code review 1736043: freetype/raster: improve the stroking algorithm.

freetype/raster: improve the stroking algorithm.
It still isn't perfect (e.g. it doesn't join), but it's getting closer.

Also fix the bug where RotateCW and RotateCCW was mixed up, since the
Y-axis grows down in a computer graphics co-ordinate system, not up as
in classical mathematics.

[nigeltao, 2010-06-23 13:53:05]

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

I'd like you to review this change.

[rog, 2010-06-23 15:13:27]

http://codereview.appspot.com/1736043/diff/2001/3001
File freetype/raster/geom.go (right):

http://codereview.appspot.com/1736043/diff/2001/3001#newcode46
freetype/raster/geom.go:46: func (p Point) Plus(q Point) Point {
it's nice to see these, but i think it would be sensible if the method names
matched those of draw.Point where possible i.e. Add, Sub, Mul.

http://codereview.appspot.com/1736043/diff/2001/3001#newcode105
freetype/raster/geom.go:105: type Path []Fixed
any particular reason why this isn't []Point?

[nigeltao, 2010-06-24 10:07:12]

http://codereview.appspot.com/1736043/diff/2001/3001
File freetype/raster/geom.go (right):

http://codereview.appspot.com/1736043/diff/2001/3001#newcode46
freetype/raster/geom.go:46: func (p Point) Plus(q Point) Point {
On 2010/06/23 15:13:27, rog wrote:
> it's nice to see these, but i think it would be sensible if the method names
> matched those of draw.Point where possible i.e. Add, Sub, Mul.

Done.

http://codereview.appspot.com/1736043/diff/2001/3001#newcode105
freetype/raster/geom.go:105: type Path []Fixed
On 2010/06/23 15:13:27, rog wrote:
> any particular reason why this isn't []Point?

A linear segment is represented as two co-ordinates and a leading and trailing
1. A []Point would take 3 * 8 = 24 bytes, a []Fixed takes 4 * 4 = 16 bytes.

[rog, 2010-06-24 10:28:09]

http://codereview.appspot.com/1736043/diff/2001/3001
File freetype/raster/geom.go (right):

http://codereview.appspot.com/1736043/diff/2001/3001#newcode105
freetype/raster/geom.go:105: type Path []Fixed
ah, i'd missed that.
i suppose another possibility would be two parallel arrays, e.g.
struct {segLen []int8; points []Point}, but that
has its own penalties.

On 2010/06/24 10:07:12, nigeltao_golang wrote:
> On 2010/06/23 15:13:27, rog wrote:
> > any particular reason why this isn't []Point?
> 
> A linear segment is represented as two co-ordinates and a leading and trailing
> 1. A []Point would take 3 * 8 = 24 bytes, a []Fixed takes 4 * 4 = 16 bytes.

[nigeltao_gnome, 2010-06-26 23:36:06]

On 23 June 2010 23:53,  <nigeltao@golang.org> wrote:
> Description:
> freetype/raster: improve the stroking algorithm.
> It still isn't perfect (e.g. it doesn't join), but it's getting closer.
>
> Also fix the bug where RotateCW and RotateCCW was mixed up, since the
> Y-axis grows down in a computer graphics co-ordinate system, not up as
> in classical mathematics.
>
> Please review this at http://codereview.appspot.com/1736043/show

Ping.

[rsc1, 2010-06-28 21:08:34]

LGTM

http://codereview.appspot.com/1736043/diff/8001/9001
File freetype/raster/geom.go (right):

http://codereview.appspot.com/1736043/diff/8001/9001#newcode40
freetype/raster/geom.go:40: // A two-dimensional point or vector, in 24.8 fixed
point format.
// A Point represents a two-dimensional ...

[nigeltao, 2010-06-29 00:48:22]

*** Submitted as
http://code.google.com/p/freetype-go/source/detail?r=5ac4ec211c87 ***

freetype/raster: improve the stroking algorithm.
It still isn't perfect (e.g. it doesn't join), but it's getting closer.

Also fix the bug where RotateCW and RotateCCW was mixed up, since the
Y-axis grows down in a computer graphics co-ordinate system, not up as
in classical mathematics.

R=r, rsc, rog
CC=golang-dev
http://codereview.appspot.com/1736043