Make GPU back-pressure work with remote CALayers

content/common/gpu/image_transport_surface_calayer_mac.mm

Index: content/common/gpu/image_transport_surface_calayer_mac.mm
diff --git a/content/common/gpu/image_transport_surface_calayer_mac.mm b/content/common/gpu/image_transport_surface_calayer_mac.mm
index 4ad8f92b4031c117f6377dce499e753738ea4993..ed8d3535cb9b26b90db5ac9d441c9a77c6a1e124 100644
--- a/content/common/gpu/image_transport_surface_calayer_mac.mm
+++ b/content/common/gpu/image_transport_surface_calayer_mac.mm
@@ -9,36 +9,39 @@
 #include "ui/base/cocoa/animation_utils.h"
 #include "ui/gfx/geometry/size_conversions.h"
 
-@interface ImageTransportLayer (Private) {
+@interface ImageTransportLayer : CAOpenGLLayer {
+  content::CALayerStorageProvider* storageProvider_;
 }
+- (id)initWithStorageProvider:(content::CALayerStorageProvider*)storageProvider;
+- (void)resetStorageProvider;
 @end
 
 @implementation ImageTransportLayer
 
-- (id)initWithContext:(CGLContextObj)context
-          withTexture:(GLuint)texture
-        withPixelSize:(gfx::Size)pixelSize
-      withScaleFactor:(float)scaleFactor {
-  if (self = [super init]) {
-    shareContext_.reset(CGLRetainContext(context));
-    texture_ = texture;
-    pixelSize_ = pixelSize;
-
-    gfx::Size dipSize(gfx::ToFlooredSize(gfx::ScaleSize(
-        pixelSize_, 1.0f / scaleFactor)));
-    [self setContentsScale:scaleFactor];
-    [self setFrame:CGRectMake(0, 0, dipSize.width(), dipSize.height())];
-  }
+- (id)initWithStorageProvider:
+    (content::CALayerStorageProvider*)storageProvider {
+  if (self = [super init])
+    storageProvider_ = storageProvider;
   return self;
 }
 
+- (void)resetStorageProvider {
+  storageProvider_ = NULL;
+}
+
 - (CGLPixelFormatObj)copyCGLPixelFormatForDisplayMask:(uint32_t)mask {
-  return CGLRetainPixelFormat(CGLGetPixelFormat(shareContext_));
+  if (!storageProvider_)
+    return NULL;
+  return CGLRetainPixelFormat(CGLGetPixelFormat(
+      storageProvider_->LayerShareGroupContext()));
 }
 
 - (CGLContextObj)copyCGLContextForPixelFormat:(CGLPixelFormatObj)pixelFormat {
+  if (!storageProvider_)
+    return NULL;
   CGLContextObj context = NULL;
-  CGLError error = CGLCreateContext(pixelFormat, shareContext_, &context);
+  CGLError error = CGLCreateContext(
+      pixelFormat, storageProvider_->LayerShareGroupContext(), &context);
   if (error != kCGLNoError)
     DLOG(ERROR) << "CGLCreateContext failed with CGL error: " << error;
   return context;
@@ -48,49 +51,21 @@
                 pixelFormat:(CGLPixelFormatObj)pixelFormat
                forLayerTime:(CFTimeInterval)timeInterval
                 displayTime:(const CVTimeStamp*)timeStamp {
-  return YES;
+  if (!storageProvider_)
+    return NO;
+  return storageProvider_->LayerCanDraw();
 }
 
 - (void)drawInCGLContext:(CGLContextObj)glContext
              pixelFormat:(CGLPixelFormatObj)pixelFormat
             forLayerTime:(CFTimeInterval)timeInterval
              displayTime:(const CVTimeStamp*)timeStamp {
-  glClearColor(1, 0, 1, 1);
-  glClear(GL_COLOR_BUFFER_BIT);
-
-  GLint viewport[4] = {0, 0, 0, 0};
-  glGetIntegerv(GL_VIEWPORT, viewport);
-  gfx::Size viewportSize(viewport[2], viewport[3]);
-
-  // Set the coordinate system to be one-to-one with pixels.
-  glMatrixMode(GL_PROJECTION);
-  glLoadIdentity();
-  glOrtho(0, viewportSize.width(), 0, viewportSize.height(), -1, 1);
-  glMatrixMode(GL_MODELVIEW);
-  glLoadIdentity();
-
-  // Draw a fullscreen quad.
-  glColor4f(1, 1, 1, 1);
-  glEnable(GL_TEXTURE_RECTANGLE_ARB);
-  glBindTexture(GL_TEXTURE_RECTANGLE_ARB, texture_);
-  glBegin(GL_QUADS);
-  {
-    glTexCoord2f(0, 0);
-    glVertex2f(0, 0);
-
-    glTexCoord2f(0, pixelSize_.height());
-    glVertex2f(0, pixelSize_.height());
-
-    glTexCoord2f(pixelSize_.width(), pixelSize_.height());
-    glVertex2f(pixelSize_.width(), pixelSize_.height());
-
-    glTexCoord2f(pixelSize_.width(), 0);
-    glVertex2f(pixelSize_.width(), 0);
+  if (storageProvider_) {
+    storageProvider_->LayerDoDraw();
+  } else {
+    glClearColor(1, 1, 1, 1);
+    glClear(GL_COLOR_BUFFER_BIT);
   }
-  glEnd();
-  glBindTexture(0, texture_);
-  glDisable(GL_TEXTURE_RECTANGLE_ARB);
-
   [super drawInCGLContext:glContext
               pixelFormat:pixelFormat
              forLayerTime:timeInterval
@@ -101,7 +76,14 @@
 
 namespace content {
 
-CALayerStorageProvider::CALayerStorageProvider() {
+CALayerStorageProvider::CALayerStorageProvider(
+    ImageTransportSurfaceFBO* transport_surface)
+        : transport_surface_(transport_surface),
+          has_pending_draw_(false),
+          can_draw_returned_false_count_(0),
+          fbo_texture_(0) {
+  // Allocate a CAContext to use to transport the CALayer to the browser
+  // process.
   base::scoped_nsobject<NSDictionary> dict([[NSDictionary alloc] init]);
   CGSConnectionID connection_id = CGSMainConnectionID();
   context_.reset([CAContext contextWithCGSConnection:connection_id
@@ -144,18 +126,33 @@ bool CALayerStorageProvider::AllocateColorBufferStorage(
   // Disable the fade-in animation as the layer is changed.
   ScopedCAActionDisabler disabler;
 
