Hi,
i found rome API very close to OpenVG.
Still OpenVG is a bit superior :)
So, i'm using it as a guide to model/implement Rome interfaces.
So, here is my thoughts (i also having a draft class skeleton for them):
Paints:
Paint is an object, which when applied to path, renders(draws) the
path using paint's unique properties.
I defined two methods in paint's base class:
fillPath: aPath on: aCanvas
self subclassResponsibility
strokePath: aPath on: aCanvas
self subclassResponsibility
So, to draw a path, one should use a concrete paint to either fill it
or stroke it (or both, if you want, but its handled by canvas and
still will end up with separate fill & stroke requests to paint).
I started from a quite basic things:
NullPaint
Paint which does not performs any drawing.
Applying this paint to any path won't lead to any
changes/processing. A simple OO approach to define 'nothing' :)
SolidColorPaint
instanceVariableNames: 'color'
Paint with solid color. Most trivial thing which can be done :)
RomePen
instanceVariableNames: 'paint capStyle joinStyle width dash'
A 'pen' paint is just encapsulating a set of properties, which is used
for stroke.
It is using another paint, which should handle the fills (in 'paint'
ivar), while various stroke properties should be handled by itself.
Filling with pen, will be the same as filling with its paint. While
doing a stoke is different (includes path processing, given the values
of pen's properties etc etc).
I'm not sure with this part. Maybe stroke properties would be better
to leave in canvas? Both OpenVG and Rome seems like following this
road,
but i don't quite like that stroke properties is global for canvas and
lacking a proper encapsulation.
CompositePaint
Quite dumb thing. Holds a list of paints. When asked to fill or
stroke the path, applies paints from own list.
GradientPaint (abstract)
LinearGradient
RadialGradient
etc..
paints which will use gradients for fills. Nothing fancy :)
Canvas protocol:
selectFill: anObject
fill := anObject asRomePaintOn: self
- selects a paint which will be used for fills.
selectPen: anObject
pen := anObject asRomePaintOn: self
- selects a paint which will be used for stokes.
stroke: anObject
| path |
path := anObject asRomePathOn: self.
fill strokePath: path on: self.
- stroke a path using currently selected 'pen' paint
fill: anObject
| path |
path := anObject asRomePathOn: self.
fill fillPath: path on: self.
- fill path using paint for fills
fillAndStroke: anObject
| path |
path := anObject asRomePathOn: self.
fill fillPath: path on: self.
pen strokePath: path on: self
- fill and stroke path.
And from that point, i wonder, do we need to have a paint's selection
mechanisms at all?
Because, we could simply do:
canvas fill: myPath with: myPaint
instead of:
canvas selectFill: myPaint.
canvas fill: myPath.
Because you anyways can't draw a paths without paints, i don't see why
canvas should have a notion of 'current fill' or 'current paint'.
I think that with paint's encapsulation, its not necessary.
I'd like to hear your thoughts about it.
--
Best regards,
Igor Stasenko AKA sig.
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