IDLE: adjust DPI before Tk() for htests.

[terryjreedy]

BPO	33975
Nosy	@terryjreedy, @miss-islington
PRs	bpo-33975: Avoid small type when running IDLE's htests. #7944 [3.7] bpo-33975: Avoid small type when running IDLE's htests. (GH-7944) #7951 [3.6] bpo-33975: Avoid small type when running IDLE's htests. (GH-7944) #7952

^{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 2018-06-27.05:32:49.595>
created_at = <Date 2018-06-27.02:22:16.529>
labels = ['3.8', 'expert-IDLE', 'type-bug', '3.7']
title = 'IDLE: adjust DPI before Tk() for htests.'
updated_at = <Date 2018-06-27.05:32:49.594>
user = 'https://github.com/terryjreedy'

bugs.python.org fields:

activity = <Date 2018-06-27.05:32:49.594>
actor = 'terry.reedy'
assignee = 'terry.reedy'
closed = True
closed_date = <Date 2018-06-27.05:32:49.595>
closer = 'terry.reedy'
components = ['IDLE']
creation = <Date 2018-06-27.02:22:16.529>
creator = 'terry.reedy'
dependencies = []
files = []
hgrepos = []
issue_num = 33975
keywords = ['patch']
message_count = 5.0
messages = ['320531', '320536', '320543', '320544', '320545']
nosy_count = 2.0
nosy_names = ['terry.reedy', 'miss-islington']
pr_nums = ['7944', '7951', '7952']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue33975'
versions = ['Python 3.6', 'Python 3.7', 'Python 3.8']

[terryjreedy]

bpo-33656 patched PyShell to call SetProcessDpiAwareness on Windows nearly first thing, *at module level*, well before calling tkinter.Tk(). The Microsoft docs warn that making the Windows API call after starting the graphics system may not work as expected. With tk 8.6,8, the result is sharp, but small type -- perhaps 7 points instead of 10. This issue is about avoiding type shrinkage, both when running the htest suite as a whole and when running the test for an individual file after running the unittests.

To do that in any process, pyshell must be imported before Tk() is called. The patch adds the following to htest.py.
import idlelib.pyshell # Set Windows DPI awareness before Tk().

I will add the same where needed to the top of if __name__ == '__main__': clauses in idlelib modules, before running unittests.

[terryjreedy]

Because of import caching, subsequent pyshell imports, after the first, do not re-call the Windows API.

Apparently, 'root.destroy()' undoes a previous 'root = Tk()', but not a previous pyshell import. Since IDLE unittests always destroy roots, a unittest before an htest does not require anything more to work right.

Since part of the purpose of human-viewed tests is to determine that widgets look right, it is important that they look the same for testing
as when running IDLE.

[terryjreedy]

New changeset 3c8043d by Terry Jan Reedy in branch 'master':
bpo-33975: Avoid small type when running IDLE's htests. (GH-7944)
3c8043d

[miss-islington]

New changeset 5d2d9d7 by Miss Islington (bot) in branch '3.6':
bpo-33975: Avoid small type when running IDLE's htests. (GH-7944)
5d2d9d7

[terryjreedy]

Both PRs have been merged.