Moving the object on the window

Question

Hello, I´d like to program some small interactive application. Just something where you cann move with the common circle as it would be in 2D game. I made it, but there is an isue with the moving itself. I want the circle to move continuously but when I press the left, right, up or down key and hold it, the circle makes one move, then it stopes and then it moves again but much faster and still it accelerates.

Here is the id for that application where you can find the source code too.

GWQ067

It would be great if there is anyone who could help.

Answer 1

2 points:

1] To get the best control of moving objects use Shapes.Move rather than Shapes.Animate.  To do this you will need to keep track of the shapoe coordinates at each screen refresh.

2] There is an auto repeat delay on button presses imposed by the OS.  To get smooth movement we need to detect key down and key up.  Between these 2 evenets the key is pressed.  The first movement you see is the initial key press and the much faster movement after a short delay is the auto-repeat kicking in and registering lots of key-down events in quick succession.

Simple example:

'Initialisation Window
gw = 800
gh = 600
GraphicsWindow.Width = gw
GraphicsWindow.Height = gh

'Initialise Key events
GraphicsWindow.KeyDown = OnKeyDown
GraphicsWindow.KeyUp = OnKeyUp
keyLeft = 0
keyRight = 0
keyUp = 0
keyDown = 0

'Initialise ball
ball = Shapes.AddEllipse(50,50)
ballX = 100
ballY = 100
speed = 3
Shapes.Move(ball,ballX-25,ballY-25)

'Main loop - just move the ball
While ("True")
  processKey()
  Shapes.Move(ball,ballX-25,ballY-25)
  Program.Delay(10)
EndWhile

'Key press event subroutines
'A separate Down and Up is checked for each key, this tells us the state for any key
'And isn't affected by auto-repeat delays for keys
Sub OnKeyDown
  lastKey = GraphicsWindow.LastKey
  If (lastKey = "Left") Then
    keyLeft = 1
  ElseIf (lastKey = "Right") Then
    keyRight = 1
  ElseIf (lastKey = "Up") Then
    keyUp = 1
  ElseIf (lastKey = "Down") Then
    keyDown = 1
  EndIf 
EndSub

Sub OnKeyUp
  lastKey = GraphicsWindow.LastKey
  If (lastKey = "Left") Then
    keyLeft = 0
  ElseIf (lastKey = "Right") Then
    keyRight = 0
  ElseIf (lastKey = "Up") Then
    keyUp = 0
  ElseIf (lastKey = "Down") Then
    keyDown = 0
  EndIf 
EndSub

Sub processKey
  'Move object - note it can move diagonally if 2 keys are pressed
  If (keyLeft = 1) Then
    ballX = ballX-speed
  EndIf 
  If (keyRight = 1) Then
    ballX = ballX+speed
  EndIf 
  If (keyUp = 1) Then
    ballY = ballY-speed
  EndIf 
  If (keyDown = 1) Then
    ballY = ballY+speed
  EndIf
  
  'Check for hitting edges
  If (ballX < 0) Then
    ballX = ballX+gw
  EndIf
  If (ballX > gw) Then
    ballX = ballX-gw
  EndIf
  If (ballY < 0) Then
    ballY = ballY+gh
  EndIf
  If (ballY > gh) Then
    ballY = ballY-gh
  EndIf
EndSub