Input Event Handling

[Thorsten Wilms]

On Wed, Apr 04, 2007 at 10:14:24PM +0300, Daniel Stone wrote:
> 
> Hi,
> Input focus is to a particular window, so you get device -> kernel -> X
> server -> app.

There are cases like sliders in a windows with scrollbars. With 
gtk+ at least, if the pointer is on the slider, mouse-wheel will 
move the slider. But with the pointer anywhere else, the wheel 
scrolls.
Does this mean that input focus has to be redone on the window/ 
application level for things like this to work?


> > Does the x-server anything special to receive all input events?
> 
> Yes, google for "x11 grab", or man XGrabKeyboard.

Ah yes, XGrabKeyboard does it :)

 
> > Does the kernel have a concept like input focus?
> 
> No, it just sends events to /dev.

There must be some mechanism for only letting a cli app in the 
current virtual console receive input events.


> This is another special case: you can grab particular _keys_.  So if you
> want Alt-F10 to maximise in the window manager, you set a grab on F10
> and check if Alt is also pressed.  If not, you let the event go through
> to its original destination (i.e. the window with input focus), else you
> intercept the event and maximise the window.

So commonly WMs set grabs on ther shortcuts, while application just 
wait and see what comes?


Thank you very much for the info!


-- 
Thorsten Wilms