Display overlay text in the UI

We still have fonts to do, so this is very ugly, but it at least shows
*something* on the screen now.

internal/data/i18n.go

@@ -13,7 +13,7 @@ import (
 // file that maps string IDs to messages
 type I18n struct {
 	Name    string
-	mapping map[int]string
+	mapping map[int]Entry
 }
 
 // FIXME: this should be put into the config file maybe, or detected from a list
@@ -22,6 +22,15 @@ const (
 	I18nFile = "USEng.dta"
 )
 
+// I18n entries may have 1 or 2 items. If two, the first is a menu item and the
+// second is a help string for that menu item.
+//
+// The text or help may contain some magic strings, as mentioned in USEng.data
+type Entry struct {
+	Text string
+	Help string
+}
+
 func LoadI18n(filename string) (*I18n, error) {
 	f, err := os.Open(filename)
 	if err != nil {
@@ -32,7 +41,7 @@ func LoadI18n(filename string) (*I18n, error) {
 
 	out := &I18n{
 		Name:    filepath.Base(filename),
-		mapping: make(map[int]string),
+		mapping: make(map[int]Entry),
 	}
 
 	scanner := bufio.NewScanner(f)
@@ -63,7 +72,12 @@ func LoadI18n(filename string) (*I18n, error) {
 
 		// TODO: Replace certain escape characters with their literals?
 
-		out.mapping[num] = string(val)
+		if entry, ok := out.mapping[num]; !ok { // first time we've seen this
+			out.mapping[num] = Entry{Text: string(val)}
+		} else { // Second time, the item is help text
+			entry.Help = string(val)
+			out.mapping[num] = entry
+		}
 	}
 
 	if err := scanner.Err(); err != nil {
@@ -78,8 +92,14 @@ func (n *I18n) Len() int {
 }
 
 // Puts the internationalized string into `out` if `in` matches a known ID
-func (n *I18n) Replace(in int, out *string) {
+func (n *I18n) ReplaceText(in int, out *string) {
 	if str, ok := n.mapping[in]; ok {
-		*out = str
+		*out = str.Text
+	}
+}
+
+func (n *I18n) ReplaceHelp(in int, out *string) {
+	if str, ok := n.mapping[in]; ok {
+		*out = str.Help
 	}
 }