Initial commit

drawer.go

@@ -0,0 +1,50 @@
+package textdraw
+
+import "image"
+import "unicode"
+import "image/draw"
+import "image/color"
+import "golang.org/x/image/math/fixed"
+
+// Drawer is an extended TypeSetter that is able to draw text. Much like
+// TypeSetter, It has no constructor and its zero value can be used safely.
+type Drawer struct { TypeSetter }
+
+// Draw draws the drawer's text onto the specified canvas at the given offset.
+func (drawer Drawer) Draw (
+	destination draw.Image,
+	color       color.RGBA,
+	offset      image.Point,
+) (
+	updatedRegion image.Rectangle,
+) {
+	drawer.For (func (
+		index    int,
+		char     rune,
+		position fixed.Point26_6,
+	) bool {
+		destinationRectangle,
+		mask, maskPoint, _, ok := drawer.face.Glyph (
+			fixed.P (
+				offset.X + position.X.Round(),
+				offset.Y + position.Y.Round()),
+			char)
+		if !ok || unicode.IsSpace(char) || char == 0 {
+			return true
+		}
+
+		// FIXME:? clip destination rectangle if we are on the cusp of
+		// the maximum height.
+
+		draw.DrawMask (
+			destination,
+			destinationRectangle,
+			image.NewUniform(color), image.Point { },
+			mask, maskPoint,
+			draw.Over)
+
+		updatedRegion = updatedRegion.Union(destinationRectangle)
+		return true
+	})
+	return
+}