[AD] yet another timer patch

["Ryan Dickie" <goalieca@xxxxxxxxxx>]

Sorry for generating more spam but no one was in #allegro-dev.

This patch adds an "error" field to the timer event and adds this error field, event overhead, and total timer overhead to the printouts for exnew_timer. I figure it is useful for timer profiling and delta timing for games.

--ryan
Index: src/timernu.c
===================================================================
--- src/timernu.c	(revision 10074)
+++ src/timernu.c	(working copy)
@@ -128,8 +128,8 @@
       timer->counter -= interval;
 
       while (timer->counter <= 0) {
+         timer_handle_tick(timer);
          timer->counter += timer->speed_secs;
-         timer_handle_tick(timer);
       }
 
       if ((timer->counter > 0) && (timer->counter < new_delay))
@@ -352,6 +352,7 @@
             event->timer.type = ALLEGRO_EVENT_TIMER;
             event->timer.timestamp = al_current_time();
             event->timer.count = this->count;
+            event->timer.error = -this->counter;
             _al_event_source_emit_event(&this->es, event);
          }
       }
Index: include/allegro5/events.h
===================================================================
--- include/allegro5/events.h	(revision 10074)
+++ include/allegro5/events.h	(working copy)
@@ -198,6 +198,7 @@
 {
    _AL_EVENT_HEADER(struct ALLEGRO_TIMER);
    long count;
+   double error;
 } ALLEGRO_TIMER_EVENT;
 
 
Index: examples/exnew_timer.c
===================================================================
--- examples/exnew_timer.c	(revision 10074)
+++ examples/exnew_timer.c	(working copy)
@@ -22,6 +22,8 @@
    double min_diff, max_diff, second_spread;
    double second;
    double timer_events;
+   double timer_error;
+   double timestamp;
 } ex;
 
 /* Initialize the example. */
@@ -30,6 +32,7 @@
    ex.FPS = 50;
    ex.first_tick = true;
 
+   /* TODO: use fixed width font */
    ex.myfont = a5font_load_font("font.tga", 0);
    if (!ex.myfont) {
       allegro_message("font.tga not found");
@@ -69,9 +72,15 @@
 static void draw(void)
 {
    int h, y, i;
+   double cur_time, event_overhead, total_error;
+   
+   cur_time = al_current_time();
+   event_overhead = cur_time - ex.timestamp;
+   total_error = event_overhead + ex.timer_error;
 
    h = a5font_text_height(ex.myfont);
    al_clear(al_map_rgb_f(1, 1, 1));
+
    print(0, 0, "%.9f target for %.0f Hz Timer", 1.0 / ex.FPS, ex.FPS);
    print(0, h, "%.9f now", ex.this_time - ex.prev_time);
    print(0, 2 * h, "%.9f accum over one second",
@@ -79,6 +88,9 @@
    print(0, 3 * h, "%.9f min", ex.min_diff);
    print(0, 4 * h, "%.9f max", ex.max_diff);
    print(300, 3.5 * h, "%.9f (max - min)", ex.second_spread);
+   print(300, 4.5 * h, "%.9f (timer error)", ex.timer_error);
+   print(300, 5.5 * h ,"%.9f (event overhead)", event_overhead);
+   print(300, 6.5 * h, "%.9f (total error)" , total_error);
 
    y = 240;
    for (i = 0; i < 4; i++) {
@@ -88,7 +100,7 @@
 }
 
 /* Called a fixed amount of times per second. */
-static void tick(void)
+static void tick(ALLEGRO_TIMER_EVENT* timer_event)
 {
    int i;
 
@@ -112,6 +124,8 @@
       if (duration > ex.max_diff) ex.max_diff = duration;
       ex.accum_time += duration;
       ex.timer_events++;
+      ex.timer_error = timer_event->error;
+      ex.timestamp = timer_event->timestamp;
    }
 
    draw();
@@ -144,7 +158,7 @@
 
          /* Is it time for the next timer tick? */
          case ALLEGRO_EVENT_TIMER:
-            tick();
+            tick(&event.timer);
             break;
       }
    }