code review 1708045: freetype/raster: new Path and Stroke API.

freetype/raster: new Path and Stroke API.

The stroking algorithm is a placeholder. A proper one will land in a
future change once the API is agreed upon.

[nigeltao, 2010-06-20 23:05:13]

Hello r, rsc (cc: golang-dev@googlegroups.com, rog),

I'd like you to review this change.

[r2, 2010-06-23 00:53:43]

http://codereview.appspot.com/1708045/diff/2001/3002
File freetype/raster/geom.go (right):

http://codereview.appspot.com/1708045/diff/2001/3002#newcode50
freetype/raster/geom.go:50: return Fixed(256 * math.Sqrt(x*x+y*y))
i think you can be clever and make this a lot faster. i think there are way more
fp ops than you need.  i know it's a TODO but i'm intrigued.... x*x>>8 is x^2 in
24.8. is that better than the floating point operations? i don't know.

whether it's worth thinking about  depends how often you do this, but it's fun

http://codereview.appspot.com/1708045/diff/2001/3002#newcode83
freetype/raster/geom.go:83: Add3(b, c, d Point)
it may be too expensive because it adds an allocation at the call site but you
could have just
   Add(a ...Point)
although i realize that might be silly since you'll never do more than 3, and
they are semantically somewhat distinct.

http://codereview.appspot.com/1708045/diff/2001/3002#newcode122
freetype/raster/geom.go:122: *p = make([]Fixed, n, 2*n)
if you make this 2*n+10 or some such, the zero value for Path is usable without
allocating a starting vector.

http://codereview.appspot.com/1708045/diff/2001/3002#newcode183
freetype/raster/geom.go:183: // A Cap signifies how to begin and end a stroked
curve.
s/and/or/

http://codereview.appspot.com/1708045/diff/2001/3002#newcode225
freetype/raster/geom.go:225: j += 7
this is clean but you could use an if and do 2*n+1

[rsc1, 2010-06-23 03:01:36]

LGTM

Seems like a reasonable API.

http://codereview.appspot.com/1708045/diff/2001/3002
File freetype/raster/geom.go (right):

http://codereview.appspot.com/1708045/diff/2001/3002#newcode187
freetype/raster/geom.go:187: ButtCap Cap = iota
Make the zero value a good default.
Same for MiterJoin.
I don't know enough to know what the good
defaults are here; you might have already done that.

[rsc1, 2010-06-23 03:15:55]

http://codereview.appspot.com/1708045/diff/2001/3002
File freetype/raster/geom.go (right):

http://codereview.appspot.com/1708045/diff/2001/3002#newcode50
freetype/raster/geom.go:50: return Fixed(256 * math.Sqrt(x*x+y*y))
At the least, I think this simplifies to

x := float64(p.X)
y := float64(p.Y)
return Fixed(math.Sqrt(x*x+y*y))

The extra factor of 256 doesn't affect floating point
precision, and when you square it and take the square
root you end up with exactly the scaling you started with.

[nigeltao, 2010-06-23 07:39:26]

*** Submitted as
http://code.google.com/p/freetype-go/source/detail?r=7841fec2baad ***

freetype/raster: new Path and Stroke API.

The stroking algorithm is a placeholder. A proper one will land in a
future change once the API is agreed upon.

R=r, rsc
CC=golang-dev, rog
http://codereview.appspot.com/1708045