Allow dialogues to be hidden or shown

To do this, MENU and SUBMENU are split into two types (at last), and
a Widget type is introduced. This should allow lots of code to be
removed at some point.

cmd/view-menu/main.go

@@ -5,6 +5,8 @@ import (
 	"log"
 	"os"
 
+	"github.com/hajimehoshi/ebiten"
+
 	"code.ur.gs/lupine/ordoor/internal/assetstore"
 	"code.ur.gs/lupine/ordoor/internal/ui"
 )
@@ -17,6 +19,12 @@ var (
 	winY = flag.Int("win-y", 1024, "Pre-scaled window Y dimension")
 )
 
+type dlg struct {
+	driver *ui.Driver
+	list   []string
+	pos    int
+}
+
 func main() {
 	flag.Parse()
 
@@ -45,7 +53,38 @@ func main() {
 		log.Fatal("Couldn't create window: %v", err)
 	}
 
+	// Change the active dialogue
+	dialogues := driver.Dialogues()
+	if len(dialogues) > 0 {
+		dlg := &dlg{
+			driver: driver,
+			list:   dialogues,
+		}
+		win.OnKeyUp(ebiten.KeyLeft, dlg.changeDialogue(-1))
+		win.OnKeyUp(ebiten.KeyRight, dlg.changeDialogue(+1))
+		for i, dialogue := range dlg.list {
+			log.Printf("Dialogue %v: %v", i, dialogue)
+		}
+	}
+
 	if err := win.Run(); err != nil {
 		log.Fatal(err)
 	}
 }
+
+func (d *dlg) changeDialogue(by int) func() {
+	return func() {
+		newPos := d.pos + by
+		if newPos < 0 || newPos > len(d.list)-1 {
+			log.Printf("Hiding dialogue %v: %q", d.pos, d.list[d.pos])
+			d.driver.HideDialogue()
+			return
+		}
+
+		locator := d.list[newPos]
+		log.Printf("Showing dialogue %v: %q", newPos, locator)
+
+		d.driver.ShowDialogue(locator)
+		d.pos = newPos
+	}
+}