Implemented some CGRect's missing APIs

Foundation/NSGeometry.swift

@@ -237,11 +237,173 @@ extension CGRect {
                                         y: -CGFloat.greatestFiniteMagnitude / 2,
                                         width: CGFloat.greatestFiniteMagnitude,
                                         height: CGFloat.greatestFiniteMagnitude)
+
+    public var width: CGFloat { return abs(self.size.width) }
+    public var height: CGFloat { return abs(self.size.height) }
+
+    public var minX: CGFloat { return self.origin.x + min(self.size.width, 0) }
+    public var midX: CGFloat { return (self.minX + self.maxX) * 0.5 }
+    public var maxX: CGFloat { return self.origin.x + max(self.size.width, 0) }
+
+    public var minY: CGFloat { return self.origin.y + min(self.size.height, 0) }
+    public var midY: CGFloat { return (self.minY + self.maxY) * 0.5 }
+    public var maxY: CGFloat { return self.origin.y + max(self.size.height, 0) }
+
+    public var isEmpty: Bool { return self.isNull || self.size.width == 0 || self.size.height == 0 }
+    public var isInfinite: Bool { return self == .infinite }
+    public var isNull: Bool { return self.origin.x == .infinity || self.origin.y == .infinity }
+
+    public func contains(_ point: CGPoint) -> Bool {
+        if self.isNull || self.isEmpty { return false }
+
+        return (self.minX..<self.maxX).contains(point.x) && (self.minY..<self.maxY).contains(point.y)
+    }
+
+    public func contains(_ rect2: CGRect) -> Bool {
+        return self.union(rect2) == self
+    }
+
+    public var standardized: CGRect {
+        if self.isNull { return .null }
+
+        return CGRect(x: self.minX,
+                      y: self.minY,
+                      width: self.width,
+                      height: self.height)
+    }
+
+    public var integral: CGRect {
+        if self.isNull { return self }
+
+        let standardized = self.standardized
+        let x = standardized.origin.x.rounded(.down)
+        let y = standardized.origin.y.rounded(.down)
+        let width = (standardized.origin.x + standardized.size.width).rounded(.up) - x
+        let height = (standardized.origin.y + standardized.size.height).rounded(.up) - y
+        return CGRect(x: x, y: y, width: width, height: height)
+    }
+
+    public func insetBy(dx: CGFloat, dy: CGFloat) -> CGRect {
+        if self.isNull { return self }
+
+        var rect = self.standardized
+
+        rect.origin.x += dx
+        rect.origin.y += dy
+        rect.size.width -= 2 * dx
+        rect.size.height -= 2 * dy
+
+        if rect.size.width < 0 || rect.size.height < 0 {
+            return .null
+        }
+
+        return rect
+    }
+
+    public func union(_ r2: CGRect) -> CGRect {
+        if self.isNull {
+            return r2
+        }
+        else if r2.isNull {
+            return self
+        }
+
+        let rect1 = self.standardized
+        let rect2 = r2.standardized
+
+        let minX = min(rect1.minX, rect2.minX)
+        let minY = min(rect1.minY, rect2.minY)
+        let maxX = max(rect1.maxX, rect2.maxX)
+        let maxY = max(rect1.maxY, rect2.maxY)
+
+        return CGRect(x: minX,
+                      y: minY,
+                      width: maxX - minX,
+                      height: maxY - minY)
+    }
+
+    public func intersection(_ r2: CGRect) -> CGRect {
+        if self.isNull || r2.isNull { return .null }
+
+        let rect1 = self.standardized
+        let rect2 = r2.standardized
+
+        let rect1SpanH = rect1.minX...rect1.maxX
+        let rect1SpanV = rect1.minY...rect1.maxY
+
+        let rect2SpanH = rect2.minX...rect2.maxX
+        let rect2SpanV = rect2.minY...rect2.maxY
+
+        if !rect1SpanH.overlaps(rect2SpanH) || !rect1SpanV.overlaps(rect2SpanV) {
+            return .null
+        }
+
+        let overlapH = rect1SpanH.clamped(to: rect2SpanH)
+        let overlapV = rect1SpanV.clamped(to: rect2SpanV)
+
+        return CGRect(x: overlapH.lowerBound,
+                      y: overlapV.lowerBound,
+                      width: overlapH.upperBound - overlapH.lowerBound,
+                      height: overlapV.upperBound - overlapV.lowerBound)
+    }
+
+    public func intersects(_ r2: CGRect) -> Bool {
+        return !self.intersection(r2).isNull
+    }
+
+    public func offsetBy(dx: CGFloat, dy: CGFloat) -> CGRect {
+        if self.isNull { return self }
+
+        var rect = self.standardized
+        rect.origin.x += dx
+        rect.origin.y += dy
+        return rect
+    }
+
+    public func divided(atDistance: CGFloat, from fromEdge: CGRectEdge) -> (slice: CGRect, remainder: CGRect) {
+        if self.isNull { return (.null, .null) }
+
+        let splitLocation: CGFloat
+        switch fromEdge {
+        case .minXEdge: splitLocation = min(max(atDistance, 0), self.width)
+        case .maxXEdge: splitLocation = min(max(self.width - atDistance, 0), self.width)
+        case .minYEdge: splitLocation = min(max(atDistance, 0), self.height)
+        case .maxYEdge: splitLocation = min(max(self.height - atDistance, 0), self.height)
+        }
+
+        let rect = self.standardized
+        var rect1 = rect
+        var rect2 = rect
+
+        switch fromEdge {
+        case .minXEdge: fallthrough
+        case .maxXEdge:
+            rect1.size.width = splitLocation
+            rect2.origin.x = rect1.maxX
+            rect2.size.width = rect.width - splitLocation
+        case .minYEdge: fallthrough
+        case .maxYEdge:
+            rect1.size.height = splitLocation
+            rect2.origin.y = rect1.maxY
+            rect2.size.height = rect.height - splitLocation
+        }
+
+        switch fromEdge {
+        case .minXEdge: fallthrough
+        case .minYEdge: return (rect1, rect2)
+        case .maxXEdge: fallthrough
+        case .maxYEdge: return (rect2, rect1)
+        }
+    }
 }
 
 extension CGRect: Equatable {
     public static func ==(lhs: CGRect, rhs: CGRect) -> Bool {
-        return lhs.origin == rhs.origin && lhs.size == rhs.size
+        if lhs.isNull && rhs.isNull { return true }
+
+        let r1 = lhs.standardized
+        let r2 = rhs.standardized
+        return r1.origin == r2.origin && r1.size == r2.size
     }
 }