lv_observer.h

Typedefs

typedef void (*lv_observer_cb_t)(lv_observer_t *observer, lv_subject_t *subject)

Callback called when the observed value changes

Param observer:

pointer to the observer of the callback

Param subject:

pointer to the subject of the observer

Enums

enum lv_subject_type_t

Values for lv_submect_t's type field.

Values:

enumerator LV_SUBJECT_TYPE_INVALID

indicates subject not initialized yet

enumerator LV_SUBJECT_TYPE_NONE

a null value like None or NILt

enumerator LV_SUBJECT_TYPE_INT

an int32_t

enumerator LV_SUBJECT_TYPE_POINTER

a void pointer

enumerator LV_SUBJECT_TYPE_COLOR

an lv_color_t

enumerator LV_SUBJECT_TYPE_GROUP

an array of subjects

enumerator LV_SUBJECT_TYPE_STRING

a char pointer

Functions

void lv_subject_init_int(lv_subject_t *subject, int32_t value)

Initialize an integer type subject

Parameters:

  • subject – pointer to the subject

  • value – initial value

void lv_subject_set_int(lv_subject_t *subject, int32_t value)

Set the value of an integer subject. It will notify all the observers as well.

Parameters:

  • subject – pointer to the subject

  • value – the new value

int32_t lv_subject_get_int(lv_subject_t *subject)

Get the current value of an integer subject

Parameters:

subject – pointer to the subject

Returns:

the current value

int32_t lv_subject_get_previous_int(lv_subject_t *subject)

Get the previous value of an integer subject

Parameters:

subject – pointer to the subject

Returns:

the current value

void lv_subject_init_string(lv_subject_t *subject, char *buf, char *prev_buf, size_t size, const char *value)

Initialize a string type subject

Note

the string subject stores the whole string, not only a pointer

Parameters:

  • subject – pointer to the subject

  • buf – pointer to a buffer to store the string

  • prev_buf – pointer to a buffer to store the previous string, can be NULL if not used

  • size – size of the buffer

  • value – initial value as a string, e.g. "hello"

void lv_subject_copy_string(lv_subject_t *subject, const char *buf)

Copy a string to a subject. It will notify all the observers as well.

Parameters:

  • subject – pointer to the subject

  • buf – the new string

const char *lv_subject_get_string(lv_subject_t *subject)

Get the current value of an string subject

Parameters:

subject – pointer to the subject

Returns:

pointer to the buffer containing the current value

const char *lv_subject_get_previous_string(lv_subject_t *subject)

Get the previous value of an string subject

Note

NULL will be returned if NULL was passed in lv_subject_init_string() as prev_buf

Parameters:

subject – pointer to the subject

Returns:

pointer to the buffer containing the current value

void lv_subject_init_pointer(lv_subject_t *subject, void *value)

Initialize an pointer type subject

Parameters:

  • subject – pointer to the subject

  • value – initial value

void lv_subject_set_pointer(lv_subject_t *subject, void *ptr)

Set the value of a pointer subject. It will notify all the observers as well.

Parameters:

  • subject – pointer to the subject

  • ptr – new value

const void *lv_subject_get_pointer(lv_subject_t *subject)

Get the current value of a pointer subject

Parameters:

subject – pointer to the subject

Returns:

current value

const void *lv_subject_get_previous_pointer(lv_subject_t *subject)

Get the previous value of a pointer subject

Parameters:

subject – pointer to the subject

Returns:

current value

void lv_subject_init_color(lv_subject_t *subject, lv_color_t color)

Initialize an color type subject

Parameters:

  • subject – pointer to the subject

  • color – initial value

void lv_subject_set_color(lv_subject_t *subject, lv_color_t color)

Set the value of a color subject. It will notify all the observers as well.

