and under post-19.29 but not early versions of emacs.
19.29 and 19.30 seems to drop mouse drag events
-sometimes. (Reproducable under XFree86-3.1.1 (X11R6pl11) and
+sometimes. (Reproducible under XFree86-3.1.1 (X11R6pl11) and
XFree86-3.1.2 under Linux 1.2.x. Doesn't occur under X11R5 and SunOS
4.1.1.)
To see if you have the problem:
-Disable this routine (with (setq mouse-copy-have-drag-bug nil))..
+Disable this routine (with (setq mouse-copy-have-drag-bug nil)).
Click and drag for a while.
If highlighting stops tracking, you have the bug.
If you have the bug (or the real fix :-), please let me know."