Window close button does not fill with main window

[dinhcongduy]

Describe the bug

Window close button have padding right in main window

Steps to reproduce the bug

_mainWindow.ExtendsContentIntoTitleBar = true
_mainWindow.SetAdjustBar(GetCurrentTheme());

Expected behavior

Remove right padding for Window Close button

Screenshots

NuGet package version

WinUI 3 - Windows App SDK 1.5.6: 1.5.240802000

Windows version

Windows 10 (21H1): Build 19043

Additional context

No response

[castorix]

On Windows 10 22H2, on "normal" Desktop/UWP apps, I have borders at top + right
For example, with Notepad :

[4OTbIPE]

It's because of this

[castorix]

With Windows App SDK 1.5.24, it can be fixed by repositioning the "ReunionWindowingCaptionControls" window
(subclassing + WM_WINDOWPOSCHANGING)
(I added a yellow border to AppTitleBar to check the rectangle) :

[michelgerritse]

With Windows App SDK 1.5.24, it can be fixed by repositioning the "ReunionWindowingCaptionControls" window (subclassing + WM_WINDOWPOSCHANGING) (I added a yellow border to AppTitleBar to check the rectangle) :

I can confirm this fixes the offset by 1 error with the caption buttons on Windows 10. I don't have Windows 11 so I was not able to test the (original) behavior on that OS version. In combination with DWM extending the top border of the main/parent window by 2 you will get rid of most, if not all, graphical issues with the caption buttons (besides the wrong colors, but we have an API to fix this). The only issue that I'm aware of is the missing OS provided tooltips for the minimize and maximize/restore caption buttons (the close tooltip does show).

I noticed something interesting while subclassing the ReunionWindowingCaptionControls class child window:
The parent will never get a WM_PARENTNOTIFY message when this child is about to be destroyed. This could be intentional, or a bug, but it should be common practice to destroy all your child windows before you destroy the parent.

[castorix]

And I did not test 1.6 experimental but they say there is a new control https://learn.microsoft.com/en-us/windows/apps/windows-app-sdk/experimental-channel#new-titlebar-control
with
Note

The new TitleBar control we released in 1.6-experimental1 is not yet available in non-experimental builds of 1.6 to allow more time to evaluate and respond to community feedback. We received a lot of great input here and want to make sure we take the time needed to address it.