[meld] dirdiff: Re-evaluate cursor-based state on model change (bgo#785859)

[Kai Willadsen <kaiw src gnome org>]

commit bb80114ec8a0b6e7a72cb0eb0d8be7f4796698f3
Author: Kai Willadsen <kai willadsen gmail com>
Date:   Sun Aug 13 05:55:29 2017 +1000

    dirdiff: Re-evaluate cursor-based state on model change (bgo#785859)
    
    Because of the linear search we do to find the prev/next file to jump
    to, we aggressively cache that particular bit of state so that it
    doesn't need to be re-evaluated every time the cursor changes. However,
    this can bite us when the model changes under us.
    
    The solution in this patch is to simply force a state re-evaluation when
    this happens, both on initial load and when individual items in the tree
    change.
    
    This also gets rid of the slightly odd allowance we had for forcing a
    re-evaluation by manually calling the cursor-changed callback, in favour
    of just using this re-evaluation toggle.

 meld/dirdiff.py |   10 +++++++---
 1 files changed, 7 insertions(+), 3 deletions(-)
---
diff --git a/meld/dirdiff.py b/meld/dirdiff.py
index cd8314e..7ba4416 100644
--- a/meld/dirdiff.py
+++ b/meld/dirdiff.py
@@ -360,6 +360,7 @@ class DirDiff(melddoc.MeldDoc, gnomeglade.Component):
             handler_id = treeview.connect("focus-out-event", self.on_treeview_focus_out_event)
             self.focus_out_events.append(handler_id)
             treeview.set_search_equal_func(self.model.treeview_search_cb, None)
+        self.force_cursor_recalculate = False
         self.current_path, self.prev_path, self.next_path = None, None, None
         self.on_treeview_focus_out_event(None, None)
         self.focus_pane = None
@@ -821,9 +822,9 @@ class DirDiff(melddoc.MeldDoc, gnomeglade.Component):
             self.treeview[0].expand_to_path(Gtk.TreePath(path))
         yield _("[%s] Done") % self.label_text
 
-        self.scheduler.add_task(self.on_treeview_cursor_changed)
         self._scan_in_progress -= 1
         self.treeview[0].get_selection().select_path(Gtk.TreePath.new_first())
+        self.force_cursor_recalculate = True
         self._update_diffmaps()
 
     def _show_identical_status(self):
@@ -1076,9 +1077,11 @@ class DirDiff(melddoc.MeldDoc, gnomeglade.Component):
             self.current_path = cursor_path
             return
 
-        # If invoked directly rather than through a callback, we always check
-        if not args:
+        if self.force_cursor_recalculate:
+            # We force cursor recalculation on initial load, and when
+            # we handle model change events.
             skip = False
+            self.force_cursor_recalculate = False
         else:
             try:
                 old_cursor = self.model.get_iter(self.current_path)
@@ -1550,6 +1553,7 @@ class DirDiff(melddoc.MeldDoc, gnomeglade.Component):
         for path in changed_paths:
             self._update_item_state( model.get_iter(path) )
         self._update_diffmaps()
+        self.force_cursor_recalculate = True
 
     def next_diff(self, direction):
         if self.focus_pane: