+### getDisplayInfo(json_object *object)
+
+**args: `{ }`**
+This function gets the display information as follows:
+ - width[pixel]
+ - height[pixel]
+ - width[mm]
+ - height[mm]
+
+It outputs the display information for json_object in the argument as follows:
+ `{"width_pixel": int value of width[pixel], "height_pixel": int value of height[pixel],
+ "width_mm": int value of width[mm], "height_mm": int value of height[mm]}`
+
+It should be called after calling init().
+It should not be called in the event handler because it occurs hang-up.
+
+#### NOTE
+It uses wl_output::geometry() for getting physical width[mm] and height[mm] of the display,
+but the value is different with measured value.
+
+ - value from wl_output::geometry(): width:320 height:520
+ - measured value : width:193 height:343
+
+### getAreaInfo(json_object *in_obj, json_object *out_obj)
+
+**args1: `{ 'kKeyDrawingName': 'application name' }`**
+**args2: `{ }`**
+This function gets the information of area drawn by the application as follows:
+ - x-coordinate
+ - y-coordinate
+ - width
+ - height
+
+It outputs the area information for json_object in the 2nd argument as follows:
+ `{"x": int value of x-coordinate, "y": int value of y-coordinate,
+ "width": int value of width, "height": int value of height}`
+
+It should be called after calling activateSurface().
+It should not be called in the event handler because it occurs hang-up.
+
+#### NOTE
+The same information can given by SyncDraw event.
+
+### getAreaInfo(const char *label, json_object *out_obj)
+
+**args1: String of application name**
+**args2: `{ }`**
+This function is same with `getAreaInfo(json_object *in_obj, json_object *out_obj)`,
+but only has difference of 1st argument.
+