Question

I am working on and changing some application, and I’ve noticed that at some specific scenario the application starts flashing in the task bar. I’ve checked the application and found a call to FlashWindowEx (a single one), but the code never gets there. In other words, I’m pretty confident Windows itself causes the flashing, and I wonder when does it happen.

An example answer (other than directing me to an article about the issue) is something like “Windows will automatically flash your task bar item if your application lost its focus but is still activated” (which isn’t true at this case, but it’s an example :-)).

Answer 1

The immediate reason for flashing is FlashWindow API call, MSDN specifies:

Typically, a window is flashed to inform the user that the window
requires attention but that it does not currently have the keyboard
focus.

A typical reason of flashing is focus/foreground stealing:

… This value is the time in milliseconds before Windows XP allows an
application to steal the focus from the foreground application. To
convert 200000 to seconds, divide it by 1000 (200 seconds). You see
the value ForegroundFlashCount in the table twice, because setting it
to 0 causes the taskbar button to flash until you click it; otherwise,
the taskbar button flashes the number of times you set in
ForegroundFlashCount.