Dialog Box Procedure
A dialog box procedure is similar to a window procedure in that Windows sends
messages to the procedure when it has information to give or tasks to carry
out. Unlike a window procedure, a dialog box procedure never calls the
DefWindowProc function. Instead, it returns the Boolean value TRUE if it processes a
message or FALSE if it does not.
Every dialog box procedure has the following form:
BOOL APIENTRY DlgProc(hwndDlg, message, wParam, lParam)
HWND hwndDlg;
UINT message;
WPARAM wParam;
LPARAM lParam;
{
switch (message) {
// Place message cases here.
default:
return FALSE;
}
}
The procedure parameters serve the same purpose as in a window procedure, with
the
hwndDlg parameter receiving the window handle of the dialog box.
Most dialog box procedures process the
WM_INITDIALOG message and the
WM_COMMAND messages sent by the controls, but process few if any other messages. If a
dialog box procedure does not process a message, it must return FALSE to direct
Windows to process the messages internally. The only exception to this rule is
the WM_INITDIALOG message. The dialog box procedure must return TRUE to direct
Windows to further process the WM_INITDIALOG message. In any case, the procedure
must not call
DefWindowProc.
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