madevgeny · September 29, 2024 18:14 · Nov 9, 2013
diff --git a/opengl3_hello.c b/opengl3_hello.c
@@ -0,0 +1,199 @@
+/*
+    Minimal SDL2 + OpenGL3 example.
+
+    Author: https://github.com/koute
+
+    This file is in the public domain; you can do whatever you want with it.
+    In case the concept of public domain doesn't exist in your jurisdiction
+    you can also use this code under the terms of Creative Commons CC0 license,
+    either version 1.0 or (at your option) any later version; for details see:
+        http://creativecommons.org/publicdomain/zero/1.0/
+
+    This software is distributed without any warranty whatsoever.
+
+    Compile and run with: gcc opengl3_hello.c `sdl2-config --libs --cflags` -lGL -Wall && ./a.out
+*/
+
+#define GL_GLEXT_PROTOTYPES
+
+#include <SDL.h>
+#include <SDL_opengl.h>
+
+#include <stdio.h>
+
+typedef float t_mat4x4[16];
+
+static inline void mat4x4_ortho( t_mat4x4 out, float left, float right, float bottom, float top, float znear, float zfar )
+{
+    #define T(a, b) (a * 4 + b)
+
+    out[T(0,0)] = 2.0f / (right - left);
+    out[T(0,1)] = 0.0f;
+    out[T(0,2)] = 0.0f;
+    out[T(0,3)] = 0.0f;
+
+    out[T(1,1)] = 2.0f / (top - bottom);
+    out[T(1,0)] = 0.0f;
+    out[T(1,2)] = 0.0f;
+    out[T(1,3)] = 0.0f;
+
+    out[T(2,2)] = -2.0f / (zfar - znear);
+    out[T(2,0)] = 0.0f;
+    out[T(2,1)] = 0.0f;
+    out[T(2,3)] = 0.0f;
+
+    out[T(3,0)] = -(right + left) / (right - left);
+    out[T(3,1)] = -(top + bottom) / (top - bottom);
+    out[T(3,2)] = -(zfar + znear) / (zfar - znear);
+    out[T(3,3)] = 1.0f;
+
+    #undef T
+}
+
+static const char * vertex_shader =
+    "#version 130\n"
+    "in vec2 i_position;\n"
+    "in vec4 i_color;\n"
+    "out vec4 v_color;\n"
+    "uniform mat4 u_projection_matrix;\n"
+    "void main() {\n"
+    "    v_color = i_color;\n"
+    "    gl_Position = u_projection_matrix * vec4( i_position, 0.0, 1.0 );\n"
+    "}\n";
+
+static const char * fragment_shader =
+    "#version 130\n"
+    "in vec4 v_color;\n"
+    "out vec4 o_color;\n"
+    "void main() {\n"
+    "    o_color = v_color;\n"
+    "}\n";
+
+typedef enum t_attrib_id
+{
+    attrib_position,
+    attrib_color
+} t_attrib_id;
+
+int main( int argc, char * argv[] )
+{
+    SDL_Init( SDL_INIT_VIDEO );
+    SDL_GL_SetAttribute( SDL_GL_DOUBLEBUFFER, 1 );
+    SDL_GL_SetAttribute( SDL_GL_ACCELERATED_VISUAL, 1 );
+    SDL_GL_SetAttribute( SDL_GL_RED_SIZE, 8 );
+    SDL_GL_SetAttribute( SDL_GL_GREEN_SIZE, 8 );
+    SDL_GL_SetAttribute( SDL_GL_BLUE_SIZE, 8 );
+    SDL_GL_SetAttribute( SDL_GL_ALPHA_SIZE, 8 );
+
+    SDL_GL_SetAttribute( SDL_GL_CONTEXT_MAJOR_VERSION, 3 );
+    SDL_GL_SetAttribute( SDL_GL_CONTEXT_MINOR_VERSION, 2 );
+    SDL_GL_SetAttribute( SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE );
+
+    static const int width = 800;
+    static const int height = 600;
+
+    SDL_Window * window = SDL_CreateWindow( "", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, width, height, SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN );
