Add next [n] - go to next frame from devtools

User can go to next frame when the game is paused. To do so he can:

* issue next command in REPL terminal (or 'n')
* press n in game window

devtools/control.go

@@ -11,8 +11,9 @@ import (
 )
 
 var (
-	gamePaused     bool
-	timeWhenPaused float64
+	gamePaused       bool
+	pauseOnNextFrame bool
+	timeWhenPaused   float64
 )
 
 var helpShown bool
@@ -35,3 +36,12 @@ func resumeGame() {
 	snapshot.Draw()
 	fmt.Println("Game resumed")
 }
+
+func resumeUntilNextFrame() {
+	if gamePaused {
+		resumeGame()
+		pauseOnNextFrame = true
+	} else {
+		fmt.Println("Game not paused")
+	}
+}

devtools/internal/help/help.go

@@ -27,7 +27,7 @@ func PrintHelp(topic string) error {
 			"\n\n" +
 			"Type help topic for more information. For example: help pi or help pi.Spr" +
 			"\n\n" +
-			"Available commands: help [h], pause [p], resume [r], undo [u]",
+			"Available commands: help [h], pause [p], resume [r], undo [u], next [n]",
 		)
 		return nil
 	default:

devtools/internal/interpreter/interpreter.go

@@ -191,6 +191,7 @@ const (
 	Paused         EvalResult = 3
 	Undoed         EvalResult = 4
 	Continued      EvalResult = 5
+	NextFrame      EvalResult = 6
 )
 
 func (i Instance) Eval(cmd string) (EvalResult, error) {
@@ -199,6 +200,8 @@ func (i Instance) Eval(cmd string) (EvalResult, error) {
 	if isHelpCommand(trimmedCmd) {
 		topic := strings.Trim(strings.TrimLeft(trimmedCmd, "help"), " ")
 		return HelpPrinted, i.printHelp(topic)
+	} else if trimmedCmd == "next" || trimmedCmd == "n" {
+		return NextFrame, nil
 	} else if trimmedCmd == "resume" || trimmedCmd == "r" {
 		return Resumed, nil
 	} else if trimmedCmd == "pause" || trimmedCmd == "p" {

devtools/scripting.go

@@ -70,6 +70,8 @@ func evaluateNextCommandFromTerminal() {
 		case interpreter.Undoed:
 			snapshot.Undo()
 			fmt.Println("Undoed last draw operation")
+		case interpreter.NextFrame:
+			resumeUntilNextFrame()
 		}
 
 		if result == interpreter.Continued {

devtools/update.go

@@ -17,7 +17,16 @@ func updateDevTools() {
 		}
 	}
 
+	if pauseOnNextFrame {
+		pauseGame()
+		pauseOnNextFrame = false
+	}
+
 	if gamePaused {
+		if key.Btnp(key.N) {
+			resumeUntilNextFrame()
+		}
+
 		inspector.Update()
 	}