xlib and keyboard events Post: 302720329

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Top Forums UNIX for Advanced & Expert Users xlib and keyboard events Post 302720329 by N7DR on Tuesday 23rd of October 2012 07:10:31 PM

10-23-2012

Registered User

xlib and keyboard events

1. If there's some better place where xlib experts hang out, please tell me. Despite an assiduous search, I could not find an xlib reflector.

2. My actual question:
In an xterm, I want to grab and process all keyboard events in a program running inside the xterm. For example, with my program running, if I press an "x", I don't the x to be displayed, and I do want to be able to see the keypress and keyrelease events myself, in the application running inside the xterm.

I have tried quite a few things, but nothing seems to do exactly what I need.

The closest I've come is the pseudo-code sequence:

Code:

XOpenDisplay() to get the correct display
getenv("WINDOWID") to get the window ID
XGrabKeyboard( <display*>, <window>, false, GrabModeAsync, GrabModeSync, CurrentTime)
XSelectInput(<everything>)
forever: (XWindowEvent() on the window)

But that seems to have two problems:
1. it seems to grab keyboard events wherever they occur on the display, not just in the xterm;
2. keyboard events inside the xterm don't actually seem to be returned by the XWindowEvent().

This is the first time I've tried to use xlib, so it's perfectly possible (even likely) that I'm missing something basic, even though I've tried to read the pertinent documentation quite carefully.

---------- Post updated at 05:10 PM ---------- Previous update was at 04:57 PM ----------

Apparently, the call to XGrabKeyboard should be:

Code:

XGrabKeyboard(<display>, <window>, false, GrabModeAsync, GrabModeAsync, CurrentTime);

although I don't undrestand why the keyboard mode should be Async. The documentation seems to indicate that this would mean that the xterm application would also receive the keyboard activity, but that isn't what happens.

(Documentation says: If the keyboard_mode argument is GrabModeAsync, keyboard event processing continues as usual. Apparently, whatever "as usual" means, it does not seem to mean "is sent to other clients as usual".)

So I'm floundering as to <i>why</i> this works, but at least it does seem to do what I need.

N7DR

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rendercheck

rendercheck(1)						      General Commands Manual						    rendercheck(1)

NAME

       rendercheck - simple tests of the X Render extension.

SYNOPSIS

       rendercheck [-d|--display display] [-i|--iter] [--sync] [-t|--tests test1,test2,test3,...] [-o|--ops op1,op2,op3,...]
       [-v|--verbose] [--minimalrendering]

DESCRIPTION

       rendercheck is a set of simple tests of the X Render extension.	It is designed for authors of Render implementations in X Servers.

OPTIONS

       -d|--display display
	      Specifies the display to test against.

       -i|--iter iterations
	      Specifies  the number of times to repeat each operation before sampling results.	Some X Servers may behave differently (hardware vs
	      software rendering paths) depending on the previous operations done, so this may be used to influence the server's choices.

       --sync Enables synchronous xlib operation, for debugging.

       -t|--tests test1,test2,test3...
	      Enables only a specific subset of the possible tests.  Test names include  fill,	dcoords,  scoords,  mcoords,  tscoords,  tmcoords,
	      blend, composite, cacomposite, gradients, repeat, triangles, and bug7366.  Names must be separated by commas and have no spaces.

       -f|--formats format1,format2,format3...
	      Enables  only  a	specific  subset  of the possible formats.  Only formats listed in the server-supported format list are available.
	      Names must be separated by commas and have no spaces.

       -o|--ops
	      Enables only a specific subset of the Render operators.

       -v|--verbose
	      Enables verbose printing of information on tests run, and successes and failures.

       --minimalrendering
	      Disables copying of offscreen destinations to the window, which is on by default to provide the user with visual feedback.

BUGS

       Several	limitations  are  documented  in  the  TODO  file  accompanying  the  source.	Please	report	any  further  bugs  you  find	to
       http://bugs.freedesktop.org/.

AUTHORS

       Eric Anholt, with help from Keith Packard.

																    rendercheck(1)