Drawing on top of a window of a third party application

Question

Here is a description of my use case:

I have a Windows application that comprised of the main window and it also creates child windows (think of MS Word for instance). What i want to do is draw frames around certain children windows of a given application. Note that when i say window i mean any visible HWND (handle) in the system. This could be a certain window in Excel, or an open pdf document in Abode reader or whatever.

My question is: Can this be implemented as AN independent API where one would for instance be able to call the following ?

DrawOutline(HWND, OutlineColor, Thikness);

Any pointers as to how to approach this ? Any limitations one might think of? This would not be a plugin to a specific application but a stand alone API. MFC is also OK. Thanx

Answer 1

The Spy++ tool draws frames around any window. Source code for several Spy++ versions is available on the net.