Bug in ZoomViewJob?

[wuxudong]

In an react native wrapper project , It use Charts as underlying lib.

After updating Charts from 3.0.3 to 3.0.5, the zoom is not behaving as expected.

barLineChart.zoom(scaleX: CGFloat(json["scaleX"].floatValue),
                    scaleY: CGFloat(json["scaleY"].floatValue),
                    xValue: json["xValue"].doubleValue,
                    yValue: json["yValue"].doubleValue,
                    axis: axisDependency)

In Charts 3.0.5, it doesn't center at (xValue, yValue), but in Charts 3.0.3, it works well.

After dig a little further, I found in commit #3041 , the code in ZoomViewJob changed from

var pt = CGPoint(
    x: CGFloat(xValue - xValsInView / 2.0),
    y: CGFloat(yValue + yValsInView / 2.0)
)

to

 var pt = CGPoint(
	x: CGFloat(xValue - xValsInView) / 2.0,
	y: CGFloat(yValue + yValsInView) / 2.0
)

notice the position of brackets, the computed pt is totally different.

is it an unintentional wrong typing ? please fix it.

[liuxuan30]

will this cause that big difference? CGFloat(xValue - xValsInView / 2.0) and CGFloat(xValue - xValsInView) / 2.0 are merely the same I think.

But you are welcome to test it on your side and let us know the results with proof and details.

[wuxudong]

/(division) is prior to -(subtraction).

eg. xValue = 20, xValsInView = 20

CGFloat(xValue - xValsInView / 2.0) = CGFloat (20-20/2.0) = CGFloat(10)

CGFloat(xValue - xValsInView) / 2.0 = CGFloat(20-20) / 2.0 = CGFloat(0) / 2.0 = CGFloat(0)

[liuxuan30]

oops, good catch. This is a mistake @jjatie . will be taken care of in 3.1