SciChart® the market leader in Fast WPF Charts, WPF 3D Charts, and iOS Chart & Android Chart Components

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Hello everyone.
We are trying to migrate to V3 in our iOS project and we have many issues.
One of the most important is the implementation of vertically-draggable horizontal lines.
I have a nice working code for SCICharts V2 but I cannot find any similar example of how we can implement a custom modifier for moving an SCIHorizontalLineAnnotation vertically in V3.
We have done it already with the V2 but now that we have to migrate to V3 there is a huge missing part in your documentation.
Our code was using-overiding onPanGesture() in order to figure out if the modifier should handle the touching event, then we were using the touch point in order to find the closer horizontal lines and choose the closest one in order to change the vertical value depending on the touching-changing point.
The only similar example that I found in your documentation (https://www.scichart.com/example/ios-custom-modifier/) is using SCIGestureModifier which is not accesible by the V3.
I am trying to use your SCIChartModifierBase class but cannot find anywhere a similar example of what we need.
I already tried to understand how you want us to use the ” override func onEvent(_ args: SCIModifierEventArgs!) ” function of the
SCIChartModifierBase but still no luck, it is impossible to figure out without any kind of a similar example.
The reason of needing an example is that this task needs much more information like these:
1. How to decide if the modifier should handle the touch event and how it should be ignored or handled by the next modifier in the same group ?
2. How to handle the touch started, changed, cancelled events ?
3. How to say in realtime to other modifiers in the same group that we need to to handle the same event simultaneously with this custom modifier ?
4. How to say to the group of modifiers that after the first modifer is taken the touch event then the rest should not use it ?

I will paste here our current implementation that we have done for V2 and needs to be transformed to V3 in case you need more details.

An important part is how we add the modifiers on the chart and this is how we are doing it right now:
let zoom = SCIPinchZoomModifier()
zoom.direction = .xDirection
let group = SCIChartModifierCollection(collection: [CustomModifier(chart: self),
PanModifier(),
zoom])
//group.handleGestureFirstOnly = true // Not existing in V3 anymore ! How should we do it in V3 ?
chart.chartModifiers = group

I believe that this code will be really useful for many people out there even for V2 or for migrating to V3.

Swift iOs code using SCICharts V2:

class Modifier: SCIGestureModifier {
private weak var control: ChartView?
private var editingProperty: ChartView.BindableProperty?
private var calculator: SCICoordinateCalculatorProtocol?

    init(chart: ChartView?) {
        self.control = chart
    }

    override func onPanGesture(_ gesture: UIPanGestureRecognizer?, at view: UIView?) -> Bool {

        guard let chart = view as? SCIChartSurface,
            let gesture_ = gesture
            else { return super.onPanGesture(gesture, at: view) }

        let location = gesture_.location(in: chart)
        switch gesture_.state {
        case .began:
            control?.sendActions(for: .touchDown)
            editingProperty = testForDraggableLine(location: location, in: chart)
            calculator = yAxis().getCurrentCoordinateCalculator()
            if editingProperty != nil {
                // Annotations on SciChart don't have Zindex and we want current line to be on the top
                let draggableLines = control?.chart.annotations.array.compactMap { $0 as? DraggableLine }
                if let myLine = draggableLines?.first(where: { $0.bindingKeyValue == editingProperty }) {
                    control?.chart.annotations.remove(myLine)
                    control?.chart.annotations.add(myLine)
                }
                control?.isTouchingLine(isTouching: editingProperty != nil)
            }
            return editingProperty != nil
        case .changed:
            if editingProperty != nil {
                handleDraggingLines(location: location, in: chart)
                return true
            }
        case UIGestureRecognizer.State.ended:
            if editingProperty != nil {
                control?.sendActions(for: .editingDidEnd)
                editingProperty = nil
                _ = control?.adjustYRange(force: true)
                control?.sendActions(for: .valueChanged)
                control?.refreshPositions()
                control?.isNotTouchingLine()
                return true
            }
        case UIGestureRecognizer.State.cancelled:
            if editingProperty != nil {
                control?.sendActions(for: .editingDidEnd)
                editingProperty = nil
                _ = control?.adjustYRange(force: true)
                control?.sendActions(for: .valueChanged)
                control?.refreshPositions()
                control?.isNotTouchingLine()
                return true
            }
        default:
            break
        }

        return false
    }

    private func handleDraggingLines(location: CGPoint, in chart: SCIChartSurface) {
        guard let renderSurface = chart.renderSurface,
            let yCalculator = self.calculator,
            let editingProperty = editingProperty else { return }

        let pointInChart = renderSurface.point(inChartFrame: location)
        let valueForYAxis = yCalculator.getDataValue(from: Double(pointInChart.y))
        control?.setValue(Decimal(valueForYAxis), forKey: editingProperty.rawValue)
    }

    // SOS: Filter possible properties that can be returned. We want to always avoid return - and then - dragging the current price bid or ask !
    private func testForDraggableLine(location: CGPoint, in chart: SCIChartSurface) -> ChartView.BindableProperty? {
        let hitTestDistance: Double = 30 // Pixels !
        let nearItems = chart.annotations.array
            .compactMap { $0 as? DraggableLine }
            .filter { item in
                return item.bindingKeyValue != ChartView.BindableProperty.ask &&
                    item.bindingKeyValue != ChartView.BindableProperty.bid &&
                    !item.isHidden &&
                    item.yDistance(from: location) <= hitTestDistance
            }
        return nearItems
            .sorted { $0.yDistance(from: location) < $1.yDistance(from: location) }
            .first?.bindingKeyValue
    }
}
  • Dxat asked 2 weeks ago
  • last active 2 weeks ago
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