Programming • Re: Can OpenGL be mixed with other game libraries

Code:

gcc test.c -o test `pkg-config --cflags --libs gl allegro-5 allegro_primitives-5 allegro_main-5 ` -lm

Code:

#define ALLEGRO_UNSTABLE#include <stdio.h>#include <math.h>#include <allegro5/allegro.h>#include <allegro5/allegro_opengl.h>#include <allegro5/allegro_primitives.h>#include <stdio.h>#include <stdarg.h>#ifdef ALLEGRO_ANDROID   #include "allegro5/allegro_android.h"#endifvoid init_platform_specific(void);void abort_example(char const *format, ...);void open_log(void);void open_log_monospace(void);void close_log(bool wait_for_user);void log_printf(char const *format, ...);void init_platform_specific(void){#ifdef ALLEGRO_ANDROID   al_install_touch_input();   al_android_set_apk_file_interface();#endif}#ifdef ALLEGRO_POPUP_EXAMPLES#include "allegro5/allegro_native_dialog.h"ALLEGRO_TEXTLOG *textlog = NULL;void abort_example(char const *format, ...){   char str[1024];   va_list args;   ALLEGRO_DISPLAY *display;   va_start(args, format);   vsnprintf(str, sizeof str, format, args);   va_end(args);   if (al_init_native_dialog_addon()) {      display = al_is_system_installed() ? al_get_current_display() : NULL;      al_show_native_message_box(display, "Error", "Cannot run example", str, NULL, 0);   }   else {      fprintf(stderr, "%s", str);   }   exit(1);}void open_log(void){   if (al_init_native_dialog_addon()) {      textlog = al_open_native_text_log("Log", 0);   }}void open_log_monospace(void){   if (al_init_native_dialog_addon()) {      textlog = al_open_native_text_log("Log", ALLEGRO_TEXTLOG_MONOSPACE);   }}void close_log(bool wait_for_user){   if (textlog && wait_for_user) {      ALLEGRO_EVENT_QUEUE *queue = al_create_event_queue();      al_register_event_source(queue, al_get_native_text_log_event_source(         textlog));      al_wait_for_event(queue, NULL);      al_destroy_event_queue(queue);   }   al_close_native_text_log(textlog);   textlog = NULL;}void log_printf(char const *format, ...){   char str[1024];   va_list args;   va_start(args, format);   vsnprintf(str, sizeof str, format, args);   va_end(args);   al_append_native_text_log(textlog, "%s", str);}#elsevoid abort_example(char const *format, ...){   va_list args;   va_start(args, format);   vfprintf(stderr, format, args);   va_end(args);   exit(1);}void open_log(void){}void open_log_monospace(void){}void close_log(bool wait_for_user){   (void)wait_for_user;}void log_printf(char const *format, ...){   va_list args;   va_start(args, format);   #ifdef ALLEGRO_ANDROID   char x[1024];   vsnprintf(x, sizeof x, format, args);   ALLEGRO_TRACE_CHANNEL_LEVEL("log", 1)("%s", x);   #else   vprintf(format, args);   #endif   va_end(args);}#endif/* vim: set sts=3 sw=3 et: *//* Simple example showing how to use an extension. It draws a yellow triangle * on red background onto a texture, then draws a quad with that texture. */GLuint tex, fbo;bool no_fbo = false;static void draw_opengl(void){   double secs = al_get_time();      ALLEGRO_TRANSFORM projection = *al_get_current_projection_transform();   ALLEGRO_TRANSFORM t;   glMatrixMode(GL_MODELVIEW);   glLoadIdentity();   /* Let's create a texture. It will only be visible if we cannot draw over    * it with the framebuffer extension.    */   if (!tex) {      unsigned char *pixels = malloc(256 * 256 * 4);      int x, y;      for (y = 0; y < 256; y++) {         for (x = 0; x < 256; x++) {            unsigned char r = x, g = y, b = 0, a = 255;            pixels[y * 256 * 4 + x * 4 + 0] = r;            pixels[y * 256 * 4 + x * 4 + 1] = g;            pixels[y * 256 * 4 + x * 4 + 2] = b;            pixels[y * 256 * 4 + x * 4 + 3] = a;         }      }      glGenTextures(1, &tex);      glBindTexture(GL_TEXTURE_2D, tex);      glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, 256, 256, 0, GL_RGBA,         GL_UNSIGNED_INT_8_8_8_8_REV, pixels);      