Wrap tick API

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

app/src/util/thread.c

@@ -123,7 +123,12 @@ sc_cond_wait(sc_cond *cond, sc_mutex *mutex) {
 }
 
 bool
-sc_cond_timedwait(sc_cond *cond, sc_mutex *mutex, uint32_t ms) {
+sc_cond_timedwait(sc_cond *cond, sc_mutex *mutex, sc_tick delay) {
+    if (delay < 0) {
+        return false; // timeout
+    }
+
+    uint32_t ms = SC_TICK_TO_MS(delay);
     int r = SDL_CondWaitTimeout(cond->cond, mutex->mutex, ms);
 #ifndef NDEBUG
     if (r < 0) {

app/src/util/thread.h

@@ -5,7 +5,8 @@
 
 #include <stdatomic.h>
 #include <stdbool.h>
-#include <stdint.h>
+
+#include "tick.h"
 
 /* Forward declarations */
 typedef struct SDL_Thread SDL_Thread;
@@ -72,7 +73,7 @@ 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);

app/src/util/tick.c

@@ -0,0 +1,16 @@
+#include "tick.h"
+
+#include <SDL2/SDL_timer.h>
+
+sc_tick
+sc_tick_now(void) {
+    // SDL_GetTicks() resolution is in milliseconds, but sc_tick are expressed
+    // in microseconds to store PTS without precision loss.
+    //
+    // As an alternative, SDL_GetPerformanceCounter() and
+    // SDL_GetPerformanceFrequency() could be used, but:
+    //  - the conversions (avoiding overflow) are expansive, since the
+    //    frequency is not known at compile time;
+    //  - in practice, we don't need more precision for now.
+    return (sc_tick) SDL_GetTicks() * 1000;
+}

app/src/util/tick.h

@@ -0,0 +1,20 @@
+#ifndef SC_TICK_H
+#define SC_TICK_H
+
+#include <stdint.h>
+
+typedef int64_t sc_tick;
+#define SC_TICK_FREQ 1000000 // microsecond
+
+// To be adapted if SC_TICK_FREQ changes
+#define SC_TICK_TO_US(tick) (tick)
+#define SC_TICK_TO_MS(tick) ((tick) / 1000)
+#define SC_TICK_TO_SEC(tick) ((tick) / 1000000)
+#define SC_TICK_FROM_US(us) (us)
+#define SC_TICK_FROM_MS(ms) ((ms) * 1000)
+#define SC_TICK_FROM_SEC(sec) ((sec) * 1000000)
+
+sc_tick
+sc_tick_now(void);
+
+#endif