erase() and noErase() support in framebuffers

[acamposuribe]

Topic

I'm trying to execute erase() and noErase() within the framebuffer.begin() and framebuffer.end() functions, but they seem to be ignored. Bug or feature missing?
Thanks in advance!

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[davepagurek]

Sounds like a bug! Are you able to make a minimal example in a p5 editor sketch to debug with?

[acamposuribe]

Sounds like a bug! Are you able to make a minimal example in a p5 editor sketch to debug with?

Yes! There you have it:
https://editor.p5js.org/acamposuribe/sketches/gaVBVGKu-

The erase() function is erasing the main canvas, rather than the framebuffer.

[davepagurek]

If I comment out the last line with the image() call, then the black background is still preserved. I think the bug isn't that it's erasing the main canvas, but that erase is actually replacing with fully opaque white. Which is definitely still a bug!

[acamposuribe]

If I comment out the last line with the image() call, then the black background is still preserved. I think the bug isn't that it's erasing the main canvas, but that erase is actually replacing with fully opaque white. Which is definitely still a bug!

Yes, you're definitely right!

[davepagurek]

Looks like the bug is here:

p5.js/src/webgl/p5.RendererGL.js

Line 1165 in 28740f9

this._applyBlendMode(constants.REMOVE);

_applyBlendMode just updates the WebGL blending to match what p5 has set it to, and doesn't actually take any arguments. I think this should be just blendMode(REMOVE), which seems to work:
https://editor.p5js.org/davepagurek/sketches/DvUOkmTwM

[acamposuribe]

This makes the whole framebuffer white, though (except for the erased part)?

[davepagurek]

You're right! Just updated the sketch again, looks like we still have to call _applyBlendMode() after setting the blend mode.

[acamposuribe]

You're right! Just updated the sketch again, looks like we still have to call _applyBlendMode() after setting the blend mode.

Yes! Although noErase() was not working, because blendMode was not reverting back to the original. We need to store the current blendmode and pass it at the end. I made a bad fix:

https://editor.p5js.org/acamposuribe/sketches/rBOTxXyvu

[davepagurek]

Thanks! Are you interested in combining the changes in that sketch into a PR?

[acamposuribe]

Thanks! Are you interested in combining the changes in that sketch into a PR?

I'm pretty new to OpenSource. Currently creating a p5 library as a first contribution to the project.
Never made a pull request before....

[davepagurek]

If youre interested, I can help walk you through it! We also have a p5 discord where you can ask questions faster. If you'd rather not though, that's also totally fine!