[mcclim-devel] performance of incremental redisplay

[Robert Strandh]

The slowness of my example from the other day seems to be caused by
the fact that each top-level output record (of which there are 1000 in
my example) is moved individually, and moving an output record
triggers a call to recompute-extent-for-changed-child.  The parent
then scans all the children to compute the new bounding rectangle,
resulting in quadratic behavior.

The solution to this problem seems to be to realize that incremental
redisplay must traverse all the output records anyway (to see what has
changed), and so it would be a better idea to put off the computation
of the bounding rectangle until the end of this entire process. 

I maintain my previous analysis that it would be a better idea to
store relative positions in output records, so that moving an output
record does not require traversing its children. 
-- 
Robert Strandh

---------------------------------------------------------------------
Greenspun's Tenth Rule of Programming: any sufficiently complicated C
or Fortran program contains an ad hoc informally-specified bug-ridden
slow implementation of half of Common Lisp.
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