[PATCH/RFC 1/2] Only transfer focus once when opening multiple file diffs

[Peter Tyser <ptyser gmail com>]

Currently if a user opens multiple file diffs at the same time from a
DirDiff or VcView the following happens:
- the 1st diff is opened in a new tab and focus is moved to this tab
- the 2nd diff is opened in a new tab and focus is moved to this tab
- the 3rd diff is opened in a new tab and focus is moved to this tab
- etc...

This behavior has 2 shortcomings:
1. The user is presented with a window that cycles focus through
   multiple diff tabs which is visually jarring.
2. During this period of time when tabs are being cycled through the
   user can't interact with Meld - the focus shifts too fast to allow
   the user to do anything.  This is especially painful if the user
   initiates a large number of diffs, the diffs are on a slow filesystem
   (eg over a slow NFS share), or if the diffs are of version-controlled
   files (VC-diffs have more overhead, which slows them down).

To resolve these issues, only transfer focus to a new tab if the current
tab is a DirDiff or VcView.  This results in the following behavior:
- the 1st diff is opened in a new tab and focus is moved to this tab
- the 2nd diff is opened in a new background tab
- the 3rd diff is opened in a new background tab
- etc...

While the background tabs are being opened Meld is still usable.

Signed-off-by: Peter Tyser <ptyser gmail com>
---
I frequently diff large git-controlled repositories (eg the Linux
kernel) shared on an NFS server, which really brings this issue out.

 meld/meldwindow.py |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/meld/meldwindow.py b/meld/meldwindow.py
index 55e3061..5fe6ce5 100644
--- a/meld/meldwindow.py
+++ b/meld/meldwindow.py
@@ -578,7 +578,14 @@ class MeldWindow(gnomeglade.Component):
     def _append_page(self, page, icon):
         nbl = notebooklabel.NotebookLabel(icon, "", lambda b: self.try_remove_page(page))
         self.notebook.append_page( page.widget, nbl)
-        self.notebook.set_current_page( self.notebook.page_num(page.widget) )
+
+        # Change focus to the newly created page only if the user is on a
+        # DirDiff or VcView page.  This prevents cycling through X pages
+        # when X diffs are initiated.
+        if isinstance(self.current_doc(), dirdiff.DirDiff) or \
+           isinstance(self.current_doc(), vcview.VcView):
+            self.notebook.set_current_page(self.notebook.page_num(page.widget))
+
         self.scheduler.add_scheduler(page.scheduler)
         page.connect("label-changed", self.on_notebook_label_changed)
         page.connect("file-changed", self.on_file_changed)
-- 
1.7.7.431.g89633