* * *

Author Topic: how to delete the canvas rectangle  (Read 6253 times)

shs

  • Full Member
  • ***
  • Posts: 201
Re: how to delete the canvas rectangle
« Reply #105 on: October 04, 2017, 07:52:39 am »
okay thank you

is there any other of writing this code by the way?

Code: Pascal  [Select]
  1. case direction of
  2.         1,3,4: if key=vk_left then
  3.            begin
  4.            direction:=1;
  5.            end;
  6.         2: if key=vk_left then
  7.            begin
  8.            direction:=2;
  9.            end;
  10.       end;
  11.  
  12.       case direction of
  13.         2,3,4: if key=vk_right then
  14.            begin
  15.            direction:=2;
  16.            end;
  17.         1: if key=vk_right then
  18.            begin
  19.            direction:=1;
  20.            end;
  21.       end;
  22.  
  23.       case direction of
  24.         1,2,3: if key=vk_up then
  25.            begin
  26.            direction:=3;
  27.            end;
  28.         4: if key=vk_up then
  29.            begin
  30.            direction:=4;
  31.            end;
  32.       end;
  33.  
  34.       case direction of
  35.         1,2,4: if key=vk_down then
  36.            begin
  37.            direction:=4;
  38.            end;
  39.         3: if key=vk_down then
  40.            begin
  41.            direction:=3;
  42.            end;
  43.       end;              

Handoko

  • Hero Member
  • *****
  • Posts: 1632
  • My goal: build my own game engine using Lazarus
Re: how to delete the canvas rectangle
« Reply #106 on: October 04, 2017, 08:13:28 am »
Try this:

Code: Pascal  [Select]
  1. case key of
  2.   vk_left:  if not(direction = 2) then direction := 1;
  3.   vk_right: if not(direction = 1) then direction := 2;
  4.   vk_up:    if not(direction = 4) then direction := 3;
  5.   vk_down:  if not(direction = 3) then direction := 4;
  6. end;

taazz

  • Hero Member
  • *****
  • Posts: 4340
Re: how to delete the canvas rectangle
« Reply #107 on: October 04, 2017, 09:12:10 am »
is there any other of writing this code by the way?

Code: Pascal  [Select]
  1. case direction of
  2.         1,3,4: if key=vk_left then
  3.            begin
  4.            direction:=1;
  5.            end;
  6.         2: if key=vk_left then
  7.            begin
  8.            direction:=2;
  9.            end;
  10.       end;
  11.  
  12.       case direction of
  13.         2,3,4: if key=vk_right then
  14.            begin
  15.            direction:=2;
  16.            end;
  17.         1: if key=vk_right then
  18.            begin
  19.            direction:=1;
  20.            end;
  21.       end;
  22.  
  23.       case direction of
  24.         1,2,3: if key=vk_up then
  25.            begin
  26.            direction:=3;
  27.            end;
  28.         4: if key=vk_up then
  29.            begin
  30.            direction:=4;
  31.            end;
  32.       end;
  33.  
  34.       case direction of
  35.         1,2,4: if key=vk_down then
  36.            begin
  37.            direction:=4;
  38.            end;
  39.         3: if key=vk_down then
  40.            begin
  41.            direction:=3;
  42.            end;
  43.       end;              

Code: Pascal  [Select]
  1. Function GetDirection(aKey, aDirection:integer):Integer;inline;
  2.  
  3. const  cDirection : array[VK_LEFT..VK_DOWN, 1..4] of integer = ((1,2,1,1),  //vk_left
  4.                                                                 (3,3,3,4),  //vk_up
  5.                                                                 (1,2,2,2),  //vk_right
  6.                                                                 (4,4,3,4)   //vk_down
  7.                                                                );
  8. begin
  9.   Result := cDirection[aKey,aDirection];
  10. end;
  11.  
  12.  
although I prefare Handoko's code it is easier to understand in a year or two.
Good judgement is the result of experience … Experience is the result of bad judgement.

OS : Windows 7 64 bit
Laz: Lazarus 1.4.4 FPC 2.6.4 i386-win32-win32/win64

bytebites

  • Full Member
  • ***
  • Posts: 116
Re: how to delete the canvas rectangle
« Reply #108 on: October 04, 2017, 10:00:47 am »
Or remove the intermediate variable direction and

Code: Pascal  [Select]
  1.  case key of
  2.    vk_left:
  3.     if xdirection=0 then begin
  4.      xdirection:=-1;
  5.      ydirection:=0;
  6.     end;
  7.  
  8. etc..
  9.            

shs

  • Full Member
  • ***
  • Posts: 201
Re: how to delete the canvas rectangle
« Reply #109 on: October 04, 2017, 10:22:00 am »
thank you guys it works really well.

but when press 2 keys really quickly it doesn't work.

for example, the snake is in direction 1 (left) but if i press key down and then key right very quickly, the direction becomes 2 (right) instead of becoming 4 (down) and then 2(right)

shs

  • Full Member
  • ***
  • Posts: 201
Re: how to delete the canvas rectangle
« Reply #110 on: October 06, 2017, 09:43:30 am »
i am trying to make the restart button when the game is finished but how can i make the snake length to be 1 again? how can i delete all the tails?

