Move a tkinter canvas with Mouse
The canvas has built-in support for scrolling with the mouse, via the scan_mark
and scan_dragto
methods. The former remembers where you clicked the mouse, and the latter scrolls the window an appropriate amount of pixels.
Note: the gain
attribute tells scan_moveto
how many pixels to move for each pixel the mouse moves. By default it is 10, so if you want 1:1 correlation between the cursor and the canvas you will need to set this value to 1 (as shown in the example).
Here's an example:
import Tkinter as tk
import random
class Example(tk.Frame):
def __init__(self, root):
tk.Frame.__init__(self, root)
self.canvas = tk.Canvas(self, width=400, height=400, background="bisque")
self.xsb = tk.Scrollbar(self, orient="horizontal", command=self.canvas.xview)
self.ysb = tk.Scrollbar(self, orient="vertical", command=self.canvas.yview)
self.canvas.configure(yscrollcommand=self.ysb.set, xscrollcommand=self.xsb.set)
self.canvas.configure(scrollregion=(0,0,1000,1000))
self.xsb.grid(row=1, column=0, sticky="ew")
self.ysb.grid(row=0, column=1, sticky="ns")
self.canvas.grid(row=0, column=0, sticky="nsew")
self.grid_rowconfigure(0, weight=1)
self.grid_columnconfigure(0, weight=1)
for n in range(50):
x0 = random.randint(0, 900)
y0 = random.randint(50, 900)
x1 = x0 + random.randint(50, 100)
y1 = y0 + random.randint(50,100)
color = ("red", "orange", "yellow", "green", "blue")[random.randint(0,4)]
self.canvas.create_rectangle(x0,y0,x1,y1, outline="black", fill=color)
self.canvas.create_text(50,10, anchor="nw",
text="Click and drag to move the canvas")
# This is what enables scrolling with the mouse:
self.canvas.bind("<ButtonPress-1>", self.scroll_start)
self.canvas.bind("<B1-Motion>", self.scroll_move)
def scroll_start(self, event):
self.canvas.scan_mark(event.x, event.y)
def scroll_move(self, event):
self.canvas.scan_dragto(event.x, event.y, gain=1)
if __name__ == "__main__":
root = tk.Tk()
Example(root).pack(fill="both", expand=True)
root.mainloop()
Basj
I work on R&D involving Python, maths, machine learning, deep learning, data science, product design, and MacGyver solutions to complex problems. I love prototyping, building proofs-of-concept. For consulting/freelancing inquiries : [email protected]
Updated on June 11, 2022Comments
-
Basj almost 2 years
I would like to move a whole tkinter
Canvas
with Mouse Click (hold) + Motion of the mouse. I tried withcanvas.move
but it doesn't work unfortunately.How can I scroll in the whole canvas ? (not move each element of the canvas, but rather scroll the displayed area of the canvas)
import Tkinter as Tk oldx = 0 oldy = 0 def oldxyset(event): global oldx, oldy oldx = event.x oldy = event.y def callback(event): # How to move the whole canvas here? print oldx - event.x, oldy - event.y root = Tk.Tk() c = Tk.Canvas(root, width=400, height=400, bg='white') o = c.create_oval(150, 10, 100, 60, fill='red') c.pack() c.bind("<ButtonPress-1>", oldxyset) c.bind("<B1-Motion>", callback) root.mainloop()