Use CallWindowProc when using WNDPROC pointers directly recurring theme I see while debugging application compatibility issues has to do with the direct use of the window proc pointer. If the intended WNDPROC exists in a DLL that is located in Slot 0, the pointer “looks right” and is often mistakenly useden-USTelligent Evolution Platform Developer Build (Build: 5.6.50428.7875)re: Use CallWindowProc when using WNDPROC pointers directly, 03 Apr 2008 14:59:12 GMT91d46819-8472-40ad-a661-2c78acb4018c:8353536ahmed_kandeel<p>ٍSome incidents i saw related to calling original window proc, is when two applications subclass a single window from two different processes. if the message parameters contain pointers, it seems that CallWindowProc switch the application context before calling the window proc. so the subclass procedure should map the pointer accordingly. i saw that in many cases such as EM_REPLACESEL editor message.</p> <div style="clear:both;"></div><img src="" width="1" height="1">