Stop should not erase last frame

[zahlenteufel]

Sometimes I stop a sketch and the canvas gets erased, it would prefer to keep the last image (or possibly add a pause button instead of stop).

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[catarak]

Thanks for the feature idea! I think keeping the behavior of the stop button is important, but maybe it would make sense to add a "pause" button? Maybe it could call noLoop() on the sketch? Though I guess that would only stop the draw loop, and other functions like mousePressed() would still work.

What do you want to do that you'd like to keep the last frame of the sketch? Maybe there's an alternate solution.

[kisielk]

Situations where this is useful: you want to save the current image, which may get updated when you pass your mouse over it or it may just be continuously updating due to the loop. Maybe a pause button would be more useful in this case so that you could pause, save the image, and then resume the generation.

[catarak]

It would be possible to put in a pause button that would call noLoop() behind the scenes, but i worry about it not working if the sketch is configured differently (e.g. the sketch is run in instance mode). It seems like the use case is saving a picture of the canvas, so why not have a "save picture" button?

[zahlenteufel]

It's also about stopping an animation that can be distracting or consuming a lot of CPU (e.g. when misbehaving), while at the same time "seeing" the effect so it's easy to iterate. When you clear the canvas you effectively force the programmer to remember what was there.

[catarak]

I hear you. I do worry about the edge cases involved in adding a pause button but I see how it could be really useful—I could see myself using it in a teaching context.

[vulongphan]

@catarak I want to work on this issue, but could you please elaborate on the edge case (i.e: the instance mode)?

Thank you!

[catarak]

Revisiting this issue, I'm not sure which direction to go in! Part of me really likes the simplicity of the play/pause buttons, and adding a pause could be confusing—like what does a "pause" really mean in this context? Taking an image of the canvas on hitting stop is also more complicated than it sounds—what if the sketch adds other DOM elements besides the canvas? The editor could take an image of the whole web page, but then it wouldn't be accessible anymore as all of the DOM elements would be flattened to a bitmap. Which then makes me lean towards adding a pause button which would call noLoop() in the iframe, but this wouldn't work with instance mode as the p5 instance isn't accessible, or there could even be multiple p5 instances. It's really hard to cover all of the edge cases here 😕