如何更改NSScroller的颜色？

Question

I'm trying to change the color of the scroller itself, it seems I need to overwrite something around drawKnob but I couldn't find any method which seemed appropriate.

One way I thought about was to inject a new style and get scroller to use it but again, I couldn't find anything about NSColor in NSScroller header.

Any idea?

Answer 1

我认为您将不得不编写一个子类，并重写drawKnob ，也许是drawKnobSlotInRect:也取决于您要更改的内容。

Answer 2

No need to redraw from scratch. It's as simple as this:

import AppKit

class CyanideScroller: NSScroller {
    private var _bkgrColour: NSColor = NSColor.black
    private var _knobColour: NSColor = NSColor.white
    private var isHorizontal = false

    var bkgrColour: NSColor {
        get { return _bkgrColour}
        set { _bkgrColour = newValue}
    }

    var knobColour: NSColor {
        get { return _knobColour}
        set { _knobColour = newValue}
    }

    override var frame: CGRect {
        didSet {
            let size = frame.size
            isHorizontal = size.width > size.height
        }
    }

    override func draw(_ dirtyRect: NSRect) {
        _bkgrColour.setFill()
        dirtyRect.fill()
        self.drawKnob()
    }


    override func drawKnob() {
        _knobColour.setFill()

        let dx, dy: CGFloat
        if isHorizontal {
            dx = 0; dy = 3
        } else {
            dx = 3; dy = 0
        }

        let frame = rect(for: .knob).insetBy(dx: dx, dy: dy)
        NSBezierPath.init(roundedRect: frame, xRadius: 3, yRadius: 3).fill()
    }

}