Add a Display and ContextProvider concept to mojom, use to recreate

examples/sample_app/gles2_client_impl.cc

Index: examples/sample_app/gles2_client_impl.cc
diff --git a/examples/sample_app/gles2_client_impl.cc b/examples/sample_app/gles2_client_impl.cc
index 29950ebc148cf372c41a653cde8bc3655fd80396..bfb01c871a993da26b6a2703b8477169228ac4a0 100644
--- a/examples/sample_app/gles2_client_impl.cc
+++ b/examples/sample_app/gles2_client_impl.cc
@@ -28,14 +28,15 @@ float GetRandomColor() {
 
 }
 
-GLES2ClientImpl::GLES2ClientImpl(mojo::CommandBufferPtr command_buffer)
-    : last_time_(mojo::GetTimeTicksNow()), waiting_to_draw_(false) {
-  context_ =
-      MojoGLES2CreateContext(command_buffer.PassMessagePipe().release().value(),
-                             &ContextLostThunk,
-                             this,
-                             mojo::Environment::GetDefaultAsyncWaiter());
-  MojoGLES2MakeCurrent(context_);
+GLES2ClientImpl::GLES2ClientImpl(mojo::ContextProviderPtr context_provider)
+    : last_time_(mojo::GetTimeTicksNow()),
+      waiting_to_draw_(false),
+      context_provider_(context_provider.Pass()),
+      context_(nullptr) {
+  context_provider_->Create(nullptr,
+                            [this](mojo::CommandBufferPtr command_buffer) {
+                              ContextCreated(command_buffer.Pass());
+                            });
 }
 
 GLES2ClientImpl::~GLES2ClientImpl() {
@@ -44,13 +45,13 @@ GLES2ClientImpl::~GLES2ClientImpl() {
 
 void GLES2ClientImpl::SetSize(const mojo::Size& size) {
   size_ = size;
-  if (size_.width == 0 || size_.height == 0)
+  cube_.set_size(size_.width, size_.height);
+  if (size_.width == 0 || size_.height == 0 || !context_)
     return;
   static_cast<gpu::gles2::GLES2Interface*>(
       MojoGLES2GetGLES2Interface(context_))->ResizeCHROMIUM(size_.width,
                                                             size_.height,
                                                             1);
-  cube_.Init(size_.width, size_.height);
   WantToDraw();
 }
 
@@ -100,27 +101,33 @@ void GLES2ClientImpl::HandleInputEvent(const mojo::Event& event) {
   }
 }
 
+void GLES2ClientImpl::ContextCreated(mojo::CommandBufferPtr command_buffer) {
+  context_ = MojoGLES2CreateContext(
+      command_buffer.PassMessagePipe().release().value(), &ContextLostThunk,
+      this, mojo::Environment::GetDefaultAsyncWaiter());
+  MojoGLES2MakeCurrent(context_);
+  cube_.Init();
+  WantToDraw();
+}
+
 void GLES2ClientImpl::ContextLost() {
+  MojoGLES2DestroyContext(context_);
+  context_ = nullptr;
+  context_provider_->Create(nullptr,
+                            [this](mojo::CommandBufferPtr command_buffer) {
+                              ContextCreated(command_buffer.Pass());
+                            });
 }
 
 void GLES2ClientImpl::ContextLostThunk(void* closure) {
   static_cast<GLES2ClientImpl*>(closure)->ContextLost();
 }
 
-struct DrawRunnable {
-  explicit DrawRunnable(GLES2ClientImpl* impl) : impl(impl) {}
-  virtual ~DrawRunnable() {}
-
-  void Run() const { impl->Draw(); }
-
-  GLES2ClientImpl* impl;
-};
-
 void GLES2ClientImpl::WantToDraw() {
-  if (waiting_to_draw_)
+  if (waiting_to_draw_ || !context_)
     return;
   waiting_to_draw_ = true;
-  mojo::RunLoop::current()->PostDelayedTask(mojo::Closure(DrawRunnable(this)),
+  mojo::RunLoop::current()->PostDelayedTask([this]() { Draw(); },
                                             MojoTimeTicks(16667));

[qsr, 2015/02/20 11:25:47]

You can lose the context between this post task and the call to Draw, no? Should
you check for the context in Draw too?

Also, (but not sure if it is worth it for this app), maybe we still want to
update the cube data while we do not have a context, but we just do not want to
try to draw...

[jamesr, 2015/02/20 22:01:05]

fixed
no, it doesn't make sense to spend time updating the math on the cube when we
can't draw it.

 }