/compositor/graph/scene_def.cc
@@ -5,16 +5,14 @@
 #include "services/gfx/compositor/graph/scene_def.h"
 
 #include <ostream>
-#include <utility>
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
 #include "base/strings/stringprintf.h"
 #include "mojo/services/gfx/composition/cpp/formatting.h"
-#include "services/gfx/compositor/graph/snapshot.h"
+#include "services/gfx/compositor/graph/scene_content.h"
 #include "services/gfx/compositor/render/render_image.h"
-#include "services/gfx/compositor/render/render_layer.h"
 
 namespace compositor {
 
@@ -31,11 +29,8 @@ void ReleaseMailboxTexture(
 }
 }  // namespace
 
-SceneDef::SceneDef(mojo::gfx::composition::SceneTokenPtr scene_token,
-                   const std::string& label)
-    : scene_token_(scene_token.Pass()), label_(label) {
-  DCHECK(scene_token_);
-}
+SceneDef::SceneDef(const SceneLabel& label)
+    : label_(label), weak_factory_(this) {}
 
 SceneDef::~SceneDef() {}
 
@@ -68,15 +63,8 @@ SceneDef::Disposition SceneDef::Present(
     end--;
   }
 
-  // Prepare to apply all publications up to this point.
-  uint32_t version = pending_publications_[end - 1]->metadata->version;
-  if (version_ != version) {
-    version_ = version;
-    formatted_label_cache_.clear();
-  }
-  Invalidate();
-
-  // Apply all updates sequentially.
+  // Apply all updates sequentially up to this point.
+  version_ = pending_publications_[end - 1]->metadata->version;
   for (size_t index = 0; index < end; ++index) {
     for (auto& update : pending_publications_[index]->updates) {
       if (!ApplyUpdate(update.Pass(), resolver, unavailable_sender, err))
@@ -88,10 +76,12 @@ SceneDef::Disposition SceneDef::Present(
   pending_publications_.erase(pending_publications_.begin(),
                               pending_publications_.begin() + end);
 
-  // Ensure the scene is in a valid state.
-  if (!Validate(err))
-    return Disposition::kFailed;
-  return Disposition::kSucceeded;
+  // Rebuild the scene content, gathering all reachable nodes and resources
+  // and verifying that everything is correctly linked.
+  SceneContentBuilder builder(this, version_, err, resources_.size(),
+                              nodes_.size());
+  content_ = builder.Build();
+  return content_ ? Disposition::kSucceeded : Disposition::kFailed;
 }
 
 bool SceneDef::ApplyUpdate(mojo::gfx::composition::SceneUpdatePtr update,
@@ -100,6 +90,12 @@ bool SceneDef::ApplyUpdate(mojo::gfx::composition::SceneUpdatePtr update,
                            std::ostream& err) {
   DCHECK(update);
 
+  // TODO(jeffbrown): We may be able to reuse some content from previous
+  // versions even when the client removes and recreates resources or nodes.
+  // To reduce unnecessary churn, consider keeping track of items which have
+  // been removed or are being replaced then checking to see whether they
+  // really changed.
+
   // Update resources.
   if (update->clear_resources) {
     resources_.clear();
@@ -109,11 +105,11 @@ bool SceneDef::ApplyUpdate(mojo::gfx::composition::SceneUpdatePtr update,
     uint32_t resource_id = it.GetKey();
     mojo::gfx::composition::ResourcePtr& resource_decl = it.GetValue();
     if (resource_decl) {
-      ResourceDef* resource = CreateResource(resource_id, resource_decl.Pass(),
-                                             resolver, unavailable_sender, err);
+      scoped_refptr<const ResourceDef> resource = CreateResource(
+          resource_id, resource_decl.Pass(), resolver, unavailable_sender, err);
       if (!resource)
         return false;
-      resources_[resource_id].reset(resource);
+      resources_[resource_id] = std::move(resource);
     } else {
       resources_.erase(resource_id);
     }
@@ -127,10 +123,11 @@ bool SceneDef::ApplyUpdate(mojo::gfx::composition::SceneUpdatePtr update,
     uint32_t node_id = it.GetKey();
     mojo::gfx::composition::NodePtr& node_decl = it.GetValue();
     if (node_decl) {
-      NodeDef* node = CreateNode(node_id, node_decl.Pass(), err);
+      scoped_refptr<const NodeDef> node =
+          CreateNode(node_id, node_decl.Pass(), err);
       if (!node)
         return false;
-      nodes_[node_id].reset(node);
+      nodes_[node_id] = std::move(node);
     } else {
       nodes_.erase(node_id);
     }
@@ -138,22 +135,6 @@ bool SceneDef::ApplyUpdate(mojo::gfx::composition::SceneUpdatePtr update,
   return true;
 }
 