-  // Resize the CAOpenGLLayer to match the size needed, and change it to be the
-  // hosted layer.
-  layer_.reset([[ImageTransportLayer alloc] initWithContext:context
-                                                withTexture:texture
-                                              withPixelSize:pixel_size
-                                            withScaleFactor:scale_factor]);
+  // Allocate a CALayer to draw texture into.
+  share_group_context_.reset(CGLRetainContext(context));
+  fbo_texture_ = texture;
+  fbo_pixel_size_ = pixel_size;
+  layer_.reset([[ImageTransportLayer alloc] initWithStorageProvider:this]);
+  gfx::Size dip_size(gfx::ToFlooredSize(gfx::ScaleSize(
+      fbo_pixel_size_, 1.0f / scale_factor)));
+  [layer_ setContentsScale:scale_factor];
+  [layer_ setFrame:CGRectMake(0, 0, dip_size.width(), dip_size.height())];
   return true;
 }
 
 void CALayerStorageProvider::FreeColorBufferStorage() {
-  [context_ setLayer:nil];
+  // We shouldn't be asked to free a texture when we still have yet to draw it.
+  DCHECK(!has_pending_draw_);
+  has_pending_draw_ = false;
+  can_draw_returned_false_count_ = 0;
+
+  // Note that |context_| still holds a reference to |layer_|, and will until
+  // a new frame is swapped in.
+  [layer_ displayIfNeeded];
+  [layer_ resetStorageProvider];
   layer_.reset();
+
+  share_group_context_.reset();
+  fbo_texture_ = 0;
+  fbo_pixel_size_ = gfx::Size();
 }
 
 uint64 CALayerStorageProvider::GetSurfaceHandle() const {
@@ -163,15 +160,80 @@ uint64 CALayerStorageProvider::GetSurfaceHandle() const {
 }
 
 void CALayerStorageProvider::WillSwapBuffers() {
+  DCHECK(!has_pending_draw_);
+  has_pending_draw_ = true;
+
   // Don't add the layer to the CAContext until a SwapBuffers is going to be
   // called, because the texture does not have any content until the
   // SwapBuffers call is about to be made.
   if ([context_ layer] != layer_.get())
     [context_ setLayer:layer_];
 
-  // TODO(ccameron): Use the isAsynchronous property to ensure smooth
-  // animation.
-  [layer_ setNeedsDisplay];
+  if (![layer_ isAsynchronous])
+    [layer_ setAsynchronous:YES];
+}
+
+void CALayerStorageProvider::CanFreeSwappedBuffer() {
+}
+
+CGLContextObj CALayerStorageProvider::LayerShareGroupContext() {
+  return share_group_context_;
+}
+
+bool CALayerStorageProvider::LayerCanDraw() {
+  if (has_pending_draw_) {
+    can_draw_returned_false_count_ = 0;
+    return true;
+  } else {
+    if (can_draw_returned_false_count_ == 30) {
+      if ([layer_ isAsynchronous])
+        [layer_ setAsynchronous:NO];
+    } else {
+      can_draw_returned_false_count_ += 1;
+    }
+    return false;
+  }
+}
+
+void CALayerStorageProvider::LayerDoDraw() {
+  DCHECK(has_pending_draw_);
+  has_pending_draw_ = false;
+
+  GLint viewport[4] = {0, 0, 0, 0};
+  glGetIntegerv(GL_VIEWPORT, viewport);
+  gfx::Size viewport_size(viewport[2], viewport[3]);
+
+  // Set the coordinate system to be one-to-one with pixels.
+  glMatrixMode(GL_PROJECTION);
+  glLoadIdentity();
+  glOrtho(0, viewport_size.width(), 0, viewport_size.height(), -1, 1);
+  glMatrixMode(GL_MODELVIEW);
+  glLoadIdentity();
+
+  // Draw a fullscreen quad.
+  glColor4f(1, 1, 1, 1);
+  glEnable(GL_TEXTURE_RECTANGLE_ARB);
+  glBindTexture(GL_TEXTURE_RECTANGLE_ARB, fbo_texture_);
+  glBegin(GL_QUADS);
+  {
+    glTexCoord2f(0, 0);
+    glVertex2f(0, 0);
+
+    glTexCoord2f(0, fbo_pixel_size_.height());
+    glVertex2f(0, fbo_pixel_size_.height());
+
+    glTexCoord2f(fbo_pixel_size_.width(), fbo_pixel_size_.height());
+    glVertex2f(fbo_pixel_size_.width(), fbo_pixel_size_.height());
+
+    glTexCoord2f(fbo_pixel_size_.width(), 0);
+    glVertex2f(fbo_pixel_size_.width(), 0);
+  }
+  glEnd();
+  glBindTexture(GL_TEXTURE_RECTANGLE_ARB, 0);
+  glDisable(GL_TEXTURE_RECTANGLE_ARB);
+
+  // Allow forward progress in the context now that the swap is complete.
+  transport_surface_->UnblockContextAfterPendingSwap();
 }
 
 }  //  namespace content