bug#62164: 29.0.60; ediff behaves poorly by default on tiling window managers

[Phil Sainty <psainty@orcon.net.nz>]

Spencer Baugh wrote:
> ediff defaults to a multiframe UI on graphical displays.  If the
> user is running a tiling window manager on X, the control panel
> frame gets tiled and the whole thing becomes either very ugly or
> unusable.
> 
> This is a very long-standing bug, but it should be fixed.  Most
> tiling window manager users work around this with:
> 
> (setq ediff-window-setup-function 'ediff-setup-windows-plain)

Myself included -- the default value tends to give me a full-screen
control frame entirely obscuring the original frame, which is very
unhelpful indeed.

That problem aside, I've observed that creating a separate GUI
frame can be *significantly* slower; so for me the plain option
is a win for performance as well as usability.

As `ediff-setup-windows-plain' is the faster and the most reliable
option across differing kinds of windowing systems, I am strongly
in favour of changing the default `ediff-window-setup-function'
value to that.

Users who prefer the separate frame can easily make that change in
their configs easily enough, and improvements to better support a
separate control frame can of course still go ahead.


-Phil