Allow a win32 window's restored size to be defined even when it is maximised or minimised

[TomEdwardsEnscape]

This PR rewrites WindowImpl.Resize to use SetWindowPlacement, which allows us to set the size of the window even when it is minimised or maximised.

Breaking changes

None

Obsoletions / Deprecations

None

Fixed issues

Fixes #13300

[hez2010]

I don't think this is the correct fix.
A minimized window is not an actual window but a placeholder without any size information on it.
If we want to change the size before the window shows up, I will rather expect to save the size information and resize it when users restore the window state to normal. But I think this should be handled by the app developer, not the framework itself.

[TomEdwardsEnscape]

A minimized window is not an actual window but a placeholder without any size information on it.

It might be a placeholder, but nevertheless the size of a minimised window is stored by Windows and is sent back to the application as a WM_SIZE message when that window is restored.

This is the behaviour that Avalonia expects, so I think that removing the inconsistency between minimised and non-minimised windows is a good approach.

If we want to change the size before the window shows up, I will rather expect to save the size information and resize it when users restore the window state to normal. But I think this should be handled by the app developer, not the framework itself.

This is OK in principle, but it doesn't map well onto the Avalonia API, in which windows have public Width and Height properties that can be read and written at any time. Should we start throwing exceptions when those properties are set while the window is minimised?

[hez2010]

This is OK in principle, but it doesn't map well onto the Avalonia API, in which windows have public Width and Height properties that can be read and written at any time. Should we start throwing exceptions when those properties are set while the window is minimised?

The behavior in other win32 applications is just to return the window size before it was last minimized, and any resize operation is ignored after the window was minimized. This is exactly what Avalonia currently doing, so I'm not sure whether this should be fixed.

[TomEdwardsEnscape]

Avalonia doesn't ignore the resize. It accepts it the new value for its own window object without transferring it to the OS, which is inconsistent. It should either apply the new value in both places, or in neither (i.e. throw an exception).

[thevortexcloud]

It should either outright reject the change or buffer it from the sound of things. Quickly making it visible then invisible feels like a hack to me, and I imagine on some slow systems may lead to noticeable flickering. If you do go with rejecting the change, you probably also need to add a new property/method that says if the window can be resized. CanResize is currently settable by user code and indicates if the end user is allowed to resize the window.

[TomEdwardsEnscape]

I don't think the window would ever appear, because we are executing on the UI thread and thus blocking it. But yeah, buffering the value is the (more complicated) alternative if we don't like re-minimising.

I'm not a fan of blocking changes to the properties because these limitations may not exist on other platforms.

[emmauss]

Wouldn't it be better to defer resizing to when the window is restored?

[StefanKoell]

Coming from WinForms, I know there's a concept called "RestoreBounds" on a form:
https://learn.microsoft.com/en-us/dotnet/api/system.windows.window.restorebounds?view=windowsdesktop-8.0

A Rect that specifies the size and location of a window before being either minimized or maximized.

Maybe something like this would be a good approach.

[thevortexcloud]

It sounds like most people would prefer buffering the value until the window is restored.

[jp2masa]

Can't this be fixed using SetWindowPlacement?

[TomEdwardsEnscape]

Can't this be fixed using SetWindowPlacement?

Well well well:

WPF_SETMINPOSITION: The coordinates of the minimized window may be specified. This flag must be specified if the coordinates are set in the ptMinPosition member.

That's our solution, and is apparently also what WPF does to handle this exact scenario.

WPF stands here for "Window Placement Flags". So it's not the silver bullet I had expected. Still worth looking at though.

[TomEdwardsEnscape]

SetWindowPlacement worked! It supports setting the window size of a minimised window without restoring it.

[TomEdwardsEnscape]

There are several other uses of AdjustWindowRectEx which could be redirected to this method. These other locations currently don't account for per-window DPI, so using this method may fix some bugs. But I decided not to make unnecessary changes in this PR.

[avaloniaui-bot]

You can test this PR using the following package version. 11.1.999-cibuild0044711-beta. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[TomEdwardsEnscape]

We still can't resize a fullscreen window, but I don't think this will ever be supported for the reasons outlined in the comment here. This is not a regression, it's the same behaviour as on master.

[avaloniaui-bot]

You can test this PR using the following package version. 11.1.999-cibuild0044717-beta. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[avaloniaui-bot]

You can test this PR using the following package version. 11.1.999-cibuild0044723-beta. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[TomEdwardsEnscape]

@emmauss this is ready for review again.

[maxkatz6]

LGTM, just want to have @emmauss opinion as well, as it might affect XPF.

[emmauss]

Could you rebase your branch?

[avaloniaui-bot]

You can test this PR using the following package version. 11.1.999-cibuild0045122-beta. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[maxkatz6]

@TomEdwardsEnscape it looks like there are conflicts. It cannot be automatically resolved, and we can't push to your remote branch.

[avaloniaui-bot]

You can test this PR using the following package version. 11.1.999-cibuild0045185-beta. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]