[fpc-pascal] OpenGL ES bitmap drawing

[Felipe Monteiro de Carvalho]

Hello,

Ok, so now I read a couple of tutorials more and I am trying to first
draw a simple rectangle, but still nothing shows. I have put
glGetError calls before every single call and yet nothing is returned
as wrong by OpenGL ES.

Here is my routine:

http://svn.freepascal.org/cgi-bin/viewvc.cgi/trunk/lcl/interfaces/customdrawn/customdrawnobject_android.inc?revision=33807&root=lazarus

procedure engine_draw_frame(engine: Pengine);
const
  vertices: array[0..7] of GLfloat =
    (0, 300,
     300, 300,
     0, 0,
     300, 0);
var
  lError: GLenum;
begin
   if engine^.display = nil then exit;

   LOGW('[engine_draw_frame]'); // <<<--- I see this tons of times

   // Set a projection which matches the screen size

   glMatrixMode(GL_PROJECTION);
   lError := glGetError();
   if lError <> GL_NO_ERROR then LOGW(PChar('[engine_draw_frame] 1
Error='+IntToStr(Integer(lError))));
   glLoadIdentity();
   lError := glGetError();
   if lError <> GL_NO_ERROR then LOGW(PChar('[engine_draw_frame] 2
Error='+IntToStr(Integer(lError))));
   glOrthof(0, engine^.width, engine^.height, 0, 0, 1);
   lError := glGetError();
   if lError <> GL_NO_ERROR then LOGW(PChar('[engine_draw_frame] 3
Error='+IntToStr(Integer(lError))));
   glMatrixMode(GL_MODELVIEW);
   lError := glGetError();
   if lError <> GL_NO_ERROR then LOGW(PChar('[engine_draw_frame] 4
Error='+IntToStr(Integer(lError))));
   glLoadIdentity();
   lError := glGetError();
   if lError <> GL_NO_ERROR then LOGW(PChar('[engine_draw_frame] 5
Error='+IntToStr(Integer(lError))));

   // Displacement trick for exact pixelization
   glTranslatef(0.357, 0.357, 0);
   lError := glGetError();
   if lError <> GL_NO_ERROR then LOGW(PChar('[engine_draw_frame] 6
Error='+IntToStr(Integer(lError))));

   // Turn on 2D mode

   glDisable(GL_DEPTH_TEST);
   lError := glGetError();
   if lError <> GL_NO_ERROR then LOGW(PChar('[engine_draw_frame] 7
Error='+IntToStr(Integer(lError))));
   glClear(GL_COLOR_BUFFER_BIT);
   lError := glGetError();
   if lError <> GL_NO_ERROR then LOGW(PChar('[engine_draw_frame] 8
Error='+IntToStr(Integer(lError))));

   // Draw a square
   glVertexPointer(2, GL_FLOAT, 0, @vertices[0]);
   lError := glGetError();
   if lError <> GL_NO_ERROR then LOGW(PChar('[engine_draw_frame] 9
Error='+IntToStr(Integer(lError))));
   glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
   lError := glGetError();
   if lError <> GL_NO_ERROR then LOGW(PChar('[engine_draw_frame] 10
Error='+IntToStr(Integer(lError))));

   eglSwapBuffers(engine^.display, engine^.surface);
   lError := glGetError();
   if lError <> GL_NO_ERROR then LOGW(PChar('[engine_draw_frame] 11
Error='+IntToStr(Integer(lError))));
end;

-- 
Felipe Monteiro de Carvalho