[meld] filediff: Check if chunk being highlighted is still valid (bgo#768298)

[Kai Willadsen <kaiw src gnome org>]

commit a0a5a7ea9299b8aac60574be77afdf1b93a5409c
Author: Kai Willadsen <kai willadsen gmail com>
Date:   Sun Jul 10 10:49:04 2016 +1000

    filediff: Check if chunk being highlighted is still valid (bgo#768298)
    
    As described in the bug report, in some situations we can get a chunk
    modification event (e.g., from a replacement) followed by a chunk
    deletion event (e.g., because the chunks are now equal on both sides).
    This messes with us because the deletion will clear the chunk
    highlighting immediately, but when the modification results come
    through asynchronously we just blindly add the highlighting, even
    though this is no longer a change chunk.
    
    With this patch, we check that the chunk we think we're highlighting
    still exists before doing anything.

 meld/filediff.py |   12 +++++++++---
 1 files changed, 9 insertions(+), 3 deletions(-)
---
diff --git a/meld/filediff.py b/meld/filediff.py
index 1aaf675..098b676 100644
--- a/meld/filediff.py
+++ b/meld/filediff.py
@@ -1278,12 +1278,17 @@ class FileDiff(melddoc.MeldDoc, gnomeglade.Component):
                     self._prompt_long_highlighting()
                     continue
 
-                def apply_highlight(bufs, tags, start_marks, end_marks, texts, matches):
+                def apply_highlight(
+                        bufs, tags, start_marks, end_marks, texts, to_pane,
+                        chunk, matches):
                     bufs[0].delete_mark(start_marks[0])
                     bufs[0].delete_mark(end_marks[0])
                     bufs[1].delete_mark(start_marks[1])
                     bufs[1].delete_mark(end_marks[1])
 
+                    if not self.linediffer.has_chunk(to_pane, chunk):
+                        return
+
                     starts = [bufs[0].get_iter_at_mark(start_marks[0]),
                               bufs[1].get_iter_at_mark(start_marks[1])]
                     ends = [bufs[0].get_iter_at_mark(end_marks[0]),
@@ -1331,8 +1336,9 @@ class FileDiff(melddoc.MeldDoc, gnomeglade.Component):
                           bufs[1].create_mark(None, starts[1], True)]
                 ends = [bufs[0].create_mark(None, ends[0], True),
                         bufs[1].create_mark(None, ends[1], True)]
-                match_cb = functools.partial(apply_highlight, bufs, tags,
-                                             starts, ends, (text1, textn))
+                match_cb = functools.partial(
+                    apply_highlight, bufs, tags, starts, ends, (text1, textn),
+                    to_pane, c)
                 self._cached_match.match(text1, textn, match_cb)
 
         self._cached_match.clean(self.linediffer.diff_count())