February 2005 | The Old New Thing

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. If we wanted to get that program to exit and sent a WM_C

"Support our troops" wristbands provide only 1/3 support

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

Over at Slate, Timothy Noah notes how much money from so-called "awareness bracelets" actually go to the causes they purport to champion. In summary, I find it ironic that the "Support our troops" bracelet doesn't actually support our troops. And is yellow really the right color to use to demonstrate support for the military?

Two brief reminiscences on the Windows XP "Comments?" button

Raymond ChenFebruary 25, 2005Feb 25, 200502/25/05

In beta versions of Windows XP, there was special code in the window manager to give every window a link in the upper right corner called "Comments?" which if clicked on displayed a dialog that allowed you to submit feedback to Microsoft about that window. Since this was a beta release, there was no anonymity when you submitted feedback.

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. We have fixed the problem by passing the correct owner window for the modal UI. Since MessageBox is modal, it disables the owner while the modal UI is being displayed, thereby preventing the user from destroying or changing the owner window's state when it is not e

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, so that we can see the consequences. Run this

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. Consequently, if you have customized your main program's message pump, those customi

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, drag the window

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" command has been selected, users have no choice but to select a file for opening (or to cancel the o

MsgWaitForMultipleObjects and the queue state

Raymond ChenFebruary 17, 2005Feb 17, 200502/17/05

It waits only for messages that have arrived since the last time you checked.

Limitations of the shell animation control

Raymond ChenFebruary 16, 2005Feb 16, 200502/16/05

The Animation control in the shell common controls library supports only a very limited class of AVI files. Why all these restrictions? Because the purpose of the Animation control is to be able to show simple animations. If you have a complex animation, you should be using one of the more advanced animation controls, like the MCIWnd win

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