printTreeRecursive uses g.children

engine/drawdfs.go

@@ -18,8 +18,10 @@ func init() {
 
 // DrawDFS is a DrawManager that does not add any structure. Components are
 // drawn in the order in which they are encountered by a depth-first search
-// through the game tree, without any extra sorting based on Z values or
-// consideration for DrawOrderer).
+// through the game tree using Scan, without any extra sorting based on Z values
+// or consideration for DrawOrderer. Also, children registered in Game but not
+// registered by subcomponents (such that they are visited with Scan) won't be
+// drawn.
 type DrawDFS struct {
 	Child interface{}
 	Hides

engine/game.go

@@ -201,7 +201,7 @@ func (g *Game) Scan(visit VisitFunc) error {
 }
 
 // Load loads a component and all subcomponents recursively.
-// Note that this method does not implement Loader.
+// Note that this method does not implement Loader itself.
 func (g *Game) Load(component interface{}, assets fs.FS) error {
 	if l, ok := component.(Loader); ok {
 		if err := l.Load(assets); err != nil {
@@ -217,7 +217,7 @@ func (g *Game) Load(component interface{}, assets fs.FS) error {
 }
 
 // Prepare prepares a component and all subcomponents recursively.
-// Note that this method does not implement Prepper.
+// Note that this method does not implement Prepper itself.
 func (g *Game) Prepare(component interface{}) error {
 	// Postorder traversal, in case ancestors depend on descendants being
 	// ready to answer queries.

engine/repl.go

@@ -102,11 +102,8 @@ func (g *Game) printTreeRecursive(dst io.Writer, depth int, c interface{}) {
 	} else {
 		fmt.Fprintf(dst, "%s%v\n", indent, c)
 	}
-	if sc, ok := c.(Scanner); ok {
-		sc.Scan(func(x interface{}) error {
-			g.printTreeRecursive(dst, depth+1, x)
-			return nil
-		})
+	for x := range g.children[c] {
+		g.printTreeRecursive(dst, depth+1, x)
 	}
 }