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);      free(pixels);   }   /* Let's create a framebuffer object. */   if (!fbo && !no_fbo) {      /* Did Allegro discover the OpenGL extension for us? */      if (al_get_opengl_extension_list()->ALLEGRO_GL_EXT_framebuffer_object) {         /* If yes, then it also filled in the function pointer. How nice. */         glGenFramebuffersEXT(1, &fbo);         glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo);         /* Attach the framebuffer object to our texture. */         glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT,            GL_TEXTURE_2D, tex, 0);         if (glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT) !=            GL_FRAMEBUFFER_COMPLETE_EXT) {            no_fbo = true;         }         glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);      }      else {         /* We are screwed, the extension is not available. */         no_fbo = true;      }   }  /* Draw a yellow triangle on red background to the framebuffer object. */   if (fbo && !no_fbo) {      glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo);      glPushAttrib(GL_VIEWPORT_BIT | GL_TRANSFORM_BIT);      glViewport(0, 0, 256, 256);      glClearColor(1, 0, 0, 1);      glClear(GL_COLOR_BUFFER_BIT);      glMatrixMode(GL_PROJECTION);      glPushMatrix();      glLoadIdentity();      glOrtho(0, 256, 256, 0, -1, 1);      glDisable(GL_TEXTURE_2D);      glColor3f(1, 1, 0);      glTranslatef(128, 128 + sin(secs * ALLEGRO_PI * 2 * 2) * 20, 0);      glBegin(GL_TRIANGLES);      glVertex2f(0, -100);      glVertex2f(100, 0);      glVertex2f(-100, 0);      glEnd();      glPopMatrix();      glPopAttrib();      glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);   }   /* Draw a quad with our texture. */   glClearColor(0, 0, 1, 1);   glClear(GL_COLOR_BUFFER_BIT);   glLoadIdentity();   glTranslatef(320, 240, 0);   glRotatef(secs * 360 / 4, 0, 0, 1);   glColor3f(1, 1, 1);   glEnable(GL_TEXTURE_2D);   glBindTexture(GL_TEXTURE_2D, tex);   glBegin(GL_QUADS);   glTexCoord2f(0, 0); glVertex2f(-100, -100);   glTexCoord2f(1, 0); glVertex2f(+100, -100);   glTexCoord2f(1, 1); glVertex2f(+100, +100);   glTexCoord2f(0, 1); glVertex2f(-100, +100);   glEnd();         /* Restore projection. */   al_identity_transform(&t);   al_use_transform(&t);   al_use_projection_transform(&projection);   al_set_render_state(ALLEGRO_DEPTH_TEST, 0);}int main(int argc, char **argv){   ALLEGRO_DISPLAY *display;   ALLEGRO_EVENT_QUEUE *queue;   ALLEGRO_EVENT event;   int frames = 0;   double start;   (void)argc;   (void)argv;   if (!al_init()) {      abort_example("Could not init Allegro.\n");   }   open_log();   al_install_keyboard();   al_set_new_display_flags(ALLEGRO_OPENGL);   display = al_create_display(640, 480);   if (!display) {      abort_example("Could not create display.\n");   }   queue = al_create_event_queue();   al_register_event_source(queue, al_get_keyboard_event_source());   al_register_event_source(queue, al_get_display_event_source(display));   start = al_get_time();   while (true) {      /* Check for ESC key or close button event and quit in either case. */      if (!al_is_event_queue_empty(queue)) {         while (al_get_next_event(queue, &event)) {            switch (event.type) {               case ALLEGRO_EVENT_DISPLAY_CLOSE:                  goto done;               case ALLEGRO_EVENT_KEY_DOWN:                  if (event.keyboard.keycode == ALLEGRO_KEY_ESCAPE)                     goto done;                  break;            }         }      }      draw_opengl();            al_draw_rectangle(20, 20, 300, 200, al_map_rgba_f(0.5, 0, 0, 1), 1);            al_flip_display();      frames++;   }done:   log_printf("%.1f FPS\n", frames / (al_get_time() - start));   al_destroy_event_queue(queue);   al_destroy_display(display);   close_log(true);   return 0;}