fix: fix pinch to zoom

[maribethb]

The basics

• I branched from develop
• My pull request is against develop
• My code follows the style guide
• I ran npm run format and npm run lint

The details

Resolves

fixes #6508

Proposed Changes

• Correctly sets the current gesture id the same way it did before fix: improve types in touch code #6099 (if the pointerId exists, use that, mostly)
• Adds tests for Blockly.Touch. I didn't write any tests for TouchEvents because I literally couldn't test Blockly in a browser that doesn't support Pointer Events (even IE 10 mostly supports them, and we can't even test in IE11 because we no longer support it in other ways). The MouseEvent tests are also pretty useless for that reason, but it was easier to write a fake MouseEvent.

Behavior Before Change

Pinch to zoom is broken because Touch.getTouchIdentifierFromEvent always returns the string 'mouse' for all pointer events, which is all events in modern browsers. The reason it always returns that is because PointerEvent is actually a subclass of MouseEvent so we always enter the first if statement.

Behavior After Change

Touch.getTouchIdentifierFromEvent returns event.pointerId for PointerEvents first. If somehow we don't have a PointerEvent, which is extremely unlikely, then we fall back to the old behavior of 'mouse' if it's a MouseEvent and checking changedTouches if it's a TouchEvent. Note that even if we have a PointerEvent where the pointerType is mouse, we still use the pointerId and not the string 'mouse' as that matches the old behavior from before #6099.

Reason for Changes

fixes broken pinch to zoom

Test Coverage

• Added unit tests
• Manually tested using BrowserStack in iOS, Android, and Windows. Also tested in local playground using mouse. Note that all of these manual tests use PointerEvents as Blockly isn't actually supported in any environment that doesn't support PointerEvents.

Documentation

Additional Information

I'm 99% certain that we could change getTouchIdentifierFromEvent to simply return e.pointerId, since PointerEvents are now robustly supported. But I'll leave that to #6543.

[BeksOmega]

Thanks for writing tests to go with it!

[BeksOmega]

Just curious: why do we want this?

[maribethb]

So this test basically makes sure the behavior is the same as it was in blockly-v8.0.5. In that code (and now this code), if e.pointerId was defined, we'd use that, no matter what. In PointerEvents, it should always be defined, so effectively, we always used that. That means for old old old MouseEvents (that are not PointerEvents) we'd use the string 'mouse' but we haven't actually used it for a long time.

I wrote this test because originally I assumed that if the PointerEvent had a pointerType that was mouse then we'd use the string 'mouse' but that is not correct. We just always use pointerId if it's available. So basically I wrote the test as a reminder of the current behavior.