#if 0
/*
** [x] Choosing a keying strategy from user code
**  [x] Using parents
**  [x] Using file and line
** [ ] Keyboard friendliness
** [x] ui_em size
** [ ] use strictness to 'solve violations'
** [ ] scrolling
** [ ] vieweing type info
** [ ] slider
** [ ] button
** [ ] pernament state
*/

typedef struct ui_id_t ui_id_t;
struct ui_id_t {
    u64 value;
};

typedef struct ui_code_loc_t ui_code_loc_t;
struct ui_code_loc_t {
    char *file;
    int line;
    int counter;
};
#define UI_CODE_LOC (ui_code_loc_t){.file = __FILE__, .line = __LINE__, .counter = __COUNTER__}

typedef enum {
    ui_axis2_x,
    ui_axis2_y,
    ui_axis2_count,
} ui_axis2_t;

typedef enum {
    ui_size_kind_null,
    ui_size_kind_pixels,
    ui_size_kind_text_content,
    ui_size_kind_percent_of_parent,
    ui_size_kind_children_sum,
} ui_size_kind_t;

typedef struct ui_size_t ui_size_t;
struct ui_size_t {
    ui_size_kind_t kind;
    f32 value;
    f32 strictness;
};

typedef struct ui_box_flags_t ui_box_flags_t;
struct ui_box_flags_t {
    b8 draw_border : 1;
    b8 draw_text   : 1;
    b8 draw_rect   : 1;

    b8 scroll      : 1;
};

typedef struct ui_box_t ui_box_t;
struct ui_box_t {
    // recreated every frame in building code
    ui_box_t     *next;
    ui_box_t     *prev;
    ui_box_t     *parent;
    ui_box_t     *first;
    ui_box_t     *last;
    i32           node_count;

    ui_box_flags_t flags;
    s8_t          string;
    ui_size_t     semantic_size[ui_axis2_count];
    ui_axis2_t    grow_axis;
    ui_code_loc_t loc;
    b32           created_new;

    // layout
    f32           iter_pos[ui_axis2_count];

    // preserving state
    ui_id_t   id; // important position!: offset(id) used for partial zeroing
    u64       last_touched_event_id;
    ui_box_t *hash_next;
    ui_box_t *hash_prev;

    // layout
    f32     computed_rel_pos[ui_axis2_count];
    f32     computed_size[ui_axis2_count];
    r2f32_t rect;
    v2f32_t view_offset;

    // state
    b32 expanded;
};

typedef struct ui_signal_t ui_signal_t;
struct ui_signal_t {
    ui_box_t *box;
    b8 clicked;
    b8 dragging;

    // b8 double_clicked;
    // b8 right_clicked;
    // b8 pressed;
    // b8 released;
    // b8 dragging;
    // b8 hovering;
};

typedef struct ui_id_flags_t ui_id_flags_t;
struct ui_id_flags_t {
    b8 use_hierarchy;
    b8 use_code_loc;
    b8 use_string;
};

typedef struct ui_t ui_t;
struct ui_t {
    ma_arena_t *box_arena; // required to be only used for boxes
    app_event_t *event;
    app_frame_t *frame;

    i32 allocated_boxes;
    ui_box_t *box_array; // first item on arena
    ui_box_t *root;
    ui_box_t *top;

    ui_box_t *free_first;
    ui_box_t *hash_first;
    ui_box_t *hash_last;

    ui_id_t hot;
    ui_id_t active;

    int indent_stack;

    ui_id_flags_t id_flags;
};

gb ui_t *ui = NULL;
gb_read_only ui_id_t ui_null_id;
gb_read_only ui_box_t ui_null_box;

fn b32 ui_is_null_id(ui_id_t id) { return id.value == 0; }
fn b32 ui_is_null_box(ui_box_t *box) { return box->id.value == 0; }
fn b32 ui_is_hot_box(ui_box_t *box) { return !ui_is_null_box(box) && box->id.value == ui->hot.value; }
fn b32 ui_is_active_box(ui_box_t *box) { return !ui_is_null_box(box) && box->id.value == ui->active.value; }

#define ev_left(ev) ((ev)->mouse_button == app_mouse_button_left)
#define ev_left_up(ev) ((ev)->kind == app_event_kind_mouse_up && ev_left(ev))
#define ev_left_down(ev) ((ev)->kind == app_event_kind_mouse_down && ev_left(ev))

fn ui_size_t ui_size(ui_size_kind_t kind, f32 value) { return (ui_size_t){.kind = kind, .value = value}; }
#define ui_pixels(value) ui_size(ui_size_kind_pixels, value)
#define ui_em(value) ui_size(ui_size_kind_pixels, value * rn_state.main_font.size)
#define ui_text() ui_size(ui_size_kind_text_content, 0)
#define ui_children_sum() ui_size(ui_size_kind_children_sum, 0)
#define ui_percent(value) ui_size(ui_size_kind_percent_of_parent, value)