[meld] filediff: Add change deletion pushing, reducing pane swaps (bgo#729838)

[Kai Willadsen <kaiw src gnome org>]

commit 80bfe200ee5c732e6cb5c3420a6f2bc316a49681
Author: Kai Willadsen <kai willadsen gmail com>
Date:   Mon Dec 15 06:34:03 2014 +1000

    filediff: Add change deletion pushing, reducing pane swaps (bgo#729838)
    
    Previously we enforced the action of pushing a change to mean that
    there had to be some text to push. As it's been requested a few times,
    this patch makes it so that it's possible to push an empty change as
    well, which has the effect of deleting the change from the target pane.
    
    This feels slightly odd mental-model-wise, but pragmatism beats purity
    and this means that you have to switch panes much less frequently.

 meld/filediff.py |   30 ++++++++++++++++++------------
 1 files changed, 18 insertions(+), 12 deletions(-)
---
diff --git a/meld/filediff.py b/meld/filediff.py
index ef9fc9a..3c556ba 100644
--- a/meld/filediff.py
+++ b/meld/filediff.py
@@ -471,13 +471,13 @@ class FileDiff(melddoc.MeldDoc, gnomeglade.Component):
                 chunk = self.linediffer.get_chunk(chunk_id, pane)
                 insert_chunk = chunk[1] == chunk[2]
                 delete_chunk = chunk[3] == chunk[4]
-                push_left = editable_left and not insert_chunk
-                push_right = editable_right and not insert_chunk
+                push_left = editable_left
+                push_right = editable_right
                 pull_left = pane == 2 and editable and not delete_chunk
                 pull_right = pane == 0 and editable and not delete_chunk
                 delete = editable and not insert_chunk
-                copy_left = push_left and not delete_chunk
-                copy_right = push_right and not delete_chunk
+                copy_left = editable_left and not (insert_chunk or delete_chunk)
+                copy_right = editable_right and not (insert_chunk or delete_chunk)
             elif pane == 1:
                 chunk0 = self.linediffer.get_chunk(chunk_id, 1, 0)
                 chunk2 = None
@@ -487,13 +487,13 @@ class FileDiff(melddoc.MeldDoc, gnomeglade.Component):
                 left_exists = chunk0 is not None and chunk0[3] != chunk0[4]
                 right_mid_exists = chunk2 is not None and chunk2[1] != chunk2[2]
                 right_exists = chunk2 is not None and chunk2[3] != chunk2[4]
-                push_left = editable_left and left_mid_exists
-                push_right = editable_right and right_mid_exists
+                push_left = editable_left
+                push_right = editable_right
                 pull_left = editable and left_exists
                 pull_right = editable and right_exists
                 delete = editable and (left_mid_exists or right_mid_exists)
-                copy_left = push_left and left_exists
-                copy_right = push_right and right_exists
+                copy_left = editable_left and left_mid_exists and left_exists
+                copy_right = editable_right and right_mid_exists and right_exists
         self.actiongroup.get_action("PushLeft").set_sensitive(push_left)
         self.actiongroup.get_action("PushRight").set_sensitive(push_right)
         self.actiongroup.get_action("PullLeft").set_sensitive(pull_left)
@@ -1949,10 +1949,16 @@ class FileDiff(melddoc.MeldDoc, gnomeglade.Component):
         new_end = b1.insert_at_line(chunk[3], t0)
         self.on_textbuffer_end_user_action()
         mark1 = b1.create_mark(None, new_end, True)
-        # FIXME: If the inserted chunk ends up being an insert chunk, then
-        # this animation is not visible; this happens often in three-way diffs
-        rgba0 = self.fill_colors['insert'].copy()
-        rgba1 = self.fill_colors['insert'].copy()
+        if chunk[1] == chunk[2]:
+            # TODO: Need a more specific colour here; conflict is wrong
+            rgba0 = self.fill_colors['conflict'].copy()
+            rgba1 = self.fill_colors['conflict'].copy()
+        else:
+            # FIXME: If the inserted chunk ends up being an insert chunk, then
+            # this animation is not visible; this happens often in three-way
+            # diffs
+            rgba0 = self.fill_colors['insert'].copy()
+            rgba1 = self.fill_colors['insert'].copy()
         rgba0.alpha = 1.0
         rgba1.alpha = 0.0
         anim = TextviewLineAnimation(mark0, mark1, rgba0, rgba1, 500000)