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

[Thomas Passin]

I haven't worked specifically with a Treeview, but I think you need to
detect the onClick event (or an onSelect event if there is one) and have
that trigger the flashing. Otherwise the selection probably overwrites
styling that you added. That's what I do for classic Tk buttons to make
them flash when selected. (I only flash once, though; I don't keep them
flashing).

[stefalem]

> Is there another way to do what I want?

try this:

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)

itemselected = t.selection()
for x in itemselected:
if (x == 'item1'):
t.selection_remove(t.get_children())

flash()
mainloop()

[stefalem]

I apologize for the 3 messages sent, I could not access the usual news
server and with Google Groups I messed up :)

[John O'Hagan]

On Mon, 2023-02-06 at 10:19 -0800, stefalem wrote:
> Il giorno sabato 4 febbraio 2023 alle 11:43:29 UTC+1 John O'Hagan ha
> scritto:
> ...

>
> > Is there another way to do what I want? 
>

> 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)
>  itemselected = t.selection()
>  for x in itemselected:
>   if (x == 'item1'):
>    t.selection_remove(t.get_children())
>
> flash()

Thank you for your reply. Unfortunately that's not quite what I'm
after, because it unselects the flashing item.

My goal was to be able to change the colour of an individual item
regardless of whether it is selected or not. To do that, it is
necessary to be able to change the colour of an individual selected
item, without changing the selection or changing the colour of other
selected items. It seems this isn't possible.

Thanks

John

[stefalem]

Il 12/02/23 12:10, John O'Hagan ha scritto:

> My goal was to be able to change the colour of an individual item
> regardless of whether it is selected or not. To do that, it is
> necessary to be able to change the colour of an individual selected
> item, without changing the selection or changing the colour of other
> selected items. It seems this isn't possible.

ok sorry. As another alternative I had thought of this:

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()

style = Style()
styleDefault = (style.map("Treeview"))

def flash():
tags = t.item('item1', 'tags')
t.item('item1', tags='' if tags else 'flashtag')
t.after(500, flash)
itemselected = t.selection()
for x in itemselected:
if (x == 'item1'):

style.configure('Treeview', selectbackground='red')
style.map('Treeview', background=[('disabled', 'white')],
foreground=[('disabled', 'red')])
else:
style.map('Treeview', background=[('selected',
styleDefault['background'][1][1])],
foreground=[('selected',
styleDefault['background'][0][1])])
flash()
mainloop()

Maybe it can be useful for other situations.

Bye bye

[Thomas Passin]

On 2/12/2023 6:10 AM, John O'Hagan wrote:
> On Mon, 2023-02-06 at 10:19 -0800, stefalem wrote:

>> Il giorno sabato 4 febbraio 2023 alle 11:43:29 UTC+1 John O'Hagan ha
>> scritto:
>> ...

>>
>>> Is there another way to do what I want?
>>

>> 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)
>>  itemselected = t.selection()
>>  for x in itemselected:
>>   if (x == 'item1'):
>>    t.selection_remove(t.get_children())
>>
>> flash()
>

> Thank you for your reply. Unfortunately that's not quite what I'm
> after, because it unselects the flashing item.
>

> My goal was to be able to change the colour of an individual item
> regardless of whether it is selected or not. To do that, it is
> necessary to be able to change the colour of an individual selected
> item, without changing the selection or changing the colour of other
> selected items. It seems this isn't possible.

I haven't worked with ttk objects or Treeviews, but judging from old
style objects, I think you have to re-apply your color and flashing when
the item becomes selected and possibly again when it becomes unselected.

Depending on exactly what effect you want, you may also need to apply
color and flashing when the mouse moves over the item and again when it
leaves. When I make changes in e.g. color, I like to save the previous
value(s) in the object itself. That way I can easily restore say a
background color without having to work out what it used to be, which
may be some color that Tk applies based on the desktop theme and who
know what else.

Here's an example (simplified) for changing color on mouse hover and
leave events:

BG_KEY = 'bg' if platform.lower().startswith('win') \
else 'activebackground' # Different for Linux!

def on_enter(event):
w = event.widget
w.old_bg = w.cget('bg')
w[BG_KEY] = BUTTON_HOVER # Color you have chosen

def on_leave(event):
w = event.widget
_bg = w.old_bg
w[BG_KEY] = _bg

[John O'Hagan]

On Sun, 2023-02-12 at 08:59 -0500, Thomas Passin wrote:

[...]

> On 2/12/2023 6:10 AM, John O'Hagan wrote:

[...]

Thank you again for your reply, Thomas. I didn't know tkinter
configuration keys have different names on different platforms, that
seems unneccesary! I also like the idea of storing the original
settings on the object itself.

However, because of the nature of ttk widgets, I think I'm stuck with
my original issue. Unlike classic tkinter widgets, a lot of the ttk
configuration options are not available on individual widgets, but must
be done through styles or tags. On Treeviews (and possibly other ttk
widgets), the colours for selected items can only be set using
style.map (AFAIK).  The colours for individual items can (only?) be set
using tags, but this is evidently overridden when the item is
selected by the selection colour dictated by the style. Treeview tags
do not have a 'selectbackground' option like many tkinter widgets do.
(Fonts _can_ be set this way, so I could flash, say, the font size, but
that's ugly!)

As as aside, IMO ttk looks great (and Treeview is really useful) but
this approach to configuration is a double-edged sword. On one hand
it's super-easy to change the whole look, but on the other, it can be
overly restrictive if you want to control the look of individual
widgets. 

I might try to put forward a feature request to add a
'selectbackground' option to ttk tags to see if there's any interest.

Thanks

--

John