Mac Overlays: Add GPU back-pressure

content/common/gpu/image_transport_surface_overlay_mac.mm

Index: content/common/gpu/image_transport_surface_overlay_mac.mm
diff --git a/content/common/gpu/image_transport_surface_overlay_mac.mm b/content/common/gpu/image_transport_surface_overlay_mac.mm
index 1a528333529330c9b8872a8f6c71be59970c170b..2e6911ce06aac51b1525d1522cc5f4edf936d62c 100644
--- a/content/common/gpu/image_transport_surface_overlay_mac.mm
+++ b/content/common/gpu/image_transport_surface_overlay_mac.mm
@@ -4,27 +4,92 @@
 
 #include "content/common/gpu/image_transport_surface_overlay_mac.h"
 
-#include <OpenGL/gl.h>
+#include <IOSurface/IOSurface.h>
+#include <OpenGL/GL.h>
 
+// This type consistently causes problem on Mac, and needs to be dealt with
+// in a systemic way.
+// http://crbug.com/517208
+#ifndef GL_OES_EGL_image
+typedef void* GLeglImageOES;
+#endif
+
+#include "base/mac/scoped_cftyperef.h"
 #include "content/common/gpu/gpu_messages.h"
 #include "ui/accelerated_widget_mac/surface_handle_types.h"
 #include "ui/base/cocoa/animation_utils.h"
 #include "ui/base/cocoa/remote_layer_api.h"
 #include "ui/gfx/geometry/dip_util.h"
+#include "ui/gl/gl_fence.h"
 #include "ui/gl/gl_image_io_surface.h"
+#include "ui/gl/scoped_api.h"
+#include "ui/gl/scoped_cgl.h"
+
+namespace {
+
+// Don't let a frame draw until 5% of the way through the next vsync interval
+// after the call to SwapBuffers. This slight offset is to ensure that skew
+// doesn't result in the frame being presented to the previous vsync interval.
+
+const double kVSyncIntervalFractionForEarliestDisplay = 0.05;
+// Target 50% of the way through the next vsync interval. Empirically, it has
+// been determined to be a good target for smooth animation.
+const double kVSyncIntervalFractionForDisplayCallback = 0.5;
+
+// If a frame takes more than 1/4th of a second for its fence to finish, just
+// pretend that the frame is ready to draw.
+const double kMaximumDelayWaitingForFenceInSeconds = 0.25;
+
+void CheckGLErrors(const char* msg) {
+  GLenum gl_error;
+  while ((gl_error = glGetError()) != GL_NO_ERROR) {
+    LOG(ERROR) << "OpenGL error hit " << msg << ": " << gl_error;
+  }
+}
+
+}  // namespace
+
+@interface CALayer(Private)
+-(void)setContentsChanged;
+@end
 
 namespace content {
 
+class ImageTransportSurfaceOverlayMac::PendingSwap {
+ public:
+  PendingSwap() : scale_factor(1) {}
+  ~PendingSwap() { DCHECK(!gl_fence); }
+
+  gfx::Size pixel_size;
+  float scale_factor;
+  std::vector<ui::LatencyInfo> latency_info;
+
+  // The IOSurface with new content for this swap.
+  base::ScopedCFTypeRef<IOSurfaceRef> io_surface;
+
+  // A fence object, and the CGL context it was issued in.
+  base::ScopedTypeRef<CGLContextObj> cgl_context;
+  scoped_ptr<gfx::GLFence> gl_fence;
+
+  // The earliest time that this frame may be drawn. A frame is not allowed
+  // to draw until a fraction of the way through the vsync interval after its
+  // This extra latency is to allow wiggle-room for smoothness.
+  base::TimeTicks earliest_allowed_draw_time;
+  // After this time, always draw the frame, no matter what its fence says. This
+  // is to prevent GL bugs from locking the compositor forever.
+  base::TimeTicks latest_allowed_draw_time;
+};
+
 ImageTransportSurfaceOverlayMac::ImageTransportSurfaceOverlayMac(
     GpuChannelManager* manager,
     GpuCommandBufferStub* stub,
     gfx::PluginWindowHandle handle)
-    : scale_factor_(1), pending_overlay_image_(nullptr) {
+    : scale_factor_(1), pending_overlay_image_(nullptr),
+      has_pending_callback_(false), weak_factory_(this) {
   helper_.reset(new ImageTransportHelper(this, manager, stub, handle));
 }
 
