python - Event when entry's xview changes -

i creating simple program using tkinter. want function called every time xview property of entry changes. there doesn't seem event this, @ least not 1 can find.

the <configure> event fires on resize, handled, doesn't fire when actual value i'm tracking changes in different way, such user dragging mouse see end of entry.

here code:

import tkinter tk import tkfiledialog  root = tk.tk()  class repositoryfolderframe(tk.frame):     def __init__(self, root):         tk.frame.__init__(self, root)         self.build_gui()          self.set_entry_text("searching...")         #root.after(0, self.find_repo)          self.prev_entry_index = len(self.entry.get())         root.bind("<configure>", self.on_entry_resize)         #self.entry.bind(???, self.on_entry_change)         #self.entry.bind("<configure>", self.on_entry_change)      def on_entry_resize(self, event):         cur_entry_index = self.entry.xview()[1]         if cur_entry_index != self.prev_entry_index:             self.entry.xview(self.prev_entry_index)      def on_entry_change(self, event):         # should called when xview changes...         cur_entry_index = self.entry.xview()[1]         self.prev_entry_index = cur_entry_index      def set_entry_text(self, text):         self.entry_text.set(text)         self.entry.xview("end")      def build_gui(self):         label = tk.label(self, text = "repository folder:")         label.pack(side = tk.left)         self.label = label          entry_text = tk.stringvar()         self.entry_text = entry_text          entry = tk.entry(self, width = 50, textvariable = entry_text)         entry.configure(state = 'readonly')         entry.pack(side = tk.left, fill = tk.x, expand = 1)         self.entry = entry          button = tk.button(self, text = "browse...")         button.pack(side = tk.left)         self.button = button  repo_frame = repositoryfolderframe(root) repo_frame.pack(fill = tk.x, expand = 1)  root.mainloop() 

there no mechanism getting notified when xview changes. there ways modifying underlying tcl code, it's more difficult it's worth.

a simple solution write function polls xview every few hundred milliseconds. can keep track of recent xview, compare current, , if has changed can fire off custom event (eg: <<xviewchanged>>) can bind to.

it this:

class repositoryfolderframe(tk.frame):     def __init__(self, root):         ...         self.entry.bind("<<xviewchanged>>", self.on_entry_change)          # keep cache of previous xviews. dictionary         # used in case want more          self._xview = {}         self.watch_xview(self.entry)      def watch_xview(self, widget):         xview = widget.xview()         prev_xview = self._xview.get(widget, "")         self._xview[widget] = xview         if xview != prev_xview:             widget.event_generate("<<xviewchanged>>")         widget.after(100, self.watch_xview, widget) 

you'll need modify edge case entry widget destroyed, though can handle simple try around code. should suitably performant, though might need verify if have literally hundreds of entry widgets.