There are a few different built-in ways to close a dialog box in the classic Windows dialog manager. Let’s run them down.<\/p>\n
First, there’s hitting the ESC<\/kbd> key.<\/p>\n The ESC<\/kbd> key, as with all keyboard navigation, is handled by the Exception<\/b>: If there is a control whose ID is Okay, what about the Close button in the title bar, the one that looks like an \u00d7?<\/p>\n The Close button in the title bar, double-clicking the dialog box icon (if there is one), selecting Close from the system menu, and pressing Alt<\/kbd>+F4<\/kbd> all behave the same way: They generate a Now that we understand what happens, next time we can look at ways of customizing the behavior.<\/p>\nIs\u00adDialog\u00adMessage<\/code> function. Assuming that the dialog control with focus did not use the WM_Is\u00adDialog\u00adMessage<\/code> function converts the ESC<\/kbd> to a simulated button click of whatever dialog control has the ID IDCANCEL<\/code>. Specifically, the message is WM_BN_IDCANCEL<\/code>, and the window handle is the handle to whatever dialog control has the ID IDCANCEL<\/code> (or nullptr<\/code> if there is no such control).<\/p>\nIDCANCEL<\/code>, and that control is disabled, then the Is\u00adDialog\u00adMessage<\/code> function merely beeps and otherwise ignores the ESC<\/kbd> key.<\/p>\nWM_wParam & 0xFFF0<\/code> is SC_WM_CLOSE<\/code> message. The default dialog procedure responds to the WM_CLOSE<\/code> in basically the same way that Is\u00adDialog\u00adMessage<\/code> does: It generates a simulated button click of whatever dialog control has the ID IDCANCEL<\/code>. Again, this is done by converting it to the WM_BN_IDCANCEL<\/code>, and the handle to whatever dialog control has the ID IDCANCEL<\/code> (or nullptr<\/code> if there is no such control). It also has the same exception: If there is a control whose ID is IDCANCEL<\/code>, and that control is disabled, then the default dialog procedure just beeps and otherwise ignores the message.<\/p>\n