 ImageTransportSurfaceOverlayMac::~ImageTransportSurfaceOverlayMac() {
-  gfx::GLImageIOSurface::SetLayerForWidget(widget_, nil);
 }
 
 bool ImageTransportSurfaceOverlayMac::Initialize() {
@@ -37,61 +102,228 @@ bool ImageTransportSurfaceOverlayMac::Initialize() {
   ca_context_.reset(
       [[CAContext contextWithCGSConnection:connection_id options:@{}] retain]);
   layer_.reset([[CALayer alloc] init]);
+  [layer_ setGeometryFlipped:YES];
+  [layer_ setOpaque:YES];
   [ca_context_ setLayer:layer_];
-
-  // Register the CALayer so that it can be picked up in GLImageIOSurface.
-  static intptr_t previous_widget = 0;
-  previous_widget += 1;
-  widget_ = reinterpret_cast<gfx::AcceleratedWidget>(previous_widget);
-  gfx::GLImageIOSurface::SetLayerForWidget(widget_, layer_);
-
   return true;
 }
 
-void ImageTransportSurfaceOverlayMac::Destroy() {}
+void ImageTransportSurfaceOverlayMac::Destroy() {
+  FinishAllPendingSwaps();
+}
 
 bool ImageTransportSurfaceOverlayMac::IsOffscreen() {
   return false;
 }
 
-gfx::SwapResult ImageTransportSurfaceOverlayMac::SwapBuffers() {
-  TRACE_EVENT0("gpu", "ImageTransportSurfaceOverlayMac::SwapBuffers");
+gfx::SwapResult ImageTransportSurfaceOverlayMac::SwapBuffersInternal(
+    const gfx::Rect& pixel_damage_rect) {
+  TRACE_EVENT0("gpu", "ImageTransportSurfaceOverlayMac::SwapBuffersInternal");
 
-  // A flush is required to ensure that all content appears in the layer.
-  {
-    TRACE_EVENT0("gpu", "ImageTransportSurfaceOverlayMac::glFlush");
-    glFlush();
+  // Use the same concept of 'now' for the entire function. The duration of
+  // this function only affect the result if this function lasts across a vsync
+  // boundary, in which case smooth animation is out the window anyway.
+  const base::TimeTicks now = base::TimeTicks::Now();
+
+  // If the previous swap is ready to display, do it before flushing the
+  // new swap. It is desirable to always be hitting this path when trying to
+  // animate smoothly with vsync.
+  if (!pending_swaps_.empty()) {
+    if (IsFirstPendingSwapReadyToDisplay(now))
+      DisplayFirstPendingSwapImmediately();
   }
 
+  // The remainder of the function will populate the PendingSwap structure and
+  // then enqueue it.
+  linked_ptr<PendingSwap> new_swap(new PendingSwap);
+  new_swap->pixel_size = pixel_size_;
+  new_swap->scale_factor = scale_factor_;
+  new_swap->latency_info.swap(latency_info_);
+
   // There should exist only one overlay image, and it should cover the whole
   // surface.
   DCHECK(pending_overlay_image_);
   if (pending_overlay_image_) {
-    TRACE_EVENT0("gpu", "ImageTransportSurfaceOverlayMac::setContents");
-    ScopedCAActionDisabler disabler;
-    gfx::Rect dip_bounds = gfx::ConvertRectToDIP(
-        scale_factor_, gfx::Rect(pixel_size_));
-    gfx::RectF crop_rect(0, 0, 1, 1);
-    pending_overlay_image_->ScheduleOverlayPlane(
-        widget_, 0, gfx::OVERLAY_TRANSFORM_NONE, dip_bounds, crop_rect);
+    gfx::GLImageIOSurface* pending_overlay_image_io_surface =
+        static_cast<gfx::GLImageIOSurface*>(pending_overlay_image_);

[reveman, 2015/08/18 08:44:11]

this static cast seems scary. how do we know that this is a GLImageIOSurface?
and how protect against changes that break that guarantee?

