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
@@ -23,6 +24,8 @@ func pauseGame() {
 		helpShown = true
 		fmt.Println("\nPress right mouse button in the game window to show the toolbar.")
 		fmt.Println("Press P in the game window to take screenshot.")
+		fmt.Println("Press N in the game window to go to next frame.")
+		fmt.Println("Press F12 in the game window to resume the game and exit devtools inspector.")
 	}
 	gamePaused = true
 	timeWhenPaused = pi.Time
@@ -35,3 +38,12 @@ 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

@@ -125,7 +125,7 @@ func ensureNameDoesNotClashWithImportedPackages(name string) error {
 	return nil
 }
 
-var allCommandNames = []string{"h", "help", "p", "pause", "r", "resume", "u", "undo"}
+var allCommandNames = []string{"h", "help", "p", "pause", "r", "resume", "u", "undo", "n", "next"}
 
 func ensureNameDoesNotClashWithCommandNames(name string) error {
 	for _, cmd := range allCommandNames {
@@ -185,12 +185,13 @@ func ExportType[T any](i Instance) error {
 type EvalResult int
 
 const (
-	HelpPrinted    EvalResult = 0
-	GoCodeExecuted EvalResult = 1
-	Resumed        EvalResult = 2
-	Paused         EvalResult = 3
-	Undoed         EvalResult = 4
-	Continued      EvalResult = 5
+	HelpPrinted        EvalResult = 0
+	GoCodeExecuted     EvalResult = 1
+	Resumed            EvalResult = 2
+	Paused             EvalResult = 3
+	Undoed             EvalResult = 4
+	Continued          EvalResult = 5
+	NextFrameRequested 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 NextFrameRequested, nil
 	} else if trimmedCmd == "resume" || trimmedCmd == "r" {
 		return Resumed, nil
 	} else if trimmedCmd == "pause" || trimmedCmd == "p" {

devtools/internal/interpreter/interpreter_test.go

@@ -85,6 +85,22 @@ func TestEval(t *testing.T) {
 				code:           "resume ",
 				expectedResult: interpreter.Resumed,
 			},
+			"next": {
+				code:           "next",
+				expectedResult: interpreter.NextFrameRequested,
+			},
+			"next with space in the beginning": {
+				code:           " next",
+				expectedResult: interpreter.NextFrameRequested,
+			},
+			"next with space in the end": {
+				code:           "next ",
+				expectedResult: interpreter.NextFrameRequested,
+			},
+			"n": {
+				code:           "n",
+				expectedResult: interpreter.NextFrameRequested,
+			},
 		}
 		for name, testCase := range tests {
 			t.Run(name, func(t *testing.T) {
@@ -273,7 +289,7 @@ func TestExport(t *testing.T) {
 	})
 
 	t.Run("should return error when name clashes with command name", func(t *testing.T) {
-		var allCommandNames = []string{"h", "help", "p", "pause", "r", "resume", "u", "undo"}
+		var allCommandNames = []string{"h", "help", "p", "pause", "r", "resume", "u", "undo", "n", "next"}
 
 		for _, cmd := range allCommandNames {
 			t.Run(cmd, func(t *testing.T) {

devtools/scripting.go

@@ -70,6 +70,8 @@ func evaluateNextCommandFromTerminal() {
 		case interpreter.Undoed:
 			snapshot.Undo()
 			fmt.Println("Undoed last draw operation")
+		case interpreter.NextFrameRequested:
+			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()
 	}