test opengl

opengl triangle.ec

//https://en.wikibooks.org/wiki/OpenGL_Programming/Modern_OpenGL_Introduction
//https://gitlab.com/wikibooks-opengl/modern-tutorials/blob/master/tut01_intro/triangle.cpp
import "ecere"
#include "gl_core_3_3.h"

GLuint program;
GLint attribute_coord2d;


GLfloat triangle_vertices[] = {
	    0.0f,  0.8f,
	   -0.8f, -0.8f,
	    0.8f, -0.8f
	};

bool init_resources(void)
{

   // Vertex shader
   const char *vs_source=
                           "#version 120\n"
                           "attribute vec2 coord2d;"
                           "void main(void) {"
                           " gl_Position = vec4(coord2d, 0.0, 1.0);"
                           "}";


   GLuint vs = glCreateShader(GL_VERTEX_SHADER);

   // Fragment Shader
   GLuint fs = glCreateShader(GL_FRAGMENT_SHADER);
   const char *fs_source =
                           "#version 120\n"
                           "void main(void) {"
                           "  gl_FragColor[0] = 0.0;"
                           "  gl_FragColor[1] = 0.0;"
                           "  gl_FragColor[2] = 1.0;"
                           "}";
   // attributes
  const char* attribute_name = "coord2d";

  //
   GLint compile_ok = GL_FALSE;
   GLint link_ok = GL_FALSE;


   glShaderSource(vs, 1, &vs_source, null);
   glCompileShader(vs);
   glGetShaderiv(vs, GL_COMPILE_STATUS, &compile_ok);
   if (!compile_ok) {
      PrintLn("Error in vertex shader");
      return false;
   }


   glShaderSource(fs, 1, &fs_source, null);
   glCompileShader(fs);
   glGetShaderiv(fs, GL_COMPILE_STATUS, &compile_ok);
   if(!compile_ok){
         PrintLn("Error in fragment shader");
         return 0;
   }

   program = glCreateProgram();
   glAttachShader(program, vs);
   glAttachShader(program, fs);
   glLinkProgram(program);
   glGetProgramiv(program, GL_LINK_STATUS, &link_ok);
   if (!link_ok) {
     PrintLn("glLinkProgram:");
     return 0;
   }


  attribute_coord2d = glGetAttribLocation(program, attribute_name);
  if (attribute_coord2d == -1) {
    PrintLn("Could not bind attribute %s\n", attribute_name);
    return 0;
  }

   PrintLn("init_complete");
   return true;
}

void free_resources()
{
   glDeleteProgram(program);
}

class Example1 : Window
{
   caption = $"OpenGL Example Triangle";
   background = formColor;
   borderStyle = sizable;
   hasMaximize = true;
   hasMinimize = true;
   hasClose = true;
   clientSize = { 632, 438 };
   displayDriver = "OpenGL";

   bool OnLoadGraphics()
   {
      ogl_LoadFunctions();
      if (!init_resources())
      {
		return false;
      }
      return true;
   }

   void OnRedraw(Surface surface)
   {
      GLint prevProgram;
     glGetIntegerv(GL_CURRENT_PROGRAM, (GLint *)&prevProgram);
      GLfloat triangle_vertices[] = {
      0.0f,  0.8f,
      -0.8f, -0.8f,
      0.8f, -0.8f
      };

   glClearColor(1.0, 1.0, 1.0, 1.0);
   glClear(GL_COLOR_BUFFER_BIT);

   glUseProgram(program);
   glEnableVertexAttribArray(attribute_coord2d);

   /* Describe our vertices array to OpenGL (it can't guess its format automatically) */
   glVertexAttribPointer(
       attribute_coord2d, // attribute
       2,                 // number of elements per vertex, here (x,y)
       GL_FLOAT,          // the type of each element
       GL_FALSE,          // take our values as-is
       0,                 // no extra data between each position
       triangle_vertices  // pointer to the C array
     );

   /* Push each element in buffer_vertices to the vertex shader */
   glDrawArrays(GL_TRIANGLES, 0, 3);

   glDisableVertexAttribArray(attribute_coord2d);
         // Restore normal Ecere program
      glUseProgram( prevProgram );
   //glutSwapBuffers();
   }

   bool OnClose(bool parentClosing)
   {
      free_resources();
      return true;
   }
}

Example1 example1 {};