implemented textAlign; unknown characters now act like a space

canvas.go

@@ -30,6 +30,7 @@ type drawState struct {
 	stroke      drawStyle
 	font        *Font
 	fontSize    float64
+	textAlign   textAlign
 	lineWidth   float64
 	lineJoin    lineJoin
 	lineEnd     lineEnd
@@ -75,6 +76,16 @@ const (
 	Butt
 )
 
+type textAlign uint8
+
+const (
+	Left = iota
+	Center
+	Right
+	Start
+	End
+)
+
 // New creates a new canvas with the given viewport coordinates.
 // While all functions on the canvas use the top left point as
 // the origin, since GL uses the bottom left coordinate, the
@@ -481,6 +492,12 @@ func (cv *Canvas) SetFont(font interface{}, size float64) {
 	cv.state.fontSize = size
 }
 
+// SetTextAlign sets the text align for any text drawing calls.
+// The value can be Left, Center, Right, Start, or End
+func (cv *Canvas) SetTextAlign(align textAlign) {
+	cv.state.textAlign = align
+}
+
 // SetLineJoin sets the style of line joints for rendering a path with Stroke.
 // The value can be Miter, Bevel, or Round
 func (cv *Canvas) SetLineJoin(join lineJoin) {

text.go

@@ -78,7 +78,7 @@ func (cv *Canvas) FillText(str string, x, y float64) {
 	for i, rn := range str {
 		idx := fnt.Index(rn)
 		if idx == 0 {
-			continue
+			idx = fnt.Index(' ')
 		}
 		bounds, err := frc.glyphBounds(idx, p)
 		if err != nil {
@@ -175,6 +175,12 @@ func (cv *Canvas) FillText(str string, x, y float64) {
 		curX += float64(advance) / 64
 	}
 
+	if cv.state.textAlign == Center {
+		x -= float64(strWidth) * 0.5
+	} else if cv.state.textAlign == Right || cv.state.textAlign == End {
+		x -= float64(strWidth)
+	}
+
 	gli.BindBuffer(gl_ARRAY_BUFFER, buf)
 
 	vertex, alphaTexCoord := cv.useAlphaShader(&cv.state.fill, 1)