ordoor/internal/assetstore/font.go

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
}