# Tk_DragAndDropDemo.py

# Tk_DragAndDropDemo.py

from Tkinter import *

#--------------------------------------------
class DragableRect:
    def __init__(self, options):
        """
        each DragableRect instance is initialised with a dict :
        d = DragableRect({"parent": canvas, "x": 10, "y": 10, ... })
        dict keys are classic options of
        Canvas's create_rectangle method :
        x, y, width, height, outline, fill, tags
        "parent" is for the container canvas
        "axis" : "both" to drag in evry
        """
        self.parent = options["parent"] # canvas
        self.x = options["x"]
        self.y = options["y"]
        self.width = options["width"]
        self.height = options["height"]
        self.outline = options["outline"]
        self.fill = options["fill"]
        self.tag = options["tag"]
        self.axis = options["axis"] # 'h', 'v' or 'both'

        self.selected = False

    def display(self):
        """
        draw rect on parent Canvas
        """
        self.parent.create_rectangle(
                self.x,
                self.y,
                self.x + self.width,
                self.y + self.height,
                fill = self.fill,
                outline = self.outline,
                tags = self.tag)

    def getPos(self):
        """
        return self coords as (x0, y0, x1, y1)
        """
        return self.parent.coords(self.tag)

class DragableCircle:
    pass

#-----------------------------------------------------------------
class DragAndDrop(Tk):
    """
    Tkinter app based on Tk()
    """
    def __init__(self):
        Tk.__init__(self)
        self.title("Tkinter Drag And Drop")
        self.geometry("400x300+40+40")
        self.can = Canvas(self, width=400, height=300, bg="#000233")
        self.can.pack()

        #these attributes are used in click, drag and drop methods
        self.click_flag = False
        self.offset_x = 0
        self.offset_y = 0

        self.items = [
            DragableRect({
                "parent": self.can,
                "x": 100,
                "y": 100,
                "width": 50,
                "height": 50,
                "outline": "red",
                "fill": "red",
                "tag": "red",
                "axis": "both"
                }),
            DragableRect({
                "parent": self.can,
                "x": 250,
                "y": 50,
                "width": 40,
                "height": 60,
                "outline": "#46b96a",
                "fill": "#46b96a",
                "tag": "green",
                "axis": "h"
                })]

        for i in self.items:
            i.display()

        self.bind("<Button-1>", self.click)
        self.bind("<ButtonRelease-1>", self.drop)
        self.bind("<B1-Motion>", self.drag)

    def click(self, evt):
        """
        if a rect is clicked :
        - switch 'click_flag' to True
        - switch rect's 'selected' attribute to True
        - detect mouse offset from top-left corner of clicked rect
        """
        x, y = evt.x, evt.y
        for i in self.items:
            coords = i.getPos()
            if x > coords[0] and x < coords[2]:
                if y > coords[1] and y < coords[3]:
                    self.click_flag = True
                    i.selected = True
                    self.offset_x = x - i.x
                    self.offset_y = y - i.y
                    break

    def drop(self, evt):
        """
        - switch 'click_flag' and dragged rect's 'selected' attribute to False
        - update rect's 'x' and 'y' attributes
        """
        if self.click_flag:
            x, y = evt.x, evt.y
            self.click_flag = False
            for i in self.items:
                if i.selected:
                    i.x = x - self.offset_x
                    i.y = y - self.offset_y
                    i.selected = False

    def drag(self, evt):
        if self.click_flag:
            x, y = evt.x, evt.y
            for i in self.items:
                if i.selected:
                    self.can.coords(i.tag,
                                    x - self.offset_x,
                                    y - self.offset_y,
                                    (x - self.offset_x) + i.width,
                                    (y - self.offset_y) + i.height)

#-------------------------------------------------------------------
if __name__ == '__main__':

    app = DragAndDrop()
    app.mainloop()