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Hello, everyone!
I am a student learning Windows programming using Python and the ctypes library. I have a question regarding the behavior of the PrintWindow function in relation to DPI awareness.
I am currently working on a project that involves capturing the screen of a game window using the PrintWindow function. I have noticed that the captured image seems to be incomplete or not capturing the entire window correctly. After some research and discussion, I suspect that this issue might be related to the DPI awareness settings of the calling process (in my case, the Python script).
My question is: Does the behavior of the PrintWindow function depend on the DPI awareness settings of the calling process? Specifically, will PrintWindow always return the actual window screen regardless of the DPI awareness context of the Python script or the current process?
I have looked through the official documentation for the PrintWindow function on Microsoft Learn (https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-printwindow), but I couldn't find any explicit information about its interaction with DPI awareness settings.
If anyone has experience or insights regarding this matter, I would greatly appreciate your help. Any information, suggestions, or resources related to the PrintWindow function and DPI awareness would be immensely helpful for my project and my understanding of the Windows API.
Thank you in advance for your time and assistance!
Best regards, Yucheng Song
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I have noticed that the captured image seems to be incomplete or not capturing the entire window correctly.
How is it incomplete, and does the same occur for all application windows, or specific ones?
I found that the image only captures a portion starting from the top-left corner. This was discovered while testing a game developed by our club. After a series of experiments, I realized that the problem is due to the win32gui.GetWindowRect(hwnd) code obtaining the window size at '100% scaling', rather than the actual displayed window size.
I found that the image only captures a portion starting from the top-left corner. This was discovered while testing a game developed by our club. After a series of experiments, I realized that the problem is due to the win32gui.GetWindowRect(hwnd) code obtaining the window size at '100% scaling', rather than the actual displayed window size.
OK, so you've solved it?
Not essentially. I believe the primary reason for this issue is that when using PrintWindow to capture screenshots of the tested program in Python, PrintWindow always returns the actual image, specifically, the image after DPI scaling. On the other hand, win32gui.GetWindowRect(hwnd) returns the window coordinates based on the current thread's DPI context, which means the behaviors of the two are not always synchronized. However, the above is my speculation about the behavior of PrintWindow; therefore, I am looking for confirmation of this speculation.
Thank you very much, Xiaopo Yang, for your insightful response. It has clarified the relationship between the PrintWindow function and DPI scaling, as well as the handling of WM_PRINT messages. Your expertise has been extremely valuable to me, and I'm grateful for the assistance you've provided.
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Hello @Yucheng Song, welcome to Microsoft Q&A. You can mark an answer for completion of the question.
While for PrintWindow, By default, the entire window is copied. Although DPI not mentioned, The DefWindowProc function should process WM_PRINT message independence of DPI. But you can process this message in your windows with DPI.