From c28b3ba4ed3156d8782484e542c25600615247b5 Mon Sep 17 00:00:00 2001
From: sotaro <sotaro.ikeda.g@gmail.com>
Date: Mon, 27 Feb 2023 05:29:24 +0000
Subject: [PATCH] Bug 1818685 - Disable video overlay if
 mVideoSwapChain->Present() is very slow on Windows r=gfx-reviewers,lsalzman

There were cases that mVideoSwapChain->Present() took long time. It caused low fps and stuttering and lots of dropped frames. When it happens, disabling video overlay could address the problem.

Differential Revision: https://phabricator.services.mozilla.com/D171039
---
 gfx/webrender_bindings/DCLayerTree.cpp   | 28 ++++++++++++++++++++++--
 gfx/webrender_bindings/DCLayerTree.h     |  1 +
 modules/libpref/init/StaticPrefList.yaml |  4 ++++
 3 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/gfx/webrender_bindings/DCLayerTree.cpp b/gfx/webrender_bindings/DCLayerTree.cpp
index 8d192ea09162..713fecdc18ca 100644
--- a/gfx/webrender_bindings/DCLayerTree.cpp
+++ b/gfx/webrender_bindings/DCLayerTree.cpp
@@ -1099,13 +1099,37 @@ void DCSurfaceVideo::PresentVideo() {
     return;
   }
 
-  HRESULT hr;
-  hr = mVideoSwapChain->Present(0, 0);
+  auto start = TimeStamp::Now();
+  HRESULT hr = mVideoSwapChain->Present(0, 0);
+  auto end = TimeStamp::Now();
+
   if (FAILED(hr) && hr != DXGI_STATUS_OCCLUDED) {
     gfxCriticalNoteOnce << "video Present failed: " << gfx::hexa(hr);
   }
 
   mPrevTexture = mRenderTextureHost;
+
+  // Disable video overlay if mVideoSwapChain->Present() is too slow. It drops
+  // fps.
+
+  if (!StaticPrefs::gfx_webrender_dcomp_video_check_slow_present()) {
+    return;
+  }
+
+  const auto maxWaitDurationMs = 2.0;
+  const auto maxSlowPresentCount = 5;
+  const auto duration = (end - start).ToMilliseconds();
+
+  if (duration > maxWaitDurationMs) {
+    mSlowPresentCount++;
+  } else {
+    mSlowPresentCount = 0;
+  }
+
+  if (mSlowPresentCount > maxSlowPresentCount) {
+    gfxCriticalNoteOnce << "Video swapchain present is slow";
+    RenderThread::Get()->HandleWebRenderError(WebRenderError::VIDEO_OVERLAY);
+  }
 }
 
 DXGI_FORMAT DCSurfaceVideo::GetSwapChainFormat() {
diff --git a/gfx/webrender_bindings/DCLayerTree.h b/gfx/webrender_bindings/DCLayerTree.h
index 25076444a967..402ffdd46487 100644
--- a/gfx/webrender_bindings/DCLayerTree.h
+++ b/gfx/webrender_bindings/DCLayerTree.h
@@ -353,6 +353,7 @@ class DCSurfaceVideo : public DCSurface {
   bool mFailedYuvSwapChain = false;
   RefPtr<RenderTextureHost> mRenderTextureHost;
   RefPtr<RenderTextureHost> mPrevTexture;
+  int mSlowPresentCount = 0;
 };
 
 /**
diff --git a/modules/libpref/init/StaticPrefList.yaml b/modules/libpref/init/StaticPrefList.yaml
index 08358b8748d6..2849daf90139 100644
--- a/modules/libpref/init/StaticPrefList.yaml
+++ b/modules/libpref/init/StaticPrefList.yaml
@@ -6528,6 +6528,10 @@
     type: bool
     value: @IS_EARLY_BETA_OR_EARLIER@
     mirror: once
+-   name: gfx.webrender.dcomp-video-check-slow-present
+    type: RelaxedAtomicBool
+    value: true
+    mirror: always
 -   name: gfx.video.convert-i420-to-nv12.force-enabled
     type: bool
     value: false