I believe the first paragraph below should not be deleted:
> - You will find a lot of redisplay optimizations when you start
> - looking at the innards of redisplay. The overall goal of all these
> - optimizations is to make redisplay fast because it is done
> - frequently.
> -
> - Two optimizations are not found in xdisp.c. These are the direct
> - operations mentioned above. As the name suggests they follow a
> - different principle than the rest of redisplay. Instead of
> - building a desired matrix and then comparing it with the current
> - display, they perform their actions directly on the display and on
> - the current matrix.
> -
> - One direct operation updates the display after one character has
> - been entered. The other one moves the cursor by one position
> - forward or backward. You find these functions under the names
> - `direct_output_for_insert' and `direct_output_forward_char' in
> - dispnew.c.
Even if we get rid of the `direct_output_*' functions, there will be
still ``a lot of optimizations'' left in xdisp.c, and the comment
should mention that, because anyone who hacks the display engine
should know about that possibility. If necessary, I'm prepared to add
a list of these optimizations with short descriptions.
I also question the decision to remove the comment about the
`direct_output_*' without actually removing the code (apologies if I
missed the latter). It's not like we are documenting a feature we
don't want to use: it's already used. As long as the code is there,
hacking redisplay without knowing about them is at best not wise.
