# nearest_px2b.py

# nearest_px2b.py

import tkinter as tk
import math

grid_rows, grid_cols = 9, 9
canvas_size = 600
cell_w = canvas_size / grid_cols
cell_h = canvas_size / grid_rows
cx, cy = grid_rows // 2, grid_cols // 2

root = tk.Tk()
root.title("# nearest_px2b.py")
root.geometry(f"+10+10")
canvas = tk.Canvas(root, width=canvas_size, height=canvas_size, bg='white')
canvas.pack()

def nearest_px2b(x, y, x0, y0):
    dx = x0 - x
    dy = y0 - y
    print(x, y, x0, y0)
    length = math.sqrt(dx*dx + dy*dy)
    if length == 0:
        return (x, y)
    step_x = int(round(dx / length))
    step_y = int(round(dy / length))
    neighbor = (x + step_x, y + step_y)
    return neighbor

def get_cell_index(x, y):
    col = int(x // cell_w)
    row = int(y // cell_h)
    col = min(grid_cols-1, col)
    row = min(grid_rows-1, row)
    return (col, row)

def on_mouse_move(event):
    canvas.delete("highlight")
    xm, ym = get_cell_index(event.x, event.y)
    ncol, nrow = nearest_px2b(xm, ym, cx, cy)

    x0 = xm * cell_w
    y0 = ym * cell_h
    x1 = x0 + cell_w
    y1 = y0 + cell_h
    canvas.create_rectangle(x0, y0, x1, y1, fill="orange", tags="highlight")

    nx0 = ncol * cell_w
    ny0 = nrow * cell_h
    nx1 = nx0 + cell_w
    ny1 = ny0 + cell_h
    canvas.create_rectangle(nx0, ny0, nx1, ny1, fill="lime", tags="highlight")

for i in range(1, grid_cols):
    canvas.create_line(i * cell_w, 0, i * cell_w, canvas_size, fill="gray")
for j in range(1, grid_rows):
    canvas.create_line(0, j * cell_h, canvas_size, j * cell_h, fill="gray")

canvas.bind("<Motion>", on_mouse_move)

root.mainloop()