An NSTableView delegate with a yellow flash effect

TableDelegate.rb

# TableDelegate.rb
#
# An example of capturing double-clicks and a yellow-fade technique in MacRuby.
# The yellow fade technique implementation is a ruby-ized translation
# of http://www.bdunagan.com/2009/04/26/core-animation-on-the-mac/
# Created by Morgan Schweers on February 26, 2011.

framework 'Cocoa'

class TableDelegate
  # Hook this up to your TableView in Interface Builder
  attr_accessor :view

  # Establish a double-click listener
  def awakeFromNib
    view.doubleAction = 'double_click:'
    view.target = self
  end

  def double_click(sender)
    # Do something with sender.clickedRow that updates it...
    yellow_fade(sender)
  end

  # Utility function for a common ObjC pattern of 'create, then call several setters'
  def mass_assign(obj, params)
    obj.tap do |object|
      params.keys.each do |key|
        msg = "#{key}="
        object.send(msg, params[key])
      end
    end
  end

  # Establish a fade-in and fade-out animation (color is set in the layer below)
  def yellow_fade(sender)
    rowIndex = sender.clickedRow
    cellFrame = view.rectOfRow(rowIndex)

    layer = CALayer.layer
    layer.delegate = self
    yellowFadeView = mass_assign(NSView.alloc.init, wantsLayer:true, frame:cellFrame, layer:layer, alphaValue:0.0)
    layer.setNeedsDisplay
    sender.addSubview(yellowFadeView)

    # Fade from 0 alpha (invisible) to opaque
    fadeIn  = mass_assign(CABasicAnimation.animationWithKeyPath("alphaValue"), beginTime:0.0, fromValue:0.0, toValue:1.0, duration:0.25)
    # Fade from opaque back to 0 alpha
    fadeOut = mass_assign(CABasicAnimation.animationWithKeyPath("alphaValue"), beginTime:0.25, fromValue:1.0, toValue:0.0, duration:0.25)

    # Pair the animations together
    yfa = mass_assign(CAAnimationGroup.animation, delegate:self, animations:[fadeIn, fadeOut], duration:2.0)

    yellowFadeView.animations = {"frameOrigin" => yfa}
    # Start the animation
    yellowFadeView.animator.frame = yellowFadeView.frame
  end

  # Utility function to extract the RGBA values from a color
  def split_color(color)
    r = Pointer.new(:double)
    g = Pointer.new(:double)
    b = Pointer.new(:double)
    a = Pointer.new(:double)
    color.getRed(r, green:g, blue:b, alpha:a)

    [r[0], g[0], b[0], a[0]]
  end

  # This draws a simple layer of a yellow outline, with a translucent yellow interior.
  # This layer is then faded in and out by the animation above.
  def drawLayer(layer, inContext:ctx)
    radius = 4
    nsGC = NSGraphicsContext.graphicsContextWithGraphicsPort(ctx, flipped:false)
    NSGraphicsContext.saveGraphicsState
    NSGraphicsContext.currentContext = nsGC

    aRect = layer.frame
    rect = NSMakeRect(aRect.origin.x, aRect.origin.y, aRect.size.width, aRect.size.height)

    # Solid outside line
    NSBezierPath.defaultLineWidth = 2
    highlightPath = NSBezierPath.bezierPathWithRoundedRect(rect, xRadius:radius, yRadius:radius)
    NSColor.yellowColor.set
    highlightPath.stroke

    # Translucent inner filled rounded rectangle
    r, g, b, a = split_color(NSColor.yellowColor)
    transparentYellow = NSColor.colorWithCalibratedRed(r, green:g, blue:b, alpha:0.5)
    fillPath = NSBezierPath.bezierPathWithRoundedRect(rect, xRadius:radius, yRadius:radius)
    transparentYellow.set
    fillPath.fill

    NSGraphicsContext.restoreGraphicsState
  end
end