add timer to push display event

sdl_opengl_bare.d

@@ -5,6 +5,7 @@ import derelict.opengl.glu;
 
 enum int WIDTH = 800;
 enum int HEIGHT = 600;
+static bool drawing = false;
 
 void init()
 {
@@ -21,6 +22,7 @@ void init()
 
 void display()
 {
+    drawing = true;
     glClear(GL_COLOR_BUFFER_BIT);
     glBegin(GL_QUADS);
         glColor3f(1, 1, 1);
@@ -33,6 +35,18 @@ void display()
         glVertex3f(5.0, -5.0, 0.0);
     glEnd();
     SDL_GL_SwapBuffers();
+    drawing = false;
+}
+
+extern (C) Uint32 timer_callback(Uint32 interval, void *param)
+{
+    if (!drawing)
+    {
+        SDL_Event event;
+        event.type = SDL_USEREVENT;
+        SDL_PushEvent(&event);
+    }
+    return interval;
 }
 
 int main(char[][] args)
@@ -58,8 +72,8 @@ int main(char[][] args)
     }
 
     init();
-    display();
     SDL_Event event;
+    SDL_AddTimer(1000 / 50, &timer_callback, null);
     while (SDL_WaitEvent(&event))
     {
         if (event.type == SDL_QUIT)
@@ -69,6 +83,10 @@ int main(char[][] args)
             if (event.key.keysym.sym == SDLK_ESCAPE)
                 break;
         }
+        else if (event.type == SDL_USEREVENT)
+        {
+            display();
+        }
     }
 
     SDL_Quit();