Wrap tick API

This avoids to use the SDL timer API directly, and will allow to handle
generic ticks (possibly negative).

app/src/fps_counter.c

@@ -1,7 +1,6 @@
 #include "fps_counter.h"
 
 #include <assert.h>
-#include <SDL2/SDL_timer.h>
 
 #include "util/log.h"
 
@@ -82,11 +81,11 @@ run_fps_counter(void *data) {
             sc_cond_wait(&counter->state_cond, &counter->mutex);
         }
         while (!counter->interrupted && is_started(counter)) {
-            uint32_t now = SDL_GetTicks();
+            sc_tick now = sc_tick_now();
             check_interval_expired(counter, now);
 
             assert(counter->next_timestamp > now);
-            uint32_t remaining = counter->next_timestamp - now;
+            sc_tick remaining = counter->next_timestamp - now;
 
             // ignore the reason (timeout or signaled), we just loop anyway
             sc_cond_timedwait(&counter->state_cond, &counter->mutex, remaining);
@@ -99,7 +98,7 @@ run_fps_counter(void *data) {
 bool
 fps_counter_start(struct fps_counter *counter) {
     sc_mutex_lock(&counter->mutex);
-    counter->next_timestamp = SDL_GetTicks() + FPS_COUNTER_INTERVAL_MS;
+    counter->next_timestamp = sc_tick_now() + FPS_COUNTER_INTERVAL_MS;
     counter->nr_rendered = 0;
     counter->nr_skipped = 0;
     sc_mutex_unlock(&counter->mutex);
@@ -165,7 +164,7 @@ fps_counter_add_rendered_frame(struct fps_counter *counter) {
     }
 
     sc_mutex_lock(&counter->mutex);
-    uint32_t now = SDL_GetTicks();
+    sc_tick now = sc_tick_now();
     check_interval_expired(counter, now);
     ++counter->nr_rendered;
     sc_mutex_unlock(&counter->mutex);
@@ -178,7 +177,7 @@ fps_counter_add_skipped_frame(struct fps_counter *counter) {
     }
 
     sc_mutex_lock(&counter->mutex);
-    uint32_t now = SDL_GetTicks();
+    sc_tick now = sc_tick_now();
     check_interval_expired(counter, now);
     ++counter->nr_skipped;
     sc_mutex_unlock(&counter->mutex);

app/src/fps_counter.h

@@ -24,7 +24,7 @@ struct fps_counter {
     bool interrupted;
     unsigned nr_rendered;
     unsigned nr_skipped;
-    uint32_t next_timestamp;
+    sc_tick next_timestamp;
 };
 
 bool

app/src/util/thread.c

@@ -2,6 +2,7 @@
 
 #include <assert.h>
 #include <SDL2/SDL_thread.h>
+#include <SDL2/SDL_timer.h>
 
 #include "log.h"
 
@@ -123,8 +124,12 @@ sc_cond_wait(sc_cond *cond, sc_mutex *mutex) {
 }
 
 bool
-sc_cond_timedwait(sc_cond *cond, sc_mutex *mutex, uint32_t ms) {
-    int r = SDL_CondWaitTimeout(cond->cond, mutex->mutex, ms);
+sc_cond_timedwait(sc_cond *cond, sc_mutex *mutex, sc_tick ms) {
+    if (ms < 0) {
+        return false; // timeout
+    }
+
+    int r = SDL_CondWaitTimeout(cond->cond, mutex->mutex, (uint32_t) ms);
 #ifndef NDEBUG
     if (r < 0) {
         LOGC("Could not wait on condition with timeout: %s", SDL_GetError());
@@ -163,3 +168,11 @@ sc_cond_broadcast(sc_cond *cond) {
     (void) r;
 #endif
 }
+
+sc_tick
+sc_tick_now(void) {
+    // SDL ticks is an unsigned 32 bits, but this is an implementation detail.
+    // It wraps if the program runs for more than ~49 days, but in practice we
+    // can assume it does not.
+    return (sc_tick) SDL_GetTicks();
+}

app/src/util/thread.h

@@ -16,6 +16,8 @@ typedef int sc_thread_fn(void *);
 typedef unsigned sc_thread_id;
 typedef atomic_uint sc_atomic_thread_id;
 
+typedef int64_t sc_tick;
+
 typedef struct sc_thread {
     SDL_Thread *thread;
 } sc_thread;
@@ -72,7 +74,7 @@ sc_cond_wait(sc_cond *cond, sc_mutex *mutex);
 
 // return true on signaled, false on timeout
 bool
-sc_cond_timedwait(sc_cond *cond, sc_mutex *mutex, uint32_t ms);
+sc_cond_timedwait(sc_cond *cond, sc_mutex *mutex, sc_tick ms);
 
 void
 sc_cond_signal(sc_cond *cond);
@@ -80,4 +82,7 @@ sc_cond_signal(sc_cond *cond);
 void
 sc_cond_broadcast(sc_cond *cond);
 
+sc_tick
+sc_tick_now(void);
+
 #endif