Created a Tiled pattern

artist/checkered.go

@@ -26,8 +26,26 @@ func (pattern Checkered) AtWhen (x, y, width, height int) (c color.RGBA) {
 	y %= pattern.CellHeight
 
 	if n % 2 == 0 {
-		return pattern.First.AtWhen(x, y, pattern.CellWidth, pattern.CellHeight)
+		return pattern.First.AtWhen (
+			x, y, pattern.CellWidth, pattern.CellHeight)
 	} else {
-		return pattern.Second.AtWhen(x, y, pattern.CellWidth, pattern.CellHeight)
+		return pattern.Second.AtWhen (
+			x, y, pattern.CellWidth, pattern.CellHeight)
 	}
 }
+
+// Tiled is a pattern that tiles another pattern accross a grid.
+type Tiled struct {
+	Pattern
+	CellWidth, CellHeight int
+}
+
+// AtWhen satisfies the Pattern interface.
+func (pattern Tiled) AtWhen (x, y, width, height int) (c color.RGBA) {
+	x %= pattern.CellWidth
+	y %= pattern.CellHeight
+	if x < 0 { x += pattern.CellWidth  }
+	if y < 0 { y += pattern.CellHeight }
+	return pattern.Pattern.AtWhen (
+		x, y, pattern.CellWidth, pattern.CellHeight)
+}

elements/testing/artist.go

@@ -175,6 +175,21 @@ func (element *Artist) Resize (width, height int) {
 			Spacing: 16,
 		},
 		element.cellAt(2, 5))
+		
+	// 3, 5
+	artist.FillRectangle (
+		element,
+		artist.Tiled {
+			Pattern: artist.QuadBeveled {
+				artist.NewUniform(hex(0x880000FF)),
+				artist.NewUniform(hex(0x00FF00FF)),
+				artist.NewUniform(hex(0x0000FFFF)),
+				artist.NewUniform(hex(0xFF00FFFF)),
+			},
+			CellWidth: 17,
+			CellHeight: 23,
+		},
+		element.cellAt(3, 5))
 }
 
 func (element *Artist) lines (weight int, bounds image.Rectangle) {