.. _indev_button:

=============== Hardware Button

Overview

A Hardware Button is an external button typically located next to the screen and assigned to specific coordinates on the screen. If a button is pressed, it simulates a press at the assigned coordinate, similar to a touchpad.

To assign Hardware Buttons to coordinates, use :cpp:expr:lv_indev_set_button_points(my_indev, points_array).

points_array should look like this:

.. code-block:: c

static const lv_point_t points_array[] = {
    {12,30}, /* First button is assigned to x=12; y=30 */
    {60,90}  /* Second button is assigned to x=60; y=90 */
};

.. admonition:: Important:

``points_array`` must not go out of scope. Declare it either as a global variable
or as a static variable inside a function.

The index of the pressed button should be set in data->btn_id in the read_cb.

data->state should also be set to either :cpp:enumerator:LV_INDEV_STATE_PRESSED or :cpp:enumerator:LV_INDEV_STATE_RELEASED.

Example

Here is a complete example:

.. code-block:: c

static const lv_point_t points_array[] = { {12,30}, /* First button is assigned to x=12; y=30 / {60,90} / Second button is assigned to x=60; y=90 */ };

lv_indev_t * indev = lv_indev_create(); lv_indev_set_type(indev, LV_INDEV_TYPE_BUTTON); lv_indev_set_button_points(indev, points_array); lv_indev_set_read_cb(indev, button_read);

...

void button_read(lv_indev_t * indev, lv_indev_data_t * data) { /* Get the ID (0,1,2...) of the pressed button. * Let's say it returns -1 if no button was pressed */ int btn_pr = my_btn_read();

   /* Is there a button press? */
   if(btn_pr >= 0) {
      data->btn_id = btn_pr;           /* Save the ID of the pressed button */
      data->state = LV_INDEV_STATE_PRESSED;  /* Set the pressed state */
   } else {
      data->state = LV_INDEV_STATE_RELEASED; /* Set the released state */
   }

}