+    SDL_GLContext context = SDL_GL_CreateContext( window );
+
+    GLuint vs, fs, program;
+
+    vs = glCreateShader( GL_VERTEX_SHADER );
+    fs = glCreateShader( GL_FRAGMENT_SHADER );
+
+    int length = strlen( vertex_shader );
+    glShaderSource( vs, 1, ( const GLchar ** )&vertex_shader, &length );
+    glCompileShader( vs );
+
+    GLint status;
+    glGetShaderiv( vs, GL_COMPILE_STATUS, &status );
+    if( status == GL_FALSE )
+    {
+        fprintf( stderr, "vertex shader compilation failed\n" );
+        return 1;
+    }
+
+    length = strlen( fragment_shader );
+    glShaderSource( fs, 1, ( const GLchar ** )&fragment_shader, &length );
+    glCompileShader( fs );
+
+    glGetShaderiv( fs, GL_COMPILE_STATUS, &status );
+    if( status == GL_FALSE )
+    {
+        fprintf( stderr, "fragment shader compilation failed\n" );
+        return 1;
+    }
+
+    program = glCreateProgram();
+    glAttachShader( program, vs );
+    glAttachShader( program, fs );
+
+    glBindAttribLocation( program, attrib_position, "i_position" );
+    glBindAttribLocation( program, attrib_color, "i_color" );
+    glLinkProgram( program );
+
+    glUseProgram( program );
+
+    glDisable( GL_DEPTH_TEST );
+    glClearColor( 0.5, 0.0, 0.0, 0.0 );
+    glViewport( 0, 0, width, height );
+
+    GLuint vao, vbo;
+
+    glGenVertexArrays( 1, &vao );
+    glGenBuffers( 1, &vbo );
+    glBindVertexArray( vao );
+    glBindBuffer( GL_ARRAY_BUFFER, vbo );
+
+    glEnableVertexAttribArray( attrib_position );
+    glEnableVertexAttribArray( attrib_color );
+
+    glVertexAttribPointer( attrib_color, 4, GL_FLOAT, GL_FALSE, sizeof( float ) * 6, 0 );
+    glVertexAttribPointer( attrib_position, 2, GL_FLOAT, GL_FALSE, sizeof( float ) * 6, ( void * )(4 * sizeof(float)) );
+
+    const GLfloat g_vertex_buffer_data[] = {
+    /*  R, G, B, A, X, Y  */
+        1, 0, 0, 1, 0, 0,
+        0, 1, 0, 1, width, 0,
+        0, 0, 1, 1, width, height,
+
+        1, 0, 0, 1, 0, 0,
+        0, 0, 1, 1, width, height,
+        1, 1, 1, 1, 0, height
+    };
+
+    glBufferData( GL_ARRAY_BUFFER, sizeof( g_vertex_buffer_data ), g_vertex_buffer_data, GL_STATIC_DRAW );
+
+    t_mat4x4 projection_matrix;
+    mat4x4_ortho( projection_matrix, 0.0f, (float)width, (float)height, 0.0f, 0.0f, 100.0f );
+    glUniformMatrix4fv( glGetUniformLocation( program, "u_projection_matrix" ), 1, GL_FALSE, projection_matrix );
+
+    for( ;; )
+    {
+        glClear( GL_COLOR_BUFFER_BIT );
+
+        SDL_Event event;
+        while( SDL_PollEvent( &event ) )
+        {
+            switch( event.type )
+            {
+                case SDL_KEYUP:
+                    if( event.key.keysym.sym == SDLK_ESCAPE )
+                        return 0;
+                    break;
+            }
+        }
+
+        glBindVertexArray( vao );
+        glDrawArrays( GL_TRIANGLES, 0, 6 );
+
+        SDL_GL_SwapWindow( window );
+        SDL_Delay( 1 );
+    }
+
+    SDL_GL_DeleteContext( context );
+    SDL_DestroyWindow( window );
+    SDL_Quit();
+
+    return 0;
+}
+