Redirect keyboard events to RGUI.

Fixes issue where libretro cores receive keyboard events even though
they are not running (inside RGUI).

frontend/frontend.c

@@ -215,6 +215,11 @@ int main_entry(int argc, char *argv[])
             driver_set_rumble_state(i, RETRO_RUMBLE_WEAK, 0);
          }
 
+         // Override keyboard callback to redirect to menu instead.
+         // We'll use this later for something ...
+         retro_keyboard_event_t key_event = g_extern.system.key_event;
+         g_extern.system.key_event = menu_key_event;
+
          if (driver.audio_data)
             audio_stop_func();
 
@@ -236,6 +241,9 @@ int main_entry(int argc, char *argv[])
          }
 
          g_extern.lifecycle_mode_state &= ~(1ULL << MODE_MENU);
+
+         // Restore libretro keyboard callback.
+         g_extern.system.key_event = key_event;
       }
       else
          break;

frontend/menu/menu_common.c

@@ -911,3 +911,12 @@ bool menu_poll_find_trigger(struct rgui_bind_state *state, struct rgui_bind_stat
    return false;
 }
 
+void menu_key_event(bool down, unsigned keycode, uint32_t character, uint16_t key_modifiers)
+{
+   // TODO: Do something with this. Stub for now.
+   (void)down;
+   (void)keycode;
+   (void)character;
+   (void)key_modifiers;
+}
+

frontend/menu/menu_common.h

@@ -355,6 +355,8 @@ bool menu_save_new_config(void);
 int menu_set_settings(unsigned setting, unsigned action);
 extern const unsigned rgui_controller_lut[];
 
+void menu_key_event(bool down, unsigned keycode, uint32_t character, uint16_t key_modifiers);
+
 #ifdef __cplusplus
 }
 #endif