Parameters:

  • subject – pointer to the subject

  • color – new value

lv_color_t lv_subject_get_color(lv_subject_t *subject)

Get the current value of a color subject

Parameters:

subject – pointer to the subject

Returns:

current value

lv_color_t lv_subject_get_previous_color(lv_subject_t *subject)

Get the previous value of a color subject

Parameters:

subject – pointer to the subject

Returns:

current value

void lv_subject_init_group(lv_subject_t *subject, lv_subject_t *list[], uint32_t list_len)

Initialize a subject group

Parameters:

  • subject – pointer to the subject

  • list – list of other subject addresses, any of these changes subject will be notified

  • list_len – number of elements in list

void lv_subject_deinit(lv_subject_t *subject)

Remove all the observers from a subject and free all allocated memories in it

Note

objects added with lv_subject_add_observer_obj should be already deleted or removed manually.

Parameters:

subject – pointer to the subject

lv_subject_t *lv_subject_get_group_element(lv_subject_t *subject, int32_t index)

Get an element from the subject group's list

Parameters:

  • subject – pointer to the subject

  • index – index of the element to get

Returns:

pointer a subject from the list, or NULL if the index is out of bounds

lv_observer_t *lv_subject_add_observer(lv_subject_t *subject, lv_observer_cb_t observer_cb, void *user_data)

Add an observer to a subject. When the subject changes observer_cb will be called.

Parameters:

  • subject – pointer to the subject

  • observer_cb – callback to call

  • user_data – optional user data

Returns:

pointer to the created observer

lv_observer_t *lv_subject_add_observer_obj(lv_subject_t *subject, lv_observer_cb_t observer_cb, lv_obj_t *obj, void *user_data)

Add an observer to a subject for an object. When the object is deleted, it will be removed from the subject automatically.

Parameters:

  • subject – pointer to the subject

  • observer_cb – callback to call

  • obj – pointer to an object

  • user_data – optional user data

Returns:

pointer to the created observer

lv_observer_t *lv_subject_add_observer_with_target(lv_subject_t *subject, lv_observer_cb_t observer_cb, void *target, void *user_data)

Add an observer to a subject and also save a target.

Parameters:

  • subject – pointer to the subject

  • observer_cb – callback to call

  • target – pointer to any data

  • user_data – optional user data

Returns:

pointer to the created observer

void lv_observer_remove(lv_observer_t *observer)

Remove an observer from its subject

Parameters:

observer – pointer to an observer

void lv_obj_remove_from_subject(lv_obj_t *obj, lv_subject_t *subject)

Remove the observers of an object from a subject or all subjects

Note

This function can be used e.g. when an object's subject(s) needs to be replaced by other subject(s)

Parameters:

  • obj – the object whose observers should be removed

  • subject – the subject to remove the object from, or NULL to remove from all subjects

void *lv_observer_get_target(lv_observer_t *observer)

Get the target of an observer

Parameters:

observer – pointer to an observer

Returns:

pointer to the saved target

lv_obj_t *lv_observer_get_target_obj(lv_observer_t *observer)

Get the target object of the observer. It's the same as lv_observer_get_target and added only for semantic reasons

Parameters:

observer – pointer to an observer

Returns:

pointer to the saved object target

void *lv_observer_get_user_data(const lv_observer_t *observer)

Get the user data of the observer.

Parameters:

observer – pointer to an observer

Returns:

void pointer to the saved user data

void lv_subject_notify(lv_subject_t *subject)

Notify all observers of subject

Parameters:

subject – pointer to a subject

lv_observer_t *lv_obj_bind_flag_if_eq(lv_obj_t *obj, lv_subject_t *subject, lv_obj_flag_t flag, int32_t ref_value)

Set an object flag if an integer subject's value is equal to a reference value, clear the flag otherwise

Parameters:

  • obj – pointer to an object

  • subject – pointer to a subject

  • flag – flag to set or clear (e.g. LV_OBJ_FLAG_HIDDEN)

  • ref_value – reference value to compare the subject's value with

Returns:

pointer to the created observer

lv_observer_t *lv_obj_bind_flag_if_not_eq(lv_obj_t *obj, lv_subject_t *subject, lv_obj_flag_t flag, int32_t ref_value)

