Conceptual > Blur Playground > Blur Amount > moving past 99 causes crash

[kmgallahan]

As per the title, going into the Conceptual > Blur Playground section and moving the Blur Amount slider all the way to the right (past 99 specifically) immediately causes the app to crash.

This is on Windows 10 build 15063.674, app version 1.1.19.0

Mitigation: cap the slider

Resolution: no idea why it crashes

[likuba]

Hey @kmgallahan! Thanks for reporting all these issues. Unfortunately, we're not currently able to reproduce this one. Are you using the version of the app downloaded from the Store? Or are you synced to an older version of this repo and building locally?

Also just to double check--are you leaving all of the other settings the same (like the dropdown on multiply, color sliders on defaults, and animation toggle to off)?

[kmgallahan]

Hi @likuba. This was using the app as found via the Store, and using version 1.1.19.0 as the initial comment mentions.

Also as mentioned, that was using Windows 10 build 15063.674. I could repro the issue multiple times after freshly launching the app and without touching anything else.

However, today after updating to Windows 10 build 16299.15 via the Fall Creators Update I can no longer repro this anymore. Previously the slider would not even indicate that the "100" value was reached in the tooltip - it would just halt at 99 and be proceeded by a crash of the app.

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Edit: I just finished typing this out, and went to close the app. Before I closed it the slider was sitting at "100" and then I tried moving it to the left a bit > this led to a crash.

After testing this more, I can report that this appears to be an intermittent issue. If I just move the slider back and for forth a bit while being sure to to hit 100, it will eventually crash the app. Sometimes on the first try, sometimes after moving it a couple times.

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Edit 2: Found a related issue:

1. Navigate to Conceptual > Video Playground
2. Load a video
3. Pick Effects > Blur
4. Move the BlurAmount slider all the way to the right
5. The app will either immediately crash, or do so after moving the slider left and all the way right again a few times

It would appear this might be related to "blur" in general, and perhaps only when applying a high amount of it to things.

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Edit 3: Apparently doing the above steps but picking Saturation and moving the slider in the same manner will also crash the app.

This one is a bit harder to repro, but it will eventually happen - especially if you move the slider all the way to the right, release the mouse, then go back to the slider and try moving it again.

Further testing shows it will also happen for HueRotation... starting to wonder if this is related to the Slider control or something else...

[daneuber]

@kmgallahan We are still unable to reproduce this; can you verify this still repros on the latest version of the Sample Gallery in the Store?

[kmgallahan]

@daneuber I've attached a gif of the behavior. Very easy to repro on my device - currently W10 build 17134.286, app version is the newer one from the Microsoft Store, fully updated.

The app crashed immediately on moving the slider all the way to the right 2 out of 3 times, and the third time I just had to move it back and forth a bit before that session also crashed.

Note: the cursor on my screen was in the expected locations, just looks offset in the gif due to the magic of screen capture software.

[kmgallahan]

@daneuber
@likuba

Finally made a connection that identifies the most likely cause of this crash, as well as two other crashes in the Windows Composition Samples app. Moving any of these sliders all the way to the right causes crashes:

• Blur Playground > Blur Amount
• Shadow Playground > Blur Radius or Opacity
• Video Playground (with a file loaded) > any sliders

The issue "Many layout problems and at least one bug caused by layout rounding" was just created in the WinUI repo, with this referenced issue.

I can indeed confirm that the crashing only occurs when my system scaling is specifically set to 125% (other values seem fine). This explains why you haven't been able to repro the crashes yet.

Definitely need to investigate this and any other hidden bugs caused by layout rounding.

[daneuber]

@kmgallahan thanks for bringing this up again and linking the two. That's a great find! We'll coordinate with XAML to stay on top of their investigation and update when there's a fix available. Thanks!