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Why SDL_RenderDrawPoints() doesn't work?

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Edson:
I'm new on SDL2 and maybe I'm doing something wrong, but, Can someone tell me why this code works perfectly :


--- Code: Pascal  [+][-]window.onload = function(){var x1 = document.getElementById("main_content_section"); if (x1) { var x = document.getElementsByClassName("geshi");for (var i = 0; i < x.length; i++) { x[i].style.maxHeight='none'; x[i].style.height = Math.min(x[i].clientHeight+15,306)+'px'; x[i].style.resize = "vertical";}};} ---    for i := 0 to nPnts-1 do begin    SDL_RenderDrawPoint( sdlRenderer, sdlPoints1[i]^.x, sdlPoints1[i]^.y);  end; 
And this fails  >:(:


--- Code: Pascal  [+][-]window.onload = function(){var x1 = document.getElementById("main_content_section"); if (x1) { var x = document.getElementsByClassName("geshi");for (var i = 0; i < x.length; i++) { x[i].style.maxHeight='none'; x[i].style.height = Math.min(x[i].clientHeight+15,306)+'px'; x[i].style.resize = "vertical";}};} ---  SDL_RenderDrawPoints( sdlRenderer, sdlPoints1[0], nPnts); 
The last code just draw some points in ramdom locations of a line (apparently).

I'm using Lazarus 1.8.0 - FPC 3.0.4 in Windows 7.

Paul_:
"It fails" .. does not define the problem and also without rest of code and variables related to SDL_RenderDrawPoints( sdlRenderer, sdlPoints1[0], nPnts) it's hard to help.

But probably you don't have defined sdlPoints1 in right way.

Edson:

--- Quote from: Paul_ on March 18, 2018, 08:53:31 pm ---"It fails" .. does not define the problem and also without rest of code and variables related to SDL_RenderDrawPoints( sdlRenderer, sdlPoints1[0], nPnts) it's hard to help.

But probably you don't have defined sdlPoints1 in right way.

--- End quote ---

Hi.  I have a test project.

It needs SDL2.dll to compile.

Paul_:
Original tutorial code (https://www.freepascal-meets-sdl.net/chapter-5-drawing-primitives/) shows some points but maybe only 10 instead of 500? :)

EDIT: this works for me:


--- Code: Pascal  [+][-]window.onload = function(){var x1 = document.getElementById("main_content_section"); if (x1) { var x = document.getElementsByClassName("geshi");for (var i = 0; i < x.length; i++) { x[i].style.maxHeight='none'; x[i].style.height = Math.min(x[i].clientHeight+15,306)+'px'; x[i].style.resize = "vertical";}};} ---var   sdlPoints1 : array[0..499] of TSDL_Point;begin  for i := 0 to 499 do begin    sdlPoints1[i].x := x + i;    sdlPoints1[i].y := y + i;  end;   SDL_RenderDrawPoints(sdlRenderer, sdlPoints1, 500);end;
It's bit weird because function variable parameter is defined as "points: PSDL_Point"

--- Code: Pascal  [+][-]window.onload = function(){var x1 = document.getElementById("main_content_section"); if (x1) { var x = document.getElementsByClassName("geshi");for (var i = 0; i < x.length; i++) { x[i].style.maxHeight='none'; x[i].style.height = Math.min(x[i].clientHeight+15,306)+'px'; x[i].style.resize = "vertical";}};} ---  PSDL_Point = ^TSDL_Point;  TSDL_Point = record    x: SInt32;    y: SInt32;  end; function SDL_RenderDrawPoints(renderer: PSDL_Renderer; points: PSDL_Point; count: SInt32): SInt32 cdecl; external SDL_LibName {$IFDEF DELPHI} {$IFDEF MACOS} name '_SDL_RenderDrawPoints' {$ENDIF} {$ENDIF};

Edson:

--- Quote from: Paul_ on March 19, 2018, 10:44:06 am ---Original tutorial code (https://www.freepascal-meets-sdl.net/chapter-5-drawing-primitives/) shows some points but maybe only 10 instead of 500? :)

EDIT: this works for me:


--- Code: Pascal  [+][-]window.onload = function(){var x1 = document.getElementById("main_content_section"); if (x1) { var x = document.getElementsByClassName("geshi");for (var i = 0; i < x.length; i++) { x[i].style.maxHeight='none'; x[i].style.height = Math.min(x[i].clientHeight+15,306)+'px'; x[i].style.resize = "vertical";}};} ---var   sdlPoints1 : array[0..499] of TSDL_Point;begin  for i := 0 to 499 do begin    sdlPoints1[i].x := x + i;    sdlPoints1[i].y := y + i;  end;   SDL_RenderDrawPoints(sdlRenderer, sdlPoints1, 500);end;
--- End quote ---

Yes I have been following that tutorial. Maybe it has an error and the correct form is using TSDL_Point. Considering SDL2 come from C language, it's possible some strange behaviour in Pascal.

It works for me too, using TSDL_Point. Thanks for helping.

The bad news is that using SDL_RenderDrawPoints() is as slow as using SDL_RenderDrawPoint() for each point.

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