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/fonts/fonts.go

@@ -10,17 +10,28 @@ import (
 	"code.ur.gs/lupine/ordoor/internal/util/asciiscan"
 )
 
+type Range struct {
+	Min Point
+	Max Point
+}
+
+type Point struct {
+	Rune   rune
+	Sprite int
+}
+
 type Font struct {
 	Name string
-	// Contains the sprite data for the font. FIXME: load this?
+	// Contains the sprite data for the font
 	ObjectFile string
 
 	// Maps ASCII bytes to a sprite offset in the ObjectFile
-	mapping map[int]int
+	Ranges  []Range
+	Mapping map[rune]int
 }
 
 func (f *Font) Entries() int {
-	return len(f.mapping)
+	return len(f.Mapping)
 }
 
 // Returns the offsets required to display a given string, returning an error if
@@ -30,7 +41,7 @@ func (f *Font) Indices(s string) ([]int, error) {
 
 	for i, b := range []byte(s) {
 
-		offset, ok := f.mapping[int(b)]
+		offset, ok := f.Mapping[rune(b)]
 		if !ok {
 			return nil, fmt.Errorf("Unknown codepoint %v at offset %v in string %s", b, i, s)
 		}
@@ -58,7 +69,7 @@ func LoadFont(filename string) (*Font, error) {
 	out := &Font{
 		Name:       filepath.Base(filename),
 		ObjectFile: objFile,
-		mapping:    make(map[int]int),
+		Mapping:    make(map[rune]int),
 	}
 
 	for {
@@ -82,15 +93,32 @@ func LoadFont(filename string) (*Font, error) {
 			cpEnd, _ := strconv.Atoi(fields[2])
 			idxStart, _ := strconv.Atoi(fields[3])
 			idxEnd, _ := strconv.Atoi(fields[4])
-			size := idxEnd - idxStart
+			cpSize := cpEnd - cpStart
+			idxSize := idxEnd - idxStart
 
 			// FIXME: I'd love this to be an error but several .fnt files do it
-			if cpEnd-cpStart != size {
-				fmt.Printf("WARNING: %v has mismatched codepoints and indices: %q\n", filename, str)
+			// Take the smallest range
+			if cpSize != idxSize {
+				fmt.Printf("WARNING: %v has mismatched codepoints (sz=%v) and indices (sz=%v): %q\n", filename, cpSize, idxSize, str)
+				if cpSize < idxSize {
+					idxEnd = idxStart + cpSize
+					idxSize = cpSize
+				} else {
+					cpEnd = cpStart + idxSize
+					cpSize = idxSize
+				}
+
 			}
 
-			for offset := 0; offset < size; offset++ {
-				out.mapping[cpStart+offset] = idxStart + offset
+			r := Range{
+				Min: Point{Rune: rune(cpStart), Sprite: idxStart},
+				Max: Point{Rune: rune(cpEnd), Sprite: idxEnd},
+			}
+
+			out.Ranges = append(out.Ranges, r)
+
+			for offset := 0; offset <= cpSize; offset++ {
+				out.Mapping[rune(cpStart+offset)] = idxStart + offset
 			}
 		case "v": // A single codepoint, 4 fields
 			if len(fields) < 3 {
@@ -99,8 +127,11 @@ func LoadFont(filename string) (*Font, error) {
 
 			cp, _ := strconv.Atoi(fields[1])
 			idx, _ := strconv.Atoi(fields[2])
+			pt := Point{Rune: rune(cp), Sprite: idx}
 
-			out.mapping[cp] = idx
+			out.Ranges = append(out.Ranges, Range{Min: pt, Max: pt})
+
+			out.Mapping[rune(cp)] = idx
 		default:
 			return nil, parseErr
 		}