XGrabPointer does not grab pointer reliably

ciotog · 09-27-2006, 02:39 PM

I'm the current maintainer of wmMand, a small dockable Mandlebrot browser for WindowMaker which was originally written by Mike Henderson in 1999. It's a small (54x54) window that shows part of the Mandelbrot fractal which can be scrolled around and zoomed in and out, and also launch a large window of the current view.

Since I've taken it over I decided to implement a much requested "autozoom" feature, as well as add keyboard input. Both of these are working fine in general, but outside of WindowMaker and Fluxbox I can't get the browser to grab the pointer as I would like.

Basically I want to confine the pointer while the button is being held down to the 54x54 window, and also grab keyboard focus when the pointer enters the small window. I've tried using XGrabPointer which works great in WindowMaker, Fluxbox and I'm sure other lightweight window managers, but not at all in any of the heavyweights (Gnome, KDE, XFCE4).

When calling XGrabPointer with the managers that work the return value is '0', but for those that don't the return value is '3' which AFAICT from X.h is a BadWindow error indicating that it doesn't recognize the identified Window (in this case it's called "iconwin" and is created in wmgeneral.c which was developed by Martijn Pieterse). Other than that, when the window does have focus it works fine.

I checked the code for gdk_pointer_grab which is in gdkmain-x11.c, and it doesn't do anything spectacularly different than what I'm trying to do. So does anyone have any ideas about how I can get it to work, without requiring the use of another library like gtk or qt? Or is anyone aware of any other applications that grab the pointer like this without using those extra libs?

Oh yeah, the current source for wmMand can be found here:
http://sourceforge.net/project/showf...roup_id=161419

ciotog · 10-16-2006, 05:33 PM

This issue has been solved. Basically for some reason when calling XGrabPointer with the Window to confine it in as the one created for that purpose as in

Code:

XGrabPointer(display, iconwin, True, 0, GrabModeAsync, GrabModeAsync, iconwin, None, CurrentTime);

it wouldn't work (threw a "invalid Window" error, I believe), but I replaced it with:

Code:

XGrabPointer(display, event.xbutton.window, True, 0, GrabModeAsync, GrabModeAsync, event.xbutton.window, None, CurrentTime);

Now it works perfectly.

The thing that still confuses me is that I use XQueryPointer elsewhere as follows

Code:

	XQueryPointer(display, iconwin, &rr, &cr, &rx, &ry, &x, &y, &mr);

where rr, cr, rx, ry, mr are dummy variables for the return values, and it works fine so I know that iconwin is a valid Window. Furthermore the program worked fine outside of Gnome/KDE/XFCE4.

Anyway, at least it's working now!