Fix fullscreen after maximize

[beviu]

Summary of the Pull Request

Fixes the sides disappearing when entering full screen mode when the window is maximized.
However, now, a Vista-style frame briefly appears when entering/exiting full screen.

References

PR Checklist

• Closes Entering Fullscreen from Maximized doesn't work right #3709
• CLA signed. If not, go over here and sign the CLA
• Tests added/passed
• Requires documentation to be updated (no)
• I've discussed this with core contributors already. If not checked, I'm ready to accept this work might be rejected in favor of a different grand plan. Issue number where discussion took place: #xxx

Detailed Description of the Pull Request / Additional comments

When the non-client island window is maximized and has the WS_OVERLAPPEDWINDOW style, SetWindowPos is "lying": the position ends up being offset compared to the one we gave it (found by debugging). So I changed it to use WS_POPUP like the client island window was already doing. But now it has the Vista frame that appears briefly when entering/exiting full screen like the client island window.

Validation Steps Performed

[zadjii-msft]

@greg904 Is there any way to not get that vista-style window frame to appear for a brief second, and fix this bug?

Overall, I'm happy that this works better, but that frame felt really jarring in my own testing :/

[beviu]

I don't know how to do it. Chromium's code https://github.com/chromium/chromium/blob/master/ui/views/win/fullscreen_handler.cc is pretty much the same as here and yet Chromium doesn't have the issue. I'm missing something somewhere.

[zadjii-msft]

Okay, I don't know if this is the right solution, but I was able to get the vista frame to hide itself when entering fullscreen if I hide the window near the top of IslandWindow::_SetIsFullscreen, and show it again at the bottom.

The vista titlebar is visible for a frame or so when leaving fullscreen, but idk how we fix that. @greg904 if you want to experiment with that, I can let you try your hand at it more. If not, that's fine too - I can submit my own PR once this is merged to fix it when entering. Whatever you prefer 😄

[beviu]

I don't really have time now unfortunately so I would prefer that you submit your own PR.

[zadjii-msft]

@greg904 No problem. Thanks for the initial fix 😄

[ghost]

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[ghost]

🎉Windows Terminal Preview v0.8.10091.0 has been released which incorporates this pull request.:tada:

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