     
     func rectForDay(offset:Int, rowIndex:Int, canvasHeight:Int) -> Rect {
         
-        let COL_WIDTH = self.COL_WIDTH
-        let ROW_HEIGHT = self.ROW_HEIGHT
-        let LEFT_MARGIN_WIDTH = self.LEFT_MARGIN_WIDTH
-        let TOP_MARGIN_HEIGTH = self.TOP_MARGIN_HEIGTH
-        
         let p = P(
-            LEFT_MARGIN_WIDTH + offset,
-            canvasHeight - TOP_MARGIN_HEIGTH - (rowIndex+1) * ROW_HEIGHT
+            self.LEFT_MARGIN_WIDTH + offset,
+            canvasHeight - self.TOP_MARGIN_HEIGTH - (rowIndex+1) * self.ROW_HEIGHT
         )
         
-        return Rect(p, width:COL_WIDTH, height:ROW_HEIGHT)
+        return Rect(p, width:self.COL_WIDTH, height:self.ROW_HEIGHT)
     }
     
     func fillColorForLineCountPerDay(count:Int, baseColor:NSColor) -> NSColor {

            
            // draw cells
            
            // for each day of the timeframe
            for (day, _, offset) in dayTuples {
                
                // for each author in the repo
                for (i, author) in authorsInRepo.enumerate() {
                    
                    // set default color
                    var fillColor = NSColor.clearColor()

                    return
            }
            
            let authorsInRepo = Array(Set(json.values.flatMap({ $0.keys }))).sort()
            
            // draw repo name
            c.drawText(repo, origin: P(LEFT_MARGIN_WIDTH, c.height() - self.TOP_MARGIN_HEIGTH - (currentRow) * ROW_HEIGHT - 18))
