IDLE add font resizing hot keys and wheel

[rhettinger]

BPO	17642
Nosy	@rhettinger, @terryjreedy, @taleinat, @giampaolo, @serwy, @roseman, @rovitotv, @ZackerySpytz
PRs	gh-61842: Add hotkeys to resize IDLE's font #17107
Files	issue17642_patch.diff ZoomInOut.patch ZoomInOut.patch2

^{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 = None
created_at = <Date 2013-04-06.06:06:25.800>
labels = ['expert-IDLE', 'type-feature', '3.8', '3.9']
title = 'IDLE add font resizing hot keys and wheel'
updated_at = <Date 2019-11-17.11:41:47.679>
user = 'https://github.com/rhettinger'

bugs.python.org fields:

activity = <Date 2019-11-17.11:41:47.679>
actor = 'taleinat'
assignee = 'terry.reedy'
closed = False
closed_date = None
closer = None
components = ['IDLE']
creation = <Date 2013-04-06.06:06:25.800>
creator = 'rhettinger'
dependencies = []
files = ['30051', '30074', '30251']
hgrepos = []
issue_num = 17642
keywords = ['patch']
message_count = 18.0
messages = ['186118', '186138', '186654', '188010', '188019', '188030', '188031', '188124', '188128', '189141', '189195', '226328', '273687', '273978', '273979', '350259', '350320', '356413']
nosy_count = 12.0
nosy_names = ['rhettinger', 'terry.reedy', 'taleinat', 'giampaolo.rodola', 'roger.serwy', 'markroseman', 'Todd.Rovito', 'python-dev', 'edmond.burnett', 'alex.rodas', 'Abhishek.Kumar', 'ZackerySpytz']
pr_nums = ['17107']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue17642'
versions = ['Python 3.8', 'Python 3.9']

[rhettinger]

Add the standard hot keys for resizing fonts (i.e. on a Mac, CMD-plus and CMD-minus).

[serwy]

IdleX provides this with the ZoomFont.py extension. (See http://idlex.sourceforge.net/extensions.html#Misc) It is useful for showing code on a projector so that students can easily read the screen.

The implementation in ZoomFont.py does not change the font size found in IDLE's configuration. Instead it queries the font size in the text widget and scales accordingly with a relative offset.

IDLE needs a better way to broadcast font configuration changes. Right now, the Code Context extension uses polling every second to check for font changes. I bring this point up because properly incorporating font zooming may require refactoring some code. Incorporating Line Numbers, from bpo-17535 would likely need to rely on this font size broadcasting as well.

[terryjreedy]

On Windows, cntl-+. cntl--

Could we use the tk event system by defining font change events and event handlers?

[alexrodas]

I have made a patch to zoom in and out with <Control-plus> and <Control-minus> events, respectively. I'll upload it soon since the test suite is giving me an error in test_multiprocessing, even before writing the patch.

I have taken a look at ZoomFont.py of IdleX and it also has the option to reset the font size to its original value, but I don't know if this feature was wanted to be added too. However, ZoomFont controls the size of the LineNumber extension, while this patch only changes the font of the editview's text widget.

[AbhishekKumar]

I have submitted a patch that is working fine on Windows and on Ubuntu. I have used ZoomFont.py of IdleX.

On pressing Ctrl+ or Ctrl- it changes the user configuration and updates the font of all open windows as there is a common user configuration for all windows. I have removed polling from CodeContext instead I set font of CodeContext on every font change.

As this is my first patch. Please review it and give your valuable feedback.

[alexrodas]

I have uploaded my patch as well, it doesn't make use of tkfont (just vanilla Tkinter methods) and it works both in Python 2.7 and 3.4 without the need of any import.

I think the main difference with Abhishek Kumar's version is that mine does not use idleConf to retrieve and set the font size. However, the original ZoomFont.py of IdleX does not use it. Is it really necessary?

[alexrodas]

Sorry, I submitted a patch which only works on Windows. This one has been tested on Ubuntu too.

[serwy]

Abhishek, Alejandro, welcome to IDLE development! If you can, please sign a contributor agreement.

We have two patches to create this enhancement, both are good. I suggest that we figure out how to merge the solutions.

The zoom-out binding should also include Ctrl-Equal, so that holding shift is no longer necessary. There's also a corner case where the zooming in on the editor may cause the cursor to go outside of viewing window.

Using idleConf to query the font information is not strictly necessary since the font configuration in the text widget contains the font size already.

In the future, please be careful with licensing. The top part of the ZoomFont.py extension places it under the NCSA license. Fortunately UIUC has allowed me to relicense parts IdleX for the Python Software Foundation.

[AbhishekKumar]

Thanks Roger, for the feedback especially the licence part. I have least idea about licences but will take care in future.

One question: Is it right to change IdleConf on Ctrl+ and Ctrl- ? I mean to change font for all open windows?
It happens with most text editors but not with browsers.

To remove those 2 hacks for CodeContext and LineNumbers, what we can do is write a ResetFont() for each extenstion and can call it from the ResetFont() of editor window like this:
for extension in self.extensions:
extension.ResetFont()
so that we don't have to write seperate font-size hacks for each extension while resetting the font.

[alexrodas]

I have merged the two patches: Now it queries the font size as I did in the original patch, and it also stores the position of the cursor based on Abhishek Kumar's modification of ZoomFont.py.

[serwy]

@abhishek: I'd rather not require extensions to have a new method for resetting font sizes. Instead, a virtual event can be bound to a callback by the extension if it needs to know about a font change.

@alejandro: It looks like there's a bug in ZoomFont.py where the cursor can go off screen which has propagated into these patches. That's my fault.

I'll take a look at these points later this week.