From fc1f225c688036b58f19f5ba1447d02e61ab55f1 Mon Sep 17 00:00:00 2001
From: Christopher Cameron <ccameron@chromium.org>
Date: Fri, 21 Jul 2023 13:02:06 +0000
Subject: [PATCH] DelayBasedBeginFrameSourceMac: Handle VSync parameter skew

The VSync parameters on macOS change over time. In compensation for
this, we re-compute them every 10 seconds (see the initial
implementation in crrev.com/343739).

This function to trigger to update update code wasn't copied
when creating DelayBasedBeginFrameSourceMac, re-introducing the the
VSync skew bug.

Re-add the function (note that all of the supporting variables, like
DelayBasedBeginFrameSourceMac::time_source_next_update_time_ were
correctly copied).

Bug: 1450617
Change-Id: Id383b64e9c9d87c1c105aa260a1f3434ced85b80
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4705225
Reviewed-by: Vasiliy Telezhnikov <vasilyt@chromium.org>
Commit-Queue: Prudhvikumar Bommana <pbommana@google.com>
Cr-Commit-Position: refs/branch-heads/5790@{#1790}
Cr-Branched-From: 1d71a337b1f6e707a13ae074dca1e2c34905eb9f-refs/heads/main@{#1148114}
---
 .../frame_sinks/external_begin_frame_source_mac.cc     | 10 ++++++++++
 .../frame_sinks/external_begin_frame_source_mac.h      |  1 +
 2 files changed, 11 insertions(+)

diff --git a/components/viz/service/frame_sinks/external_begin_frame_source_mac.cc b/components/viz/service/frame_sinks/external_begin_frame_source_mac.cc
index 818a46df8059fe..1070c95dcf1d93 100644
--- a/components/viz/service/frame_sinks/external_begin_frame_source_mac.cc
+++ b/components/viz/service/frame_sinks/external_begin_frame_source_mac.cc
@@ -135,4 +135,14 @@ void DelayBasedBeginFrameSourceMac::OnTimeSourceParamsUpdate(
   OnUpdateVSyncParameters(params.display_timebase, params.display_interval);
 }
 
+void DelayBasedBeginFrameSourceMac::OnTimerTick() {
+  // The VSync parameters skew over time (astonishingly quickly -- 0.1 msec per
+  // second). If too much time has elapsed since the last time the vsync
+  // parameters were calculated, re-calculate them.
+  if (base::TimeTicks::Now() >= time_source_next_update_time_) {
+    RequestTimeSourceParamsUpdate();
+  }
+  DelayBasedBeginFrameSource::OnTimerTick();
+}
+
 }  // namespace viz
diff --git a/components/viz/service/frame_sinks/external_begin_frame_source_mac.h b/components/viz/service/frame_sinks/external_begin_frame_source_mac.h
index 8148fd996402f9..15290954940a8c 100644
--- a/components/viz/service/frame_sinks/external_begin_frame_source_mac.h
+++ b/components/viz/service/frame_sinks/external_begin_frame_source_mac.h
@@ -86,6 +86,7 @@ class VIZ_COMMON_EXPORT DelayBasedBeginFrameSourceMac
 
   // BeginFrameSource implementation.
   void SetVSyncDisplayID(int64_t display_id) override;
+  void OnTimerTick() override;
 
  private:
   // Request a callback from DisplayLinkMac, and the callback function.