Set an object flag if an integer subject's value is not equal to a reference value, clear the flag otherwise

Parameters:

  • obj – pointer to an object

  • subject – pointer to a subject

  • flag – flag to set or clear (e.g. LV_OBJ_FLAG_HIDDEN)

  • ref_value – reference value to compare the subject's value with

Returns:

pointer to the created observer

lv_observer_t *lv_obj_bind_state_if_eq(lv_obj_t *obj, lv_subject_t *subject, lv_state_t state, int32_t ref_value)

Set an object state if an integer subject's value is equal to a reference value, clear the flag otherwise

Parameters:

  • obj – pointer to an object

  • subject – pointer to a subject

  • state – state to set or clear (e.g. LV_STATE_CHECKED)

  • ref_value – reference value to compare the subject's value with

Returns:

pointer to the created observer

lv_observer_t *lv_obj_bind_state_if_not_eq(lv_obj_t *obj, lv_subject_t *subject, lv_state_t state, int32_t ref_value)

Set an object state if an integer subject's value is not equal to a reference value, clear the flag otherwise

Parameters:

  • obj – pointer to an object

  • subject – pointer to a subject

  • state – state to set or clear (e.g. LV_STATE_CHECKED)

  • ref_value – reference value to compare the subject's value with

Returns:

pointer to the created observer

lv_observer_t *lv_obj_bind_checked(lv_obj_t *obj, lv_subject_t *subject)

Set an integer subject to 1 when an object is checked and set it 0 when unchecked.

Note

Ensure the object's LV_OBJ_FLAG_CHECKABLE flag is set

Parameters:

  • obj – pointer to an object

  • subject – pointer to a subject

Returns:

pointer to the created observer

lv_observer_t *lv_label_bind_text(lv_obj_t *obj, lv_subject_t *subject, const char *fmt)

Bind an integer, string, or pointer subject to a label.

Note

fmt == NULL can be used only with string and pointer subjects.

Note

if the subject is a pointer must point to a \0 terminated string.

Parameters:

  • obj – pointer to a label

  • subject – pointer to a subject

  • fmt – optional format string with 1 format specifier (e.g. "%d °C") or NULL to bind the value directly.

Returns:

pointer to the created observer

lv_observer_t *lv_arc_bind_value(lv_obj_t *obj, lv_subject_t *subject)

Bind an integer subject to an arc's value

Parameters:

  • obj – pointer to an arc

  • subject – pointer to a subject

Returns:

pointer to the created observer

lv_observer_t *lv_slider_bind_value(lv_obj_t *obj, lv_subject_t *subject)

Bind an integer subject to a slider's value

Parameters:

  • obj – pointer to a slider

  • subject – pointer to a subject

Returns:

pointer to the created observer

lv_observer_t *lv_roller_bind_value(lv_obj_t *obj, lv_subject_t *subject)

Bind an integer subject to a roller's value

Parameters:

  • obj – pointer to a roller

  • subject – pointer to a subject

Returns:

pointer to the created observer

lv_observer_t *lv_dropdown_bind_value(lv_obj_t *obj, lv_subject_t *subject)

Bind an integer subject to a dropdown's value

Parameters:

  • obj – pointer to a drop down

  • subject – pointer to a subject

Returns:

pointer to the created observer

union lv_subject_value_t
#include <lv_observer.h>

A common type to handle all the various observable types in the same way

Public Members

int32_t num

Integer number (opacity, enums, booleans or "normal" numbers)

const void *pointer

Constant pointer (string buffer, format string, font, cone text, etc)

lv_color_t color

Color

struct lv_subject_t
#include <lv_observer.h>

The subject (an observable value)

Public Members

lv_ll_t subs_ll

Subscribers

uint32_t type
uint32_t size

Might be used to store a size related to type

lv_subject_value_t value

Actual value

lv_subject_value_t prev_value

Previous value

uint32_t notify_restart_query

If an observer deleted start notifying from the beginning.

void *user_data

Additional parameter, can be used freely by the user