/* RT-4D custom UI layer (Phase 1: custom standby/home screen).
 * Compiled with clang --target=thumbv7em, linked at 0x08029000, injected over
 * the russified stock image. Calls stock SDK functions by absolute address.
 * Reads only RAM caches + calls display/ADC primitives -> codeplug & CPS untouched.
 */
typedef unsigned char  u8;
typedef unsigned short u16;
typedef unsigned int   u32;

/* --- stock SDK (thumb entry = addr|1) --- */
#define DRAW_STRING ((void (*)(u8 pg, u8 x, const void *s, u16 n, u8 mode))0x08008A51)
#define STOCK_DRAW  ((void (*)(void))0x0801E1BD)          /* ui_draw_dispatch */

/* --- RAM state --- */
#define GSCR   (*(volatile u8 *)0x200008B3)               /* current screen id */
#define GDISP  ((volatile u8 *)0x200009C3)                /* home display struct */

/* draw one full-width (18-char) space-padded line from a source field.
 * Full-coverage fixed-width paint => no clear needed, no flicker. */
static void line_field(u8 pg, const volatile u8 *src, int n)
{
    char b[18];
    int i;
    for (i = 0; i < 18; i++) {
        u8 c = (i < n) ? src[i] : 0x20;
        if (c == 0 || c == 0xFF) c = 0x20;               /* pad -> space */
        b[i] = (char)c;
    }
    DRAW_STRING(pg, 0, b, 18, 0);
}

static void my_home(void)
{
    line_field(0, GDISP + 0x00, 16);                     /* line 0: name / mode tag   */
    line_field(2, GDISP + 0x20, 16);                     /* line 1: Area A freq/chan   */
    line_field(4, GDISP + 0x32, 16);                     /* line 2: Area B            */
    line_field(6, GDISP + 0x15, 7);                      /* line 3: CH-/A-/D- prefix   */
}

/* hooked in at the ui_tick_normal draw dispatch (bl @0x080207E6). */
void my_draw_router(void)
{
    if (GSCR == 0)
        my_home();                                       /* our custom home screen */
    else
        STOCK_DRAW();                                    /* stock draws all other screens */
}