Add event for KeyRelease-Up and KeyRelease-Down to change sample font.

Current code only changed font when using button-click on listbox.

New changeset bb2bae84d6b29f991b757b46430c3c15c60059e9 by terryjreedy (Louie Lu) in branch 'master':
bpo-30870: IDLE: Change sample font when select by key-up/down (#2617)
https://github.com/python/cpython/commit/bb2bae84d6b29f991b757b46430c3c15c60059e9

If one scrolls with the mousewheel or scrollbar, the selection does not change and the example should not change, and I presume it will not with the patch.  If one presses up or down, the selection does change, just as if one clicked, and the example should change.  I consider it a bug that it does not.  Good catch.

New changeset 7ab334233394070a25344d481c8de1402fa12b29 by terryjreedy in branch '3.6':
[3.6] bpo-30870: IDLE: Change sample font when select by key-up/down (GH-2617) (#2640)
https://github.com/python/cpython/commit/7ab334233394070a25344d481c8de1402fa12b29

We already know that setting StringVar font_name triggers a change to changes.  We also know that manually clicking or Up or Down triggers <<ListBoxSelect>>, which sets font_name and redraws the box.  The challenge is to do something that will trigger the virtual event.  Then we can write a test methods something like

    def test_sample(self):
        fontlist = configure.fontlist
        if fontlist.size():
            name0 = fontlist.get(0).lower()
            # fontlist.selection_set(0)  # or something
            print('\n', changes)  # temp to testing that changes changes
            self.assertEqual(changes['main']['EditorWindow']['font'], name0)
But selection_set does not trigger the event.  After fiddling around with various bindings event_generate()s and update()s and update_idletasks(), I concluded, again, that either event_generate or its documentation is badly broken.  The only thing I got to work in hours of experiments is this:

import tkinter as tk
root = tk.Tk()
seq = '<ButtonRelease-1>'
root.bind(seq, lambda event: print('generated', event))
root.update_idletasks()  # or update()
root.event_generate(seq)
# update here fails

Adding a widget and binding to the widget always failed.

Here is my attempt using Serhiy's simulate_mouse_click.  (This goes in test_configdialog.FontTabTest.

    def test_sample(self):
        fontlist = configure.fontlist
        if fontlist.size():
            name0 = fontlist.get(0).lower()
            fontlist.see(0)
            x, y, dx, dy = fontlist.bbox(0)
            fontlist.bind('<ButtonRelease-1>', lambda event: print(event))
            mouse_click(fontlist, x + dx//2, y + dy//2)
            fontlist.update()
            print('\n', changes)  # temporary, see if changes has anything
            self.assertEqual(changes['main']['EditorWindow']['font'], name0)

Serhiy, do you have any idea why I cannot get event_generate to work for a listbox, even with your function? I have tried somewhere close to 20 variations.

Serhiy, I tried tkinter.test.support.simulate_mouse_click to test this patch but it seems not to work.  Code at end of previous message. Any idea on how to fix?

It isn't my. It was added by Guilherme in r69050.

I'll take a look at code tomorrow.

I don't know how to make the testing code working.

My manual test procedure was faulty.  Without a unit test, I should have asked for another person to verify.

I believe I read somewhere (SO?) that root.withdraw sometimes affects the effectiveness of event_generate.  I will try de-iconifying for just this.

New changeset 5b62b35e6fcba488da2f809965a5f349a4170b02 by terryjreedy in branch 'master':
bpo-30870: IDLE -- fix logic error in eae2537. (#2660)
https://github.com/python/cpython/commit/5b62b35e6fcba488da2f809965a5f349a4170b02

New changeset 953e527763f5af293668135acdf5f0a20c3f6f4f by terryjreedy in branch '3.6':
[3.6] bpo-30870: IDLE -- fix logic error in eae2537. (GH-2660) (#2661)
https://github.com/python/cpython/commit/953e527763f5af293668135acdf5f0a20c3f6f4f

It just get wierd, I can't do event_generate with Terry, too.

Attach poc.py that should print out a 'testing', but it didn't.

It seem setUpModule will smash out the test, I've add a trust-will-work test inside the test_configdialog.py:

class Test(unittest.TestCase):
    def setUp(self):
        self.root = tkinter.Tk()

    def test_test(self):
        self.root.bind('<KeyRelease-Up>', lambda x: print('testing'))
        self.root.update()
        self.root.event_generate('<KeyRelease-Up>')


This will print out `testing` when commet out setUpModule's `root = Tk()` line. But if this line is running, then the trust-test won't print out `testing`

configdialog misuse `self.withdraw` at init, it should be `self.wm_withdraw`, #30900 fix this problem. After that, it should be a success to use event_generate in configdialog unittest with no `self.withdraw`.

The new gui tests passed on Travis (linux), which I strongly suspect does not run gui tests.  The generate key test failed on Appveyor (Windows), which means is does run gui tests.  It also failed on my machine: generate key release did not work.  The generate click test does pass on both Appveyor and my machine, which is progress.

Adding config.fontlist.focus_force() before the key event worked. Louie, I will push that along with other edits tomorrow.  I will try exposing the window just for the tests.

Serhiy: question about tkinter.wantobjects.

ConfigDialog sets the font options of label font_sample and text text_highlight_sample with a font tuple such as font=('courier', 12, '').

In the test, I expected retrieval of the font option with
        sample_font = dialog.font_sample['font']
        hilight_font = dialog.text_highlight_sample['font']
to return tuples, but I get a string: '{courier new} 10 normal'. 

I checked and root.wantobjects() is returning the default True.  Should not the options be returned as tuples?

PR2666 adds 4% test coverage.  40% left to go.  I expect some tests will cover more lines with less code.

I am working on a test for set_font_sample.

New changeset 9b622fb90331f259894e6edb29b5c64b9366491a by terryjreedy (Louie Lu) in branch 'master':
bpo-30870: IDLE: Add configdialog fontlist selection unittest (#2666)
https://github.com/python/cpython/commit/9b622fb90331f259894e6edb29b5c64b9366491a

New changeset 42abf7f9737f78a5da311a42945d781dfcd6c6c0 by terryjreedy in branch '3.6':
[3.6] bpo-30870: IDLE: Add configdialog fontlist selection unittest (GH-2666) (#2701)
https://github.com/python/cpython/commit/42abf7f9737f78a5da311a42945d781dfcd6c6c0

I am closing this as basically complete.  I opened #30981 to add and perhaps complete font page tests.