feat(evdev): pass raw keycodes to user through event (#9771)

docs/src/main-modules/indev/keypad.mdx

@@ -93,6 +93,25 @@ void key_event_cb(lv_event_t *e)
 lv_indev_add_event_cb(keyboard, key_event_cb, LV_EVENT_KEY, NULL);
 ```
 
+LVGL automatically converts direction keys to `LV_KEY_XXX`. For other keys
+you can get their value by querying <ApiLink name="lv_evdev_get_raw_key" /> in a <ApiLink name="LV_EVENT_KEY" /> handler.
+
+```c
+
+void key_event_cb(lv_event_t *e)
+{
+    if(lv_evdev_is_raw_key(e))
+    {
+        LV_LOG_USER("%d", lv_evdev_get_raw_key(e));
+    }
+}
+
+...
+
+lv_obj_add_event_cb(lv_screen_active(), key_event_cb, LV_EVENT_KEY, NULL);
+
+```
+
 ## Key Remapping
 
 Some applications require assigning physical buttons to multiple key events depending

include/lvgl/drivers/indev/lv_evdev.h

@@ -91,6 +91,21 @@ void lv_evdev_set_swap_axes(lv_indev_t * indev, bool swap_axes);
  */
 void lv_evdev_set_calibration(lv_indev_t * indev, int min_x, int min_y, int max_x, int max_y);
 
+/**
+ * Returns the status indicating whether an LV_KEY could not be processed.
+ * @param e         pointer to an event
+ * @return true     if it is a raw key
+ * @return false    if it is not a raw key
+ */
+bool lv_evdev_is_raw_key(lv_event_t * e);
+
+/**
+ * Returns the raw keycode if LV_KEY could not be processed
+ * @param e         pointer to an event
+ * @return uint16_t raw keycode
+ */
+uint16_t lv_evdev_get_raw_key(lv_event_t * e);
+
 /**
  * Remove evdev input device.
  * @param indev evdev input device to close and free

src/drivers/evdev/lv_evdev.c

@@ -112,7 +112,7 @@ static int _evdev_process_key(uint16_t code)
         case KEY_END:
             return LV_KEY_END;
         default:
-            return 0;
+            return code + 0xFFFF;
     }
 }
 
@@ -660,6 +660,30 @@ void lv_evdev_set_calibration(lv_indev_t * indev, int min_x, int min_y, int max_
     dsc->max_y = max_y;
 }
 
+bool lv_evdev_is_raw_key(lv_event_t * e)
+{
+    LV_CHECK_ARG(e != NULL, return false);
+
+    uint32_t key = lv_event_get_key(e);
+    return (key > 0xFFFF);
+}
+
+uint16_t lv_evdev_get_raw_key(lv_event_t * e)
+{
+    LV_CHECK_ARG(e != NULL, return 0);
+
+    uint32_t key = lv_event_get_key(e);
+
+    if(key > 0xFFFF) {
+        return (uint16_t)(key - 0xFFFF);
+    }
+    else {
+        LV_LOG_WARN("key is an LV_KEY");
+    }
+
+    return 0;
+}
+
 void lv_evdev_delete(lv_indev_t * indev)
 {
     lv_indev_delete(indev);