+    new_swap->io_surface = pending_overlay_image_io_surface->io_surface();
     pending_overlay_image_ = nullptr;
   }
 
+  // A flush is required to ensure that all content appears in the layer.
+  {
+    gfx::ScopedSetGLToRealGLApi scoped_set_gl_api;
+    TRACE_EVENT1("gpu", "ImageTransportSurfaceOverlayMac::glFlush", "surface",
+                 new_swap->io_surface.get());
+    CheckGLErrors("before flushing frame");
+    new_swap->cgl_context.reset(CGLGetCurrentContext(),
+                                base::scoped_policy::RETAIN);
+    if (gfx::GLFence::IsSupported())
+      new_swap->gl_fence.reset(gfx::GLFence::Create());
+    else
+      glFlush();
+    CheckGLErrors("while flushing frame");
+  }
+
+  // Compute the deadlines for drawing this frame.
+  if (display_link_mac_) {
+    new_swap->earliest_allowed_draw_time =
+        display_link_mac_->GetNextVSyncTimeAfter(
+            now, kVSyncIntervalFractionForEarliestDisplay);
+    new_swap->latest_allowed_draw_time = now +
+        base::TimeDelta::FromSecondsD(kMaximumDelayWaitingForFenceInSeconds);
+  } else {
+    // If we have no display link (because vsync is disabled or because we have
+    // not received display parameters yet), immediately attempt to display the
+    // surface.
+    new_swap->earliest_allowed_draw_time = now;
+    new_swap->latest_allowed_draw_time = now;
+  }
+
+  pending_swaps_.push_back(new_swap);
+  PostCheckPendingSwapsCallbackIfNeeded(now);
+  return gfx::SwapResult::SWAP_ACK;
+}
+
+bool ImageTransportSurfaceOverlayMac::IsFirstPendingSwapReadyToDisplay(
+    const base::TimeTicks& now) {
+  DCHECK(!pending_swaps_.empty());
+  linked_ptr<PendingSwap> swap = pending_swaps_.front();
+
+  // If more that a certain amount of time has passed since the swap,
+  // unconditionally continue.
+  if (now > swap->latest_allowed_draw_time)
+    return true;
+
+  // Frames are disallowed from drawing until the vsync interval after their
+  // swap is issued.
+  if (now < swap->earliest_allowed_draw_time)
+    return false;
+
+  // If there is no fence then this is either for immediate display, or the
+  // fence was aready successfully checked and deleted.
+  if (!swap->gl_fence)
+    return true;
+
+  // Check if the pending work has finished (and early-out if it is not, and
+  // this is not forced).
+  bool has_completed = true;
+  if (swap->gl_fence) {
+    gfx::ScopedSetGLToRealGLApi scoped_set_gl_api;
+    gfx::ScopedCGLSetCurrentContext scoped_set_current(swap->cgl_context);
+
+    CheckGLErrors("before testing fence");
+    has_completed= swap->gl_fence->HasCompleted();
+    CheckGLErrors("after testing fence");
+    if (has_completed) {
+      swap->gl_fence.reset();
+      CheckGLErrors("while deleting fence");
+    }
+  }
+  return has_completed;
+}
+
+void ImageTransportSurfaceOverlayMac::DisplayFirstPendingSwapImmediately() {
+  TRACE_EVENT0("gpu",
+      "ImageTransportSurfaceOverlayMac::DisplayFirstPendingSwapImmediately");
+  DCHECK(!pending_swaps_.empty());
+  linked_ptr<PendingSwap> swap = pending_swaps_.front();
+
+  // If there is a fence for this object, delete it.
+  if (swap->gl_fence) {
+    gfx::ScopedSetGLToRealGLApi scoped_set_gl_api;
+    gfx::ScopedCGLSetCurrentContext scoped_set_current(swap->cgl_context);
+
+    CheckGLErrors("before deleting active fence");
+    swap->gl_fence.reset();
+    CheckGLErrors("while deleting active fence");
+  }
+
+  // Update the CALayer hierarchy.
+  {
+    TRACE_EVENT1("gpu", "ImageTransportSurfaceOverlayMac::setContents",
+                 "surface", swap->io_surface.get());
+    ScopedCAActionDisabler disabler;
+
+    id new_contents = static_cast<id>(swap->io_surface.get());
+    [layer_ setContents:new_contents];
+
+    CGRect new_frame = gfx::ConvertRectToDIP(
+        swap->scale_factor, gfx::Rect(swap->pixel_size)).ToCGRect();
+    if (!CGRectEqualToRect([layer_ frame], new_frame))
+      [layer_ setFrame:new_frame];
+  }
+
+  // Send acknowledgement to the browser.
   GpuHostMsg_AcceleratedSurfaceBuffersSwapped_Params params;
   params.surface_handle =
       ui::SurfaceHandleFromCAContextID([ca_context_ contextId]);
   params.size = pixel_size_;
   params.scale_factor = scale_factor_;
-  params.latency_info.swap(latency_info_);
+  params.latency_info.swap(swap->latency_info);
   helper_->SendAcceleratedSurfaceBuffersSwapped(params);
-  return gfx::SwapResult::SWAP_ACK;
+
+  // Remove this from the queue, and reset any callback timers.
+  pending_swaps_.pop_front();
+}
+
+void ImageTransportSurfaceOverlayMac::FinishAllPendingSwaps() {
+  TRACE_EVENT0("gpu", "ImageTransportSurfaceOverlayMac::FinishAllPendingSwaps");
+  while (!pending_swaps_.empty())
+    DisplayFirstPendingSwapImmediately();
+}
+
+void ImageTransportSurfaceOverlayMac::CheckPendingSwapsCallback() {
+  TRACE_EVENT0("gpu",
+      "ImageTransportSurfaceOverlayMac::CheckPendingSwapsCallback");
+
+  DCHECK(has_pending_callback_);
+  has_pending_callback_ = false;
+
+  if (pending_swaps_.empty())
+    return;
+
+  const base::TimeTicks now = base::TimeTicks::Now();
+  if (IsFirstPendingSwapReadyToDisplay(now))
+    DisplayFirstPendingSwapImmediately();
+  PostCheckPendingSwapsCallbackIfNeeded(now);
+}
+
+void ImageTransportSurfaceOverlayMac::PostCheckPendingSwapsCallbackIfNeeded(
+    const base::TimeTicks& now) {
+  TRACE_EVENT0("gpu",
+      "ImageTransportSurfaceOverlayMac::PostCheckPendingSwapsCallbackIfNeeded");
+
+  if (has_pending_callback_)
+    return;
+  if (pending_swaps_.empty())
+    return;
+
+  base::TimeTicks target;
+  if (display_link_mac_) {
+    target = display_link_mac_->GetNextVSyncTimeAfter(
+          now, kVSyncIntervalFractionForDisplayCallback);
+  } else {
+    target = now;
+  }
+  base::TimeDelta delay = target - now;
+
+  base::MessageLoop::current()->PostDelayedTask(
+      FROM_HERE,
+      base::Bind(&ImageTransportSurfaceOverlayMac::CheckPendingSwapsCallback,
+                     weak_factory_.GetWeakPtr()), delay);
+  has_pending_callback_ = true;
+}
+
+gfx::SwapResult ImageTransportSurfaceOverlayMac::SwapBuffers() {
+  return SwapBuffersInternal(gfx::Rect(pixel_size_));
 }
 
