Make a start on font rendering

I was hopeful I could use ebiten/text, but font.Face doesn't seem set
up for fixed-colour fonts.

internal/ui/noninteractive.go

@@ -5,7 +5,6 @@ import (
 	"log"
 
 	"github.com/hajimehoshi/ebiten"
-	"github.com/hajimehoshi/ebiten/ebitenutil"
 
 	"code.ur.gs/lupine/ordoor/internal/menus"
 )
@@ -28,7 +27,8 @@ type noninteractive struct {
 	rect   image.Rectangle
 
 	// Some non-interactives, e.g., overlays, are an image + text to be shown
-	textImg *ebiten.Image
+	textImg    *ebiten.Image
+	textOffset image.Point
 
 	clickImpl // Alright, alright, it turns out the bridge mission briefing is clickable
 	hoverImpl
@@ -102,14 +102,27 @@ func registerOverlay(d *Driver, r *menus.Record) error {
 	}
 
 	if r.Text != "" {
-		// FIXME: we should be rendering the text much more nicely than this
-		textImg, err := ebiten.NewImage(sprite.Rect.Dx(), sprite.Rect.Dy(), ebiten.FilterDefault)
+		// FIXME: is this always right? Seems to make sense for Main.mnu
+		fnt := d.menu.Font(r.FontType/10 - 1)
+
+		textImg, err := fnt.DrawLine(r.Text)
 		if err != nil {
 			return err
 		}
 
-		ebitenutil.DebugPrint(textImg, r.Text)
 		ni.textImg = textImg
+
+		// Centre the image
+		xSlack := ni.rect.Dx() - textImg.Bounds().Dx()
+		if xSlack > 0 {
+			ni.textOffset.X = xSlack / 2
+		}
+
+		ySlack := ni.rect.Dy() - textImg.Bounds().Dy()
+		if ySlack > 0 {
+			ni.textOffset.Y = ySlack / 2
+		}
+
 	} else {
 		log.Printf("Overlay without text detected: %#+v", r)
 	}
@@ -189,12 +202,16 @@ func (n *noninteractive) regions(tick int) []region {
 	out := oneRegion(n.bounds().Min, n.frames.image(tick))
 
 	if n.textImg != nil {
-		out = append(out, oneRegion(n.bounds().Min, n.textImg)...)
+		out = append(out, oneRegion(n.textPos(), n.textImg)...)
 	}
 
 	return out
 }
 
+func (n *noninteractive) textPos() image.Point {
+	return image.Pt(n.rect.Min.X+n.textOffset.X, n.rect.Min.Y+n.textOffset.Y)
+}
+
 func (a *animationHover) regions(tick int) []region {
 	if a.opening || a.closing {
 		var anim animation