Add RecommendedHeight to TypeSetter

recommend.go

@@ -0,0 +1,37 @@
+package typeset
+
+import "golang.org/x/image/font"
+import "golang.org/x/image/math/fixed"
+
+func recommendHeight (tokens []token, face font.Face, width fixed.Int26_6) fixed.Int26_6 {	
+	metrics := face.Metrics()
+	var dot fixed.Point26_6
+
+	newline := func () {
+		dot.Y  += metrics.Height
+		dot.X   = 0
+	}
+
+	sawLineBreak := false
+	for _, token := range tokens {
+		// demarcate lines
+		if sawLineBreak {
+			newline()
+			sawLineBreak = false
+		}
+		if token.kind == tokenKindLineBreak {
+			sawLineBreak = true
+		} else {
+			needWrap :=
+				token.kind == tokenKindWord &&
+				dot.X + token.width > width
+			if needWrap {
+				newline()
+			}
+			dot.X += token.width
+		}
+	}
+	newline()
+	
+	return dot.Y
+}

typesetter.go

@@ -175,6 +175,14 @@ func (this *TypeSetter) PositionAt (index int) fixed.Point26_6 {
 	return position
 }
 
+// ReccomendedHeightFor returns the reccomended max height if the text were to
+// have its maximum width set to the given width. This does not actually move
+// any text, it only simulates it.
+func (this *TypeSetter) RecommendedHeight (width fixed.Int26_6) fixed.Int26_6 {
+	this.needMeasurement()
+	return recommendHeight(this.tokens, this.face, width)
+}
+
 // SetAlign sets the horizontal and vertical alignment of the text.
 func (this *TypeSetter) SetAlign (x, y Align) {
 	if this.xAlign == x && this.yAlign == y { return }