[meld] Track cross-TextBuffer changes to check TextIter validity

[Kai Willadsen <kaiw src gnome org>]

commit 13897f8b091efcba07a1650fcf3bb2477d6370df
Author: Kai Willadsen <kai willadsen gmail com>
Date:   Fri Oct 12 06:13:29 2012 +1000

    Track cross-TextBuffer changes to check TextIter validity
    
    In our async callbacks for updating inline highlighting, we have no
    guarantee that the TextIters passed in are still valid. One option
    would be to use TextMarks instead, but this isn't actually what we want;
    we actually want the TextIters to invalidate, and not highlight when
    they're not valid.
    
    Since GTK+ doesn't expose a check for the validity of TextIters, we
    reproduce a dodgy version here. We keep a counter of changes to all
    TextBuffers, and check that the counters match in the highlighting
    callback.

 meld/filediff.py |   24 +++++++++++++++---------
 1 files changed, 15 insertions(+), 9 deletions(-)
---
diff --git a/meld/filediff.py b/meld/filediff.py
index 50df799..17ae4dd 100644
--- a/meld/filediff.py
+++ b/meld/filediff.py
@@ -192,6 +192,15 @@ class FileDiff(melddoc.MeldDoc, gnomeglade.Component):
         for buf in self.textbuffer:
             buf.create_tag("inline")
 
+        # We need to keep track of gtk.TextIter validity, but this isn't
+        # exposed anywhere. Instead, we keep our own counter for changes
+        # across all of our buffers.
+        self._buffer_changed_stamp = 0
+        def buffer_change(buf):
+            self._buffer_changed_stamp += 1
+        for buf in self.textbuffer:
+            buf.connect("changed", buffer_change)
+
         actions = (
             ("MakePatch", None, _("Format as patch..."), None, _("Create a patch using differences between files"), self.make_patch),
             ("PrevConflict", None, _("Previous conflict"), "<Ctrl>I", _("Go to the previous conflict"), lambda x: self.on_next_conflict(gtk.gdk.SCROLL_UP)),
@@ -1145,19 +1154,15 @@ class FileDiff(melddoc.MeldDoc, gnomeglade.Component):
                         bufs[i].apply_tag(tags[i], starts[i], ends[i])
                     continue
 
-                def apply_highlight(bufs, tags, starts, matches):
+                def apply_highlight(bufs, tags, starts, change_stamp, matches):
+                    if change_stamp != self._buffer_changed_stamp:
+                        return
+
                     # Remove equal matches of size greater than 3; highlight
                     # the remainder.
                     matches = [m for m in matches if m.tag != "equal" or
                         (m.end_a - m.start_a < 3) or (m.end_b - m.start_b < 3)]
 
-                    # FIXME: At this point, there's no guarantee that the
-                    # gtk.TextIters are valid. Any rapid typing and they're
-                    # not... Should used marks instead, and also probably keep
-                    # a list of being-highlighted blocks, and ensure that
-                    # there's only ever one callback per block, cancelling the
-                    # old one and restarting it on each change.
-
                     for i in range(2):
                         start, end = starts[i].copy(), starts[i].copy()
                         offset = start.get_offset()
@@ -1171,7 +1176,8 @@ class FileDiff(melddoc.MeldDoc, gnomeglade.Component):
                     bufs[1].remove_tag(tags[1], starts[1], ends[1])
 
                 match_cb = functools.partial(apply_highlight,
-                                             bufs, tags, starts)
+                                             bufs, tags, starts,
+                                             self._buffer_changed_stamp)
                 matches = self._cached_match.match(text1, textn, match_cb)
 
         self._cached_match.clean(self.linediffer.diff_count())