Windows: Parent of owned child window not visible

[msiglreith]

Declaring one windows as owner will make the owner window invisible which is unintentional and a regression from 0.25.
Seems to be caused by #1933

Minimum example:

fn main() -> anyhow::Result<()> {
    let event_loop = EventLoop::new();

    let owner = WindowBuilder::new()
        .with_title("owner")
        .build(&event_loop)
        .unwrap();

    let child = WindowBuilder::new()
        .with_title("child")
        .with_owner_window(owner.hwnd() as _)
        .build(&event_loop)
        .unwrap();

    event_loop.run(move |event, _, control_flow| {
        *control_flow = ControlFlow::Wait;
    })
}

[msiglreith]

hm looks like only the child window receives a WM_PAINT event

[msiglreith]

Not passing the parent HWND on window creation for owned windows (which is optional anyway for popups) seems to alleviate the issue and show the parent window correctly - doing the initialization in WM_CREATE instead of WM_NCCREATE as well but that would defeat the purpose of #1933
Unsure what's the underlying issue tho

[maroider]

If I've understood the issue correctly, it seems you've run into what Raymond Chen describes here. That is, a window can optionally have a parent XOR an owner.

[msiglreith]

@maroider sorry, forget that part - not setting the handle delete the ownership which isn't the goal either 😓

[maroider]

I think there were only a couple of things that absolutely had to happen in response to WM_NCCREATE rather than WM_CREATE, like a call to EnableNonClientDpiScaling (which strictly speaking doesn't require our window state to be initialized). We don't currently dispatch any events in response to WM_NCCREATE and WM_CREATE, so it should be feasible to move most of the initialization logic into WM_CREATE (with some care).

(I should probably try to reproduce this bug, TBH, but I no longer have Windows installed on my main machine)

[maroider]

I finally have a Windows 10 VM I can test with, and I managed to reproduce the bug.
Strangely enough, the owner window still appears when I hover over the preview in the taskbar.
I'll get you a review for #2062 shortly.