[Gallery] feat: Added onZoomBegin and onZoomEnd callbacks for gallery

[HadesShadows]

I was the one who raised the issue, this is a code that I have written for gallery. I have not used other components therefore not added these callback support there as I haven't seen the code

These callbacks will support index: number to allow developers to have more control on the zoom event

What is added?

Name	Type	Default	Description
onZoomBegin	(index: number) => void	undefined	Callback triggered when component is zoomed.
onZoomEnd	(index: number) => void	undefined	Callback triggered when component returns back to original state.

How it works?

useAnimatedReaction(
    () => scale.value,
    (value, previousValue) => {
      if (value !== 1 && !hasZoomed.value) { //if the value != 1, that means it is not in default state
        hasZoomed.value = true;
        onZoomBegin && runOnJS(onZoomBegin)(activeIndex.value);
      } else if (value === 1 && previousValue !== 1 && hasZoomed.value) { 
        /* 
          when the component is initally rendered, the value will be 1 and prevValue
            will not be 1, this condition will be true, and onZoomEnd() will be triggered
            to counter that, hasZoomed is used 
        */
        hasZoomed.value = false;
        onZoomEnd && runOnJS(onZoomEnd)(activeIndex.value);
      }
    },
    [scale]
  );

Note: I haven't tested the code snippet in iOS since I don't have macOS, but it is working as expected in android

[Glazzes]

Hi there, I'll not have time to review and test your changes until monday because of personal reasons, but I will be sure to test it as soon as I can.

[HadesShadows]

No Problem, take your time

[cw-nikhilnaik]

Whats the status on the pr?

[Glazzes]

@cw-nikhilnaik Pending, I've been working on another issue these days and personal issues are a thing aswell.

[Glazzes]

@HadesShadows Hi there, I just tested your changes against one of the newest features I've made and it works pretty well with it, I'm merging it 👍

I will release a new version soon!