docs/src/common-widget-features/flags.rst
.. _lv_obj_flags:
Some widget attributes can be enabled or disabled using
:cpp:expr:lv_obj_add_flag(widget, LV_OBJ_FLAG_...) and
:cpp:expr:lv_obj_remove_flag(widget, LV_OBJ_FLAG_...).
To save memory, widgets store these flags in a bitfield. To check if a flag is set, use:
:cpp:expr:lv_obj_has_flag(obj, LV_OBJ_FLAG_...).
The available flags are:
LV_OBJ_FLAG_HIDDEN: Make the widget hidden (as if it weren’t there at all).LV_OBJ_FLAG_CLICKABLE: Make the widget clickable by input devices.LV_OBJ_FLAG_CLICK_FOCUSABLE: Add the focused state to the widget when clicked.LV_OBJ_FLAG_CHECKABLE: Toggle the checked state when the widget is clicked.LV_OBJ_FLAG_SCROLLABLE: Make the widget scrollable.LV_OBJ_FLAG_SCROLL_ELASTIC: Allow elastic scrolling with slower movement.LV_OBJ_FLAG_SCROLL_MOMENTUM: Enable momentum scrolling (continue scrolling when “thrown”).LV_OBJ_FLAG_SCROLL_ONE: Allow scrolling only one snappable child.LV_OBJ_FLAG_SCROLL_CHAIN_HOR: Propagate horizontal scrolling to the parent.LV_OBJ_FLAG_SCROLL_CHAIN_VER: Propagate vertical scrolling to the parent.LV_OBJ_FLAG_SCROLL_CHAIN: Shorthand for SCROLL_CHAIN_HOR | SCROLL_CHAIN_VER.LV_OBJ_FLAG_SCROLL_ON_FOCUS: Automatically scroll to make the widget visible when focused.LV_OBJ_FLAG_SCROLL_WITH_ARROW: Allow scrolling the focused widget with arrow keys.LV_OBJ_FLAG_SNAPPABLE: Allow the widget to be snapped if the parent has scroll snapping enabled.LV_OBJ_FLAG_PRESS_LOCK: Keep the widget in the pressed state even if the pointer moves outside it.LV_OBJ_FLAG_EVENT_BUBBLE: Propagate events to the parent.LV_OBJ_FLAG_EVENT_TRICKLE: Propagate events to children.LV_OBJ_FLAG_STATE_TRICKLE: Propagate state changes to children.LV_OBJ_FLAG_GESTURE_BUBBLE: Propagate gestures to the parent.LV_OBJ_FLAG_ADV_HITTEST: Enable more accurate hit (click) testing (e.g., account for rounded corners).LV_OBJ_FLAG_IGNORE_LAYOUT: Exclude the widget from layout positioning.LV_OBJ_FLAG_FLOATING: Do not scroll with the parent and ignore layout.LV_OBJ_FLAG_SEND_DRAW_TASK_EVENTS: Enable sending :cpp:enumerator:LV_EVENT_DRAW_TASK_ADDED events.LV_OBJ_FLAG_OVERFLOW_VISIBLE: Allow children to overflow outside the widget's bounds.LV_OBJ_FLAG_RADIO_BUTTON: Allow only one RADIO_BUTTON sibling to be checked.LV_OBJ_FLAG_FLEX_IN_NEW_TRACK: Start a new flex track on this item.LV_OBJ_FLAG_LAYOUT_1: Custom flag, free to use by layouts.LV_OBJ_FLAG_LAYOUT_2: Custom flag, free to use by layouts.LV_OBJ_FLAG_WIDGET_1: Custom flag, free to use by widgets.LV_OBJ_FLAG_WIDGET_2: Custom flag, free to use by widgets.LV_OBJ_FLAG_USER_1: Custom flag, free to use by the user.LV_OBJ_FLAG_USER_2: Custom flag, free to use by the user.Some examples:
.. code-block:: c
/* Hide a Widget */
lv_obj_add_flag(widget, LV_OBJ_FLAG_HIDDEN);
/* Make a Widget non-clickable */
lv_obj_remove_flag(widget, LV_OBJ_FLAG_CLICKABLE);
/* Check if it is clickable */
if(lv_obj_has_flag(widget, LV_OBJ_FLAG_CLICKABLE)) printf("Clickable\n");
Adding and/or Removing Multiple Flags
When adding or removing multiple flags, you have two options:
Option 1: Multiple calls (Recommended)
This approach is clearer and works seamlessly in both C and C++:
.. code-block:: c
lv_obj_add_flag(widget, LV_OBJ_FLAG_CLICKABLE);
lv_obj_add_flag(widget, LV_OBJ_FLAG_EVENT_BUBBLE);
Option 2: Single call with bitwise OR
You can combine multiple flags in one call using the bitwise OR operator (|). When using a C++ compiler, you must cast the result:
.. code-block:: c
lv_obj_add_flag(widget, (lv_obj_flag_t)(LV_OBJ_FLAG_CLICKABLE | LV_OBJ_FLAG_EVENT_BUBBLE));
.. note::
The cast to ``lv_obj_flag_t`` is required in C++ due to stricter type checking, but is optional in C.