Added a macro SDL_TICKS_PASSED() to correctly compare two 32-bit tick values.

Went through the code and used the macro and fixed a couple places that were using incorrect timestamp comparisons.

include/SDL_timer.h

@@ -44,6 +44,17 @@ extern "C" {
  */
 extern DECLSPEC Uint32 SDLCALL SDL_GetTicks(void);
 
+/**
+ * \brief Compare SDL ticks values, and return true if A has passed B
+ *
+ * e.g. if you want to wait 100 ms, you could do this:
+ *  Uint32 timeout = SDL_GetTicks() + 100;
+ *  while (!SDL_TICKS_PASSED(SDL_GetTicks(), timeout)) {
+ *      ... do work until timeout has elapsed
+ *  }
+ */
+#define SDL_TICKS_PASSED(A, B)  ((Sint32)((B) - (A)) <= 0)
+
 /**
  * \brief Get the current value of the high resolution counter
  */

src/audio/arts/SDL_artsaudio.c

@@ -220,7 +220,7 @@ static int
 ARTS_Suspend(void)
 {
     const Uint32 abortms = SDL_GetTicks() + 3000; /* give up after 3 secs */
-    while ( (!SDL_NAME(arts_suspended)()) && (SDL_GetTicks() < abortms) ) {
+    while ( (!SDL_NAME(arts_suspended)()) && !SDL_TICKS_PASSED(SDL_GetTicks(), abortms) ) {
         if ( SDL_NAME(arts_suspend)() ) {
             break;
         }

src/audio/bsd/SDL_bsdaudio.c

@@ -125,9 +125,7 @@ BSDAUDIO_WaitDevice(_THIS)
         /* Use timer for general audio synchronization */
         Sint32 ticks;
 
-        ticks =
-            ((Sint32) (this->hidden->next_frame - SDL_GetTicks())) -
-            FUDGE_TICKS;
+        ticks = ((Sint32) (this->hidden->next_frame - SDL_GetTicks())) - FUDGE_TICKS;
         if (ticks > 0) {
             SDL_Delay(ticks);
         }

src/audio/esd/SDL_esdaudio.c

@@ -135,8 +135,7 @@ ESD_WaitDevice(_THIS)
     }
 
     /* Use timer for general audio synchronization */
-    ticks =
-        ((Sint32) (this->hidden->next_frame - SDL_GetTicks())) - FUDGE_TICKS;
+    ticks = ((Sint32) (this->hidden->next_frame - SDL_GetTicks())) - FUDGE_TICKS;
     if (ticks > 0) {
         SDL_Delay(ticks);
     }

src/audio/paudio/SDL_paudio.c

@@ -133,9 +133,7 @@ PAUDIO_WaitDevice(_THIS)
         /* Use timer for general audio synchronization */
         Sint32 ticks;
 
-        ticks =
-            ((Sint32) (this->hidden->next_frame - SDL_GetTicks())) -
-            FUDGE_TICKS;
+        ticks = ((Sint32) (this->hidden->next_frame - SDL_GetTicks())) - FUDGE_TICKS;
         if (ticks > 0) {
             SDL_Delay(ticks);
         }

src/events/SDL_events.c

@@ -443,7 +443,7 @@ SDL_WaitEventTimeout(SDL_Event * event, int timeout)
                 /* Polling and no events, just return */
                 return 0;
             }
-            if (timeout > 0 && ((int) (SDL_GetTicks() - expiration) >= 0)) {
+            if (timeout > 0 && SDL_TICKS_PASSED(SDL_GetTicks(), expiration)) {
                 /* Timeout expired and no events */
                 return 0;
             }

src/haptic/windows/SDL_syshaptic.c

@@ -1567,7 +1567,7 @@ SDL_RunXInputHaptic(void *arg)
         SDL_LockMutex(hwdata->mutex);
         /* If we're currently running and need to stop... */
         if (hwdata->stopTicks) {
-            if ((hwdata->stopTicks != SDL_HAPTIC_INFINITY) && (hwdata->stopTicks < SDL_GetTicks())) {
+            if ((hwdata->stopTicks != SDL_HAPTIC_INFINITY) && SDL_TIMESTAMP_PASSED(SDL_GetTicks(), hwdata->stopTicks)) {
                 XINPUT_VIBRATION vibration = { 0, 0 };
                 hwdata->stopTicks = 0;
                 XINPUTSETSTATE(hwdata->userid, &vibration);

