nodes/_back_button.py

Part of Dungeon Explorer.

"""Back-button helpers shared across popup screens.

Renders a circular touch-friendly back glyph in the top-left corner. Hit-test
returns True for clicks landing on the disc. Used by popups that want a tap
target equivalent to pressing Esc.
"""

import math

__all__ = [
    "BACK_BTN_CX",
    "BACK_BTN_CY",
    "BACK_BTN_R",
    "draw_back_button",
    "back_button_hit",
    "check_menu_click",
]

# Circular back button anchored to the top-left corner. ~56px diameter is
# finger-friendly and visually consistent across popups.
BACK_BTN_CX = 40.0
BACK_BTN_CY = 40.0
BACK_BTN_R = 28.0


def draw_back_button(renderer) -> None:
    """Draw a tappable "back" glyph (curved arrow) in the top-left corner."""
    cx, cy, r = BACK_BTN_CX, BACK_BTN_CY, BACK_BTN_R
    renderer.circle((cx, cy), r, fill=(0.08, 0.08, 0.10, 0.85))
    renderer.circle((cx, cy), r - 3, fill=(0.22, 0.22, 0.26, 0.9))
    arc_r = r * 0.55
    for deg in range(-70, 200, 12):
        rad = math.radians(deg)
        px = cx + math.cos(rad) * arc_r
        py = cy + math.sin(rad) * arc_r
        renderer.rect((px - 1.5, py - 1.5), (3, 3), fill=(1.0, 0.9, 0.3, 1.0))
    ax = cx + math.cos(math.radians(200)) * arc_r
    ay = cy + math.sin(math.radians(200)) * arc_r
    renderer.polygon([(ax - 8, ay), (ax + 4, ay - 7), (ax + 4, ay + 7)], fill=(1.0, 0.9, 0.3, 1.0))


def back_button_hit(mx: float, my: float) -> bool:
    """True when a click/touch lands on the back button."""
    dx = mx - BACK_BTN_CX
    dy = my - BACK_BTN_CY
    return (dx * dx + dy * dy) <= BACK_BTN_R * BACK_BTN_R


def check_menu_click(
    mx: float, my: float, count: int, origin_x: float, origin_y: float, item_w: float, item_h: float, spacing: float
) -> int | None:
    """Return the index of the clicked menu item in a vertical list, or None."""
    for i in range(count):
        iy = origin_y + i * spacing
        if origin_x <= mx <= origin_x + item_w and iy - 4 <= my <= iy + item_h:
            return i
    return None