tkinter ttk.Treeview: changing background colour of single item when selected

[John O'Hagan]

Hi list

I'm using a ttk Treeview to display a hierarchical data structure. When
an error condition arises in a node, I want the corresponding item in
the Treeview to flash its background color. 

Using a tag to flash the item background works, except when the item is
selected, when the tag has no effect. I want the item to keep flashing
even when selected.

The code below is a minimal example of the issue. It displays a
Treeview containing two items with the first one flashing. If you
select it, you don't see the flashing anymore.

from tkinter import *
from tkinter.ttk import *

root = Tk()
t = Treeview(root)

t.insert('', 0, iid='item1', text='item1')
t.insert('', 1, text='item2')
t.tag_configure('flashtag', background='red')
t.pack()

def flash():
 tags = t.item('item1', 'tags')
 t.item('item1', tags='' if tags else 'flashtag')
 t.after(500, flash)

flash()
mainloop()

Other than tags, the only other way I've found to dynamically change
Treeview backgrounds is using styles, in particular Style.map to
configure the background of a selected item, but they apply to all
items in the Treeview and would flash all selected items, not just the
one I want to keep flashing.

Is there another way to do what I want?

Thanks

--

John