Flags

Some widget attributes can be enabled or disabled using lv_obj_add_flag and lv_obj_remove_flag.

Some widget attributes can be enabled or disabled using lv_obj_add_flag(widget, LV_OBJ_FLAG_...) and 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: 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 LV_EVENT_DRAW_TASK_ADDED events.
• LV_OBJ_FLAG_OVERFLOW_VISIBLE: Allow children to overflow outside the widget's bounds. See lv_obj_set_ext_draw_size.
• 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:

/* 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++:

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:

lv_obj_add_flag(widget, (lv_obj_flag_t)(LV_OBJ_FLAG_CLICKABLE | LV_OBJ_FLAG_EVENT_BUBBLE));