Pass initial size and GPU preference via context attributes

gpu/command_buffer/service/gles2_cmd_decoder.cc

 // Copyright (c) 2012 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 "gpu/command_buffer/service/gles2_cmd_decoder.h"
 
 #include <limits.h>
 #include <stddef.h>
 #include <stdint.h>
 #include <stdio.h>
@@ skipping 567 matching lines @@
                               int num_entries,
                               int* entries_processed);
 
   // Overridden from AsyncAPIInterface.
   const char* GetCommandName(unsigned int command_id) const override;
 
   // Overridden from GLES2Decoder.
   bool Initialize(const scoped_refptr<gl::GLSurface>& surface,
                   const scoped_refptr<gl::GLContext>& context,
                   bool offscreen,
-                  const gfx::Size& offscreen_size,
                   const DisallowedFeatures& disallowed_features,
                   const ContextCreationAttribHelper& attrib_helper) override;
   void Destroy(bool have_context) override;
   void SetSurface(const scoped_refptr<gl::GLSurface>& surface) override;
   void ReleaseSurface() override;
   void TakeFrontBuffer(const Mailbox& mailbox) override;
   void ReturnFrontBuffer(const Mailbox& mailbox, bool is_lost) override;
   bool ResizeOffscreenFrameBuffer(const gfx::Size& size) override;
   bool MakeCurrent() override;
   GLES2Util* GetGLES2Util() override { return &util_; }
@@ skipping 2306 matching lines @@
   DCHECK(group);
 }
 
 GLES2DecoderImpl::~GLES2DecoderImpl() {
 }
 
 bool GLES2DecoderImpl::Initialize(
     const scoped_refptr<gl::GLSurface>& surface,
     const scoped_refptr<gl::GLContext>& context,
     bool offscreen,
-    const gfx::Size& offscreen_size,
     const DisallowedFeatures& disallowed_features,
     const ContextCreationAttribHelper& attrib_helper) {
   TRACE_EVENT0("gpu", "GLES2DecoderImpl::Initialize");
   DCHECK(context->IsCurrent(surface.get()));
   DCHECK(!context_.get());
-  DCHECK(!offscreen || !offscreen_size.IsEmpty());
 
   surfaceless_ = surface->IsSurfaceless() && !offscreen;
 
   set_initialized();
   gpu_state_tracer_ = GPUStateTracer::Create(&state_);
 
   if (group_->gpu_preferences().enable_gpu_debugging)
     set_debug(true);
 
   if (group_->gpu_preferences().enable_gpu_command_logging)
@@ skipping 275 matching lines @@
     offscreen_target_stencil_render_buffer_->Create();
 
     // Create the saved offscreen texture. The target frame buffer is copied
     // here when SwapBuffers is called.
     offscreen_saved_frame_buffer_.reset(new BackFramebuffer(this));
     offscreen_saved_frame_buffer_->Create();
     //
     offscreen_saved_color_texture_.reset(new BackTexture(this));
     offscreen_saved_color_texture_->Create();
 
+    gfx::Size initial_size = attrib_helper.offscreen_framebuffer_size;
+    if (initial_size.IsEmpty()) {
+      // If we're an offscreen surface with zero width and/or height, set to a
+      // non-zero size so that we have a complete framebuffer for operations
+      // like glClear.
+      // TODO(piman): allow empty framebuffers, similar to
+      // EGL_KHR_surfaceless_context / GL_OES_surfaceless_context.
+      initial_size = gfx::Size(1, 1);
+    }
+
     // Allocate the render buffers at their initial size and check the status
     // of the frame buffers is okay.
-    if (!ResizeOffscreenFrameBuffer(offscreen_size)) {
+    if (!ResizeOffscreenFrameBuffer(initial_size)) {
       LOG(ERROR) << "Could not allocate offscreen buffer storage.";
       Destroy(true);
       return false;
     }
 
-    state_.viewport_width = offscreen_size.width();
-    state_.viewport_height = offscreen_size.height();
+    state_.viewport_width = initial_size.width();
+    state_.viewport_height = initial_size.height();
 
     // Allocate the offscreen saved color texture.
     DCHECK(offscreen_saved_color_format_);
     offscreen_saved_color_texture_->AllocateStorage(
         gfx::Size(1, 1), offscreen_saved_color_format_, true);
 
     offscreen_saved_frame_buffer_->AttachRenderTexture(
         offscreen_saved_color_texture_.get());
     if (offscreen_saved_frame_buffer_->CheckStatus() !=
         GL_FRAMEBUFFER_COMPLETE) {
@@ skipping 13810 matching lines @@
 }
 
 // Include the auto-generated part of this file. We split this because it means
 // we can easily edit the non-auto generated parts right here in this file
 // instead of having to edit some template or the code generator.
 #include "base/macros.h"
 #include "gpu/command_buffer/service/gles2_cmd_decoder_autogen.h"
 
 }  // namespace gles2
 }  // namespace gpu