-bool SceneDef::Validate(std::ostream& err) {
-  // Validate all nodes.
-  // TODO(jeffbrown): Figure out how to do this incrementally if it gets
-  // too expensive to process all nodes each time.
-  root_node_ = nullptr;
-  for (auto& pair : nodes_) {
-    uint32_t node_id = pair.first;
-    NodeDef* node = pair.second.get();
-    if (!node->Validate(this, err))
-      return false;
-    if (node_id == mojo::gfx::composition::kSceneRootNodeId)
-      root_node_ = node;
-  }
-  return true;
-}
-
 bool SceneDef::UnlinkReferencedScene(
     SceneDef* scene,
     const SceneUnavailableSender& unavailable_sender) {
@@ -162,11 +143,11 @@ bool SceneDef::UnlinkReferencedScene(
   bool changed = false;
   for (auto& pair : resources_) {
     if (pair.second->type() == ResourceDef::Type::kScene) {
-      auto scene_resource = static_cast<SceneResourceDef*>(pair.second.get());
-      if (scene_resource->referenced_scene() == scene) {
-        scene_resource->clear_referenced_scene();
-        Invalidate();
+      auto scene_resource =
+          static_cast<const SceneResourceDef*>(pair.second.get());
+      if (scene_resource->referenced_scene().get() == scene) {
         changed = true;
+        pair.second = scene_resource->Unlink();
         unavailable_sender.Run(pair.first);
       }
     }
@@ -174,86 +155,7 @@ bool SceneDef::UnlinkReferencedScene(
   return changed;
 }
 
-bool SceneDef::Snapshot(SnapshotBuilder* snapshot_builder,
-                        RenderLayerBuilder* layer_builder) {
-  DCHECK(snapshot_builder);
-  DCHECK(layer_builder);
-
-  // Detect cycles.
-  if (visited_) {
-    if (snapshot_builder->block_log()) {
-      *snapshot_builder->block_log()
-          << "Scene blocked due to recursive cycle: " << FormattedLabel()
-          << std::endl;
-    }
-    return false;
-  }
-
-  // Snapshot the contents of the scene.
-  visited_ = true;
-  bool success = SnapshotInner(snapshot_builder, layer_builder);
-  visited_ = false;
-  return success;
-}
-
-bool SceneDef::SnapshotInner(SnapshotBuilder* snapshot_builder,
-                             RenderLayerBuilder* layer_builder) {
-  // Note the dependency even if blocked.
-  snapshot_builder->AddSceneDependency(this);
-
-  // Ensure we have a root node.
-  if (!root_node_) {
-    if (snapshot_builder->block_log()) {
-      *snapshot_builder->block_log()
-          << "Scene blocked due because it has no root node: "
-          << FormattedLabel() << std::endl;
-    }
-    return false;
-  }
-
-  // Snapshot and draw the layer.
-  std::shared_ptr<RenderLayer> scene_layer = SnapshotLayer(snapshot_builder);
-  if (!scene_layer)
-    return false;
-  layer_builder->DrawLayer(scene_layer);
-  return true;
-}
-
-std::shared_ptr<RenderLayer> SceneDef::SnapshotLayer(
-    SnapshotBuilder* snapshot_builder) {
-  if (cached_layer_)
-    return cached_layer_;
-
-  RenderLayerBuilder scene_layer_builder;
-  scene_layer_builder.PushScene(scene_token_->value, version_);
-  if (!root_node_->Snapshot(snapshot_builder, &scene_layer_builder, this))
-    return nullptr;
-  scene_layer_builder.PopScene();
-
-  // TODO(jeffbrown): Implement caching even when the scene has dependencies.
-  // There are some subtleties to be dealt with to ensure that caches
-  // are properly invalidated and that we don't accidentally cache layers which
-  // bake in decisions which counteract the intended cycle detection and
-  // avoidance behavior.  Basically just need better bookkeeping.
-  std::shared_ptr<RenderLayer> scene_layer = scene_layer_builder.Build();
-  if (!HasSceneResources())
-    cached_layer_ = scene_layer;
-  return scene_layer;
-}
-
-void SceneDef::Invalidate() {
-  cached_layer_.reset();
-}
-
-bool SceneDef::HasSceneResources() {
-  for (auto& pair : resources_) {
-    if (pair.second->type() == ResourceDef::Type::kScene)
-      return true;
-  }
-  return false;
-}
-
-ResourceDef* SceneDef::CreateResource(
+scoped_refptr<const ResourceDef> SceneDef::CreateResource(
     uint32_t resource_id,
     mojo::gfx::composition::ResourcePtr resource_decl,
     const SceneResolver& resolver,
@@ -264,12 +166,13 @@ ResourceDef* SceneDef::CreateResource(
   if (resource_decl->is_scene()) {
     auto& scene_resource_decl = resource_decl->get_scene();
     DCHECK(scene_resource_decl->scene_token);
-    SceneDef* referenced_scene =
-        resolver.Run(scene_resource_decl->scene_token.get());
-    if (!referenced_scene) {
+
+    const mojo::gfx::composition::SceneToken& scene_token =
+        *scene_resource_decl->scene_token;
+    base::WeakPtr<SceneDef> referenced_scene = resolver.Run(scene_token);
+    if (!referenced_scene)
       unavailable_sender.Run(resource_id);
-    }
-    return new SceneResourceDef(referenced_scene);
+    return new SceneResourceDef(scene_token, referenced_scene);
   }
 
