Merge 74937f4b8c into 561a5cee96

internal/c/libqb.cpp

@@ -27227,49 +27227,61 @@ void GLUT_SPECIAL_FUNC(int key, int x, int y) {
 }
 void GLUT_SPECIALUP_FUNC(int key, int x, int y) { GLUT_key_special(key, 0); }
 
-#ifdef QB64_WINDOWS
-void GLUT_TIMER_EVENT(int ignore) {
-    libqb_process_glut_queue();
+static int64_t lastTick = 0;
+static double deltaTick = 0;
 
-#    ifdef QB64_GLUT
-    glutPostRedisplay();
-    int32 msdelay = 1000.0 / max_fps;
-    Sleep(4);
-    msdelay -= 4; // this forces GLUT to relinquish some CPU time to other threads but still allow for _FPS 100+
-    if (msdelay < 1)
-        msdelay = 1;
-    glutTimerFunc(msdelay, GLUT_TIMER_EVENT, 0);
-#    endif
-}
-#else
 void GLUT_IDLEFUNC() {
     libqb_process_glut_queue();
 
-#    ifdef QB64_MACOSX
-#        ifdef DEPENDENCY_DEVICEINPUT
+#ifdef QB64_MACOSX
+#    ifdef DEPENDENCY_DEVICEINPUT
     // must be in same thread as GLUT for OSX
     QB64_GAMEPAD_POLL();
     //[[[[NSApplication sharedApplication] mainWindow] standardWindowButton:NSWindowCloseButton] setEnabled:YES];
-#        endif
 #    endif
+#endif
 
-#    ifdef QB64_GLUT
+#ifdef QB64_GLUT
 
+#    ifdef QB64_LINUX
     if (x11_lock_request) {
         x11_locked = 1;
         x11_lock_request = 0;
         while (x11_locked)
             Sleep(1);
     }
+#    endif
+    int64_t curTime = GetTicks();
+
+    // This is how long the frame took to render
+    int64_t elapsed = curTime - lastTick;
+
+    // Calculate out the error between how long the frame was 'supposed' to take vs. how long it actually took.
+    deltaTick += ((double)1000 / max_fps) - (double)elapsed;
+
+    lastTick = curTime;
+
+    // If the error is positive, we sleep for that period of time.
+    if (deltaTick > 0) {
+        int32 msdelay = deltaTick;
+        Sleep(msdelay);
+
+        int64_t sleepTime = GetTicks();
+
+        // Subtract off the time we spent sleeping. This should leave deltaTick at zero or slightly negative.
+        // If it ends up negative, then we'll sleep less next frame to compensate
+        deltaTick -= sleepTime - lastTick;
+        lastTick = sleepTime;
+    } else {
+        // If we fall behind by a full frame or more, then skip to the next one
+        while (deltaTick < -((double)1000 / max_fps))
+            deltaTick += ((double)1000 / max_fps);
+    }
 
     glutPostRedisplay();
-    int32 msdelay = 1000.0 / max_fps;
-    if (msdelay < 1)
-        msdelay = 1;
-    Sleep(msdelay);
-#    endif
-}
 #endif
+}
+
 
 #ifdef QB64_MACOSX
 #    include <sys/sysctl.h>
@@ -29468,6 +29480,8 @@ int32 func__scaledheight() { return environment_2d__screen_scaled_height; }
 extern void set_dynamic_info();
 
 int main(int argc, char *argv[]) {
+    clock_init();
+
 
 #if defined(QB64_LINUX) && defined(X11)
     XInitThreads();

internal/c/libqb/include/datetime.h

@@ -4,6 +4,14 @@
 #include <stdint.h>
 #include "qbs.h"
 
+#ifdef QB64_LINUX
+// Initializes the clock returned by 'GetTicks()' so that it starts from zero
+// Should be called at the very beginning of the program
+void clock_init();
+#else
+static inline void clock_init() { }
+#endif
+
 int64_t GetTicks();
 
 double func_timer(double accuracy, int32_t passed);

internal/c/libqb/src/datetime.cpp

@@ -37,10 +37,18 @@ static int64_t orwl_gettime(void) {
 #endif
 
 #ifdef QB64_LINUX
+static int64_t initial_tick = 0;
+
+void clock_init() {
+    // When GetTicks() is called here initial_tick is zero, so as a result
+    // GetTicks() returns the original value of the clock.
+    initial_tick = GetTicks();
+}
+
 int64_t GetTicks() {
     struct timespec tp;
     clock_gettime(CLOCK_MONOTONIC, &tp);
-    return tp.tv_sec * 1000 + tp.tv_nsec / 1000000;
+    return (tp.tv_sec * 1000 + tp.tv_nsec / 1000000) - initial_tick;
 }
 #elif defined QB64_MACOSX
 int64_t GetTicks() { return orwl_gettime(); }

internal/c/libqb/src/glut-main-thread.cpp

@@ -43,11 +43,7 @@ void GLUT_MOTION_FUNC(int x, int y);
 void GLUT_PASSIVEMOTION_FUNC(int x, int y);
 void GLUT_RESHAPE_FUNC(int width, int height);
 
-#ifdef QB64_WINDOWS
-void GLUT_TIMER_EVENT(int ignore);
-#else
 void GLUT_IDLEFUNC();
-#endif
 
 #ifdef CORE_FREEGLUT
 void GLUT_MOUSEWHEEL_FUNC(int wheel, int direction, int x, int y);
@@ -97,11 +93,7 @@ static void initialize_glut(int argc, char **argv) {
 
     glutDisplayFunc(GLUT_DISPLAY_REQUEST);
 
-#ifdef QB64_WINDOWS
-    glutTimerFunc(8, GLUT_TIMER_EVENT, 0);
-#else
     glutIdleFunc(GLUT_IDLEFUNC);
-#endif
 
     glutKeyboardFunc(GLUT_KEYBOARD_FUNC);
     glutKeyboardUpFunc(GLUT_KEYBOARDUP_FUNC);