Revised comments and variable names. Removed unused fps variable and update method

Author: Avid29

ui/xemu.c

@@ -106,7 +106,7 @@ static bool alt_grab;
 static bool ctrl_grab;
 static int gui_saved_grab;
 static int gui_fullscreen;
-static float frame_deadline = (NANOSECONDS_PER_SECOND / 60);
+static float min_frame_duration = (NANOSECONDS_PER_SECOND / 60);
 static int gui_grab_code = KMOD_LALT | KMOD_LCTRL;
 static SDL_Cursor *sdl_cursor_normal;
 static SDL_Cursor *sdl_cursor_hidden;
@@ -140,7 +140,7 @@ void xemu_update_frame_rate_cap(void)
 
     // No framerate cap
     if (!selection) {
-        frame_deadline = 0;
+        min_frame_duration = 0;
         return;
     }
 
@@ -156,7 +156,7 @@ void xemu_update_frame_rate_cap(void)
 
     // Calculate the minimum time allowed between frames based on
     // the desired frame rate
-    frame_deadline = (float)NANOSECONDS_PER_SECOND / frame_rate;
+    min_frame_duration = (float)NANOSECONDS_PER_SECOND / frame_rate;
 }
 
 #define SDL2_REFRESH_INTERVAL_BUSY 16
@@ -1031,29 +1031,13 @@ void sdl2_gl_switch(DisplayChangeListener *dcl,
     }
 }
 
-float fps = 1.0;
-
-static void update_fps(void)
-{
-    static int64_t last_update = 0;
-    const float r = 0.5;//0.1;
-    static float avg = 1.0;
-    int64_t now = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
-    float ms = ((float)(now-last_update)/1000000.0);
-    last_update = now;
-    if (fabs(avg-ms) > 0.25*avg) avg = ms;
-    else avg = avg*(1.0-r)+ms*r;
-    fps = 1000.0/avg;
-}
-
 void sdl2_gl_refresh(DisplayChangeListener *dcl)
 {
     struct sdl2_console *scon = container_of(dcl, struct sdl2_console, dcl);
     assert(scon->opengl);
     bool flip_required = false;
 
     SDL_GL_MakeCurrent(scon->real_window, scon->winctx);
-    update_fps();
 
     /* XXX: Note that this bypasses the usual VGA path in order to quickly
      * get the surface. This is simple and fast, at the cost of accuracy.
@@ -1108,10 +1092,10 @@ void sdl2_gl_refresh(DisplayChangeListener *dcl)
     qemu_mutex_unlock_main_loop();
 
     /*
-     * Throttle to make sure swaps happen at 60Hz
+     * Throttle to make sure swaps happen at the desired frame rate cap
      */
-    static int64_t last_update = 0;
-    int64_t deadline = last_update + frame_deadline;
+    static int64_t last_frame_update = 0;
+    int64_t frame_expiration = last_frame_update + min_frame_duration;
 
 #ifdef DEBUG_XEMU_C
     int64_t sleep_acc = 0;
@@ -1126,8 +1110,8 @@ void sdl2_gl_refresh(DisplayChangeListener *dcl)
 
     while (1) {
         int64_t now = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
-        int64_t time_remaining = deadline - now;
-        if (now < deadline) {
+        int64_t time_remaining = frame_expiration - now;
+        if (now < frame_expiration) {
             if (time_remaining > sleep_threshold) {
                 // Try to sleep until the until reaching the sleep threshold.
                 sleep_ns(time_remaining - sleep_threshold);
@@ -1144,11 +1128,10 @@ void sdl2_gl_refresh(DisplayChangeListener *dcl)
             }
         } else {
             DPRINTF("zzZz %g %ld\n", (double)sleep_acc/1000000.0, spin_acc);
-            last_update = now;
+            last_frame_update = now;
             break;
         }
     }
-
 }
 
 void sdl2_gl_redraw(struct sdl2_console *scon)