Idle: require tk 8.5 and ttk widgets, and drop unneeded code.

[terryjreedy]

BPO	24759
Nosy	@terryjreedy, @ncoghlan, @ned-deily, @roseman, @serhiy-storchaka
Files	require85.diff require85-v2.diff require85-v3.diff

^{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 = 'https://github.com/terryjreedy'
closed_at = <Date 2016-06-10.22:41:41.175>
created_at = <Date 2015-07-30.22:18:35.616>
labels = ['expert-IDLE', 'type-feature']
title = 'Idle: require tk 8.5 and ttk widgets, and drop unneeded code.'
updated_at = <Date 2019-03-23.04:15:36.380>
user = 'https://github.com/terryjreedy'

bugs.python.org fields:

activity = <Date 2019-03-23.04:15:36.380>
actor = 'terry.reedy'
assignee = 'terry.reedy'
closed = True
closed_date = <Date 2016-06-10.22:41:41.175>
closer = 'terry.reedy'
components = ['IDLE']
creation = <Date 2015-07-30.22:18:35.616>
creator = 'terry.reedy'
dependencies = []
files = ['43149', '43210', '43254']
hgrepos = []
issue_num = 24759
keywords = ['patch']
message_count = 31.0
messages = ['247701', '247702', '247703', '247721', '247722', '247810', '247811', '247816', '247843', '247845', '247854', '247860', '247862', '247896', '247963', '247993', '248031', '266743', '266803', '267077', '267080', '267108', '267145', '267154', '267156', '267180', '267311', '267313', '267502', '268073', '268074']
nosy_count = 7.0
nosy_names = ['terry.reedy', 'ncoghlan', 'ned.deily', 'markroseman', 'python-dev', 'Al.Sweigart', 'serhiy.storchaka']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue24759'
versions = ['Python 3.6']

[terryjreedy]

PyShell currently has this code

try:
from tkinter import *
except ImportError:
print("** IDLE can't import Tkinter.\n"
"Your Python may not be configured for Tk. **", file=sys.__stderr__)
sys.exit(1)
import tkinter.messagebox as tkMessageBox

When Idle is started from an icon, there is no place for the error message to go, so it appears than nothing happens. But this is the best we can do without invoking system specific error message functions. (This, if possible, would be another issue.) The second import assumes that messagebox is available, which is should be without modification of the tkinter package since long ago. But I think we should guard against someone trying to start Idle on pre 8.5. The following seems to work nicely. This is a prerequisite for any ttk patches. Any comment before I apply?

try:
from tkinter import ttk
except:
root = Tk()
root.withdraw()
tkMessageBox.showerror("Fatal Idle Import Error",
"Idle cannot import required module tkinter.ttk.\n"
"Click OK to exit.",
parent=root)
sys.exit(1)

[terryjreedy]

I tested by renaming installed 3.5 ttk, editing 3.5 PyShell with 3.4, and clicking 3.5 icon.

[roseman]

Sounds good. Only suggestion, given it's user facing, is to have the error message point them towards a solution. Off the top of my head, maybe something like "IDLE requires Python be configured to use Tk 8.5 or newer (you have Tk x.x)" with a title of "IDLE Cannot be Started"

[python-dev]

New changeset 8203fc75b3d2 by Terry Jan Reedy in branch '2.7':
bpo-24759: Gracefull exit Idle if ttk import fails.
https://hg.python.org/cpython/rev/8203fc75b3d2

New changeset 13a8782a775e by Terry Jan Reedy in branch '3.4':
bpo-24759: Gracefull exit Idle if ttk import fails.
https://hg.python.org/cpython/rev/13a8782a775e

[terryjreedy]

Improved message. Thanks. Should be good enough for the extremely few times it should ever be triggered.

[serhiy-storchaka]

IMHO Tcl and Tk should be in title case (as Python or Django) or at least all in upper case (as APL or SDL).

[serhiy-storchaka]

I don't see any mentions of ttk in IDLE source code except added check. Is ttk really required for IDLE?

[terryjreedy]

Re-opened for tweak.

This patch, to exit gracefully if ttk is not available, is the first step before using ttk in Idle. Mark, a long-time tk/ttk expert and site/book author, has volunteered to help upgrade Idle with ttk. Please see "ttk in idle" on Idle-Sig list for general discussion and bpo-24750 for the first substantive patches. The only reason I have not applied the ttk.Scrollbar patch, on that issue, is because Ned mentioned, on that issue, that the OS 8.5 python requires tcl/tk 8.4. I strongly feel that this should not stop the use of ttk, but I an first doing a few non-ttk patches, including Mark's patch for bpo-24745, before continuing.

[terryjreedy]

Re-reading PEP-434, I was mistaken to apply this patch to 2.7 and 3.4 without further discussion. The PEP says "The PEP would apply to minor ..., but not necessarily to possible major re-writes such as switching to themed widgets ... ."

Nick, should I post something on python-ideas or pydev, or continue here (moved from bpo-24750) about making the switch also in 2.7 and 3.4?

I believe it would be best overall to at upgrade Idle 2.7, but I will not cry if we stop patching it now. Ditto for 3.4, which will soon get security fixes only anyway. I am ok with using ttk starting with 3.5.

[roseman]

Got it re: 2.7/3.4. So the only stumbling block left to 8.5/ttk in 3.5 would be the current Mac build that is ok with Tcl/Tk 8.4...?