Add WebGraphicsContext support for readbacks from any framebuffer.

This is needed for https://bugs.webkit.org/show_bug.cgi?id=65658 .

BUG=55927
TEST=


Review URL: http://codereview.chromium.org/7566046

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@95898 0039d316-1c4b-4281-b951-d872f2087c98

4 files changed, 38 insertions, 13 deletions

diff --git a/webkit/gpu/webgraphicscontext3d_in_process_command_buffer_impl.cc b/webkit/gpu/webgraphicscontext3d_in_process_command_buffer_impl.cc
index 0c70da7..661003b 100644
--- a/webkit/gpu/webgraphicscontext3d_in_process_command_buffer_impl.cc
+++ b/webkit/gpu/webgraphicscontext3d_in_process_command_buffer_impl.cc
@@ -822,10 +822,13 @@ void WebGraphicsContext3DInProcessCommandBufferImpl::FlipVertically(
 
 bool WebGraphicsContext3DInProcessCommandBufferImpl::readBackFramebuffer(
     unsigned char* pixels,
-    size_t buffer_size) {
+    size_t buffer_size,
+    WebGLId framebuffer,
+    int width,
+    int height) {
   // TODO(gmam): See if we can comment this in.
   // ClearContext();
-  if (buffer_size != static_cast<size_t>(4 * width() * height())) {
+  if (buffer_size != static_cast<size_t>(4 * width * height)) {
     return false;
   }
 
@@ -836,11 +839,11 @@ bool WebGraphicsContext3DInProcessCommandBufferImpl::readBackFramebuffer(
   // vertical flip is only a temporary solution anyway until Chrome
   // is fully GPU composited, it wasn't worth the complexity.
 
-  bool mustRestoreFBO = (bound_fbo_ != 0);
+  bool mustRestoreFBO = (bound_fbo_ != framebuffer);
   if (mustRestoreFBO) {
-    gl_->BindFramebuffer(GL_FRAMEBUFFER, 0);
+    gl_->BindFramebuffer(GL_FRAMEBUFFER, framebuffer);
   }
-   gl_->ReadPixels(0, 0, cached_width_, cached_height_,
+   gl_->ReadPixels(0, 0, width, height,
                    GL_RGBA, GL_UNSIGNED_BYTE, pixels);
 
   // Swizzle red and blue channels
@@ -855,13 +858,19 @@ bool WebGraphicsContext3DInProcessCommandBufferImpl::readBackFramebuffer(
 
 #ifdef FLIP_FRAMEBUFFER_VERTICALLY
   if (pixels) {
-    FlipVertically(pixels, cached_width_, cached_height_);
+    FlipVertically(pixels, width, height);
   }
 #endif
 
   return true;
 }
 
+bool WebGraphicsContext3DInProcessCommandBufferImpl::readBackFramebuffer(
+    unsigned char* pixels,
+    size_t buffer_size) {
+  return readBackFramebuffer(pixels, buffer_size, 0, width(), height());
+}
+
 void WebGraphicsContext3DInProcessCommandBufferImpl::synthesizeGLError(
     WGC3Denum error) {
   if (find(synthetic_errors_.begin(), synthetic_errors_.end(), error) ==
diff --git a/webkit/gpu/webgraphicscontext3d_in_process_command_buffer_impl.h b/webkit/gpu/webgraphicscontext3d_in_process_command_buffer_impl.h
index 6330a34..d100522 100644
--- a/webkit/gpu/webgraphicscontext3d_in_process_command_buffer_impl.h
+++ b/webkit/gpu/webgraphicscontext3d_in_process_command_buffer_impl.h
@@ -70,6 +70,8 @@ class WebGraphicsContext3DInProcessCommandBufferImpl
   virtual void reshape(int width, int height);
 
   virtual bool readBackFramebuffer(unsigned char* pixels, size_t buffer_size);
+  virtual bool readBackFramebuffer(unsigned char* pixels, size_t buffer_size,
+                                   WebGLId framebuffer, int width, int height);
 
