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Why does my transparent-background window turn into black screen after window ghosting?

Aditya Pingle 0 Reputation points
2024-05-10T14:33:43.0133333+00:00

I have a pop-up window that acts as a watermark on my application over a parent window. It has a transparent background (WS_EX_TRANSPARENT), but when the application becomes non-responsive, Windows adds a ghost window with a black background. I tried using different window styles, but it did not work. I'm currently attempting to show the watermark dialog in a background thread, but I would prefer a solution to fix the black background instead. Is there any way to prevent this from happening besides using DisableProcessWindowGhosting? I also don't want to go for child window as it adds another issues to my application.

Windows
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Windows API - Win32
Windows API - Win32
A core set of Windows application programming interfaces (APIs) for desktop and server applications. Previously known as Win32 API.
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C++
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A high-level, general-purpose programming language, created as an extension of the C programming language, that has object-oriented, generic, and functional features in addition to facilities for low-level memory manipulation.
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2 answers

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  1. Tong Xu - MSFT 2,036 Reputation points Microsoft Vendor
    2024-05-14T02:02:26.03+00:00

    Hello, @Aditya Pingle
    Welcome to Microsoft Q&A!

    I would prefer a solution to fix the black background instead.

    You want to modify the background of ghost window?
    My answer is No.

    The ghost window will replace it when top-level window stops responding in z-order, location, size, and visual attributes. You can move, resize and close but just these actions you can do. Don't try changing the attributes of ghost window.
    **
    You can see the last part of remarks.
    Thank you.

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  2. RLWA32 40,941 Reputation points
    2024-05-17T10:16:52.16+00:00

    Windows will use the background brush specified in a WNDCLASS when it creates a ghost window. If that brush is the stock object NULL_BRUSH or HOLLOW_BRUSH a black background results. If the window class does not specify a background brush but the window procedure handles WM_ERASEBKGND then windows will use whatever brush the handler uses when it creates the ghost window. If the handler does not actually erase the background (simply returns TRUE/FALSE) then the black background results. Also, if the handler uses the abovementioned stock objects the ghost window will also have a black background.

    For example using Sleep() to temporarily stop pumping messages,

    GhostWindow

    To avoid the black background for a ghost window do something other than the above.