lv_subject_t Size

[vwheeler63]

Introduce the problem

Hi, @kisvegabor

Proposal

What would you think of changing

typedef struct {
    lv_ll_t subs_ll;                    /**< Subscribers */
    uint32_t type   : 4;                /**< One of the LV_SUBJECT_TYPE_... values */
    uint32_t size   : 28;               /**< String buffer size or group length */
    lv_subject_value_t value;           /**< Current value */
    lv_subject_value_t prev_value;      /**< Previous value */
    uint32_t notify_restart_query : 1;  /**< If an Observer was deleted during notifcation, start notifying from the beginning. */
    void * user_data;                   /**< Additional parameter, can be used freely by user */
} lv_subject_t;

to

typedef struct {
    lv_ll_t subs_ll;                    /**< Subscribers */
    lv_subject_value_t value;           /**< Current value */
    lv_subject_value_t prev_value;      /**< Previous value */
    void * user_data;                   /**< Additional parameter, can be used freely by user */
    uint32_t type                 : 4;  /**< One of the LV_SUBJECT_TYPE_... values */
    uint32_t size                 : 27; /**< String buffer size or group length */
    uint32_t notify_restart_query : 1;  /**< If an Observer was deleted during notifcation, start notifying from the beginning. */
} lv_subject_t;

to save 4 bytes of memory (32 bytes => 28 bytes) for each lv_subject_t?

Since these are internal values, it would not break the API, and would limit the size of string buffers and group lists to 134217727. It might even be worth considering to reduce the number of bits in the size field even further to reserve a few bits for the future. Just a thought.