Add support for "when timer greater than" #130
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| // Find triggers which match conditions | ||
| let matchingTriggers = []; | ||
| for (let i = 0; i < this.spritesAndStage.length; i++) { | ||
| const sprite = this.spritesAndStage[i]; |
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Interesting quirk about the old code I noticed: spritesAndStage is actually a getter which returns a new array every time it's called 😬
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Who would ever write such a thing 🙄
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Right now it looks like the trigger is timer-specific. Could it be better to simply have a That way you could trigger when loudness is greater than some number, but also when other conditions are true. |
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I thought about that--I was kinda worried there's some reason Scratch itself hasn't just implemented that. It seems that Scratch previously wanted to implement a "when touching" block but ran into some issues--for instance, a script running in parallel that messes with the predicate you're testing for, which technically makes logical sense but is very unintuitive behavior. |
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In general, I think any sort of "when predicate" block is unintuitive because you have to be acutely aware of execution order (IIRC, there were a ton of bugs in 3.0 relating to edge cases in the "when timer" block, showing that the developers themselves didn't even understand the behavior). I'd prefer to steer users away from using a "when this predicate evaluates to true" block and only implementing the hat blocks that are necessary to ensure compatibility with Scratch. EDIT: as an example of the silliness that results, this script allows you to create an infinite loop of meows that even the "stop all" button can't end: |
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Okay, that makes sense. I am on board with the current choice then. 👍 |
Resolves part of #122.
This PR adds support for "edge-activated" triggers, so named because they evaluate a predicate every step (e.g. "is the timer greater than N?") and trigger their script on the rising edge (when the predicate changes from
falsetotrue).Trigger predicates/options can now be functions (which are passed the current target) as well as values. This is necessary because the input to a "greater than" block is actually droppable and can contain arbitrary scripts. For codegen purposes, it may be easier to have the function take no arguments and just bind the
thisvalue to the current target, but that seems jankier.