When hiding titlebar a few white pixels still show on top

[dotMorten]

Describe the bug

When hiding the titlebar using OverlappedPresenter.SetBorderAndTitleBar(true, false) a few pixels of white titlebar still shows.

Steps to reproduce the bug

1. Create a new WinUI app.
2. in app.xaml root tag, set RequestedTheme="Dark"
3. in MainWindow.xaml.cs constructor add this code to hide the titlebar

            var hWnd = WinRT.Interop.WindowNative.GetWindowHandle(this);
            Microsoft.UI.WindowId windowId = Microsoft.UI.Win32Interop.GetWindowIdFromWindow(hWnd);
            Microsoft.UI.Windowing.AppWindow appWindow = Microsoft.UI.Windowing.AppWindow.GetFromWindowId(windowId);
            var presenter = appWindow.Presenter as Microsoft.UI.Windowing.OverlappedPresenter;
            presenter.SetBorderAndTitleBar(true, false);

Run the app, and observe the white color on top of the window.

Expected behavior

Entire window is black

Screenshots

NuGet package version

1.1.3

Packaging type

Packaged (MSIX)

Windows version

Windows 11 version 21H2 (22000)

IDE

Visual Studio 2022-preview

Additional context

First reported in WinUIEx: dotMorten/WinUIEx#67

[gabbybilka]

@mevey can you take a look?

cc: @btueffers

[riverar]

pong @rkarman

[mevey]

I've successfully repro-ed this bug :( and filed it task.ms/40617153

[mevey]

Hi @dotMorten, what is the intended goal of hiding the title bar? To draw your own? To have a PIP experience? To have a window that is not movable or resizable perhaps? This is helpful as we try to figure out how to solve this problem.

[dotMorten]

@mevey I'd ask the Windows App SDK team who added that API :-)
But a few things come to mind, like splash screens or more custom drawn windows.

[dotMorten]

Perhaps @ArchieCoder can add details, since he originally logged this bug in WinUIEx

[ArchieCoder]

Here is my original issue in WinUIEx: dotMorten/WinUIEx#67

Someone has the workaround: dotMorten/WinUIEx#67 (comment)

[dotMorten]

@ArchieCoder thanks but I think they are looking for the ‘why’ you were doing this to justify fixing their API

[ArchieCoder]

The original goal was to hide the color of the title bar because it didn't find the rest of the app. If the title bar color can be changed, this is then a non-issue anymore.

[ACGNnsj]

It seems unchanged in WAS 1.3, so should I consider it a normal behavior? At least, 'ExtendsContentIntoTitleBar' helps eliminate the white space.

[stevenbrix]

we would like to get rid of this little white border as well. we want to have full control over the appearance of the window for our app and this prevents us from doing that

[riverar]

@stevenbrix That's the caption area peeking out there; here's a workaround for now:

var windowHandle = WinRT.Interop.WindowNative.GetWindowHandle(this);
int colorBlack = 0x00_00_00_00;
unsafe
{
    DwmSetWindowAttribute(new HWND(windowHandle),
        DWMWINDOWATTRIBUTE.DWMWA_CAPTION_COLOR, &colorBlack, sizeof(int));
}

Notes:

• Congrats, you've now signed up to monitor for DWM theme/colorization, high contrast, etc. changes and set this caption color accordingly! This involves a number of events and window messages. Some documented, some not.
• You'll want to bind that to the user's color preferences.
• Solid colors only. No fancy art up there or the bar will "reappear".
• This doesn't work on Windows 10 or Windows 11 before build 22000.

[pratikone]

I am aware of this issue. Seems like something Windows shell puts and unless it gets patched, it cannot be removed. I suggest not using this api (if rest of appwindow/winui3 custom titlebar apis are not filling the requirements, because they cover a lot cases now including interactive controls within the titlebar), but rolling out a custom titlebar solution using a custom WndProc and using WS_EX_LAYERED and WS_OVERLAPPED styles, but using 1.4 newly introduced InputNonClientPointerSource apis (can find it only in preview2/experimental1 builds for now) for doing the heavy lifting around Non client message handling. Let me know if any of you need a sample, I can put together a solution you can refer.
Adding @tiberiu2 as he is the owner of appwindow titlebar apis as well as these new ones

[riverar]

@pratikone Are you saying OverlappedPresenter.SetBorderAndTitleBar(..., false) is forever broken and that developers will have to handle NC painting/messages manually for no-titlebar scenarios?

[riverar]

@pratikone @tiberiu2 Can either of you answer my question? I was simply asking for clarification of @pratikone's comment above. Thanks!

[pratikone]

@pratikone Are you saying OverlappedPresenter.SetBorderAndTitleBar(..., false) is forever broken and that developers will have to handle NC painting/messages manually for no-titlebar scenarios?

I am not saying that at all. I am saying that while this issue gets fixed (given the fix has to be in windows shell code) , there exists a immediate workaround which is much simpler than earlier i.e. let InputNonClientPointerSource apis handle NC messages for a vanilla custom solution.

[riverar]

Sounds like we're in disagreement over "forever", that's fair.

Maybe we can get this documented as a known issue when using this API for future devs?

[pratikone]

Yeah, that seems right. This issue has existed for some time and affects any app which does custom titlebar. If you are quick enough, you can spot it during launch of Visual Studio too. It goes away quickly.

Let me check internally if we can make some progress on fixing this.if not, getting it documented would be a good step too. Thanks for the suggestion

[duncanmacmichael]

Fixed in 1.4.3, closing issue.

[khoabui1412]

I just tested in ver 1.4.3 but issue still remains

[dotMorten]

I see the same thing. @duncanmacmichael Can we're open this?

[LucaCris]

Not fixed, when app is maximized:

(I assure you, there is an one pixel white line on top, try to open image out of this page).