[Mikolaj Machowski]
[Mohsin]:
Vim only has syntax coloring with regexps. Emacs has functions to
apply properties to text blocks, and I was hoping vim has something
comparable.
Of course it is possible:
:help /\%l
:help /\%c
Humph, not really!
Text properties in Emacs span text regions, which move, expand or shrink
while text is being edited outside or within them. Besides
highlighting, text properties may also be used for making regions
invisible (fully collapsed, not using any estate on the display),
intangible (the cursor skips over them as if they were a single
character), and many other things as well.
Efficiently adjusting tons of text properties in a buffer is
a computational challenge: markers just cannot be used, as the time for
updating markers at each editing action is proportional to the number of
markers. If I remember well, text boundaries for an Emacs buffer are
all held within a single heap structure. I think some people called
them "priority queues", Python lovers may look for module "heapq", and
the boundaries only get updated when the cursor moves through them. To
understand this, one should know that within Emacs, the buffer text is
split into the physical memory buffer as two parts on each end, with all
the free space (nicknamed "the hole") kept in the middle. The cursor
coincides with the hole, moving the cursor moves bits of the text over
that hole. The heap helps at quickly finding the nearest boundaries for
text properties, and updating them rather lazily, not far from the least
often possible.
I would not think (but I do not really know) that users could easily
reimplement equivalent features in Vim. This particular problem
interests me somehow: I once wrote an Emacs package called `xxml.el'
which does a decent job at highlighting SGML, HTML and XML, or cleverly
refilling it (building over an astonishingly powerful packages named
PSGML, written by Lennart Staflin). More than once, I pondered porting
this `xxml.el' to Vim, but as it heavily uses text properties, I would
have needed a replacement first. Reimplementing PSGML for Vim would
have been a major undertaking as well, yet here, I would have went the
Python way, in a Python-enabled Vim. Dreams, dreams, dreams... :-)
--
François Pinard http://pinard.progiciels-bpi.ca
