Ponx - High DPI aware PONG style game for Linux

[SilverWarior]

The reason for this to simplify the programming of course. I'm afraid letting the ball cross that line may cause a host of new programming headaches. If I had tried that apporoach I'd probably still be sweating over special cases and have nothing to show. On the other hand it may not be so bad and improved gameplay is priceless.

If you start using relative distance from the center of the ball against center of the playfield I believe you could perhaps even simplify your programming quite a bit.

First you need to make sure that your playfield coordinates are position so that the position 0:0 will be in the center of your playfield. I'm guessing you are now working with Window coordinates. So you would make this transformation by simply subtracting half of the width of your playfield window width from X coordinate and half of your playfield window height from Y coordinate.

For instance in my quick mock up I use mouse for moving the ball so I transform my mouse coordinates to PlayfIeld coordinates using

PlayfieldX := X-(PaintBox1.ClientWidth div 2);
PlayfieldY := Y-(PaintBox1.ClientHeight div 2);

I then pass this Playfield coordinates to my Collision detection procedure that looks like this

procedure TForm5.CheckCollision(X,Y: Integer);begin
  //Reset collisions
  TopBorderCollision := False;
  BottomBorderCollision := False;
  LeftBorderCollision := False;
  RightBorderCollision := False;


  //Check for top/bottom collisions
  if Abs(Y) > ((PaintBox1.ClientHeight div 2)-BorderThickenss) then
  begin
    if Y < 0 then
    begin
      TopBorderCollision := True;
    end
    else BottomBorderCollision := True;
  end;


  //Check for left/right border collisions
  if Abs(X) > ((PaintBox1.ClientWidth div 2)-BorderThickenss) then
  begin
    if X < 0 then
    begin
      LeftBorderCollision := True;
    end
    else RightBorderCollision := True;
  end;


  //Check to see if ball is in slowdown area then reduce its speed
  if ABS(X) > ((PaintBox1.ClientWidth div 2)-BorderThickenss-SlowdownAreaWidth) then BallSpeed := 20
  //else keep it moving at full speed
  else BallSpeed := 20;


  //Check paddle collision
  if X > 0 then
  //Player padle collision
  begin
    //Simple collision checling against paddle using X coordinate of the ball
    //Ball Y position si within player paddle area
    if (Y >= PlayerPaddle.Top) and (Y <= (PlayerPaddle.Bottom)) then
    begin
      if ABS(X) > ((PaintBox1.ClientWidth div 2)-PlayerPaddle.Width) then //Bounce the ball from the paddle by multiplying X speed by -1;
    end
    //Because the ball Y position is not within the PlayerPaddle area it means we will have to check collision
    //against PlayePaddle corners instead
    else
    begin
      //Top corner
      if System.Math.Hypot(ABS(X-PlayerPaddle.Right),ABS(Y-PlayerPaddle.Top)) < BallDiameter then
      begin
        //Bounce ball from top paddle corner. It would probably result in great change of the ball trajectory angle
      end;
      //Bottom corner
      if System.Math.Hypot(ABS(X-PlayerPaddle.Right),ABS(Y-PlayerPaddle.Bottom)) < BallDiameter then
      begin
        //Bounce ball from top paddle corner. It would probably result in great change of the ball trajectory angle
      end;
    end;
  end;
end;

I hope my code mock up can give you good enough idea of how to work with such approach and how easy it actually is. I tried to comment it as good as I can so ti can be even more understandable.
I'm guessing you will have to make some changes so that it will work with your data structures