src/power/uikit/SDL_syspower.m

@@ -38,11 +38,7 @@ void
 SDL_UIKit_UpdateBatteryMonitoring(void)
 {
     if (SDL_UIKitLastPowerInfoQuery) {
-        const Uint32 prev = SDL_UIKitLastPowerInfoQuery;
-        const UInt32 now = SDL_GetTicks();
-        const UInt32 ticks = now - prev;
-        /* if timer wrapped (now < prev), shut down, too. */
-        if ((now < prev) || (ticks >= BATTERY_MONITORING_TIMEOUT)) {
+        if (SDL_TICKS_PASSED(SDL_GetTicks(), SDL_UIKitLastPowerInfoQuery + BATTERY_MONITORING_TIMEOUT)) {
             UIDevice *uidev = [UIDevice currentDevice];
             SDL_assert([uidev isBatteryMonitoringEnabled] == YES);
             [uidev setBatteryMonitoringEnabled:NO];

src/thread/pthread/SDL_syssem.c

@@ -156,7 +156,7 @@ SDL_SemWaitTimeout(SDL_sem * sem, Uint32 timeout)
 #else
     end = SDL_GetTicks() + timeout;
     while ((retval = SDL_SemTryWait(sem)) == SDL_MUTEX_TIMEDOUT) {
-        if ((Sint32)(SDL_GetTicks() - end) >= 0) {
+        if (SDL_TICKS_PASSED(SDL_GetTicks(), end)) {
             break;
         }
         SDL_Delay(1);

src/video/cocoa/SDL_cocoaevents.m

@@ -271,7 +271,7 @@ Cocoa_PumpEvents(_THIS)
         SDL_VideoData *data = (SDL_VideoData *)_this->driverdata;
         Uint32 now = SDL_GetTicks();
         if (!data->screensaver_activity ||
-            (int)(now-data->screensaver_activity) >= 30000) {
+            SDL_TICKS_PASSED(now, data->screensaver_activity + 30000)) {
             UpdateSystemActivity(UsrActivity);
             data->screensaver_activity = now;
         }

src/video/x11/SDL_x11events.c

@@ -909,7 +909,7 @@ X11_HandleFocusChanges(_THIS)
             SDL_WindowData *data = videodata->windowlist[i];
             if (data && data->pending_focus != PENDING_FOCUS_NONE) {
                 Uint32 now = SDL_GetTicks();
-                if ( (int)(data->pending_focus_time-now) <= 0 ) {
+                if (SDL_TICKS_PASSED(now, data->pending_focus_time)) {
                     if ( data->pending_focus == PENDING_FOCUS_IN ) {
                         X11_DispatchFocusIn(data);
                     } else {
@@ -963,7 +963,7 @@ X11_PumpEvents(_THIS)
     if (_this->suspend_screensaver) {
         Uint32 now = SDL_GetTicks();
         if (!data->screensaver_activity ||
-            (int) (now - data->screensaver_activity) >= 30000) {
+            SDL_TICKS_PASSED(now, data->screensaver_activity + 30000)) {
             X11_XResetScreenSaver(data->display);
 
             #if SDL_USE_LIBDBUS

src/video/x11/SDL_x11window.c

@@ -66,7 +66,7 @@ X11_XIfEventTimeout(Display *display, XEvent *event_return, Bool (*predicate)(),
     Uint32 start = SDL_GetTicks();
 
     while (!X11_XCheckIfEvent(display, event_return, predicate, arg)) {
-        if ((SDL_GetTicks() - start) >= timeoutMS) {
+        if (SDL_TICKS_PASSED(SDL_GetTicks(), start + timeoutMS)) {
             return False;
         }
     }