Skip drawing unsupported layers in forced software mode

cc/layers/texture_layer_impl.cc

 // 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/layers/texture_layer_impl.h"
 
 #include "base/stringprintf.h"
 #include "cc/layers/quad_sink.h"
 #include "cc/output/renderer.h"
 #include "cc/quads/texture_draw_quad.h"
@@ skipping 45 matching lines @@
   texture_layer->set_vertex_opacity(vertex_opacity_);
   texture_layer->set_premultiplied_alpha(premultiplied_alpha_);
   if (uses_mailbox_ && own_mailbox_) {
     texture_layer->SetTextureMailbox(texture_mailbox_);
     own_mailbox_ = false;
   } else {
     texture_layer->set_texture_id(texture_id_);
   }
 }
 
-void TextureLayerImpl::WillDraw(ResourceProvider* resource_provider) {
-  if (uses_mailbox_ || !texture_id_)
-    return;
-  DCHECK(!external_texture_resource_);
-  external_texture_resource_ =
-      resource_provider->CreateResourceFromExternalTexture(
-          GL_TEXTURE_2D,
-          texture_id_);
+bool TextureLayerImpl::WillDraw(DrawMode draw_mode,
+                                ResourceProvider* resource_provider) {
+  if (!texture_id_ ||
+      draw_mode == DRAW_MODE_RESOURCELESS_SOFTWARE)
+    return false;

[piman, 2013/05/31 00:48:15]

still nak, because if uses_mailbox_, then texture_id_ will be 0.

Basically you have 2 modes (mailbox and non-mailbox).

In the mailbox mode, the resource is created in DidBecomeActive, if the mailbox
is not empty. If it's empty, we leave the resource as 0 and we skip drawing in
AppendQuads.

In the texture mode, the resource is created here if the texture is non-0,
otherwise we leave the resource as 0 and skip drawing in AppendQuads

You can refactor this as:
if (draw_mode == DRAW_MODE_RESOURCELESS_SOFTWARE)
  return false;
if (!uses_mailbox_) {
  DCHECK(!external_texture_resource_);
  external_texture_resource_ =
resource_provider->CreateResourceFromExternalTexture(
          GL_TEXTURE_2D,
          texture_id_);
}
return LayerImpl::WillDraw(draw_mode, resource_provider) &&
!!external_texture_resource_;

And then leave out the early return in AppendQuads.

[boliu, 2013/05/31 02:50:07]

Second try! Should be fixed now. The second if condition should be
(!uses_mailbox_ && texture_id_). Also added a test just for this.

+
+  if (!uses_mailbox_) {
+    DCHECK(!external_texture_resource_);
+    external_texture_resource_ =
+        resource_provider->CreateResourceFromExternalTexture(
+            GL_TEXTURE_2D,
+            texture_id_);
+  }
+  return LayerImpl::WillDraw(draw_mode, resource_provider);
 }
 
 void TextureLayerImpl::AppendQuads(QuadSink* quad_sink,
                                    AppendQuadsData* append_quads_data) {
   if (!external_texture_resource_)
     return;
 
   SharedQuadState* shared_quad_state =
       quad_sink->UseSharedQuadState(CreateSharedQuadState());
   AppendDebugBorderQuad(quad_sink, shared_quad_state, append_quads_data);
@@ skipping 12 matching lines @@
                flipped_);
 
   // Perform explicit clipping on a quad to avoid setting a scissor later.
   if (shared_quad_state->is_clipped && quad->PerformClipping())
     shared_quad_state->is_clipped = false;
   if (!quad->rect.IsEmpty())
     quad_sink->Append(quad.PassAs<DrawQuad>(), append_quads_data);
 }
 
 void TextureLayerImpl::DidDraw(ResourceProvider* resource_provider) {
+  LayerImpl::DidDraw(resource_provider);
   if (uses_mailbox_ || !external_texture_resource_)
     return;
   // FIXME: the following assert will not be true when sending resources to a
   // parent compositor. A synchronization scheme (double-buffering or
   // pipelining of updates) for the client will need to exist to solve this.
   DCHECK(!resource_provider->InUseByConsumer(external_texture_resource_));
   resource_provider->DeleteResource(external_texture_resource_);
   external_texture_resource_ = 0;
 }
 
@@ skipping 40 matching lines @@
   } else if (external_texture_resource_) {
     DCHECK(!own_mailbox_);
     ResourceProvider* resource_provider =
         layer_tree_impl()->resource_provider();
     resource_provider->DeleteResource(external_texture_resource_);
     external_texture_resource_ = 0;
   }
 }
 
 }  // namespace cc