Drawing from thread

[Mohith Manoj <mohithmanoj gmail com>]

I have a gtkmm application in which there is a running waveform widget (custom of course) which draws a waveform from left to right and in real-time. I feed data to the widget from a timer, which is then stored inside the widget until it is drawn. The drawing operation is triggered from another process (a thread).

When I test the setup in my target (a DirectFB based system), it all goes well. But in my machine (X11) it crashes with the following backtrace
<My_App_Name>: xcb_lock.c:33: _XCBUnlockDisplay: Assertion `xcb_get_request_sent(dpy->xcb->connection) == dpy->request' failed.
Locking assertion failure.  Backtrace:
#0 /usr/lib/libxcb-xlib.so.0 [0x11e767]
#1 /usr/lib/libxcb-xlib.so.0(xcb_xlib_lock+0x2e) [0x11e90e]
#2 /usr/lib/libX11.so.6 [0x496159]
#3 /usr/lib/libX11.so.6(XUngrabPointer+0x25) [0x48bda5]
#4 /usr/lib/libgdk-x11-2.0.so.0(gdk_display_pointer_ungrab+0x99) [0x7d24d09]
#5 /usr/lib/libgdk-x11-2.0.so.0(gdk_pointer_ungrab+0x1a) [0x7cffbca]
#6 /usr/lib/gtk-2.0/modules/libgnomebreakpad.so [0x84319e]
#7 /usr/lib/gtk-2.0/modules/libgnomebreakpad.so [0x8436e5]
#8 [0x9c9400]
#9 [0x9c9416]
#10 /lib/libc.so.6(gsignal+0x50) [0xdd0450]
#11 /lib/libc.so.6(abort+0x188) [0xdd1e18]
#12 /lib/libc.so.6(__assert_fail+0xee) [0xdc93fe]
#13 /usr/lib/libX11.so.6 [0x4960ee]
#14 /usr/lib/libXrender.so.1(XRenderCompositeTrapezoids+0x1fc) [0x6bd3bc]
#15 /usr/lib/libcairo.so.2 [0x7cb6d87]
#16 /usr/lib/libcairo.so.2 [0x7c9b921]
#17 /usr/lib/libcairo.so.2 [0x7c9f474]
#18 /usr/lib/libcairo.so.2 [0x7c9e547]
#19 /usr/lib/libcairo.so.2 [0x7c9ef65]
RedWheel: xcb_lock.c:77: _XGetXCBBuffer: Assertion `((int) ((xcb_req) - (dpy->request)) >= 0)' failed.
Multiple segmentation faults occurred; can't display error dialog

Any idea what going on?

Also when I draw to a surface from another process (which did not create the surface), is there anything else I should be doing. I am using cairo for all my drawing needs.