TreeMenu.h

// TreeMenu — a small hierarchical menu renderer on top of LVGL.
//
// Data model: a static const tree of TreeMenuNode. A node is either a leaf
// (on_activate set, children NULL) or a branch (children set, on_activate
// ignored). Every non-root level automatically gets a "back" row injected
// at position 0 — you never declare it yourself.
//
// Input-agnostic: this library never reads any button/input device. The
// host app wires its own input (physical buttons, touch, ...) to
// treemenu_next()/treemenu_prev()/treemenu_activate().
#ifndef TREEMENU_H
#define TREEMENU_H

#include <lvgl.h>
#include <stdint.h>

#ifdef __cplusplus
extern "C" {
#endif

typedef struct TreeMenuNode {
    const char *label;
    void (*on_activate)(const struct TreeMenuNode *self, void *userdata);  // NULL for a branch node
    const struct TreeMenuNode *children;        // NULL for a leaf node
    uint16_t children_count;
} TreeMenuNode;

typedef struct {
    lv_obj_t *parent;            // where to create the menu container
    int16_t  x, y;               // position within parent (default 0,0)
    int16_t  width, height;      // size of the menu area (0 = fill parent)
    int16_t  row_height;         // height of one row, e.g. 18
    uint32_t color_active;       // fill of the selected row
    uint32_t color_text;         // label color of every other (unselected) row
    uint32_t bg_color;           // background of `parent` itself (visible
                                  // behind/below the menu when it doesn't
                                  // fill the whole area)
    int16_t  text_margin_left;   // left margin of each row's label, in px
    const char *back_label;      // NULL = "< Back"
    const lv_font_t *font_row;   // row label font, NULL = LV_FONT_DEFAULT
    uint32_t color_separator;    // bottom border of every unselected row
    int16_t  select_radius;      // corner radius of the selected row's fill
    uint32_t color_text_active;  // label color of the selected row
    uint32_t color_chevron;      // submenu-arrow color (fixed, not selection-dependent)
    const char *root_label;      // breadcrumb label for the top level, e.g. "Home". NULL = no breadcrumb.
    int16_t  breadcrumb_height;  // height reserved for the breadcrumb strip above the rows. 0 = disabled.
    int16_t  breadcrumb_gap;     // extra gap between the breadcrumb and the first row
    uint32_t color_breadcrumb;   // breadcrumb text color
    const lv_font_t *font_breadcrumb;  // NULL = LV_FONT_DEFAULT
    void     *userdata;          // passed as-is to on_activate callbacks
} TreeMenuConfig;

// Builds the root level and displays it. Call once, after the LVGL display
// driver is registered.
void treemenu_init(TreeMenuConfig *cfg, const TreeMenuNode *root_children, uint16_t root_count);

// Moves the selection to the next / previous row, wrapping around. Redraws
// only the highlight (cheap — no widget rebuild).
void treemenu_next(void);
void treemenu_prev(void);

// Activates the selected row:
//   - "back" row      -> pops one level, restores the parent's selection
//   - branch node      -> pushes the current level, descends into it
//   - leaf node         -> calls its on_activate(self, userdata)
void treemenu_activate(void);

#ifdef __cplusplus
}
#endif

#endif  // TREEMENU_H