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/assetstore/assetstore.go

@@ -34,6 +34,7 @@ type AssetStore struct {
 	entries entryMap
 
 	// These members are used to store things we've already loaded
+	fonts   map[string]*Font
 	maps    map[string]*Map
 	menus   map[string]*Menu
 	objs    map[string]*Object
@@ -84,6 +85,7 @@ func (a *AssetStore) Refresh() error {
 
 	// Refresh
 	a.entries = newEntryMap
+	a.fonts = make(map[string]*Font)
 	a.maps = make(map[string]*Map)
 	a.menus = make(map[string]*Menu)
 	a.objs = make(map[string]*Object)

internal/assetstore/font.go

@@ -0,0 +1,116 @@
+package assetstore
+
+import (
+	"fmt"
+	"log"
+
+	"github.com/hajimehoshi/ebiten"
+
+	"code.ur.gs/lupine/ordoor/internal/fonts"
+)
+
+type Font struct {
+	Name    string
+	mapping map[rune]*Sprite
+}
+
+func (a *AssetStore) Font(name string) (*Font, error) {
+	name = canonical(name)
+
+	// FIXME: these fonts don't exist. For now, point at one that does.
+	switch name {
+	case "imfnt13", "imfnt14":
+		name = "wh40k_12"
+	}
+
+	if font, ok := a.fonts[name]; ok {
+		return font, nil
+	}
+	log.Printf("Loading font %v", name)
+
+	filename, err := a.lookup(name, "fnt", "Fonts")
+	if err != nil {
+		return nil, err
+	}
+
+	raw, err := fonts.LoadFont(filename)
+	if err != nil {
+		return nil, err
+	}
+
+	objFile, err := a.lookup(raw.ObjectFile, "", "Fonts")
+	if err != nil {
+		return nil, err
+	}
+
+	obj, err := a.ObjectByPath(objFile)
+	if err != nil {
+		return nil, err
+	}
+
+	out := &Font{
+		Name:    name,
+		mapping: make(map[rune]*Sprite, len(raw.Mapping)),
+	}
+
+	for r, offset := range raw.Mapping {
+		spr, err := obj.Sprite(offset)
+		if err != nil {
+			return nil, err
+		}
+
+		out.mapping[r] = spr
+	}
+
+	a.fonts[name] = out
+
+	return out, nil
+}
+
+// FIXME: this violates the ebiten rules for fast drawing. We may need to do the
+// draw ourselves, with image.Paletted for each glyph to a single ebiten.Image
+//
+// FIXME: it'd be great if we didn't have to implement this all by ourselves;
+// golang.org/x/image/font and github.com/hajimehoshi/ebiten/text are *almost*
+// sufficient, but don't seem to like it when the glyphs are literal colours
+// instead of a mask.
+//
+// TODO: draw text in a bounding box, multiple lines, etc
+func (f *Font) DrawLine(text string) (*ebiten.Image, error) {
+	sprites := make([]*Sprite, 0, len(text))
+	width := 0
+	height := 0
+
+	for _, r := range text {
+		spr, ok := f.mapping[r]
+		if !ok {
+			return nil, fmt.Errorf("Font %v does not specify rune %v", f.Name, r)
+		}
+
+		width += spr.Rect.Dx()
+		if y := spr.Rect.Dy(); y > height {
+			height = y
+		}
+
+		sprites = append(sprites, spr)
+	}
+
+	img, err := ebiten.NewImage(width, height, ebiten.FilterDefault)
+	if err != nil {
+		return nil, err
+	}
+
+	xOff := 0
+	for _, spr := range sprites {
+		op := &ebiten.DrawImageOptions{}
+		op.GeoM.Translate(float64(xOff), 0)
+
+		xOff += spr.Rect.Dx()
+
+		if err := img.DrawImage(spr.Image, op); err != nil {
+			return nil, err
+		}
+	}
+
+	return img, nil
+}

internal/assetstore/menu.go

@@ -8,8 +8,9 @@ import (
 
 type Menu struct {
 	assets *AssetStore
-	obj    *Object // TODO: handle multiple objects in the menu
-	raw    *menus.Menu
+	fonts  []*Font     // TODO: place the fonts directly into the relevant records
+	obj    *Object     // TODO: handle multiple objects in the menu
+	raw    *menus.Menu // TODO: remove raw
 
 	Name string
 }
@@ -19,6 +20,11 @@ func (m *Menu) Records() []*menus.Record {
 	return m.raw.Records
 }
 
+// FIXME: don't expose this
+func (m *Menu) Font(idx int) *Font {
+	return m.fonts[idx]
+}
+
 func (m *Menu) Images(start, count int) ([]*ebiten.Image, error) {
 	out := make([]*ebiten.Image, count)
 
@@ -70,6 +76,16 @@ func (a *AssetStore) Menu(name string) (*Menu, error) {
 		return nil, err
 	}
 
+	var fonts []*Font
+	for _, fontName := range raw.FontNames {
+		fnt, err := a.Font(fontName)
+		if err != nil {
+			return nil, err
+		}
+
+		fonts = append(fonts, fnt)
+	}
+
 	i18n, err := a.i18n()
 	if err != nil {
 		return nil, err
@@ -84,6 +100,7 @@ func (a *AssetStore) Menu(name string) (*Menu, error) {
 
 	menu := &Menu{
 		assets: a,
+		fonts:  fonts,
 		obj:    obj,
 		raw:    raw,
 		Name:   name,