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Canvas Threading: Difference between revisions
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→Canvas Architecture: https://forum.flightgear.org/viewtopic.php?f=30&t=36614&p=357608&hilit=#p357608
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In addition, there are higher level helpers implemented in scripting space, e.g. a "window" class implemented on top of the image element. Or support for SVG graphics, implemented on top of the OpenVG based path handling support. Also, there is a special group type to handle specifically geographic projections, for mapping/charting purposes. | In addition, there are higher level helpers implemented in scripting space, e.g. a "window" class implemented on top of the image element. Or support for SVG graphics, implemented on top of the OpenVG based path handling support. Also, there is a special group type to handle specifically geographic projections, for mapping/charting purposes. | ||
== Approach == | |||
telling the canvas system to use another property tree (SGPropertyNode instance) is really straightforward - but at that point, it's no longer accessible to the rest of the sim. | |||
You can easily try it for yourself, and just add a "text" element to that private canvas. | |||
The interesting part is making that show up again (i.e. via placements). | |||
Once you are able to tell a placement to use such a private property tree, you can use synchronize access by using a separate thread for each canvas texture (property tree). | |||
But again, it would be a static property tree until you provide /some/ access to it - so that it can be modified at runtime, and given what we have already, hooking up FGNasalSys is the most convenient method. But all of the canvas bindings/APIs we have already would need to be reviewed to get rid of the hard-coded assumption that there is only a single canvas tree in use. | |||
Like you said, changing fgfs to operate on a hidden/private property tree is the easy part, interacting with that property tree is the interesting part. | |||
Also, it would be a very different way of coding, we would need to use some kind of dedicated scheduling mechanism, or such background threads might "busy wait" unnecessarily. | |||
If you know how to build sg/fg from source (git) and how to apply patches, I can provide the corresponding pointers to get you started experimenting with such an adapted Canvas system, we experimented with it a couple of years ago, and there should still be patches somewhere on the forum or the wiki. | |||
== References == | == References == | ||
{{Appendix}} | {{Appendix}} | ||