Decompose ObjectKind.String and doMotion (refactor step 7)

String's tail moves into stringRest; doMotion's erase step moves into
eraseFlight and the inverted loop drops a nesting level. Behavior
unchanged.

game/weapons.go

@@ -35,34 +35,38 @@ func (g *RogueGame) doMotion(obj *Object, ydelta, xdelta int) {
 	// Come fly with us ...
 	obj.Pos = p.Pos
 	for {
-		// Erase the old one
-		if obj.Pos != p.Pos && g.canSee(obj.Pos.Y, obj.Pos.X) && !g.Options.Terse {
-			ch := g.Level.Char(obj.Pos.Y, obj.Pos.X)
-			if ch == Floor && !g.showFloor() {
-				ch = ' '
-			}
-
-			g.mvaddch(obj.Pos.Y, obj.Pos.X, ch)
-		}
+		g.eraseFlight(obj, p.Pos)
 		// Get the new position
 		obj.Pos.Y += ydelta
 		obj.Pos.X += xdelta
 
 		ch := g.Level.VisibleChar(obj.Pos.Y, obj.Pos.X)
-		if stepOk(ch) && ch != Door {
-			// It hasn't hit anything yet, so display it if it's alright.
-			if g.canSee(obj.Pos.Y, obj.Pos.X) && !g.Options.Terse {
-				g.mvaddch(obj.Pos.Y, obj.Pos.X, obj.Kind.Glyph())
-				g.refresh()
-			}
-
-			continue
+		if !stepOk(ch) || ch == Door {
+			break
+		}
+		// It hasn't hit anything yet, so display it if it's alright.
+		if g.canSee(obj.Pos.Y, obj.Pos.X) && !g.Options.Terse {
+			g.mvaddch(obj.Pos.Y, obj.Pos.X, obj.Kind.Glyph())
+			g.refresh()
 		}
-
-		break
 	}
 }
 
+// eraseFlight erases a flying object from its current square, unless it
+// still sits on the hero (the erase step of weapons.c do_motion).
+func (g *RogueGame) eraseFlight(obj *Object, heroPos Coord) {
+	if obj.Pos == heroPos || !g.canSee(obj.Pos.Y, obj.Pos.X) || g.Options.Terse {
+		return
+	}
+
+	ch := g.Level.Char(obj.Pos.Y, obj.Pos.X)
+	if ch == Floor && !g.showFloor() {
+		ch = ' '
+	}
+
+	g.mvaddch(obj.Pos.Y, obj.Pos.X, ch)
+}
+
 // fall drops an item someplace around here (weapons.c fall).
 func (g *RogueGame) fall(obj *Object, pr bool) {
 	if fpos, ok := g.fallpos(obj.Pos); ok {