[Tkinter-discuss] Hiding and unhiding frames and/or widgets in general

[Jeff Epler]

If you are using "pack" to manage your widgets, then "pack_forget" will
make the widget disappear.  Similarly, there are "grid_forget" and
"place_forget" methods.

When a widget is packed or unpacked, the size of its containing frame
may change, and that propogates up in the widget hierarchy to the
toplevel.  Having the window change size when a field appears or
disappears is probably going to be jarring to the eye.  You can "fix"
this by turning off "geometry propagation" in the frame that contains
the changing widget.  This is done by the grid_propagate or
pack_propagate method of the *container* object.

from Tkinter import *

def size_for_alternatives(parent, kids):
    w = max([k.winfo_reqwidth() for k in kids])
    h = max([k.winfo_reqheight() for k in kids])
    print ([k.winfo_reqwidth() for k in kids]), w
    print ([k.winfo_reqheight() for k in kids]), h
    parent.pack_propagate(0)
    parent.grid_propagate(0)
    parent.configure(width=w, height=h)

def swap():
    if v.get():
        e.pack_forget()
        mb.pack(anchor="w", side="left")

    else:
        mb.pack_forget()
        e.pack(anchor="w", side="left")
        e.focus()
t = Tk()
v = IntVar(t)
c = Checkbutton(t, command=swap, text="Order from menu?", variable=v)
c.pack(anchor="w")

f1 = Frame(t)
l = Label(f1, text="Your order:")
l.pack(side="left")
f = Frame(f1)
f.pack(side="left")
e = Entry(f, width=18)
mb = Menubutton(f, width=8, text="eggs", indicatoron=1, relief="sunken", anchor="w")
m = Menu(mb, tearoff=0); mb.configure(menu=m)
for s in "eggs bacon sausage spam".split():
    m.add_command(label=s, command=lambda s=s: mb.configure(text=s))
f.after_idle(lambda: size_for_alternatives(f, (e, mb)))

f.pack()
f1.pack()
swap()

b = Button(t, text="Place order", command=t.destroy); b.pack(side="top")

f.mainloop()

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