Fixed unnecessary window displacement on resize

[codecat]

What does the pull request do?

This fixes unnecessary window displacement on resize introduced by #16608. Also related: #17559. (Edit: It was introduced sometime earlier even, probably..)

What is the current behavior?

When a window on Windows programmatically resizes, it also sets the position for the window placement in workspace coordinates. The coordinates are however fetched from screen coordinates, which causes the window to shift every time the window resizes when the user's taskbar is located on the left or top side of the screen.

Recording.2025-01-20.144204.mp4

For this video, I added a timer to the application that adds 10px to the window height every second using Height += 10.

What is the updated/expected behavior with this PR?

The window should not be moving, and/or be using workspace coordinates instead of screen space coordinates when using SetWindowPlacement.

How was the solution implemented (if it's not obvious)?

The struct that's passed into SetWindowPlacement is already fetched from GetWindowPlacement which returns workspace coordinates. We don't need to assign this at all, as it should already be assigned.

Simply removing the code for left & top assignment is enough to fix this.

Checklist

• Added unit tests (if possible)?
• Added XML documentation to any related classes? Doesn't seem relevant here.
• Consider submitting a PR to https://github.com/AvaloniaUI/avalonia-docs with user documentation

Fixed issues

This fixes #16217

[avaloniaui-bot]

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[cla-avalonia]

• All contributors have signed the CLA.

[codecat]

@cla-avalonia agree

[maxkatz6]

@codecat thanks! Can you try to add integrational test for this? This issue seems like something that could be easily caught by tests:
https://github.com/AvaloniaUI/Avalonia/blob/master/tests/Avalonia.IntegrationTests.Appium/WindowTests.cs#L25

See
https://github.com/AvaloniaUI/Avalonia/tree/master/samples/IntegrationTestApp
https://github.com/AvaloniaUI/Avalonia/tree/master/tests/Avalonia.IntegrationTests.Appium#running-integration-tests

[codecat]

Ah, I missed those! Will do.

[codecat]

I've added a new integration test now, and force pushed this PR so the commits are matching the contributor guidelines:

• f739a62 adds the failing test
• be913e3 makes the test pass

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[codecat]

Test was failing. Had to set my Windows resolution to 800x600 to reproduce this one; apparently the test driver was not actually clicking the buttons because they didn't fit in the window, which can not be scrolled. As a workaround, I simply wrapped all buttons in a horizontal stack panel so that they fit inside the window.

The more elegant solution would probably be to make the view scrollable, but that's assuming that the test driver handles that correctly (though it seems to work for the Window page in the test app).

Anyway, hope this works now 🤞

[codecat]

I'm not sure why the tests are still failing, they pass on my machine, even on 800x600 resolution. Maybe @maxkatz6 has more insights into this?

[MrJul]

I'm not sure why the tests are still failing, they pass on my machine, even on 800x600 resolution.

The new integration test passes on Windows, but fails on macOS.
Either the bug is also present on that platform (I'll check), or we need to wait a bit for the new position to be properly reported.

[emmauss]

I'm not sure why the tests are still failing, they pass on my machine, even on 800x600 resolution. Maybe @maxkatz6 has more insights into this?

What's your default screen resolution and scaling? Are you using any non-default Windows style, like compact, or high-contrast?
Also could you rebase so the tests run again.

[codecat]

What's your default screen resolution and scaling?

I normally run 3840x1600, at 100% scaling, and default Windows 11 styles. I have not tested with different scaling actually, perhaps that might be causing some tests to fail?

[emmauss]

What's your default screen resolution and scaling?

I normally run 3840x1600, at 100% scaling, and default Windows 11 styles. I have not tested with different scaling actually, perhaps that might be causing some tests to fail?

Are you running the integration tests?

[codecat]

Yes, but only the test I added, which is passing. I have not tested running all of them, in case that changes anything.

[emmauss]

Yes, but only the test I added, which is passing. I have not tested running all of them, in case that changes anything.

You run all tests, both unit and integration tests. Your change affects all window positioning tests.

[codecat]

The actual test that is failing is the one I wrote (Changing_Size_Should_Not_Change_Position), specifically on Mac, which I have not ran the tests on locally yet.

I can't get Avalonia to build on Mac currently, but I'll do my best to figure that out.

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[codecat]

It looks like on Mac, the Width and Height getters are returning default values rather than the actual window size (from _effectiveValues). In this case, it is even returning NaN.

Not sure where the real values are supposed to come from, but I'd be happy to include a fix for that in this PR too, if I can figure it out 😅

[emmauss]

If the fix and test is specifically for Windows, then exclude Mac from the test.

[codecat]

That would be a lot easier, but would sweep a bug under the rug. I'll do that and open another issue.

[emmauss]

That would be a lot easier, but would sweep a bug under the rug. I'll do that and open another issue.

Check if the bug occurs on Mac then.

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[codecat]

Check if the bug occurs on Mac then.

Sorry, I was talking about the Mac-specific bug that I filed in #18060 now 😄

If you're wondering about the issue that this PR fixes, no, it is not reproducible on Mac.

[codecat]

To match the notes raised in #18060, I've slightly updated the integration app code.

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[MrJul]

I've checked that #13300 (which initially introduced the bug) is still working after this fix.
Nice work adding an integration test.

LGTM, thank you!