Re: Progress Dialog Box

"Scott McPhillips [MVP]" <org-dot-mvps-at-scottmcp>
Fri, 23 Mar 2007 09:49:56 -0400
<#b0kgIVbHHA.4312@TK2MSFTNGP05.phx.gbl> wrote:

Hi All,

   I'm very new to VC++ , MFC programming. I have a Button in a
property page. On clicking this button i want a "Progress Dialog Box"
to pop up and run as a seperate thread. The problem is i'm not able to
see the "Progress Dialog Box" and the application goes to hang state.
Please help.

There are two issues that you need to understand. (1) If a dialog is
created in a thread that is the only thread in which it can run. All
windows use the message pump of the thread in which they were created.
You cannot do anything to a window created in another thread.

(2) A window needs to be processing messages in order to paint (so it
can respond to the WM_PAINT message). In your code you have a while
loop in the main thread, so the main thread is not processing messages,
and you have a Sleep loop in the secondary thread, so the secondary
thread is not processing messages, and you created a "worker" thread,
which does not even have a message loop.

Don't make waiting loops: They prevent processing messages. The best
overall approach is to keep ALL windows in the main thread and do your
lengthy non-window processing in secondary threads.

Scott McPhillips [VC++ MVP]

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