Refresh rate is capped at 60hz for Project Reunion 0.5 Desktop apps.

[bkaankose]

Describe the bug
This is kind of a strange bug but I will do my best to explain. Time to time (usually after doing some visually expensive stuff like navigating frames, running XAML animations) WinUI 3 Desktop apps are not rendering at max refresh rate that my monitor supports. I have 144hz monitor. When I run XAML Controls Gallery (UWP, WinUI 2.5) everything runs smoothly. I can see my mouse rendering faster and all the animations etc. running at 144hz. However, as I run WinUI 3 Controls Gallery (Desktop, WinUI 3, released today) everything becomes sluggish, refresh rate looks like capped at 60hz, animations are not at high performance.

I assume this might be related to my Windows build (Insider Preview 21343) or UWP apps being GPU accelerated (don't know the case about WinUI3 Desktop apps), but definitely not something to experience as a user and can be frustrating for both devs and customers.

Legacy WPF or Win32 apps that don't use WinUI don't have this problem, they run smoothly at 144hz. This problem is only observed in the apps that uses WinUI 3. I described it as Project Reunion 0.5, but problem also appears on the apps that use WinUI3 Preview versions too. I had an old blank app that uses WinUI Preview 4 in my machine and this behavior is also seen in that app.

Steps to reproduce the bug

1. Download and run UWP WinUI 2.5 Controls Gallery app, see app is rendering at max refresh rate.
2. Download and run WinUI3 Controls Gallery app from the store, see ap is rendering at 60hz refresh rate max.

Expected behavior
Everything should run as smoothly possible.

Version Info
NuGet package version:
WinUI 3 - Project Reunion 0.5 (not Preview)
WinUI 3.0 Preview 4

Windows app type:

UWP	Win32
No	Yes

Windows 10 version	Saw the problem?
Insider Build (21343)	Yes
October 2020 Update (19042)
May 2020 Update (19041)
November 2019 Update (18363)
May 2019 Update (18362)
October 2018 Update (17763)
April 2018 Update (17134)
Fall Creators Update (16299)
Creators Update (15063)

Device form factor	Saw the problem?
Desktop	Yes
Xbox
Surface Hub
IoT

Additional context

[kevinguo305]

Hi bkaankose,

Can you let me know if you're still experiencing this issue on the current WinUI3 build?

[bkaankose]

Looks like it's fixed now thanks. However scrolling performance is still better in WinUI 2.x app. Somehow the content renders more smoothly in WinUI 2.x. Not sure if it's related to this bug though. This bug seems to be fixed, but there might be other open bugs correlated to this one.

[kevinguo305]

Understood. In that case, I'll close this issue then. Thanks for reporting this!