[FFmpeg-trac] #11539(ffmpeg:new): ffmpeg hangs when using gdigrab with show_region on Windows

[FFmpeg]

#11539: ffmpeg hangs when using gdigrab with show_region on Windows
-------------------------------------+-------------------------------------
             Reporter:  elem         |                     Type:  defect
               Status:  new          |                 Priority:  minor
            Component:  ffmpeg       |                  Version:  7.1
             Keywords:  gdigrab      |               Blocked By:
  show_region hang                   |
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 Summary of the bug:
 How to reproduce:
 {{{
 % ffmpeg -y -f gdigrab -show_region 1 -offset_x 20 -offset_y 20
 -video_size 400x80 -i desktop -vcodec libx264 -preset ultrafast -pix_fmt
 yuv420p "C:\temp\test.mp4"
 ffmpeg version 7.1.1-full_build-www.gyan.dev
 built with gcc 14.2.0 (Rev1, Built by MSYS2 project)
 }}}

 Then if you move your cursor on the border of the show_region window,
 Windows will show a "working in background" cursor. If you click it
 multiple times, Windows will show an "app not responding" window.

 ffmpeg doesn't hang on versions 5.x so I did a bisect and the issue
 appeared with commit d8bf53710f. I guess the big CLI multithreading
 refactoring done in 6.x and ffmpeg having to draw UI for show_region don't
 work well together.

 Using ffmpeg built with commit d8bf53710f, I have this warning: "Thread
 message queue blocking; consider raising the thread_queue_size option".
 With the latest non hanging commit cc2b7f4625, no warning, because
 thread_queue_size was 0, but if I understand correctly since the CLI
 multithreading refactoring, thread_queue_size is always at least 1.

 I'm not sure if this is reproducible on Linux. Let me know if I can help
 in any way.
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/11539>
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