The Old New Thing

Building a dialog template at run-time

April 29, 2005 Apr 29, 2005 04/29/05

Raymond Chen

We've spent quite a bit of time over the past year learning about dialog templates and the dialog manager. Now we're going to put the pieces together to do something interesting: Building a dialog template on the fly. What we're going to write is an extremely lame version of the MessageBox function. Why bother writing a bad version of ...

Rescuing thread messages from modal loops via message filters

April 28, 2005 Apr 28, 2005 04/28/05

Raymond Chen

As we have seen recently, thread messages are eaten by modal loops because they have nowhere to go when dispatched. However, there is a way to see them before they vanish, provided the modal loop is cooperative. The WH_MSGFILTER message hook allows you to receive messages passed to the CallMsgFilter function. Fortunately, all the modal ...

Watching thread messages disappear

April 27, 2005 Apr 27, 2005 04/27/05

Raymond Chen

We saw last time that thread messages are eaten by modal loops. Today we'll illustrate, and then we'll try to fix it next time. Start with our scratch program and make the following changes: Run this program and notice that it beeps every two seconds, or at least it does most of the time. If you right-click on the caption bar or grab ...

Thread messages are eaten by modal loops

April 26, 2005 Apr 26, 2005 04/26/05

Raymond Chen

Thread messages (as generated by the PostThreadMessage function) do not go anywhere when passed to the DispatchMessage function. This is obvious if you think about it, because there is no window handle associated with a thread message. DispatchMessage has no idea what to do with a message with no associated window. It has no choice but to ...

What is the HINSTANCE passed to SetWindowsHookEx used for?

April 25, 2005 Apr 25, 2005 04/25/05

Raymond Chen

The SetWindowsHookEx function accepts a HINSTANCE parameter. The documentation explains that it is a handle to the DLL containing the hook procedure. Why does the window manager need to have this handle? It needs the handle so it knows which DLL to load into each process when the hook fires. It injects the DLL you pass, then calls the ...

The new scratch program

April 22, 2005 Apr 22, 2005 04/22/05

Raymond Chen

I think it's time to update the scratch program we've been using for the past year. I hear there's this new language called C++ that's going to become really popular any day now, so let's hop on the bandwagon! The basic idea of this program is the same as our old scratch program, but now it has that fresh lemony C++ scent. Instead of ...

The Itanium’s so-called stack

April 21, 2005 Apr 21, 2005 04/21/05

Raymond Chen

Last year I alluded to the fact that the Itanium processor has two stacks. The one that is traditionally thought of as "the stack" (and the one that the sp register refers to) is a manually managed block of memory from which a function can carve out space to use during its execution. For example, if you declare a local variable like then ...