Python Tkinter: Canvas scrolling with MouseWheel

Question

I have created a tree inside a Canvas, and I have also allowed MouseWheel to scroll up and down.

However, how do I prevent scrolling if tree content has not exceed c

Answer 1

I'm pretty unfamiliar with Trees, but it looks like it's just a bunch of Labels. You can measure their heights and compare them with the height of the Canvas to determine if you need to scroll. This is a little sloppy, but it worked for me:

if self.canvas.winfo_reqheight() < len(self.canvas.winfo_children()) * self.canvas.winfo_children()[0].winfo_reqheight():
    self.canvas.yview_scroll(direction, "units")
else:
    pass

EDIT: in case that's too messy, here's the pseudo code:

if CANVAS_HEIGHT < NUMBER_OF_LABELS * LABEL_HEIGHT:
    scroll

Answer 2

You can use the bbox method of canvas to retrieve the actual height of drawn items on canvas. bbox return a tuple defining a rectangle. You can compare it with the height of your canvas widget.

  height = self.canvas.winfo_height()
  _,_,_,items_height = self.canvas.bbox(Tkinter.ALL)
  if (items_height < height):
     direction = 0