[Mojo] Remove dependency between mojo/public and gpu

This CL restructures how sample_app integrates with the GPU command buffer.
Instead of mojo/public containing code that depends directly on
gpu/command_buffer, this CL isolates that dependency into a dynamically linked
library modelled after mojo_system.

1) mojo/public/gles2 contains a simple C API to libmojo_gles2.so.
2) mojo/gles2 contains a "thin" implementation of this API in terms of
   gpu/command_buffer.
3) Instead of subclassing GLES2ClientStub in mojo/public/bindings, we now
   subclass the stub directly in sample_app and control the GLES2 C API via
   mojo/public/gles2.

I've also added a couple of README.md files that describe the purposes of the
various directories and the reasons why the code is structured in this way.

R=darin@chromium.org

Review URL: https://codereview.chromium.org/101413002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238517 0039d316-1c4b-4281-b951-d872f2087c98

5 files changed, 88 insertions, 122 deletions

diff --git a/mojo/public/README.md b/mojo/public/README.md
new file mode 100644
index 0000000..08f9881
--- /dev/null
+++ b/mojo/public/README.md
@@ -0,0 +1,41 @@
+Mojo Public API
+===============
+
+The Mojo Public API is a binary stable API to the Mojo system. There are
+several components to the API:
+
+Bindings
+--------
+
+This directory contains a static library that clients can link into their
+binary. The contents of this directory are not binary stable because each
+client is free to use whichever version they prefer.
+
+This directory also contains a compiler that translates mojom interface
+definition files into idiomatic bindings for various languages, including
+C++ and JavaScript. Clients are expected to statically link with the generated
+code, which reads and writes the binary stable IPC message format.
+
+GLES2
+-----
+
+The IPC protocol used to communicate between Mojo client and the GLES2
+service is not binary stable. To insulate themselves from changes in this
+protocol, clients are expected to link dynamically against the standard GLES2
+headers from Khronos and the headers in this directory, which provide an
+adaptor between the GLES2 C API and the underlying IPC protocol.
+
+System
+------
+
+This directory defines the interface between Mojo clients and the Mojo IPC
+system. Although the Mojo IPC message format is binary stable, the mechanism
+by which these messages are transported is not stable. To insulate themselves
+from changes in the underlying transport, clients are expected to link against
+these headers dynamically.
+
+Tests
+-----
+
+This directory contains tests for code contained in the public API. Mojo
+clients are expected to ignore this directory.
diff --git a/mojo/public/bindings/gles2_client/DEPS b/mojo/public/bindings/gles2_client/DEPS
deleted file mode 100644
index 08992c3..0000000
--- a/mojo/public/bindings/gles2_client/DEPS
+++ /dev/null
@@ -1,3 +0,0 @@
-include_rules = [
-  "+gpu/command_buffer/client",
-]
diff --git a/mojo/public/bindings/gles2_client/gles2_client_impl.cc b/mojo/public/bindings/gles2_client/gles2_client_impl.cc
deleted file mode 100644
index 2fea93c..0000000
--- a/mojo/public/bindings/gles2_client/gles2_client_impl.cc
+++ /dev/null
@@ -1,75 +0,0 @@
-// Copyright 2013 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/bindings/gles2_client/gles2_client_impl.h"
-
-#include <assert.h>
-
-#include "gpu/command_buffer/client/gles2_lib.h"
-
-namespace mojo {
-namespace {
-
-bool g_gles2_initialized = false;
-
-}  // namespace
-
-GLES2Delegate::~GLES2Delegate() {
-}
-
-void GLES2Delegate::DidCreateContext(
-    GLES2ClientImpl* gl, uint32_t width, uint32_t height) {
-}
-
-void GLES2Delegate::ContextLost(GLES2ClientImpl* gl) {
-}
-
-GLES2ClientImpl::GLES2ClientImpl(GLES2Delegate* delegate,
-                                 ScopedMessagePipeHandle gl)
-    : delegate_(delegate),
-      gl_(gl.Pass()) {
