[ros-kernel] Suggested implementation ideas for the various
WndProc, CallWndProc etc fixes
jonwil at tpgi.com.au
Mon Nov 10 17:51:31 CET 2003
One problem with this is that we need to free these structures at some point.
From further analysis (and from reading MSDN), the best time to delete
these structures from their storage in win32k is when the app that called
the function that created the structure, i.e. SetWindowLong, SetClassLong
or RegisterClassEx terminates, since this is when the handle would become
invalid due to the WNDPROC disappearing from memory when the app terminates
and the code is unloaded from memory (because a Window Procedure handle).
Given that the pointer passed to SetClassLong, SetWindowLong and
RegisterClassEx and so on is a pointer thats relative to the local address
space of the app, when the app disappears, the code will disappear and the
pointer we store in the structure is now pointing to god knows what.
MSDN explicitly says that you can only subclass a window if you are the
owner of that window and that you can only superclass a window class if it
is a system class or if it is a class you registered.
So, we need to store the "process ID" (whatever ROS/windows has that passes
for one) in the structure. And we need to implement clean-up code when the
module is unloaded and/or the app terminates to remove all the "owned by
this process" structures. Of course, should the process terminate wierdly
and not call the usual cleanups, it will leak. However, my experience shows
that even a dead simple program will leak memory on real windows if
teminated unexpectedly so we should be fine here. (unless someone wants to
suggest a work-around)
Lets get these implementation details (like figuring out how to store the
data and when to delete the memory we are storing the data in) worked out
ASAP so that someone (probobly me unless someone else gets to it first) can
get this thing coded.
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