SDL 2 Unit -x position

[DiCri]

Hi guys, why if i set render viewport with x = -1, the image i want to show is not shown?
Bad english.
If i write an image (width:100px) to x = 1, it is normal written, but not written if x was under 0 (ex -1).
How can i solve this? Please help

[molly]

That's probably clipping at work for you.

Instead of 'blitting' to position -1, you could consider blitting to position 0, but subtract the absolute minus value from the width that your are blitting.

[Carver413]

the viewport is used to define a drawing area within surface boundary's   not to move images, try SDL_BlitSurface

[DiCri]

That's probably clipping at work for you.

Instead of 'blitting' to position -1, you could consider blitting to position 0, but subtract the absolute minus value from the width that your are blitting.

I'm italian so i dont know the meaning of blitting and in the sdl2 tutorial i didn't found any example of PSDL_Surface. The only things there are in my gamealgoryrhm: SDL_RenderClear, SDL_RenderSetViewport, SDL_RenderCopy, SDL_RenderPresent.. nothing other (of sdl istructions)

[Carver413]

http://www.freepascal-meets-sdl.net/

[DiCri]

http://www.freepascal-meets-sdl.net/

No tutorial there. I learned sdl2 in that website

[Carver413]

I managed to get it working, I usually don't work with surfaces just opengl the texture I'm using is here
http://www.aaroncox.net/tutorials/2dtutorials/bat.bmp

Code: Pascal  [Select][+][-]

1. program Example1;
2.  
3. {$mode objfpc}{$H+}
4.  
5. uses
6.   {$IFDEF UNIX}{$IFDEF UseCThreads}
7.   cthreads,
8.   {$ENDIF}{$ENDIF}
9.   Classes,SDL2
10.   { you can add units after this };
11. Var
12.   Window:PSDL_Window;
13.   Renderer:PSDL_Renderer;
14.   Bat:PSDL_Surface;
15.   TexBat:PSDL_Texture;
16.   ImageRect:TSDL_Rect;
17.   Position:TSDL_Rect;
18. begin
19.   SDL_CreateWindowAndRenderer(640,480,0, @Window, @Renderer);
20.   SDL_RenderClear(Renderer);
21.   Bat:=SDL_LoadBMP('bat.bmp');
22.   SDL_SetColorKey( Bat, 1,SDL_MapRGB(Bat^.format, 255, 0, 255));
23.   TexBat:=SDL_CreateTextureFromSurface(Renderer,Bat);
24.   with ImageRect do begin
25.     x:=0;
26.     y:=0;
27.     w:=100;
28.     h:=200;
29.   end;
30.   with Position do begin
31.     x:=-30;
32.     y:=0;
33.     w:=100;
34.     h:=200;
35.   end;
36.   SDL_RenderCopy(Renderer,TexBat,@ImageRect,@Position);
37.   SDL_RenderPresent(Renderer);          
38.   SDL_Delay(3000);
39.   SDL_FreeSurface(Bat);
40.   SDL_DestroyTexture(TexBat);
41.   SDL_DestroyRenderer(Renderer);
42.   SDL_DestroyWindow(Window);
43.   SDL_Quit();
44.  
45. end.