[mcclim-devel] deftype coordinate

[Christophe Rhodes]

Hi,

A little bit of empirical measurement by Juho Snellman reveals that in
certain circumstances, such as waving the mouse over the gsharp
window, mcclim under sbcl spends 70% or so of its time in bignum
operations related to converting floating point numbers to rational
ones.  I believe that this is an artifact of the "permissive"
coordinate type (currently set to real, apparently after a version of
cmucl started doing some kind of type checking or inference).

Attached is a patch which restores the double-float coordinate type,
along with at least some of the necessary coercions here and there.
I'd probably not merge this directly, because I'm still confused over
when something is a coordinate and when it isn't.

I believe that bounding-rectangles and regions are coordinate-based,
and that output-records are rational-based, at least in terms of their
position.  If this is the case, I'd suggest adding completely separate
slots for the two "worlds"; rather than having coercions on accesses,
there would be coupled setter methods.  In this patch, I've instead
been somewhat conservative: anywhere where I was uncertain what was
happening, I inserted a call to the COORDINATE function.

This version has survived a certain amount of rudimentary testing in
the listener and gsharp.  I'd be interested to know if there is any
perceptual speed change, and also whether there are coordinate-related
bugs remaining.

[ this patch was driven by a branch of SBCL in CVS tagged as
  clos-typechecking-branch, which includes type checks for most (setf
  slot-value), (setf accessor) and make-instance calls ]

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Cheers,

Christophe