Changes to tkinter result in (unexpected) widget map call return changes wrt. 3.7

[jslvtr]

BPO	38661
Nosy	@pfmoore, @tjguk, @zware, @serhiy-storchaka, @zooba, @j4321, @jslvtr
Superseder	bpo-42328: ttk style.map function incorrectly handles the default state for element options.

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2020-12-19.17:47:23.960>
created_at = <Date 2019-11-01.14:32:27.901>
labels = ['3.8', 'type-bug', 'expert-tkinter', 'OS-windows']
title = 'Changes to tkinter result in (unexpected) widget map call return changes wrt. 3.7'
updated_at = <Date 2020-12-19.17:47:23.959>
user = 'https://github.com/jslvtr'

bugs.python.org fields:

activity = <Date 2020-12-19.17:47:23.959>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = True
closed_date = <Date 2020-12-19.17:47:23.960>
closer = 'serhiy.storchaka'
components = ['Tkinter', 'Windows']
creation = <Date 2019-11-01.14:32:27.901>
creator = 'jslvtr'
dependencies = []
files = []
hgrepos = []
issue_num = 38661
keywords = []
message_count = 2.0
messages = ['355818', '383091']
nosy_count = 7.0
nosy_names = ['paul.moore', 'tim.golden', 'zach.ware', 'serhiy.storchaka', 'steve.dower', 'j-4321-i', 'jslvtr']
pr_nums = []
priority = 'normal'
resolution = 'duplicate'
stage = 'resolved'
status = 'closed'
superseder = '42328'
type = 'behavior'
url = 'https://bugs.python.org/issue38661'
versions = ['Python 3.8']

[jslvtr]

Hello!

I've encountered what might be a bug.

Up till now we had some working code that did this:

maps = self.style.map('TCombobox')
if maps:
    self.style.map('DateEntry', **maps)

Modifying a custom style to mimic the map of another. This has worked fine until Python 3.7, because the return value of .map is something that you can pass to .map as kw and it'll process it fine.

The return value of .map in Python 3.7 is something like this, for the TCombobox:

<class 'dict'>: {'focusfill': [('readonly', 'focus', 'SystemHighlight')], 'foreground': [('disabled', 'SystemGrayText'), ('readonly', 'focus', 'SystemHighlightText')], 'selectforeground': [('!focus', 'SystemWindowText')], 'selectbackground': [('!focus', 'SystemWindow')]}

Which is as you'd expect (and the docs say): a dictionary of properties to lists, where each list can contain multiple tuples describing the required state and final value of the property.

However in Python 3.8, the value returned by .map is this:

<class 'dict'>: {'focusfill': ['readonly focus', 'SystemHighlight'], 'foreground': ['disabled', 'SystemGrayText', 'readonly focus', 'SystemHighlightText'], 'selectforeground': ['!focus', 'SystemWindowText'], 'selectbackground': ['!focus', 'SystemWindow']}

The tuples are missing. This then causes a number of problems downstream, such as the final property values being split into the constituent letters instead of the values within each tuple.

[serhiy-storchaka]

This was likely caused by different versions of Tk.

It should be fixed now in bpo-42328. Style.map() should convert result to uniform representation on all versions and platforms, and accept input in different forms. Please check.