ShimmerTextView.swift

//
//  ShinyTextView.swift
//

import Foundation
import Cocoa

class ShimmerTextView : NSTextView {
    
    // define your colors and locations
    var count = 0
    var wait = false
    var colors = [NSColor.white.cgColor, NSColor.white.cgColor, NSColor.black.cgColor, NSColor.white.cgColor, NSColor.white.cgColor]
    var locs:[CGFloat] = [0.0, 0.4, 0.5, 0.6, 1.0]
    
    override var allowsVibrancy: Bool { return true }
    
    override func draw(_ dirtyRect: NSRect) {
        NSGraphicsContext.saveGraphicsState()
        
        // set the image context
        let colorSpace:CGColorSpace = CGColorSpaceCreateDeviceRGB()
        let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedLast.rawValue)
        var ctx = CGContext(data: nil, width: Int(self.bounds.size.width), height: Int(self.bounds.size.height), bitsPerComponent: 8, bytesPerRow: 0, space: colorSpace, bitmapInfo: bitmapInfo.rawValue)
        let ngc = NSGraphicsContext(cgContext: ctx!, flipped: true)
        NSGraphicsContext.setCurrent(ngc)
        
        // flip context
        ctx!.scaleBy(x: 1, y: -1)
        ctx!.translateBy(x: 0, y: -bounds.size.height)
        // get the superclass to draw text
        super.draw(dirtyRect)
        
        // get image and end context
        let img = NSGraphicsContext.current()?.cgContext.makeImage()
        NSGraphicsContext.restoreGraphicsState()
        
        // get drawRect context
        ctx = NSGraphicsContext.current()?.cgContext
        
        // flip context
        ctx!.scaleBy(x: 1, y: -1)
        ctx!.translateBy(x: 0, y: -bounds.size.height)
        
        // clip context to image
        ctx!.clip(to: bounds, mask: img!)
        
        // create your gradient
        let grad = CGGradient(colorsSpace: CGColorSpaceCreateDeviceRGB(), colors: colors as CFArray, locations: locs)

        // draw gradient
        ctx!.drawLinearGradient(grad!, start: CGPoint(x: 0, y:bounds.size.height*0.5), end: CGPoint(x:bounds.size.width, y:bounds.size.height*0.5), options: CGGradientDrawingOptions(rawValue: 0))
    }
    
    func shimmer() {
        let runner = Timer(fireAt: Date(), interval: 0.1, target: self, selector: #selector(drawShimmer), userInfo: nil, repeats: true)
        RunLoop.current .add(runner, forMode: RunLoopMode.defaultRunLoopMode)
    }
    
    func drawShimmer() {
        if self.wait {
            if count % 20 == 0 {
                self.wait = false
            }
        } else {
            locs[1] = locs[1]+0.05
            locs[2] = locs[2]+0.05
            locs[3] = locs[3]+0.05
            if locs[3] >= 1.0 {
                locs[1] = 0.1
                locs[2] = 0.2
                locs[3] = 0.3
                self.wait = true
            }
            // force redraw
            self.needsDisplay = true
        }
        count = count + 1
    }
}