[FFmpeg-trac] #1738(undetermined:new): x11grab BadCursor

[FFmpeg]

#1738: x11grab BadCursor
-------------------------------------+-------------------------------------
             Reporter:  idooley      |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:  git-
  undetermined                       |  master
             Keywords:  x11grab      |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 Summary of the bug:
 ffmpeg exits when calling "xcim = XFixesGetCursorImage(dpy);" from
 x11grab.c, if X11 cursor has not been set yet. In most X11 servers, a
 cursor has already been set. But in simple Xvfb instances, the cursor may
 not yet have been set.

 Affected Versions: 0.11.1, 47277c4, f7cba73 on Ubuntu 12.10

 How to reproduce:
 {{{
 % Xvfb :10 -screen 0 800x600x24 &

 % ./ffmpeg -an -f x11grab -s 800x600 -r 30 -i :10.0 -vcodec libx264
 -threads 1 ${HOME}/capturedvideoXvfb.avi
 ffmpeg version 0.11.1 Copyright (c) 2000-2012 the FFmpeg developers
   built on Sep 15 2012 14:48:09 with gcc 4.6.3
   configuration: --enable-network --enable-protocol=tcp --enable-libx264
 --enable-x11grab --enable-gpl
   libavutil      51. 54.100 / 51. 54.100
   libavcodec     54. 23.100 / 54. 23.100
   libavformat    54.  6.100 / 54.  6.100
   libavdevice    54.  0.100 / 54.  0.100
   libavfilter     2. 77.100 /  2. 77.100
   libswscale      2.  1.100 /  2.  1.100
   libswresample   0. 15.100 /  0. 15.100
   libpostproc    52.  0.100 / 52.  0.100
 [x11grab @ 0x1614360] device: :10.0 -> display: :10.0 x: 0 y: 0 width: 800
 height: 600
 [x11grab @ 0x1614360] shared memory extension found
 X Error of failed request:  BadCursor (invalid Cursor parameter)
   Major opcode of failed request:  142 (XFIXES)
   Minor opcode of failed request:  25 (XFixesGetCursorImageAndName)
   Resource id in failed request:  0x200001
   Serial number of failed request:  14
   Current serial number in output stream:  14
 }}}
 or, for a different ffmpeg version:
 {{{
 % Xvfb :10 -screen 0 800x600x24 &

 %  ./ffmpeg -an -f x11grab -s 800x600 -r 30 -i :10.0 -vcodec libx264
 -threads 1 ${HOME}/capturedvideoXvfb.avi
 rm: cannot remove `/home/isaacdooley/capturedvideo*': No such file or
 directory
 ffmpeg version N-42091-gf7cba73 Copyright (c) 2000-2012 the FFmpeg
 developers
   built on Sep 15 2012 14:38:41 with gcc 4.6.3
   configuration: --enable-network --enable-protocol=tcp --enable-libx264
 --enable-x11grab --enable-gpl
   libavutil      51. 63.100 / 51. 63.100
   libavcodec     54. 31.100 / 54. 31.100
   libavformat    54. 14.100 / 54. 14.100
   libavdevice    54.  0.100 / 54.  0.100
   libavfilter     3.  0.100 /  3.  0.100
   libswscale      2.  1.100 /  2.  1.100
   libswresample   0. 15.100 /  0. 15.100
   libpostproc    52.  0.100 / 52.  0.100
 [x11grab @ 0x1eeb380] device: :10.0 -> display: :10.0 x: 0 y: 0 width: 800
 height: 600
 [x11grab @ 0x1eeb380] shared memory extension found
 X Error of failed request:  BadCursor (invalid Cursor parameter)
   Major opcode of failed request:  142 (XFIXES)
   Minor opcode of failed request:  25 (XFixesGetCursorImageAndName)
   Resource id in failed request:  0x200001
   Serial number of failed request:  14
   Current serial number in output stream:  14
 }}}

 Fix:
 I found a post in the mailing list that appears to correctly identify the
 problem and reference a fix to a perl module for this same issue:
 http://ffmpeg.org/pipermail/ffmpeg-user/2012-August/008804.html

 I've made some changes to x11grab.c, similar to those in the perl module,
 namely adding a call to set the cursor immediately before calling
 XFixesGetCursorImage(). The patch below makes ffmpeg work properly:

 {{{
 $ git diff
 diff --git a/libavdevice/x11grab.c b/libavdevice/x11grab.c
 index b6bd486..b8271d5 100644
 --- a/libavdevice/x11grab.c
 +++ b/libavdevice/x11grab.c
 @@ -43,6 +43,7 @@
  #include "libavutil/parseutils.h"
  #include "libavutil/time.h"
  #include <time.h>
 +#include <X11/cursorfont.h>
  #include <X11/X.h>
  #include <X11/Xlib.h>
  #include <X11/Xlibint.h>
 @@ -357,6 +358,12 @@ paint_mouse_pointer(XImage *image, struct x11grab *s)
      if (image->bits_per_pixel != 24 && image->bits_per_pixel != 32)
          return;

 +    Cursor c = XCreateFontCursor(dpy, XC_left_ptr);
 +    Window w = DefaultRootWindow(dpy);
 +    XSetWindowAttributes attr;
 +    attr.cursor = c;
 +    XChangeWindowAttributes(dpy, w, CWCursor, &attr);
 +
      xcim = XFixesGetCursorImage(dpy);

      x = xcim->x - xcim->xhot;
 }}}

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/1738>
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