 gfx::SwapResult ImageTransportSurfaceOverlayMac::PostSubBuffer(int x,
                                                                int y,
                                                                int width,
                                                                int height) {
-  return SwapBuffers();
+  return SwapBuffersInternal(gfx::Rect(x, y, width, height));
 }
 
 bool ImageTransportSurfaceOverlayMac::SupportsPostSubBuffer() {
@@ -129,10 +361,18 @@ bool ImageTransportSurfaceOverlayMac::IsSurfaceless() const {
 }
 
 void ImageTransportSurfaceOverlayMac::OnBufferPresented(
-    const AcceleratedSurfaceMsg_BufferPresented_Params& params) {}
+    const AcceleratedSurfaceMsg_BufferPresented_Params& params) {
+  if (display_link_mac_ &&
+      display_link_mac_->display_id() == params.display_id_for_vsync)
+    return;
+  display_link_mac_ = ui::DisplayLinkMac::GetForDisplay(
+      params.display_id_for_vsync);
+}
 
 void ImageTransportSurfaceOverlayMac::OnResize(gfx::Size pixel_size,
                                                float scale_factor) {
+  // Flush through any pending frames.
+  FinishAllPendingSwaps();
   pixel_size_ = pixel_size;
   scale_factor_ = scale_factor;
 }