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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.
Did you also try using the WS_EX_LAYERED style and related features?
Yes, I have used WS_EX_LAYERED | WS_EX_COMPOSITED | WS_EX_TRANSPARENT styles.
@Aditya Pingle
Maybe you should not use WS_EX_TRANSPARENT directly.
Try Using Layered Windows.
// Set WS_EX_LAYERED on this window
SetWindowLong(hwnd,
GWL_EXSTYLE,
GetWindowLong(hwnd, GWL_EXSTYLE) | WS_EX_LAYERED);
// Make this window 70% alpha
SetLayeredWindowAttributes(hwnd, 0, (255 * 70) / 100, LWA_ALPHA);
@Tong Xu - MSFT same issue. whole window is turning to black screen.
@Aditya Pingle Hello, have you checked answer? Does it help you?
@Aditya Pingle Are there any updates for this issue? Has your question about the black ghost window been answered?
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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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,
To avoid the black background for a ghost window do something other than the above.
Hi @RLWA32
Can you provide a sample code for the solution that you suggested?
I am wondering if ghosting logic removes the entire transparency.
I am wondering if ghosting logic removes the entire transparency.
It seems that the ghost window is not transparent. Using the customary white background for a window -
My recommendation is that you make the necessary code changes to eliminate anything that interferes with message pumping and causes Windows to identify the application as Not Responding.
@RLWA32 Is there any other way I can continue showing transparent pop up window when application goes into not responding state?
I am working on Office-Addin. My Add-in uses transparent popup window to show watermark over the user's content. I can do necessary changes to not hang application in my add-in , but there can be any other reason for application hang. During that also, the watermark window is going black.
@Aditya Pingle I'm not aware of any way to maintain transparency for a ghost window. And since your code is an add-in to an Office application in my opinion it wouldn't be appropriate for your code to call DisableProcessWindowsGhosting.
@RLWA32 I tried to show watermark from the background thread after I tested out that ghosting is thread specific. I am able to show the watermark from background thread. But when main window is ghosted, it is brought on top of watermark window
@Aditya Pingle, If the application hosting your add-in has become unresponsive and its main window has been replaced by a ghost window then it seems to me there are bigger problems than the appearance of your transparent pop-up. Even though you may maintain transparency by using a different thread wouldn't your add-in still be precluded from interacting with the host while the main UI thread is non-responsive?
@RLWA32 you are correct. That is why I have discarded that approach and looking for alternate option. The black ghost window is hampering the user experience in certain scenarios. I was wondering if using WPF would solve this issue or not. I haven’t tried that approach yet. What do you think?
@Aditya Pingle I have no idea whether or not WPF is suitable for your add-in or is a solution to avoid ghost windows.