WPF window stops rendering when using a BitmapCache inside while another window is invisible

[walterlv]

• .NET Core Version: 3.0
• Windows version: Windows 7/8/8.1/10 (Any Windows 10 versions including 10.0.18362.329)
• Does the bug reproduce also in WPF for .NET Framework 4.8?: Yes

Problem description:
If a Window contains any UIElement with a BitmapCache and another window is hidden, the first Window will stop rendering in two different situations:

1. Lock and unlock the screen
2. Wait for a while (e.g. 10~30min)

Actual behavior:

See this animation below and you'll see that the window stops rendering after a locking and unlocking screen.

Expected behavior:

The window should keep rendering.

Minimal repro:

1. Make a window shown with a BitmapCache inside
2. Show and hide another window
3. Lock and unlock the screen
4. Resize the first window to view the behavior

See this minimal reproduction repository below:

• wpf-issues/BitmapCache at master · dotnet-campus/wpf-issues

[Erapchu]

Hello!
I have the same issue. To resolve it you can disable HW acceleration in registry or just set ProcessRenderMode property before any window is showing.
RenderOptions.ProcessRenderMode = RenderMode.SoftwareOnly;
You can catch the same behavior after tap Ctrl + Alt + Del

[predavid]

@Erapchu and @lindexi for re-iterating this issue. We'd like to track it via a single bug/Issue. So let's use the newer one WPF Rendering issue on any machine #4276, and close this one.

[lindexi]

Reference #5672

[onesounds]

@lindexi Is there any improvement on this issue? I think it's been four years since I learned about this problem, but It still not fixed on .net9 recently. Most wpf programs suffer from this problem, and almost all open source wpf programs I've seen use software render mode.

[lindexi]

@onesounds Based on my investigation, this appears to be a device loss issue. After enabling the cache, when a device is lost and a new device is created, the cached data from the old device does not expire, leading to improper cross-device caching. This problem occurs at a lower-level rendering module and seems related to GFX.

And you should not fix this issus by use software render mode. You can just remove the bitmap cache when the window hide to fix this issues.

[onesounds]

@lindexi Thank you for your reply. I had actually expected you to address this issue, since I've seen you respond to similar problems before.

In my case, I have both a primary and a secondary window. I tried setting the CacheMode to null for all visual elements in the primary window just before hiding it, as you suggested—but unfortunately, it didn’t resolve the issue. I also tried resetting(CacheMode=null) the cache during both OnLoad and Hide, but the problem persists.

I've read through over a decade’s worth of posts on this issue and examined a number of other WPF project implementations, but I haven’t found a proper fix. In some cases, people try to work around it by temporarily switching the render mode when receiving a system transition event. If you have a good example or reference, I’d really appreciate it if you could share it.

I'm a designer involved in open source projects, and even our developers haven’t been able to fix this, so we’ve ended up using software rendering as a workaround. I'm wondering—do you think there's any possibility the WPF team will officially fix this issue someday? Because your current suggestion seems to imply we still need to choose between caching and hardware acceleration, which feels like a compromise rather than a solution.

[lindexi]

@onesounds Actually, modifications to the GFX code layer are beyond my capacity. I'm worried these changes could lead to even more severe issues. Therefore, I can only offer some compromised solutions.

In my case, I have both a primary and a secondary window. I tried setting the CacheMode to null for all visual elements in the primary window just before hiding it, as you suggested—but unfortunately, it didn’t resolve the issue. I also tried resetting(CacheMode=null) the cache during both OnLoad and Hide, but the problem persists.

Could you give the repro demo?

[onesounds]

@lindexi Here. Flow-Launcher/Flow.Launcher#3384

[lindexi]

@onesounds Flow.Launcher is too complexity. It's hard for me to know all the cache be clear. And as your reference, how about test the #4276 (comment)