API Review RT:17407 Canvas Node

[Kevin Rushforth]

It seems like there is quite a bit of interest in a more generic 
immediate-mode rendering interface.

One problem with making GraphicsContext an interface is that you are 
then precluded from evolving it in a compatible manner. You are stuck 
introducing GraphicsContext2, GraphicsContext3, etc., and doing 
instanceof checks. Also, I would guess that some of the methods would 
not want to be part of the interface for non-Canvas implementations. I 
hope Jim can chime in here and respond.

Going out with a publicly-exposed javafx.scene.canvas.GraphicsContext 
class wouldn't preclude later introducing a generic interface that 
GraphicsContext could then implement (with all or a subset of the 
methods), which would then allow other implementations.

 > I even dare to propose to rewrite the charting package based on this 
interface.

I question the value of this, but in any case it would be an 
implementation detail.

-- Kevin


Dr. Michael Paus wrote:
> Yes, this interface should be a general purpose 2D drawing interface 
> and should contain
> nothing specific to Canvas and should also not reside in the canvas 
> package. Canvas only
> provides one possible implementation of it with possibly some 
> additional canvas specific features.
>
> I even dare to propose to rewrite the charting package based on this 
> interface. This would increase
> the longterm usefulness of the charting package and at the same time 
> would be a very good test-case
> for the completeness and usefulness of the canvas implementation itself.
>
> LG, Michael
>
> Am 19.04.2012 12:08, schrieb Daniel Zwolenski:
>> I like what Michael Paus is suggesting. Unless there is a need to 
>> couple this with Canvas it would be good to keep it seperate.
>>
>>
>> On 19/04/2012, at 2:57 PM, "Dr. Michael Paus"<mp at jugs.org>  wrote:
>>
>>> A Canvas node is very important but we should not limit the 
>>> GraphicsContext to be only usable for it.
>>> Instead we should make GraphicsContext an interface and Canvas 
>>> should then provide a CanvasGraphicsContext
>>> which implements this interface. The advantage would be that code 
>>> can be written against that interface and
>>> if someone else writes a renderer for other output formats you can 
>>> then immediately render into that format
>>> too like it is currently done for SVG, PDF and other formats by 
>>> tools like Batik, iText, etc.
>>>
>>> LG, Michael
>>>
>>> Am 19.04.2012 00:36, schrieb joe andresen:
>>>> Hello Everyone,
>>>>
>>>> We propose to add a Canvas node and GraphicsContext to a new
>>>> javafx.scene.canvas package for JavaFX 2.2. The  javafx.scene.canvas
>>>> package provides a pair of classes for an immediate mode style API for
>>>> rendering.  Canvas Node works seemlessly with effects as well as
>>>> Animation timers, and will be tightly bound to the new ImageOps API.
>>>>
>>>> This new API will allow HTML5 Canvas users to easily port their
>>>> existing applications that make heavy use of the HTML5 canvas directly
>>>> to JavaFX without the need to morph their application to fit the
>>>> scenegraph model.
>>>>
>>>> You can Download and unzip the (preliminary) relevant docs here:
>>>> JIRA: http://javafx-jira.kenai.com/browse/RT-17407
>>>>
>>>> Note that the docs are a work in progress but should be enough for API
>>>> Review. (Also, Jira will be down Thursday 4/19 at 1400 PDT for a 
>>>> while).
>>>>
>>>> A list of the the methods for Canvas and GraphicsContext are listed
>>>> below.
>>>>
>>>> Canvas:
>>>>
>>>> GraphicsContext    getGraphicsContext2D()
>>>> double    getHeight()
>>>> double    getWidth()
>>>> DoubleProperty    heightProperty()
>>>> void    setHeight(double value)
>>>> void    setWidth(double value)
>>>> DoubleProperty    widthProperty()
>>>>
>>>> GraphicsContext:
>>>> void    appendSVGPath(java.lang.String svgpath)
>>>> void    applyEffect(Effect e)
>>>> void    arc(double centerX, double centerY, double radiusX, double
>>>> radiusY, double startAngle, double length)
>>>> void    arcTo(double x1, double y1, double x2, double y2, double 
>>>> radius)
>>>> void    beginPath()
>>>> void    bezierCurveTo(double xc1, double yc1, double xc2, double yc2,
>>>> double x1, double y1)
>>>> void    clearRect(double x, double y, double w, double h)
>>>> void    clip()
>>>> void    closePath()
>>>> void    drawArc(double x, double y, double w, double h, double
>>>> startAngle, double arcExtent, ArcType closure)
>>>> void    drawImage(Image img, double x, double y)
>>>> void    drawImage(Image img, double x, double y, double w, double h)
>>>> void    drawImage(Image img, double sx, double sy, double sw, double
>>>> sh, double dx, double dy, double dw, double dh)
>>>> void    drawLine(double x1, double y1, double x2, double y2)
>>>> void    drawOval(double x, double y, double w, double h)
>>>> void    drawPolygon(double[] xPoints, double[] yPoints, int nPoints)
>>>> void    drawPolyline(double[] xPoints, double[] yPoints, int nPoints)
>>>> void    drawRoundRect(double x, double y, double w, double h, double
>>>> arcWidth, double arcHeight)
>>>> void    fill()
>>>> void    fillArc(double x, double y, double w, double h, double
>>>> startAngle, double arcExtent, ArcType closure)
>>>> void    fillOval(double x, double y, double w, double h)
>>>> void    fillPolygon(double[] xPoints, double[] yPoints, int nPoints)
>>>> void    fillRect(double x, double y, double w, double h)
>>>> void    fillRoundRect(double x, double y, double w, double h, double
>>>> arcWidth, double arcHeight)
>>>> void    fillText(java.lang.String text, double x, double y)
>>>> void    fillText(java.lang.String text, double x, double y, double
>>>> maxWidth)
>>>> Canvas    getCanvas()
>>>> boolean    isPointInPath(double x, double y)
>>>> void    lineTo(double x1, double y1)
>>>> double    measureText(java.lang.String text)
>>>> void    moveTo(double x0, double y0)
>>>> void    putImageData(GraphicsContext.ImageData imagedata, double dx,
>>>> double dy)
>>>> void    putImageData(GraphicsContext.ImageData imagedata, double dx,
>>>> double dy, double dirtyX, double dirtyY, double dirtyWidth, double
>>>> dirtyHeight)
>>>> void    quadraticCurveTo(double xc, double yc, double x1, double y1)
>>>> void    rect(double x, double y, double w, double h)
>>>> void    restore()
>>>> void    rotate(double degrees)
>>>> void    save()
>>>> void    scale(double x, double y)
>>>> void    setEffect(Effect e)
>>>> void    setFill(Paint p)
>>>> void    setFont(Font f)
>>>> void    setGlobalAlpha(double alpha)
>>>> void    setGlobalCompositeOperation(GraphicsContext.CompositeOperation
>>>> op)
>>>> void    setLineCap(StrokeLineCap cap)
>>>> void    setLineJoin(StrokeLineJoin join)
>>>> void    setLineWidth(double lw)
>>>> void    setMiterLimit(double ml)
>>>> void    setStroke(Paint p)
>>>> void    setTextAlign(TextAlignment align)
>>>> void    setTextBaseline(VPos baseline)
>>>> void    setTransform(double mxx, double myx, double mxy, double myy,
>>>> double mxt, double myt)
>>>> void    stroke()
>>>> void    strokeRect(double x, double y, double w, double h)
>>>> void    strokeText(java.lang.String text, double x, double y)
>>>> void    strokeText(java.lang.String text, double x, double y, double
>>>> maxWidth)
>>>> void    transform(double mxx, double myx, double mxy, double myy,
>>>> double mxt, double myt)
>>>> void    translate(double x, double y)
>>>
>>> -- 
>>> -------------------------------------------------------------------------------------- 
>>>
>>> Dr. Michael Paus, Chairman of the Java User Group Stuttgart e.V. 
>>> (JUGS).
>>> For more information visit www.jugs.de.
>
>