   virtual WebGLId getPlatformTextureId();
   virtual void prepareTexture();
diff --git a/webkit/gpu/webgraphicscontext3d_in_process_impl.cc b/webkit/gpu/webgraphicscontext3d_in_process_impl.cc
index 6b8d7fc..9bcea10 100644
--- a/webkit/gpu/webgraphicscontext3d_in_process_impl.cc
+++ b/webkit/gpu/webgraphicscontext3d_in_process_impl.cc
@@ -588,8 +588,9 @@ void WebGraphicsContext3DInProcessImpl::FlipVertically(
 #endif
 
 bool WebGraphicsContext3DInProcessImpl::readBackFramebuffer(
-    unsigned char* pixels, size_t bufferSize) {
-  if (bufferSize != static_cast<size_t>(4 * width() * height()))
+    unsigned char* pixels, size_t bufferSize, WebGLId framebuffer,
+    int width, int height) {
+  if (bufferSize != static_cast<size_t>(4 * width * height))
     return false;
 
   makeContextCurrent();
@@ -601,8 +602,14 @@ bool WebGraphicsContext3DInProcessImpl::readBackFramebuffer(
   // vertical flip is only a temporary solution anyway until Chrome
   // is fully GPU composited, it wasn't worth the complexity.
 
-  ResolveMultisampledFramebuffer(0, 0, cached_width_, cached_height_);
-  glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo_);
+  // In this implementation fbo_, not 0, is the drawing buffer, so
+  // special-case that.
+  if (framebuffer == 0)
+    framebuffer = fbo_;
+
+  if (framebuffer == fbo_)
+    ResolveMultisampledFramebuffer(0, 0, width, height);
+  glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, framebuffer);
 
   GLint pack_alignment = 4;
   bool must_restore_pack_alignment = false;
@@ -616,13 +623,13 @@ bool WebGraphicsContext3DInProcessImpl::readBackFramebuffer(
     // FIXME: consider testing for presence of GL_OES_read_format
     // and GL_EXT_read_format_bgra, and using GL_BGRA_EXT here
     // directly.
-    glReadPixels(0, 0, cached_width_, cached_height_,
+    glReadPixels(0, 0, width, height,
                  GL_RGBA, GL_UNSIGNED_BYTE, pixels);
     for (size_t i = 0; i < bufferSize; i += 4) {
       std::swap(pixels[i], pixels[i + 2]);
     }
   } else {
-    glReadPixels(0, 0, cached_width_, cached_height_,
+    glReadPixels(0, 0, width, height,
                  GL_BGRA, GL_UNSIGNED_BYTE, pixels);
   }
 
@@ -633,12 +640,17 @@ bool WebGraphicsContext3DInProcessImpl::readBackFramebuffer(
 
 #ifdef FLIP_FRAMEBUFFER_VERTICALLY
   if (pixels)
-    FlipVertically(pixels, cached_width_, cached_height_);
+    FlipVertically(pixels, width, height);
 #endif
 
   return true;
 }
 
+bool WebGraphicsContext3DInProcessImpl::readBackFramebuffer(
+    unsigned char* pixels, size_t bufferSize) {
+  return readBackFramebuffer(pixels, bufferSize, fbo_, width(), height());
+}
+
 void WebGraphicsContext3DInProcessImpl::synthesizeGLError(WGC3Denum error) {
   if (synthetic_errors_set_.find(error) == synthetic_errors_set_.end()) {
     synthetic_errors_set_.insert(error);
diff --git a/webkit/gpu/webgraphicscontext3d_in_process_impl.h b/webkit/gpu/webgraphicscontext3d_in_process_impl.h
index 65bf9cb..2d40506 100644
--- a/webkit/gpu/webgraphicscontext3d_in_process_impl.h
+++ b/webkit/gpu/webgraphicscontext3d_in_process_impl.h
@@ -70,6 +70,8 @@ class WebGraphicsContext3DInProcessImpl : public WebGraphicsContext3D {
   virtual void reshape(int width, int height);
 
   virtual bool readBackFramebuffer(unsigned char* pixels, size_t bufferSize);
+  virtual bool readBackFramebuffer(unsigned char* pixels, size_t buffer_size,
+                                   WebGLId framebuffer, int width, int height);
 
   virtual WebGLId getPlatformTextureId();
   virtual void prepareTexture();