* only update the representation if anything was changed (this gives a
huge speedup), fixes#2452
* minor cleanup of the code, especially setting up the coordinate
cache. Without this can lead to crashes if the macros do not mention
all the arguments.
* And a last fix included makes sure that the metrics are always in
sync with the drawing. Before it was possible to go into the macro
with the cursor in a way that the metrics were for the viewing mode,
but the drawing was done for editing.
git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@18489 a592a061-630c-0410-9148-cb99ea01b6c8
