Support programatic zoom

[masato1230]

Description

Add two functions that allow zooming to be executed programmatically.

• zoomToOnContentCoordinate
  • zoomTo the position based on content size coordinate. This function can be used to implement the initial zoom functionality.
• zoomToOnLayoutCoordinate
  • zoom to the position based on layout size coordinate. This function can be used to programatic zoom with some user gestures.

Sample(Capture)

• initial zoom(0~2s)
• zoom with long press(5s~)

device-2023-05-25-002658.mp4

Sample code used in video

@Composable
fun AsyncImageSample() {
    val zoomState = rememberZoomState()
    val coroutineScope = rememberCoroutineScope()
    AsyncImage(
        model = "https://github.com/usuiat.png",
        contentDescription = "GitHub icon",
        contentScale = ContentScale.Fit,
        onSuccess = { state ->
            zoomState.setContentSize(state.painter.intrinsicSize)
            coroutineScope.launch {
                zoomState.zoomToOnContentCoordinate(zoomTo = Offset(x = 230f, y = 203f))
            }
        },
        modifier = Modifier
            .fillMaxSize()
            .zoomable(zoomState)
            .pointerInput(1) {
                detectTapGestures(
                    onLongPress = {
                        coroutineScope.launch {
                            zoomState.zoomToOnLayoutCoordinate(it)
                        }
                    }
                )
            }
    )
}

[usuiat]

Thank you for submitting the PR!
I think it's a good idea to support programatic zoom.
I will review.

[usuiat]

The Image should be zoomed around a specified point, but this is not currently the case.

I will explain the case of zoomToOnContentCoordinate using a sample image.
The image is 512x512 pixel. If I specify Offset(128, 256), the specified point should not move on the screen. But actually it moves.

Original size	Expected	Actual

The same problem exists with zoomToOnLayoutCoordinate.

[usuiat]

I have just merged another branch to main branch.

• Support double tap zoom #60

In it, there is an internal function called changeScale.
Since changeScale is almost same to zoomToOnLayoutCoordinate, I would like to make this function public and rename it zoomToOnLayoutCoordinate.

And I think zoomToOnContentCoordinate can be achieved by transforming the coordinates and calling zoomToOnLayoutCoordinate.

[usuiat]

Sorry for the consecutive posts.
Did you implement it so that the specified point will be centered on the screen?
If so, I was misunderstood.

[masato1230]

@usuiat

Did you implement it so that the specified point will be centered on the screen?

Yes! I have created this Pull Request with the intention of implementing the functionality to center a specified point on the screen.

[usuiat]

@masato1230
fitContentSizeFactor is calculated in width / height, but not width / width?

Suggested change

	val fitContentSizeFactor = fitContentSize.width / contentSize.height
	val fitContentSizeFactor = fitContentSize.width / contentSize.width

[usuiat]

@masato1230
I have two requests so that the library users will understand that the specified coordinates move to the center of the screen.

• Change the function name. For example, how about centerByContentCoordinate(offset, scale, animationSpec) and centerByLayoutCoordinate(offset, scale, animationSpec)?
• Add description to Kdoc of the functions.

[masato1230]

@usuiat
Thank you for your review.
I've made the revisions you requested. Could you please review it again?

[usuiat]

LGTM👍 Thanks.