add MovingBlock example

src/main/scala/introprog/examples/TestBlockGame.scala

@@ -1,12 +1,17 @@
 package introprog.examples
 
-/** Example of a simple BlockGame app with overridden callbacks to handle events
+/** Examples of a simple BlockGame app with overridden callbacks to handle events
   * See the documentation of BlockGame and the source code of TestBlockGame
   * for inspiration on how to inherit BlockGame to create your own block game.
   */
 object TestBlockGame:
   /** Create Game and start playing. */
-  def main(args: Array[String]): Unit = (new RandomBlocks).play()
+  def main(args: Array[String]): Unit = 
+    println("Press Enter to toggle random blocks. Close window to continue.")
+    (new RandomBlocks).play()
+    println("Opening MovingBlock. Press Ctrl+C to exit.")
+    (new MovingBlock).start()
+    println("MovingBlock has ended.")
 
   /** A class extending `introprog.BlockGame`, see source code. */
   class RandomBlocks extends introprog.BlockGame:
@@ -61,3 +66,57 @@ object TestBlockGame:
       showEnterMessage()
       gameLoop(stopWhen = state == GameOver)
       println("Goodbye!")
+
+  end RandomBlocks
+
+  class MovingBlock extends introprog.BlockGame(
+    title                 = "MovingBlock",
+    dim                   = (10,5),
+    blockSize             = 40,
+    background            = java.awt.Color.BLACK,
+    framesPerSecond       = 50,
+    messageAreaHeight     = 1,
+    messageAreaBackground =  java.awt.Color.DARK_GRAY
+  ):
+
+    var movesPerSecond: Double = 2
+
+    def millisBetweenMoves: Int = (1000 / movesPerSecond).round.toInt max 1
+
+    var _timestampLastMove: Long = System.currentTimeMillis
+
+    def timestampLastMove = _timestampLastMove
+
+    var x = 0
+    var y = 0
+
+    def move(): Unit = 
+      if x == dim._1 - 1 then 
+          x = -1
+          y += 1 
+      end if
+      x = x+1
+
+    def erase(): Unit = drawBlock(x, y, java.awt.Color.BLACK)
+
+    def draw(): Unit = drawBlock(x, y, java.awt.Color.CYAN)
+
+    def update(): Unit  =
+      if System.currentTimeMillis > _timestampLastMove + millisBetweenMoves then
+        move()
+        _timestampLastMove = System.currentTimeMillis()
+
+    var loopCounter: Int = 0
+
+    override def gameLoopAction(): Unit = 
+        erase()
+        update()
+        draw()
+        clearMessageArea()
+        drawTextInMessageArea(s"Loop number: $loopCounter", 1, 0, java.awt.Color.PINK, size = 30)
+        loopCounter += 1
+
+    final def start(): Unit = 
+        pixelWindow.show()  // möjliggör omstart även om fönstret stängts...
+        gameLoop(stopWhen = x == dim._1 - 1 && y == dim._2 - 1)
+  end MovingBlock