-  assert(g_gles2_initialized);
-  gl_.SetPeer(this);
-}
-
-GLES2ClientImpl::~GLES2ClientImpl() {
-  gl_->Destroy();
-}
-
-void GLES2ClientImpl::Initialize() {
-  assert(!g_gles2_initialized);
-  gles2::Initialize();
-  g_gles2_initialized = true;
-}
-
-void GLES2ClientImpl::Terminate() {
-  assert(g_gles2_initialized);
-  gles2::Terminate();
-  g_gles2_initialized = false;
-}
-
-void GLES2ClientImpl::SwapBuffers() {
-  gles2::GetGLContext()->SwapBuffers();
-}
-
-void GLES2ClientImpl::DidCreateContext(
-    uint64_t encoded, uint32_t width, uint32_t height) {
-  // Ack, Hans! It's the giant hack.
-  // TODO(abarth): Replace this hack with something more disciplined. Most
-  // likley, we should receive a MojoHandle that we use to wire up the
-  // client side of an out-of-process command buffer. Given that we're
-  // still in-process, we just reinterpret_cast the value into a GL interface.
-  gpu::gles2::GLES2Interface* gl_interface =
-      reinterpret_cast<gpu::gles2::GLES2Interface*>(
-          static_cast<uintptr_t>(encoded));
-  gles2::SetGLContext(gl_interface);
-
-  delegate_->DidCreateContext(this, width, height);
-}
-
-void GLES2ClientImpl::ContextLost() {
-  delegate_->ContextLost(this);
-}
-
-}  // mojo
diff --git a/mojo/public/bindings/gles2_client/gles2_client_impl.h b/mojo/public/bindings/gles2_client/gles2_client_impl.h
deleted file mode 100644
index 9213905..0000000
--- a/mojo/public/bindings/gles2_client/gles2_client_impl.h
+++ /dev/null
@@ -1,44 +0,0 @@
-// Copyright 2013 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.
-
-#ifndef MOJO_PUBLIC_BINDINGS_GLES2_CLIENT_GLES2_CLIENT_IMPL_H_
-#define MOJO_PUBLIC_BINDINGS_GLES2_CLIENT_GLES2_CLIENT_IMPL_H_
-
-#include "mojo/public/bindings/lib/remote_ptr.h"
-#include "mojom/gles2.h"
-
-namespace mojo {
-class GLES2ClientImpl;
-
-class GLES2Delegate {
- public:
-  virtual ~GLES2Delegate();
-  virtual void DidCreateContext(
-      GLES2ClientImpl* gl, uint32_t width, uint32_t height);
-  virtual void ContextLost(GLES2ClientImpl* gl);
-};
-
-class GLES2ClientImpl : public GLES2ClientStub {
- public:
-  explicit GLES2ClientImpl(GLES2Delegate* delegate,
-                           ScopedMessagePipeHandle gl);
-  virtual ~GLES2ClientImpl();
-
-  static void Initialize();
-  static void Terminate();
-
-  void SwapBuffers();
-
- private:
-  virtual void DidCreateContext(
-    uint64_t encoded, uint32_t width, uint32_t height) MOJO_OVERRIDE;
-  virtual void ContextLost() MOJO_OVERRIDE;
-
-  GLES2Delegate* delegate_;
-  RemotePtr<GLES2> gl_;
-};
-
-}  // mojo
-
-#endif  // MOJO_PUBLIC_BINDINGS_GLES2_CLIENT_GLES2_CLIENT_IMPL_H_
diff --git a/mojo/public/gles2/gles2.h b/mojo/public/gles2/gles2.h
new file mode 100644
index 0000000..0a32cdd
--- /dev/null
+++ b/mojo/public/gles2/gles2.h
@@ -0,0 +1,47 @@
+// Copyright 2013 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.
+
+#ifndef MOJO_PUBLIC_GLES2_ADAPTOR_H_
+#define MOJO_PUBLIC_GLES2_ADAPTOR_H_
+
+// Note: This header should be compilable as C.
+
+#include <stdint.h>
+
+#if defined(COMPONENT_BUILD)
+#if defined(WIN32)
+
+#if defined(MOJO_GLES2_IMPLEMENTATION)
+#define MOJO_GLES2_EXPORT __declspec(dllexport)
+#else
+#define MOJO_GLES2_EXPORT __declspec(dllimport)
+#endif  // defined(GFX_IMPLEMENTATION)
+
+#else  // defined(WIN32)
+#if defined(MOJO_GLES2_IMPLEMENTATION)
+#define MOJO_GLES2_EXPORT __attribute__((visibility("default")))
+#else
+#define MOJO_GLES2_EXPORT
+#endif
+#endif
+
+#else  // defined(COMPONENT_BUILD)
+#define MOJO_GLES2_EXPORT
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+MOJO_GLES2_EXPORT void MojoGLES2Initialize();
+MOJO_GLES2_EXPORT void MojoGLES2Terminate();
+// TODO(abarth): MojoGLES2MakeCurrent should take a MojoHandle.
+MOJO_GLES2_EXPORT void MojoGLES2MakeCurrent(uint64_t encoded);
+MOJO_GLES2_EXPORT void MojoGLES2SwapBuffers();
+
+#ifdef __cplusplus
+}  // extern "C"
+#endif
+
+#endif  // MOJO_PUBLIC_GLES2_ADAPTOR_H_