Before this change, the two renderers both had special case code for
approximating strokes they don't support natively. This change moves
that conversion to clip.Op.Add, for several reasons:
- The compute renderer no longer need fallback logic and caches for
strokes it doesn't support.
- The approximation logic is slow. Moving it to clip.Op.Add will not
speed it up, but will make the cost easier to spot in profiles. Until all
strokes are supported natively, users can use macros to cache
expensive strokes.
- Reduced garbage: Op.Add takes an op.Ops anyway, and can use that for
storing the approximated stroke outline.
Signed-off-by: Elias Naur <mail@eliasnaur.com>
There's an argument that rounded caps and joins are the simplest stroke,
in that it can be defined to cover all pixels within lineWidth distance
from the supporting path.
However, the more important reason is that the compute renderer natively
supports this stroke style (without dashes), and users that don't care
(much) about the particular stroke style should get the efficient
implementation. A good example is op/clip.Border that strokes a closed
path, where the StrokeCap is irrelevant.
This is a (subtle) API change. If you have code that relies on the
default values of clip.StrokeStyle you may want to set Cap and Join
explicitly. See the test changes for examples. On the other hand, you
will get much better performance from the default Cap and Join values
once the compute renderer becomes the default.
Disablethe TestPaintClippedBorder test; dashes round-capped,
round-joined strokes doesn't seem to work correctly.
Signed-off-by: Elias Naur <mail@eliasnaur.com>
This CL introduces 2 new path builders:
- Outline which takes a PathSpec to be outlined
- Stroke which takes a PathSpec and a stroke style, to stroke a path.
typically, code like this:
var p clip.Path
...
p.Outline().Add(o)
should be replaced with:
var p clip.Path
...
clip.Outline{Path: p.End()}.Op().Add(o)
similarly, stroking should be modified from:
var p clip.Path
...
p.Stroke(width, clip.StrokeStyle{...}).Add(o)
to:
var p clip.Path
...
clip.Stroke{Path: p.End(), Style: clip.StrokeStyle{Width:...}}.Op().Add(o)
here are tentative 'rf' scripts (see rsc.io/rf for more details):
```
ex {
import "gioui.org/op";
import "gioui.org/op/clip";
var p clip.Path;
var o *op.Ops;
p.Outline().Add(o) -> clip.Outline{Path:p.End()}.Op().Add(o);
}
ex {
import "gioui.org/op";
import "gioui.org/op/clip";
var o *op.Ops;
var p clip.Path;
var sty clip.StrokeStyle;
var width float32;
p.Stroke(width, sty).Add(o) -> \
clip.Stroke{ \
Path:p.End(), \
Style: clip.StrokeStyle{ \
Width: width, \
}}.Op().Add(o);
}
```
Signed-off-by: Sebastien Binet <s@sbinet.org>
Flat and Square caps are implemented.
Bevel joins are implemented.
Round caps, Round joins and Miter joins are left for another PR.
Signed-off-by: Sebastien Binet <s@sbinet.org>
Elias Naur