Problem with scrolling image
lazarus / 39-Graphics

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ITomi · 2021-01-19 09:14

Hello everybody!

I'm still new here and in the world of Lazarus.
I started to develop a game, in which there is a larger bitmap on the
Form1. You can move this bitmap with the arrow buttons.
But I have a big problem with this: I can't delete the graphical
elements from the previous places, and so these pull a strip as you
can see on the attached image.
How can I delete the graphical components from the previouis places?
The invalidate; command doesn't work with it.

Pieces from my code:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TForm1.FormCreate(Sender: TObject);begin  width:=Screen.width; 
height:=Screen.height;  palyakep:=TBitmap.Create; 
palyakep.SetSize(width*2,height*2); 
palyakep.canvas.brush.color:=clblue; 
palyakep.canvas.fillrect(0,0,width*2,height*2);(...) 
palyafrissito:=TTimer.Create(nil);  palyafrissito.interval:=10; 
palyafrissito.ontimer:=@palyafrissites; procedure
TForm1.palyafrissites(Sender: TObject);begin//figures moving...with
palyakep.canvas do invalidate; procedure TForm1.FormPaint(Sender:
TObject);var puffalkepe: byte;  i: integer;begin 
canvas.draw(palyakepx,palyakepy,palyakep);  for i:=0 to puffancsdb-1
do  begin    puffalkepe:=trunc(puffancs[i].iranya*8/360);    if
puffalkepe>7 then puffalkepe:=0;    palyakep.canvas.draw(puffancs[i].x
hely,puffancs[i].yhely,puffancskep[puffalkepe]);  end;end;

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Handoko · 2021-01-19 13:37

Hello ITomi,
Welcome to the forum.

Glad to find someone who is interested to develop games here. I want
to provide you a detailed answer, unfortunately I'm a bit busy at the
moment.

You can download some simple demos, especially Pong Game, Game Map
Editor, Simple Animation, Bullet and Asteroid Collision Detection,
Moving Circles, Move a Shape With a Mouse on the Graphics category in
the link below. Those should provide you some basic knowledge how to
create games using Lazarus:
https://wiki.freepascal.org/Portal:HowTo_Demos

Have fun!

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ITomi · 2021-01-20 12:27

Hello and thanks, Handoko!
I didn't know that "HowTo Demos" portal yet, but I will look it.
Till this moment, I have only one small game written in Lazarus, and
it can be found on my website:
http://www.programozzunk.ucoz.hu/lazjatekok.html
This is a simple space shooter: "Space defender".
But now I would like make a real time strategy game, therefore I
should know the technique to how can I draw images on a canvas bigger
than canvas of TForm1.

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Handoko · 2021-01-21 02:57

Your Space Defender looks good. Please consider to showcase it on the
wiki page:
https://wiki.freepascal.org/Projects_using_Lazarus_-_Games

Did you draw the graphics yourself?

For the original issue, I remember there was a similar case. Maybe
this thread can be useful to you:
https://forum.lazarus.freepascal.org/index.php/topic,43985.msg308825.h
tml#msg308825

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ITomi · 2021-01-21 08:18

Thank you, Handoko! 
The graphics origins from an old good shoot'em up game called
"Tyrian".
And thanks for your link! It seems to be similar problem like mine. I
look closely it.