Error feedback on graph data selection entries

[Emmanuel Pacaud <emmanuel pacaud lapp in2p3 fr>]

Hi,

I'm working on a patch for fixing an issue I've introduced a few months
ago, when trying to update the graph data when a data selection entry
lose the focus.

http://svn.gnome.org/viewvc/gnumeric/trunk/src/wbc-gtk.c?view=diff&r1=15757&r2=15758

The issue introduced is if the expression is invalid when the expression
entry lose the focus, an error dialog appears, and will reappear as soon
as you close it.

My patch removes the error dialog and instead paint the expression entry
background in red when the expression is invalid, in  order to keep an
error feedback.

It's there:

http://cgit.freedesktop.org/~emmanuel/gnumeric/commit/?h=expr-fb&id=5e23118586e9bdb804d18a3e509522f91168f8c1

One thing I don't like is the additional "update_entry" parameter I've
added to gnm_expr_entry_parse. But it's needed to avoid the automatic
quoting of entry.

Any comments ?

        Emmanuel.