   if (resource_decl->is_mailbox_texture()) {
@@ -277,8 +180,9 @@ ResourceDef* SceneDef::CreateResource(
     DCHECK(mailbox_texture_resource_decl->mailbox_name.size() ==
            GL_MAILBOX_SIZE_CHROMIUM);
     DCHECK(mailbox_texture_resource_decl->size);
-    int32_t width = mailbox_texture_resource_decl->size->width;
-    int32_t height = mailbox_texture_resource_decl->size->height;
+
+    const int32_t width = mailbox_texture_resource_decl->size->width;
+    const int32_t height = mailbox_texture_resource_decl->size->height;
     if (width < 1 || width > kMaxTextureWidth || height < 1 ||
         height > kMaxTextureHeight) {
       err << "MailboxTexture resource has invalid size: "
@@ -286,10 +190,12 @@ ResourceDef* SceneDef::CreateResource(
           << ", height=" << height;
       return nullptr;
     }
+    const GLbyte* const mailbox_name = reinterpret_cast<GLbyte*>(
+        mailbox_texture_resource_decl->mailbox_name.data());
+    const GLuint sync_point = mailbox_texture_resource_decl->sync_point;
+
     std::shared_ptr<RenderImage> image = RenderImage::CreateFromMailboxTexture(
-        reinterpret_cast<GLbyte*>(
-            mailbox_texture_resource_decl->mailbox_name.data()),
-        mailbox_texture_resource_decl->sync_point, width, height,
+        mailbox_name, sync_point, width, height,
         base::MessageLoop::current()->task_runner(),
         base::Bind(
             &ReleaseMailboxTexture,
@@ -307,86 +213,97 @@ ResourceDef* SceneDef::CreateResource(
   return nullptr;
 }
 
-NodeDef* SceneDef::CreateNode(uint32_t node_id,
-                              mojo::gfx::composition::NodePtr node_decl,
-                              std::ostream& err) {
+scoped_refptr<const NodeDef> SceneDef::CreateNode(
+    uint32_t node_id,
+    mojo::gfx::composition::NodePtr node_decl,
+    std::ostream& err) {
   DCHECK(node_decl);
 
-  NodeOp* op = nullptr;
-  if (node_decl->op) {
-    op = CreateNodeOp(node_id, node_decl->op.Pass(), err);
-    if (!op)
-      return nullptr;
+  mojo::TransformPtr content_transform = node_decl->content_transform.Pass();
+  mojo::RectPtr content_clip = node_decl->content_clip.Pass();
+  const mojo::gfx::composition::Node::Combinator combinator =
+      node_decl->combinator;
+  const std::vector<uint32_t>& child_node_ids =
+      node_decl->child_node_ids.storage();
+
+  if (!node_decl->op) {
+    return new NodeDef(node_id, content_transform.Pass(), content_clip.Pass(),
+                       combinator, child_node_ids);
   }
 
-  return new NodeDef(node_id, node_decl->content_transform.Pass(),
-                     node_decl->content_clip.Pass(), node_decl->hit_id,
-                     node_decl->combinator, node_decl->child_node_ids.storage(),
-                     op);
-}
+  if (node_decl->op->is_rect()) {
+    auto& rect_node_decl = node_decl->op->get_rect();
+    DCHECK(rect_node_decl->content_rect);
+    DCHECK(rect_node_decl->color);
 
-NodeOp* SceneDef::CreateNodeOp(uint32_t node_id,
-                               mojo::gfx::composition::NodeOpPtr node_op_decl,
-                               std::ostream& err) {
-  DCHECK(node_op_decl);
-
-  if (node_op_decl->is_rect()) {
-    auto& rect_node_op_decl = node_op_decl->get_rect();
-    DCHECK(rect_node_op_decl->content_rect);
-    DCHECK(rect_node_op_decl->color);
-    return new RectNodeOp(*rect_node_op_decl->content_rect,
-                          *rect_node_op_decl->color);
+    const mojo::Rect& content_rect = *rect_node_decl->content_rect;
+    const mojo::gfx::composition::Color& color = *rect_node_decl->color;
+    return new RectNodeDef(node_id, content_transform.Pass(),
+                           content_clip.Pass(), combinator, child_node_ids,
+                           content_rect, color);
   }
 
