Window size not correctly applied

[char8t]

Describe the bug

When specifiying the Window size via AppWindow.Resize(new SizeInt32(800, 450)) the actual window size appears to be little bit smaller than what is requested:

One Idea of @dotMorten was (dotMorten/WinUIEx#200) that setting the window dimension is "taking the drop shadow into account". Is that true? If so how to get a window of exactly the size specified?

dotMorten/WinUIEx#200

Steps to reproduce the bug

1. Create WinUI3 app
2. Specifiy window dimensions
3. Measure real results

Expected behavior

The window size to be exact to the requested size minus border

Screenshots

No response

NuGet package version

WinUI 3 - Windows App SDK 1.6.3: 1.6.241114003

Windows version

Windows 11 (24H2): Build 26100

Additional context

No response

[castorix]

It is because of DWM
On Windows 10, If I add the difference from GetWindowRect - (DwmGetWindowAttribute and DWMWA_EXTENDED_FRAME_BOUNDS), I get the right size (got after the window has been displayed, not at beginning)
(I get 786 * 443 :
104-904 vs 111-897 => 2 * 7
104-554 vs 104-547 => 7
=> 786 + 14, 443 + 7 => 800, 450
(maybe there are other values than DWMWA_EXTENDED_FRAME_BOUNDS on Windows 11...)

[DarranRowe]

If you want the client area to be set to the size specified, remember that AppWindow has the ResizeClient member. This will set the client area to the size specified by taking the styles into account.

Since the screenshot of your code shows that you are using ExtendContentIntoTitleBar, then what you are measuring there is the client area. Resize sets the window size and ResizeClient sets the window size to give a specified client size.

[char8t]

Oh i didn't know about ResizeClient. It works as expected just one thing to note: When using ExtendContentIntoTitleBar = true the client area will become a little bit bigger then what is requested 800, 450 -> 800, 480. Is there a way to programmatically get the title bar height so i can account for the extra size when using ExtendContentIntoTitleBar?

[DarranRowe]

The implementation of the title bar customisation functionality is shared with AppWindow in current versions. This means that you should be able to go through AppWindow to get an AppWindowTitleBar instance. AppWindowTitleBar has a Height property which reports the height of the title bar.

[char8t]

Thank you. Using AppWindow.TitleBar.Height together with ResizeClient when using ExtendContentIntoTitleBar = true does the job