Animations using after_draw() don't work properly #97
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The Sparkle animation uses `after_draw` to setup the pixels currently being sparkled for the next frame, assuming `show()` will not be called until then. It also calls `show()` itself first to show the changes made in `draw()`. The problem is that `animate()` already calls `show()` after calling draw and after_draw. So the frame where the sparkle should show is actually skipped and only briefly appears instead of staying for a frame according to the speed parameter. The refactor from PR adafruit#23 changed the protocol where animations should no longer call `show()` themselves. We can't change `after_draw` to be called after the call to show() in animate(), because it will break on animation groups using the same strip. If another animation triggers a show() sooner, it will show the next frame of the sparkle prematurely. It also makes the protocol less predictable. I have used `animate(False)`, followed by setting a pixel an calling `show()` for example to force the color of a single or a few pixels without going through the hassle of creating pixelmaps or groups (and also to simply make it look like it's superimposed over the animation). So the solution would be to drop `after_draw` and instead memorize the previous list of pixels and set them back in the next draw.
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This looks good to me -- The only comment to add is that the show and immediate clear was intentional and might change the visual impact of some existing uses. With the frame remaining set until the next interval, its more of a random pixel animation. |
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Oh, and I'm all for cleaning up the API! |
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Ah. I wasn't sure I understood how the animation works. We can close this then. |
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The Sparkle animation uses
after_drawto setup the pixels currently being sparkled for the next frame, assumingshow()will not be called until then. It also callsshow()itself first to show the changes made indraw().The problem is that
animate()already callsshow()after calling draw and after_draw. So the frame where the sparkle should show is actually "skipped": it only briefly appears instead of staying for a frame according to the speed parameter. The refactor from PR #23 changed the protocol where animations should no longer callshow()themselves.We can't change
after_drawto be called after the call toshow()inanimate(), because it will break for example on animation groups using the same strip: if another animation triggers ashow(), it will show the next frame of the sparkle prematurely. It also makes the protocol less predictable in general.This PR drops
after_draw()altogether and instead does everything indraw().I don't think there is a need to preserve backwards compatibility with potential 3rd party animations using it, since it can't have worked properly since #23.