Button lost WM_LBUTTONUP after a modal dialog window show up

Question

I have a win32 application, there is an button on the main window.

When i click the mouse left button, i receive the WM_LBUTTONDOWN message, when i release the mouse left button, i receive the WM_LBUTTONUP message, that is normal.

However, if in the processing of message WM_LBUTTONDOWN, (while i am holding the mouse left button), the program show a modal dialog window, the button will never receive the WM_LBUTTONUP.

This becomes an issue because in the WM_LBUTTONDOWN the program did something that needs to be clear up in the WM_LBUTTONUP. Now because of the modal dialog, there is no chance to clear up anymore.

Is there a better way to handle this? I tried SetCapture, seems still can not receive the WM_LBUTTONUP.

Answer 1

This is quite reasonable. When you show the modal dialog it starts its own modal message loop. And so it will receive the WM_LBUTTONUP message.

The fundamental problem that you have is that you are showing the modal dialog in response to WM_LBUTTONDOWN, when in fact you should show it in response to WM_LBUTTONUP. Try pressing buttons in other applications and note that the action occurs only when the button goes up. You should do likewise and follow the platform standards.