I can see how this could be useful to a certain class of applications,
but I'm not convinced there is enough value, since the work that the
application would need to do is pretty much the same even if we added
the ability to subclass. As for providing an interface, I think that a
third-party library could do that just as easily. What you wouldn't get
is standardization of that interface.
-- Kevin
On 11/2/2020 2:34 PM, Bruce Johnson wrote:
I should not even have mentioned the GraphicsContext for scene graph rendering.
There is something elegant about being able to easily make the whole scene
render to some other device/file, but I’m well aware of the practical issues.
But I do wish there was a better solution for the original question. Libraries
like VectorGraphics and JFreeSVG are really useful for actual real world
applications and I don’t see comparable tools appearing for JavaFX without some
changes like I propose (or better ones than I can think of).
Bruce
On Nov 2, 2020, at 5:04 PM, Kevin Rushforth <[email protected]> wrote:
Yeah, there is no chance we would consider changing the JavaFX to use Canvas
GraphicsContext for scene graph rendering.
As for the original question, we are unlikely to make GraphicsContext
extensible in the core JavaFX. I think the solution you came up with for your
application (with a proxy class and interface) is a reasonable approach.
-- Kevin
On 11/2/2020 6:58 AM, Michael Paus wrote:
At this point I would disagree with you. Doing so would just
result in a sever performance hit. I will not go into the details
here because that idea is out of reach anyway.
Am 02.11.20 um 15:42 schrieb Bruce Johnson:
And if you want to think of even further advances (which I’d avoid at this
point because I’d like this to get done in a useful time frame), I’ve often
thought that all JavaFX scene drawing should use the Canvas GraphicsContext.
So with the changes I’m suggesting that would allow export of the complete
scene graph to another device (vector graphics files etc.)
Bruce
On Nov 2, 2020, at 9:17 AM, Michael Paus <[email protected]> wrote:
Hi,
I very much like the idea in general but I think it falls too short.
Such an interface should not be tied to any existing graphics
framework. Instead it should be just pure Java. This would allow
to write complex graphics rendering code for a lot of different
platforms and not only platforms where JavaFX already exists
and can be used. Just think of the Android canvas or, via cross-
compilation, even the HTML 5 canvas.
Just my two €ent.
Michael
Am 02.11.20 um 14:18 schrieb Bruce Johnson:
A variety of packages (for example, VectorGraphics or JFreeSVG) exist that
allow redirecting Java2D drawing to output other than the Java2D canvas.
These work by extending java.awt.Graphics2D. By passing the extended
Graphics2D object into a paint method, output can be redirected to a file
(.svg, .pdf, etc.).
The GraphicsContext class of JavaFX serves a similar function to Graphics2D of
java.awt, but because it is a final class it cannot be extended to create
similar functionality as found in VectorgGraphics or JFreeSVG.
This is a serious limitation (at least as far as I can tell) to JavaFX
applications. It would be highly desirable to be able to redirect drawing on a
Canvas to other output formats such as vector graphics files (.svg, .pdf etc.).
I currently work around this by using composition. I have a Java interface
that has most methods of GraphicsContext. Then a GraphicsContextProxy class
implements the interface and contains an instance of GraphicsContext. This
class is used for drawing to the Canvas. I’ve then created a
SVGGraphicsContext and PDFGraphicsContext that implement the interface and
these can be used to draw to .svg or .pdf files.
This works, but means that all code that draws on the canvas has to be
rewritten to take the GraphicsContextInterface rather than the normal
GraphicsContext.
It would be much simpler if
1) GraphicsContext was not final and could be extended.
or
2) A GraphicsContextInterface existed that GraphicsContext implemented.
Developers could then have alternative GraphicsContext implementations that
implemented that interface. This would require canvas drawing code to be
written to use the interface, but would still be very useful.
Either solution could (I think) be easily implemented in JavaFX without
breaking existing code and add a significant advance to the toolkit.
If there are alternative solutions to the problem, that would allow exporting
canvas drawing to vector graphics files without requiring a change to the code
that draws to the canvas, I’d appreciate hearing them.
— Bruce
