gfx: toggle Sync to Exact Content Framerate without a driver reinit

vrr_runloop_enable ("Sync to Exact Content Framerate") fired CMD_EVENT_REINIT
on change, reinitialising video/audio/input and flashing the screen. But the
VRR frame-timing is read per-frame in the runloop (swap-interval logic), so
that part needs no reinit -- the hotkey toggle already flips the setting with
none. The only init-time effect is the audio/video system-rate recompute in
driver_adjust_system_rates(): VRR locks audio to the exact content rate rather
than adjusting it to the display refresh.

That recompute has a lightweight, existing entry point --
RARCH_DRIVER_CTL_SET_REFRESH_RATE, already used by the refresh-rate settings --
which calls driver_adjust_system_rates() without recreating any driver. So:

  - general_write_handler(): for VRR_RUNLOOP_ENABLE, re-adjust the rates via
    that ctl, and point the setting at CMD_EVENT_NONE instead of the reinit.
  - CMD_EVENT_VRR_RUNLOOP_TOGGLE (the hotkey): do the same rate re-adjust
    after flipping the value. Previously the hotkey changed frame timing but
    never recomputed the audio rate, leaving it stale until the next reinit;
    this makes the hotkey and the menu toggle consistent.

Compile-verified. Reuses the existing SET_REFRESH_RATE rate-adjust path rather
than a new lifecycle, but it does touch runtime audio timing, so it warrants
an on-device check that toggling VRR still switches audio between exact-rate
and adjusted correctly.

Signed-off-by: LibretroAdmin <LibretroAdmin@users.noreply.github.com>

Author: LibretroAdmin

menu/menu_setting.c

@@ -8937,6 +8937,14 @@ static void general_write_handler(rarch_setting_t *setting)
 #ifdef HAVE_CHEEVOS
          rcheevos_validate_config_settings();
 #endif
+         /* Sync to Exact Content Framerate only changes the audio/video
+          * system rates (audio locks to the exact content rate instead of the
+          * display refresh) plus the per-frame swap interval, so re-adjust the
+          * rates in place rather than reinitialising the drivers -- the runloop
+          * reads vrr_runloop_enable every frame. */
+         if (setting->enum_idx == MENU_ENUM_LABEL_VRR_RUNLOOP_ENABLE)
+            driver_ctl(RARCH_DRIVER_CTL_SET_REFRESH_RATE,
+                  &settings->floats.video_refresh_rate);
          break;
 
       case MENU_ENUM_LABEL_VIDEO_REFRESH_RATE_AUTO:
@@ -17325,7 +17333,7 @@ static bool setting_append_list(
                SDESC_BOOL_ROW(fastforward_frameskip, FASTFORWARD_FRAMESKIP,
                      DEFAULT_FASTFORWARD_FRAMESKIP, SD_FLAG_NONE, 0, 0),
                SDESC_BOOL_ROW_EX(vrr_runloop_enable, VRR_RUNLOOP_ENABLE,
-                     false, SD_FLAG_CMD_APPLY_AUTO, 0, CMD_EVENT_REINIT,
+                     false, SD_FLAG_CMD_APPLY_AUTO, 0, CMD_EVENT_NONE,
                      setting_bool_action_left_with_refresh, NULL, NULL, NULL, setting_bool_action_left_with_refresh, setting_bool_action_right_with_refresh, 0),
             };
             settings_list_add_desc(list, list_info, settings,

retroarch.c

@@ -5890,6 +5890,11 @@ bool command_event(enum event_command cmd, void *data)
                      settings->bools.vrr_runloop_enable ? MSG_VRR_RUNLOOP_ENABLED
                      : MSG_VRR_RUNLOOP_DISABLED);
             settings->bools.vrr_runloop_enable = !(settings->bools.vrr_runloop_enable);
+            /* Re-adjust audio/video system rates for the new VRR mode so the
+             * hotkey matches the menu toggle instead of leaving the audio
+             * input rate stale until the next reinit. */
+            driver_ctl(RARCH_DRIVER_CTL_SET_REFRESH_RATE,
+                  &settings->floats.video_refresh_rate);
             runloop_msg_queue_push(_msg, strlen(_msg), 1, 100, false, NULL,
                   MESSAGE_QUEUE_ICON_DEFAULT, MESSAGE_QUEUE_CATEGORY_INFO);
          }