how to select multiple objects with mouse in tkinter python gui? - user-interface

Question

I am trying to select multiple objects using mouse just like in windows click and drag. i am using tkinter in python to buils this gui. i am creating objects as shown in below code.
import Tkinter as tk
from Tkinter import *
root = Tk()
w= Canvas(root, width=800, height=768)
w.grid()
w.create_line(200,200,300,300, width=3, tags="line1")
w.create_oval(150,100,170,300, fill="red", tags="oval")
mainloop()
what i am trying to do is if i drag my mouse over multiple objects some def should return the tags of the objects. how can i do this.
Thank you

Answer 1

Save the coordinates on a button-down event, and then on a button-up event use the find_enclosed or find_overlapping method of the canvas to find all items enclosed by the region.

Answer 2

The following code renders a rectangle that follows the cursor and returns a list of element IDs of elements within the rectangle. It uses bindings for when the mouse is pressed within the canvas, when it moves, and when it is released. I then kept a list of elements with their canvas identifier and used that to back lookup the object from the list of selected IDs.
# used to record where dragging from
originx,originy = 0,0
canvas.bind("<ButtonPress-1>", __SelectStart__)
canvas.bind("<B1-Motion>", __SelectMotion__)
canvas.bind("<ButtonRelease-1>", __SelectRelease__)
# binding for drag select
def __SelectStart__(self, event):
oiginx = canvas.canvasx(event.x)
originy = canvas.canvasy(event.y)
selectBox = canvas.create_rectangle(originx,originy,\
originx,originy)
# binding for drag select
def __SelectMotion__(self, event):
xnew = canvas.canvasx(event.x)
ynew = canvas.canvasy(event.y)
# correct cordinates so it gives (upper left, lower right)
if xnew < x and ynew < y:
canvas.coords(selectBox,xnew,ynew,originx,originy)
elif xnew < x:
canvas.coords(selectBox,xnew,originy,originx,ynew)
elif ynew < y:
canvas.coords(selectBox,originx,ynew,xnew,originy)
else:
canvas.coords(selectBox,originx,originy,xnew,ynew)
# binding for drag select
def __SelectRelease__(self, event):
x1,y1,x2,y2 = canvas.coords(selectBox)
canvas.delete(selectBox)
# find all objects within select box
selectedPointers = []
for i in canvas.find_withtag("tag"):
x3,y3,x4,y4 = canvas.coords(i)
if x3>x1 and x4<x2 and y3>y1 and y4<y2:
selectedPointers.append(i)
Callback(selectedPointers)
# function to receive IDs of selected items
def Callback(pointers):
print(pointers)