Weird 1 pixel layout bug when a control is loaded. Repro and video included.

[dbriard]

Describe the bug
There is a layout issue when a control is loaded and before it is touched. It is 1 pixel too long in width. After its state change, the control with is reduce by 1 pixel.
This is related to ContentDialog foreground change.

To Reproduce

1. Create a new Avalonia Application.
2. Add a button (for example)
3. Run the app
4. MouseOver the Button
5. The width of the button change, it is reduced by 1 pixel ??!!!

To better see the result, put the button inside a LayoutTransformControl with x8 scaling, and set padding to 0
When you run the app, there is 2 pixels between text and border on left side, and 1 pixel on right side.
When you mouseover (in fact, when the state of the foreground change), the left side become 1 px.

If you create a custom theme for the button, with BrushA for Foreground, BrushA again for MouseOver, and BrushB for Pressed.
The 1-pixel shift only happen when the button is pressed, that allow to measure with the inspector, and we can see that the DesiredSize of the text is reduced by 1 pixel after the foreground state change.

Expected behavior
The layout must be good when the control is loaded, and should not change after.

Screenshots

1pixel_bug.mp4

Repro sample
OnePixelBug.zip

Desktop (please complete the following information):

• OS: Windows 11 (with OS scaling 100%)
• Version: tested with v11.0.2, v11.0.4 and latest nighly

Additional context
Add any other context about the problem here.

[timunie]

👀

can reproduce on my machine. Great and easy sample 👍

[dbriard]

👀

can reproduce on my machine. Great and easy sample 👍

Thanks for looking, I have no idea why that happen, but I hope it can be fixed :)

[timunie]

place your sample into samples > Sandbox and add breakpoints into the layout pass if you want to investigate it on your own further.

[Gillibald]

Could be related to rounding differences. First layout snaps the control to the left. Second to the right. Just some theory.

[MrJul]

I had a look at this: please see #12765 for details about the problem and a potential fix.