Issues for win32 app with "PerMonitorV2" dpi awareness context when changing dpi while the window is minimized

孟轩郝 6

I've created a native win32 app with "PerMonitorV2" dpi awareness context set in the manifest. It is a dialog app and the dpi awareness feature works as expected in most cases. But when I minimize the window and change the monitor dpi from the system settings by changing the scale factor, things start getting wierd. After restoring the app, the only thing appears in the screen is a tiny box as below

239699-%E6%97%A0%E6%A0%87%E9%A2%98.png

I've found that the app doesn't recieve the WM_GETDPISCALEDSIZE message from the system when minimized, and I think this may be the cause. Then I refered to the documents for WM_GETDPISCALEDSIZE message and it says "This message is only sent to top-level windows". I've also got the definition for top-level windows here "[about-windows][2]". I'm sure my app dialog is a top-level window when it is in the foreground but I'm not sure if it is still a top-level window when minimized.

I'm wondering if there is a method to let the system send WM_GETDPISCALEDSIZE message to a minimized wiondow when dpi changed (e.g. restore the dialog just before the system send the WM_GETDPISCALEDSIZE message), or is there any other way to make a minimized window respond to dpi changed properly.

Many thanks. [2]: https://learn.microsoft.com/en-us/windows/win32/winmsg/about-windows#parent-or-owner-window-handle

Jeanine Zhang-MSFT 9,586 Reputation points Microsoft Vendor

2022-09-12T06:23:23.42+00:00

@孟轩郝

A window that has no parent, or whose parent is the desktop window, is called a top-level window. If the window is a top-level window, whether minimized or not.

I couldn't reproduce the issue on my computer.

Could you please tell us how do you set dpi awareness context in the manifest? I suggest you could refer to the Doc: Setting default awareness with the application manifest

"the only thing appears in the screen is a tiny box" What is the tiny box?

Could you please reproduce the issue in a blank desktop application ? Could you please provide some steps for us to reproduce the issue?

孟轩郝 6

I've created a new desktop application which has a simple dialog as the main window, and then added a manifest identical to that in the Doc: setting-the-default-dpi-awareness-for-a-process
All my codes are as below.

INT_PTR CALLBACK dlgProc(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam)  
{  
	switch (message)  
	{  
	case WM_COMMAND:  
		if (LOWORD(wParam) == IDOK || LOWORD(wParam) == IDCANCEL)  
		{  
			PostQuitMessage(0);  
			return (INT_PTR)TRUE;  
		}  
		break;  
	}  
	return (INT_PTR)FALSE;  
}  
  
int APIENTRY wWinMain(_In_ HINSTANCE hInstance,  
	_In_opt_ HINSTANCE hPrevInstance,  
	_In_ LPWSTR    lpCmdLine,  
	_In_ int       nCmdShow)  
{  
	HWND hDlg = CreateDialog(hInstance, MAKEINTRESOURCE(IDD_DIALOG), nullptr, dlgProc);  
  
	MSG msg;  
  
	while (GetMessage(&msg, nullptr, 0, 0))  
	{  
		if (!IsDialogMessage(hDlg, &msg))  
		{  
			TranslateMessage(&msg);  
			DispatchMessage(&msg);  
		}  
	}  
  
	return (int)msg.wParam;  
}

The dpi awareness works well if my window is not minimized. But when I minimize the window, change the scale of the current monitor and then try to restore it, it becomes the tiny box as below.

Jeanine Zhang-MSFT 9,586 Reputation points Microsoft Vendor

2022-09-16T01:22:13.083+00:00

@孟轩郝

I could not reproduce the problem on my system. Could you please tell us what version of system are you using?
孟轩郝 6 Reputation points

2022-09-16T04:05:31.223+00:00

I'm using Windows11 21H2. I've just tried it on another device with Windows10 21H2 after seeing your post and this issue doesn't happen on that one.
So maybe this issue is only on Windows11, or only on my current device? I don't have another Windows11 device to verify.
Jeanine Zhang-MSFT 9,586 Reputation points Microsoft Vendor

2022-09-16T06:29:47.333+00:00

@孟轩郝

It seems a issue on win11. I suggest you could post the issue via Feedback Hub for Windows Insider: Windows Insider.

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Issues for win32 app with "PerMonitorV2" dpi awareness context when changing dpi while the window is minimized

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