Setting maximum zoom scale causes a scroll problem on reaching maximum zoom scale

[yigitserin]

What did you do?

I set my chart's maximum zoom scale to a value by using:

barChartView.viewPortHandler.setMaximumScaleX(100.0)

What did you expect to happen?

I expected my chart to be zoomed to 100x scale without problems.

What happened instead?

My chart can be scrolled to 100x scale. But when you reach this zoom level, chart offset slightly changes and user loses their zoom position. Check the attached video.

Charts Environment

Charts version/Branch/Commit Number: 3.2.2 Xcode version: 10.2 Swift version: 4.2 Platform(s) running Charts: iOS macOS version running Xcode: 10.14.4

Demo Video

Demo Video Link

Demo Code

import UIKit
import Charts

class ViewController: UIViewController {

    @IBOutlet weak var barChartView: BarChartView!
    override func viewDidLoad() {
        super.viewDidLoad()

        //Set Chart.
        var dataSets: [BarChartDataSet] = []

        for i in 1...5{
            let entry = BarChartDataEntry(x: Double(i * 10), y: 10.0)
            let dataSet = BarChartDataSet(values: [entry], label: String(i))
            dataSets.append(dataSet)
        }

        barChartView.data = BarChartData(dataSets: dataSets)
        barChartView.viewPortHandler.setMaximumScaleX(100.0)
    }
}

[liuxuan30]

seems a known issue. but a tough one to fix.

[Andy1984]

My product manager is arguing about this. Is there any solution, or a compromise solution to hide the bug?

[yigitserin]

My workaround was not setting maximum zoom scale and allowing infinite zoom.

[Andy1984]

Thank you. My workaround is in ViewPortHandler.swift， private func limitTransAndScale(matrix: inout CGAffineTransform, content: CGRect?)

_scaleX = max(_minScaleX, matrix.a)
_scaleY = max(_minScaleY,  matrix.d)

[haemi]

is there any update on this?