-  if (node_op_decl->is_image()) {
-    auto& image_node_op_decl = node_op_decl->get_image();
-    DCHECK(image_node_op_decl->content_rect);
-    return new ImageNodeOp(*image_node_op_decl->content_rect,
-                           image_node_op_decl->image_rect.Pass(),
-                           image_node_op_decl->image_resource_id,
-                           image_node_op_decl->blend.Pass());
+  if (node_decl->op->is_image()) {
+    auto& image_node_decl = node_decl->op->get_image();
+    DCHECK(image_node_decl->content_rect);
+
+    const mojo::Rect& content_rect = *image_node_decl->content_rect;
+    mojo::RectPtr image_rect = image_node_decl->image_rect.Pass();
+    const uint32 image_resource_id = image_node_decl->image_resource_id;
+    mojo::gfx::composition::BlendPtr blend = image_node_decl->blend.Pass();
+    return new ImageNodeDef(node_id, content_transform.Pass(),
+                            content_clip.Pass(), combinator, child_node_ids,
+                            content_rect, image_rect.Pass(), image_resource_id,
+                            blend.Pass());
   }
 
-  if (node_op_decl->is_scene()) {
-    auto& scene_node_op_decl = node_op_decl->get_scene();
-    return new SceneNodeOp(scene_node_op_decl->scene_resource_id,
-                           scene_node_op_decl->scene_version);
+  if (node_decl->op->is_scene()) {
+    auto& scene_node_decl = node_decl->op->get_scene();
+
+    const uint32_t scene_resource_id = scene_node_decl->scene_resource_id;
+    const uint32_t scene_version = scene_node_decl->scene_version;
+    return new SceneNodeDef(node_id, content_transform.Pass(),
+                            content_clip.Pass(), combinator, child_node_ids,
+                            scene_resource_id, scene_version);
   }
 
-  if (node_op_decl->is_layer()) {
-    auto& layer_node_op_decl = node_op_decl->get_layer();
-    DCHECK(layer_node_op_decl->layer_size);
-    return new LayerNodeOp(*layer_node_op_decl->layer_size,
-                           layer_node_op_decl->blend.Pass());
+  if (node_decl->op->is_layer()) {
+    auto& layer_node_decl = node_decl->op->get_layer();
+    DCHECK(layer_node_decl->layer_size);
+
+    const mojo::Size& layer_size = *layer_node_decl->layer_size;
+    mojo::gfx::composition::BlendPtr blend = layer_node_decl->blend.Pass();
+    return new LayerNodeDef(node_id, content_transform.Pass(),
+                            content_clip.Pass(), combinator, child_node_ids,
+                            layer_size, blend.Pass());
   }
 
   err << "Unsupported node op type: node_id=" << node_id
-      << ", node_op=" << node_op_decl;
+      << ", node_op=" << node_decl->op;
   return nullptr;
 }
 
-NodeDef* SceneDef::FindNode(uint32_t node_id) {
+const NodeDef* SceneDef::FindNode(uint32_t node_id) const {
   auto it = nodes_.find(node_id);
   return it != nodes_.end() ? it->second.get() : nullptr;
 }
 
-ResourceDef* SceneDef::FindResource(uint32_t resource_id,
-                                    ResourceDef::Type resource_type) {
+const ResourceDef* SceneDef::FindResource(uint32_t resource_id) const {
   auto it = resources_.find(resource_id);
-  return it != resources_.end() && it->second->type() == resource_type
-             ? it->second.get()
-             : nullptr;
+  return it != resources_.end() ? it->second.get() : nullptr;
 }
 
-std::string SceneDef::FormattedLabel() {
-  if (formatted_label_cache_.empty()) {
-    formatted_label_cache_ =
-        label_.empty()
-            ? base::StringPrintf("<%d/%d>", scene_token_->value, version_)
-            : base::StringPrintf("<%d:%s/%d>", scene_token_->value,
-                                 label_.c_str(), version_);
-  }
-  return formatted_label_cache_;
+const SceneContent* SceneDef::FindContent(uint32_t version) const {
+  if (!content_)
+    return nullptr;
+
+  // TODO(jeffbrown): Consider briefly caching older versions to allow them
+  // to be used to provide alternate content for node combinators.
+  if (version != mojo::gfx::composition::kSceneVersionNone &&
+      version != content_->version() &&
+      content_->version() != mojo::gfx::composition::kSceneVersionNone)
+    return nullptr;
+  return content_.get();
 }
 
 SceneDef::Publication::Publication(