I think were’ not too far different in our ideas, but I think the practical odds of getting this implemented are much higher if the existing GraphicsContext methods are the base for the interface I propose. I think (but could be wrong) that in fact the GraphicsContext was modeled after the HTML 5 canvas so in that sense it forms a good base for what you suggest. One could write code that drew to the Canvas, to an HTML 5 canvas, to graphics files etc. It’s just that now, with GraphicsContext being a final class rather than non-final or an interface, one can’t do any of this.
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 >> >
