Can anybody tell me how to subclass a window from another process, i.e.
how to receive its messages?
SpyWorks (for VB) can do this, how to they do that?

And I have another problem: One of the messages I receive from the window
is a pointer to a structure which is (of course) in the memory space of
the other application. How can i change this structure before the message
is processed by the standard window message function.

Jan

Jan,

The easiest way is not to subclass the window at all, but to insert a
WH_GETMESSAGE hook into the window's owner thread. Look up
SetWindowsHookEx() for details.

You are using the wrong approach here. It would be easier to use a real IPC
method, say a memory mapped file would work. Also, you might want to use
WM_COPYDATA instead, which will give you a real copy of the memory to work
with, and then you can send it back with another WM_COPYDATA message.

--
Tomas Restrepo
http://members.xoom.com/trestrep/

OK, I will try that!

No, you misunderstood my problem.
The other application is not mine? It's not my code and not my compiled
EXE file. I really need to influence a 'foreign' application!

Jan

Jan,

The your only options are to either hook into the app, where your own code
can execute localy and access the memory directly, or use
ReadProcessMemory()/WriteProcessMemory().

However, I'd urge you to try to avoid this, since there's no way you can
synchronize access to that memory between threads in both processes, and you
might easily cause the app to read an invalid value from the memory, or
simply crash allright.

--
Tomas Restrepo
http://members.xoom.com/trestrep/

How can i 'hook into an app'? Can i use normal hooks there?

And do you have an example for ReadProcessMemory? Does it work with all
pointer of other apps??

I am consciously that i will probably have lots of problems but i have to
do it!

Jan

Jan,

Sure. In fact, that's the easiest way, although there are others. Jeffrey
Richter's "Advanced Windows" book covers some others.

It's straightforward to use. However, ReadProcessMemory() has no knowledge
of structure or anything, it simply reads an area of contigous bytes of a
certain length, or your choosing.

--
Tomas Restrepo
http://members.xoom.com/trestrep/

But, how can i get access to the app's memory space?? I thought a hook
just catches the window messages?!

But I believe these functions only work with apps that are supposed to
use them or to be accessed by these functions, right??

Jan

Jan,

They can because a hook has to run on the same process context as the window
it has hooked, that's why they are called hooks in the first place. It's
alseo teh reason why the hook function has to be on a dll.

The functions will work for any app that has enough rights to open the
target process using OpenProcess() with PROCESS_VM_READ/PROCESS_VM_WRITE
access. There's no other requirement.

--
Tomas Restrepo
http://members.xoom.com/trestrep/

OK, thank you very much for your help!

Jan

Oh, i have one question left. What's the best way to hook into an
application? SetWindowsHookEx? Are there other ways?

Jan

Jan,

Depends on what you want to do... SWHE() is useful if you need to do things
having to do with keeping track of windows, hooking messages, etc, but are
not so good when you simply need to execute some small code in another
process' context. Also, SWHE() won't work for, say, console applications,
since you can't hook the console.

Another way is, on NT, to use Read/WriteProcessMemory(), and
CreateRemoteThread(), or use one registry key that's available that can get
your dll loaded by any process that loads user32.dll... there are others,
too.

--
Tomas Restrepo
http://members.xoom.com/trestrep/

Is this necessary even for subclassing windows' controls? I have been
trying to do it with the usual subclassing/superclassing and it looks
like I am missing some messages (e.g. when the user adds/changes the
contents of an edit control it looks like windows is not reflecting
this internally).

Thanks for any help you can give me, Hernan.

Sent via Deja.com http://www.deja.com/
Before you buy.