Modality, part 6: Interacting with a program that has gone modal

Raymond ChenFebruary 28, 2005Feb 28, 200502/28/05

Earlier we saw the importance of setting the right owner window for modal UI. It is also important, when manipulating a window, to respect its modality. For example, consider the program we ended up with last time, the one which calls the MessageBox function to display a modal dialog.

Modality, part 5: Setting the correct owner for modal UI

Raymond ChenFebruary 24, 2005Feb 24, 200502/24/05

Here is the very simple fix for

the buggy program we presented last time.

void OnChar(HWND hwnd, TCHAR ch, int cRepeat)
{
switch (ch) {
case ‘ ‘:
MessageBox(hwnd, TEXT(“Message”), TEXT(“Title”), MB_OK);
if (!IsWindow(hwnd)) MessageBeep(-1);
break;
}
}

We have fixed the problem by passing the correct owner window
for the modal UI.

Modality, part 4: The importance of setting the correct owner for modal UI

Raymond ChenFebruary 23, 2005Feb 23, 200502/23/05

If you decide to display some modal UI, it is important that
you set the correct owner for that UI. If you fail to heed
this rule, you will find yourself chasing some very strange bugs.

Let’s return to

our scratch program and intentionally introduce a bug
related to incorrect owner windows,

Modality, part 3: The WM_QUIT message

Raymond ChenFebruary 22, 2005Feb 22, 200502/22/05

After

our two quick introductions

to modality,
we’re now going to dig in a little deeper.

The trick with modality is that when you call a modal function,
the responsibility of message dispatch is handled by that function
rather than by your main program.

Modality, part 2: Code-modality vs UI-modality

Raymond ChenFebruary 21, 2005Feb 21, 200502/21/05

Last time, we saw an example of code that was UI-modal but not code-modal. The opposite is also true: You can have code-modality without UI-modality. In fact, this is far more common than the UI-modal-but-not-code-modal scenario.
You encounter modal loops without a visible change in UI state when you drag the scroll bar thumb,

Modality, part 1: UI-modality vs code-modality

Raymond ChenFebruary 18, 2005Feb 18, 200502/18/05

From the end-users’ point of view, modality occurs when the
users are locked into completing a task once it is begun,
with the only escape being to cancel the entire operation.
Opening a file is an example of a modal operation:
Once the “Open”