Add MGL entry points and port spinning_cube to use them

mojo/gles2/mgl_impl.cc

+// Copyright 2015 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 "mojo/public/c/gles2/gles2.h"
+#include "mojo/public/c/gpu/MGL/mgl.h"
+#include "mojo/public/c/gpu/MGL/mgl_onscreen.h"
+#include "mojo/public/cpp/system/message_pipe.h"
+
+// This file implements the MGL and MGL onscreen entry points exposed to the

[viettrungluu, 2015/08/12 02:48:10]

nit: I think you should put the file-level comment before the includes

+// Mojo application by the shell.
+//
+// TODO(jamesr): These entry points are implemented on top of the MojoGLES2
+// family, which for control functions is backwards.  The MojoGLES2 control
+// entry points

[viettrungluu, 2015/08/12 02:48:10]

nit: rewrap this comment?

+// should be implemented on top of these entry points while we deprecate them.
+extern "C" {

[viettrungluu, 2015/08/12 02:48:10]

nit: blank line after this one, and maybe also before

+MGLContext MGLCreateContext(MGLOpenGLAPIVersion version,
+                            MojoHandle command_buffer_handle,
+                            MGLContext share_group,
+                            MGLContextLostCallback lost_callback,
+                            void* lost_callback_closure,
+                            const struct MojoAsyncWaiter* async_waiter) {
+  // TODO(jamesr): Support ES 3.0 / 3.1 where possible.
+  if (version != MGL_API_VERSION_GLES2) {
+    MojoClose(command_buffer_handle);
+    return MGL_NO_CONTEXT;
+  }
+  // TODO(jamesr): Plumb through share groups.
+  if (share_group != MGL_NO_CONTEXT) {
+    MojoClose(command_buffer_handle);
+    return MGL_NO_CONTEXT;
+  }
+
+  return reinterpret_cast<MGLContext>(
+      MojoGLES2CreateContext(command_buffer_handle, lost_callback,
+                             lost_callback_closure, async_waiter));
+}
+
+void MGLDestroyContext(MGLContext context) {
+  MojoGLES2DestroyContext(reinterpret_cast<MojoGLES2Context>(context));
+}
+
+int MGLMakeCurrent(MGLContext context) {
+  MojoGLES2MakeCurrent(reinterpret_cast<MojoGLES2Context>(context));
+  // TODO(jamesr): Plumb through loss information through the return value.
+  return 0;

[viettrungluu, 2015/08/12 02:48:10]

Aha, so your comment in the header about MGLMakeCurrent()'s return value is
wrong.

+}
+
+MGLContext MGLGetCurrentContext() {
+  // TODO(jamesr): Implement.
+  return MGL_NO_CONTEXT;
+}
+
+// TODO(jamesr): Hack - this symbol is defined in //mojo/gles2/gles2_impl.cc.
+// What should really happen here is this should call into the data structure
+// underlying MGLContext, but that can't happen until control is inverted.
+void MojoGLES2glResizeCHROMIUM(uint32_t width,
+                               uint32_t height,
+                               float scale_factor);
+
+void MGLResizeSurface(uint32_t width, uint32_t height) {
+  // TODO(jamesr): Implement
+  MojoGLES2glResizeCHROMIUM(width, height, 1.f);
+}
+
+void MGLSwapBuffers() {
+  MojoGLES2SwapBuffers();
+}
+
+}  // extern "C"