Better default font for editor

[roseman]

BPO	24745
Nosy	@terryjreedy, @kbkaiser, @larryhastings, @benjaminp, @ned-deily, @serwy, @roseman
Files	defaultfont.png: Screenshots of default and proposed improved fonts on OS X, Windows, Linux defaultfont.patch: Patch to look for TkFixedFont in config file

^{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 2015-09-04.08:42:25.063>
created_at = <Date 2015-07-29.00:17:07.792>
labels = ['expert-IDLE', 'type-feature']
title = 'Better default font for editor'
updated_at = <Date 2016-05-09.16:10:12.632>
user = 'https://github.com/roseman'

bugs.python.org fields:

activity = <Date 2016-05-09.16:10:12.632>
actor = 'terry.reedy'
assignee = 'terry.reedy'
closed = True
closed_date = <Date 2015-09-04.08:42:25.063>
closer = 'terry.reedy'
components = ['IDLE']
creation = <Date 2015-07-29.00:17:07.792>
creator = 'markroseman'
dependencies = []
files = ['40048', '40091']
hgrepos = []
issue_num = 24745
keywords = ['patch']
message_count = 20.0
messages = ['247549', '247555', '247556', '247614', '247639', '247679', '247787', '247835', '247836', '247837', '248333', '248336', '248347', '248348', '248466', '249727', '249742', '249743', '263200', '265205']
nosy_count = 8.0
nosy_names = ['terry.reedy', 'kbk', 'larry', 'benjamin.peterson', 'ned.deily', 'roger.serwy', 'markroseman', 'python-dev']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue24745'
versions = ['Python 2.7', 'Python 3.4', 'Python 3.5', 'Python 3.6']

[roseman]

By default, IDLE chooses courier for the text editor font.

As you'll see from the attached screenshot, while this looks ok on Windows, it's inconsistent with the standard fixed width fonts on Linux and OS X, and borders on unreadable particularly on the latter.

While this can be changed via the configuration dialog (the 'fixed' versions in the screenshots do just that), this is one of the things that really jumps out at you the first time you run IDLE, and not in a good way.

Tk defines a font named 'TkFixedFont', which we should take advantage of instead of hardcoding courier; details of the font can be retrieved via

tkinter.font.nametofont('TkFixedFont').actual()

Note there's a bit of an overlap here with #<20580>, but suggests that there may be some cases where determining defaults programmatically rather than hardcoding multiple defaults may be appropriate.

[terryjreedy]

I agree that Courier is ugly and a bad thing to hardcode. I long ago switched to Lucida Console, which other than i and l is very close to the Mac/linux examples. I had forgotten that Courier was the default.

Ned, am I correct in thinking you would like this?

Mark, please submit a patch. Too bad that tk does not use something better for Windows too, but I agree that Courier is least bad here.

PS. Leave brackets off issue references like bpo-20580 so they become links. The overlap is minimal; in any case, that issue will need several patches and subissues.

[ned-deily]

With current ActiveTcl 8.5.18 on OS X, "TkFixedFont" translates to Monaco 11 point which looks fine on my laptop. I don't have a Retina display handy to see how it looks there but it's probably an improvement over Courier so changing the default sounds good to me.

[roseman]

Quick question how best to represent this in the config-main.def file. My thought is to leave a "font=" line there so that the GetOption call returns an empty string. The editor code can then detect that and substitute TkFixedFont.

Would this break anything and/or would there be a more preferred approach?

[terryjreedy]

For the benefit of anyone reading the file, I would prefer "font = TkFixedFont", though I notice that LoadFontConfig has a backup default.

Just as important, I think: IDLE Preferences => Font/Tabs => Editor Base Font needs a [Default] button so people can unselect a non-default selection without remembering what the default was. Other changes (re-arrangements) are needed to use the space better, but for now, I think increasing the height to make room would be sufficient. Or perhaps 'TkFixedFont could be added to the top of the list before adding the sorted list of those available.

The tricky issue is this: when a user changes a setting, the change is saved to a change dictionary. When [Apply] or [OK] are clicked, the new values are compared to the defaults and non-defaults are written to the user file. (Some files get sets of values written). So a user needs to be able to select 'TkFixedFont' to avoid having a specific font written to the user file (which might be the only item in the file, and which would override a future change to the binding of TkFixedFont).

[roseman]

I'm ok with putting TkFixedFont in the config file. Only potential downside I see is that the code will look for this specific value, but people may read the config file and assume it could be changed to any Tk*Font.

I'd strongly argue against putting in a default button and/or including TkFixedFont in the list for the following reasons:

1. The config dialog should really be using the platform-specific font chooser for this anyway. (Tk 8.6 does include this dialog btw). The default dialogs don't allow anything like that, and I can't off the top of my head think of any common applications that allow you to revert back to a default.

2. I see no real advantage to being able to switch 'back' to a default. In fact, from the user perspective, there isn't conceptually a default font separate than whatever the 'actual' version of TkFixedFont is (courier, monaco, whatever). What they know is it starts with a certain font, and if they go into the dialog, it shows that font. If they change to a different font (or even back to the original font), that's what shows up next time they start the app.

Is there actually a downside to writing out the per-user config file even if there isn't a "real" change in the font?

[roseman]

I've attached defaultfont.patch which will look for the magic value 'TkFixedFont' in the configuration file and do some appropriate magic with it. Most of the font handling smarts are now in a 'GetFont' call in configHandler, which as a bonus reduces some of the complexity and duplication elsewhere.

[python-dev]

New changeset 55e5f7766d2c by Terry Jan Reedy in branch '2.7':
bpo-24745: Switch from Courier to platform-sensitive TkFixedFont as default
https://hg.python.org/cpython/rev/55e5f7766d2c

New changeset 5c992189414f by Terry Jan Reedy in branch '3.4':
bpo-24745: Switch from Courier to platform-sensitive TkFixedFont as default
https://hg.python.org/cpython/rev/5c992189414f

New changeset 90c02a0bec08 by Terry Jan Reedy in branch '3.5':
bpo-24745: Merge with 3.4
https://hg.python.org/cpython/rev/90c02a0bec08

New changeset 3a731756f9cc by Terry Jan Reedy in branch 'default':
bpo-24745: Merge with 3.5
https://hg.python.org/cpython/rev/3a731756f9cc

[terryjreedy]

Review published with the changes I made, tested, and committed.

I am not convinced that writing all 3 font attributes is needed, which is good since existing user files do not have all 3. But safer for future. Part of my preference to avoid user file when not needed (because only config matches default) is because user files are an occasional point of failure. But we should fix bugs noted in TODOs and on tracker.

[python-dev]

New changeset 82198ae039cd by Terry Jan Reedy in branch '3.4':
bpo-24745: Add ACKS entry.
https://hg.python.org/cpython/rev/82198ae039cd

New changeset bf14b74d6fc0 by Terry Jan Reedy in branch '3.5':
bpo-24745: Add ACKS entry.
https://hg.python.org/cpython/rev/bf14b74d6fc0

New changeset 5744985ad8dc by Terry Jan Reedy in branch '2.7':
bpo-24745: Add ACKS entry.
https://hg.python.org/cpython/rev/5744985ad8dc