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 <m...@jugs.org> 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
