[FFmpeg-cvslog] lavd/x11grab: fix vertical repositioning

[Octavio Alvarez]

ffmpeg | branch: master | Octavio Alvarez <octalffdev at alvarezp.org> | Wed Mar 27 22:52:32 2019 -0600| [f4f40cbb578a09319f9ddafc80388a5556ec7713] | committer: Carl Eugen Hoyos

lavd/x11grab: fix vertical repositioning

There is a calculation error in xcbgrab_reposition() that breaks
vertical repositioning on follow_mouse. It made the bottom
reposition occur when moving the mouse lower than N pixels after
the capture bottom edge, instead of before.

This commit fixes the calculation to match the documentation.

follow_mouse: centered or number of pixels. The documentation says:

When it is specified with "centered", the grabbing region follows
the mouse pointer and keeps the pointer at the center of region;
otherwise, the region follows only when the mouse pointer reaches
within PIXELS (greater than zero) to the edge of region.

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=f4f40cbb578a09319f9ddafc80388a5556ec7713
---

 libavdevice/xcbgrab.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavdevice/xcbgrab.c b/libavdevice/xcbgrab.c
index 6d142abd4f..b7e689343e 100644
--- a/libavdevice/xcbgrab.c
+++ b/libavdevice/xcbgrab.c
@@ -127,7 +127,7 @@ static int xcbgrab_reposition(AVFormatContext *s,
         int left   = x + f;
         int right  = x + w - f;
         int top    = y + f;
-        int bottom = y + h + f;
+        int bottom = y + h - f;
         if (p_x > right) {
             x += p_x - right;
         } else if (p_x < left) {