Handoko

  • Hero Member
  • *****
  • Posts: 1632
  • My goal: build my own game engine using Lazarus
Re: how to delete the canvas rectangle
« Reply #111 on: October 06, 2017, 01:24:10 pm »
The pseudocode should be:

For each item in SnakeBody do begin
   Set SnakeSegment to point to the memory location
   Free the SnakeSegment
end
Call SnakeBody Clear


https://www.freepascal.org/docs-html/rtl/classes/tlist.clear.html

And don't forget to call ClearWorld to clear the game's world.
« Last Edit: October 06, 2017, 01:27:56 pm by Handoko »

shs

  • Full Member
  • ***
  • Posts: 201
Re: how to delete the canvas rectangle
« Reply #112 on: October 06, 2017, 01:49:21 pm »
oh okay thank you!

thank you guys it works really well.

but when press 2 keys really quickly it doesn't work.

for example, the snake is in direction 1 (left) but if i press key down and then key right very quickly, the direction becomes 2 (right) instead of becoming 4 (down) and then 2(right)

can you help me with this please?

bytebites

  • Full Member
  • ***
  • Posts: 116
Re: how to delete the canvas rectangle
« Reply #113 on: October 06, 2017, 05:54:14 pm »
See previous page.

Handoko

  • Hero Member
  • *****
  • Posts: 1632
  • My goal: build my own game engine using Lazarus
Re: how to delete the canvas rectangle
« Reply #114 on: October 06, 2017, 07:23:01 pm »
@shs

You misunderstand how the game works. You give the snake 1 move per the time you give, in your case it is 10 moves per second (or 1 move in 1/10 second).

So no matter how quickly the player press the keyboards, s/he only can move 10 tiles per second. If there are several keys in 1/10 second, only the last one counts.

You can modify the logic of the game, but I don't think that would be a good idea. For example, if I quickly and repeatably pressing forward, then the snake will move faster than it should be. If this is REALLY what you want, simple call the Time1Timer after the keypressing event.

shs

  • Full Member
  • ***
  • Posts: 201
Re: how to delete the canvas rectangle
« Reply #115 on: October 07, 2017, 03:01:27 am »
yes but you know how direction changes when i press the different keys right?

Code: Pascal  [Select]
  1. case key of
  2.   vk_left:  if not(direction = 2) then direction := 1;
  3.   vk_right: if not(direction = 1) then direction := 2;
  4.   vk_up:    if not(direction = 4) then direction := 3;
  5.   vk_down:  if not(direction = 3) then direction := 4;
  6. end;

and this is the code i am using

so let's say the direction is 1 so it's going left. And if i press right it won't work because it only works when the direction is not 1. But if change directions really quickly bu pressing up key and right key, it just goes left instead of going up and left.

And i think this is because the direction is changed but the snake didn't move because i pressed so quickly

so it's  vk_left --> vk_up --> vk_right

direction 1 --> direction 3 --> direction 2

so the direction was changed without any problems but the snake just went to right from left without going up.
so is there any way i can fix this problem? if my explanation is not clear please compile the game and see what happens if you press two keys really quickly



Handoko

  • Hero Member
  • *****
  • Posts: 1632
  • My goal: build my own game engine using Lazarus
Re: how to delete the canvas rectangle
« Reply #116 on: October 07, 2017, 03:42:46 am »
I fully understood what you're saying but you didn't understand what I said.

These are the key points:

- You use Timer as the main game loop and you set the interval = 100.
- Your FormKeyDown event only set the direction without calling update.
- You update the snake movement in the Timer event only.

shs

  • Full Member
  • ***
  • Posts: 201
Re: how to delete the canvas rectangle
« Reply #117 on: October 07, 2017, 03:55:59 am »
so what should i do to fix these problems?

Handoko

  • Hero Member
  • *****
  • Posts: 1632
  • My goal: build my own game engine using Lazarus
Re: how to delete the canvas rectangle
« Reply #118 on: October 07, 2017, 04:00:20 am »
I've already provided you the solution, you didn't read it?
http://forum.lazarus.freepascal.org/index.php/topic,38136.msg261825.html#msg261825

shs

  • Full Member
  • ***
  • Posts: 201
Re: how to delete the canvas rectangle
« Reply #119 on: October 07, 2017, 04:04:00 am »
oh i did read it but i don't get it

 

Recent

Get Lazarus at SourceForge.net. Fast, secure and Free Open Source software downloads Open Hub project report for Lazarus