=== modified file 'src/ChangeLog'
*** src/ChangeLog	2013-12-08 08:05:36 +0000
--- src/ChangeLog	2013-12-08 16:00:41 +0000
***************
*** 1,3 ****
--- 1,9 ----
+ 2013-12-08  Jarek Czekalski  <jarekczek@poczta.onet.pl>
+ 
+ 	Fix freezing with scroll bars of GTK3 Toolkit (Bug#15801).
+ 	* keyboard.c: A comment to unblock_input.
+ 	* xgselect.c: Prevent Glib main loop recursion.
+ 
  2013-12-08  Paul Eggert  <eggert@cs.ucla.edu>
  
  	Use libcrypto's checksum implementations if available, for speed.

=== modified file 'src/keyboard.c'
*** src/keyboard.c	2013-12-07 23:04:10 +0000
--- src/keyboard.c	2013-12-08 15:20:00 +0000
*************** unblock_input_to (int level)
*** 7118,7124 ****
  /* End critical section.
  
     If doing signal-driven input, and a signal came in when input was
!    blocked, reinvoke the signal handler now to deal with it.  */
  
  void
  unblock_input (void)
--- 7118,7129 ----
  /* End critical section.
  
     If doing signal-driven input, and a signal came in when input was
!    blocked, reinvoke the signal handler now to deal with it.
! 
!    It will also process queued input, if it was not read before.
!    When a longer code sequence does not use block/unblock input
!    at all, the whole input gathered up to the next call to
!    unblock_input will be processed inside that call. */
  
  void
  unblock_input (void)

=== modified file 'src/xgselect.c'
*** src/xgselect.c	2013-08-27 19:36:28 +0000
--- src/xgselect.c	2013-12-08 22:54:04 +0000
*************** along with GNU Emacs.  If not, see <http
*** 27,32 ****
--- 27,44 ----
  #include <errno.h>
  #include <timespec.h>
  #include "frame.h"
+ #include "blockinput.h"
+ 
+ /* xg_select is a pselect replacement. Why do we need a separate function?
+    1. Timeouts. Glib and Gtk rely on timer events. If we did pselect
+       with a greater timeout then the one scheduled by Glib, we would
+       not allow Glib to process its timer events. We want Glib to
+       work smoothly, so we need to reduce our timeout to match Glib.
+    2. Descriptors. Glib may listen to more file descriptors than we do.
+       So we add Glib descriptors to our pselect pool, but we don't change
+       the value returned by the function. The return value  matches only
+       the descriptors passed as arguments, making it compatible with
+       plain pselect. */
  
  int
  xg_select (int fds_lim, fd_set *rfds, fd_set *wfds, fd_set *efds,
*************** xg_select (int fds_lim, fd_set *rfds, fd
*** 45,56 ****
    int i, nfds, tmo_in_millisec;
    USE_SAFE_ALLOCA;
  
-   /* Do not try to optimize with an initial check with g_main_context_pending
-      and a call to pselect if it returns false.  If Gdk has a timeout for 0.01
-      second, and Emacs has a timeout for 1 second, g_main_context_pending will
-      return false, but the timeout will be 1 second, thus missing the gdk
-      timeout with a lot.  */
- 
    context = g_main_context_default ();
  
    if (rfds) all_rfds = *rfds;
--- 57,62 ----
*************** xg_select (int fds_lim, fd_set *rfds, fd
*** 132,139 ****
--- 138,150 ----
  #ifdef USE_GTK
        if (retval == 0)
  #endif
+         /* Prevent g_main_dispatch recursion, that would occur without
+            block_input wrapper, because event handlers call
+            unblock_input. Event loop recursion was causing Bug#15801. */
+         block_input();
          while (g_main_context_pending (context))
            g_main_context_dispatch (context);
+         unblock_input();
  
        /* To not have to recalculate timeout, return like this.  */
        if (retval == 0)