# Tk_swap_menu.py

# Tk_swap_menu.py

import tkinter as tk

COLORS = '''
red
orange
yellow
lime green
blue
violet
gold
lawn green
royal blue
turquoise
cyan
gold3
dark khaki
khaki
gray
light grey
deep pink
hot pink
pink
'''.strip().splitlines()

block = {}
seq = []

from ctypes import windll, Structure, c_ulong, byref
import ctypes
class POINT(Structure):
    _fields_ = [("x", c_ulong), ("y", c_ulong)]
def xyMouse():
    pt = POINT()
    windll.user32.GetCursorPos(byref(pt))
    return pt

class DragAndDrop(tk.Frame):
    def __init__(self, parent):
        tk.Frame.__init__(self, parent)
        self.parent = parent
        self.parent.columnconfigure(0, weight=1)
        self.grid_columnconfigure(0, weight=1)

        self.block_count = 0
        self.block_h = 25

        self.button = tk.Button(self, text='Add', command=self.addblock)
        self.button.grid(row=0, column=0, columnspan=2, sticky='new')

        self.container = tk.Frame(self)
        self.container.grid(row=1, column=0, sticky='nsew')

        self.canvas = tk.Canvas(self.container, width=200, height=240)
        self.scrollbar = tk.Scrollbar(self.container,
                orient='vertical',command=self.canvas.yview)
        self.canvas.config(yscrollcommand=self.scrollbar.set)
        self.canvas.grid(row=0, column=0, sticky='nsew')
        self.scrollbar.grid(row=0, column=1, sticky='nse')

        self.container.bind('<Configure>', self.handle_scroll)

    def addblock(self):
        if COLORS:
            color=COLORS.pop(0)
            b = str(self.block_count)
            block[b] = tk.Frame(self.canvas, bd=1, relief='solid', bg=color)
            block[b].columnconfigure(0, weight=1)

            grip = tk.Label(block[b], bitmap="gray25", bg=color)
            grip.grid(row=0, column=0, sticky='w')

            grip.bind("<ButtonPress-1>", self.StartMove)
            grip.bind("<ButtonRelease-1>", self.StopMove)
            grip.bind("<B1-Motion>", self.OnMotion)
            idt = tk.Label(block[b], text=self.block_count+1, bg=color, anchor='center')
            idt.grid(row=0, columnspan=2)

            self.canvas.create_window((0, (self.block_count*self.block_h)),
                window=block[b], anchor="nw",
                width=200, height=24)
            seq.append(self.block_count+1)
            self.block_count += 1
        self.handle_scroll(self)

    def handle_scroll(self, event):
        self.canvas.configure(scrollregion=self.canvas.bbox("all"))

    def StartMove(self, event):
        ry = root.winfo_y()+56
        pt = xyMouse()
        self.ym = pt.y
        self.y = self.canvas.canvasy(self.ym)-ry
        self.current = self.canvas.find_closest(10, self.y)[0]
        block[str(self.current-1)].lift()
        self.prev = int((self.canvas.coords(self.current)[1])/self.block_h)

    def OnMotion(self, event):
        pt = xyMouse()
        ym = pt.y
        yy = ym-self.ym
        h = self.block_h
        pp = int((self.canvas.coords(self.current)[1]+h/2)/h)
        if pp != self.prev:
            self.canvas.coords(seq[pp], (0,self.prev*h))
            seq[pp],seq[self.prev] = seq[self.prev],seq[pp]
            self.prev = pp
        mv = min(self.block_h*(self.block_count-1)+h/2, max(0+h/2,self.y+yy))
        self.canvas.coords(self.current, (0,(mv-h/2)))

    def StopMove(self, event):
        h = self.block_h
        mv = int((self.canvas.coords(self.current)[1]+h/2)/h)*h
        self.canvas.coords(self.current, (0,(mv)))


root = tk.Tk()

app = DragAndDrop(root)
app.grid(row=0, column=0, sticky='ew')
root.mainloop()