X under full keyboard control

Harold L Hunt II huntharo@msu.edu
Sat Apr 3 03:52:00 GMT 2004


Takuma Murakami wrote:
> Michael,
>>I don't know what you mean with "hook DLL" though.
> I'm not sure if we need a separate DLL...  See this article
> and follow links in it for details.
> http://sources.redhat.com/ml/cygwin-xfree/2004-02/msg00149.html

Here is why we don't need a separate DLL for hooking these keyboard 
messages, from MSDN:

"A global hook monitors messages for all threads in the same desktop as 
the calling thread. A thread-specific hook monitors messages for only an 
individual thread. A global hook procedure can be called in the context 
of any application in the same desktop as the calling thread, so the 
procedure must be in a separate dynamic-link library (DLL) module. A 
thread-specific hook procedure is called only in the context of the 
associated thread. If an application installs a hook procedure for one 
of its own threads, the hook procedure can be in either the same module 
as the rest of the application's code or in a DLL. If the application 
installs a hook procedure for a thread of a different application, the 
procedure must be in a DLL. For information, see Dynamic-Link Libraries."

You see, we are only hooking messages in our own thread, so this 
approach works fine.  The reason we keep mentioning a hook DLL is that 
we also want to hook mouse messages when our application is not 
receiving mouse events; in those cases the hook is processed in the 
context of whatever process/thread is currently receiving mouse events, 
which is why those "global" hooks need to be DLLs.

The only problem with the hook approach for the key combinations in 
question is that it will only work for NT-based platforms and for only 
those running NT 4.0 SP3 or later; we will need to check for this before 
we turn on this hook and we need to make sure that all of this is 
conditional on whether or not this feature is enabled at runtime or not.

I would go ahead and make this the default, but I would add a runtime 
option called "-nokeyhook" that allows it to be turned off on platforms 
that support it.


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