IDLE: on macOS, scroll slider 'sticks' at bottom of file

[belgort]

BPO	34047
Nosy	@rhettinger, @terryjreedy, @taleinat, @ned-deily, @csabella, @miss-islington
PRs	bpo-34047: IDLE: fix mousewheel scrolling direction on macOS #8678 [3.7] bpo-34047: IDLE: fix mousewheel scrolling direction on macOS (GH-8678) #8723 [3.6] bpo-34047: IDLE: fix mousewheel scrolling direction on macOS (GH-8678) #8724
Superseder	bpo-34796: Tkinter scrollbar issues on Mac.
Files	tk_scroll.py: tkinter-only skeleton of IDLE editor with scrollbar tk_scroll2.py tktest.py tkinter_scroll_issues.mov

^{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 2018-08-10.08:33:22.587>
created_at = <Date 2018-07-04.17:14:47.653>
labels = ['3.8', 'expert-IDLE', 'type-bug', '3.7']
title = "IDLE: on macOS, scroll slider 'sticks' at bottom of file"
updated_at = <Date 2018-09-25.00:10:13.400>
user = 'https://bugs.python.org/belgort'

bugs.python.org fields:

activity = <Date 2018-09-25.00:10:13.400>
actor = 'terry.reedy'
assignee = 'terry.reedy'
closed = True
closed_date = <Date 2018-08-10.08:33:22.587>
closer = 'taleinat'
components = ['IDLE']
creation = <Date 2018-07-04.17:14:47.653>
creator = 'belgort'
dependencies = []
files = ['47676', '47677', '47737', '47738']
hgrepos = []
issue_num = 34047
keywords = ['patch']
message_count = 38.0
messages = ['321058', '321060', '321064', '321127', '321137', '321144', '321151', '321152', '321153', '321250', '321251', '321258', '321265', '321685', '321927', '321929', '321931', '322702', '322719', '322762', '322826', '322844', '323147', '323148', '323149', '323153', '323154', '323174', '323348', '323349', '323350', '323351', '323356', '323358', '323359', '323360', '323361', '326300']
nosy_count = 9.0
nosy_names = ['rhettinger', 'terry.reedy', 'taleinat', 'wordtech', 'ned.deily', 'cheryl.sabella', 'miss-islington', 'belgort', 'vtudorache']
pr_nums = ['8678', '8723', '8724']
priority = 'high'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = '34796'
type = 'behavior'
url = 'https://bugs.python.org/issue34047'
versions = ['Python 3.6', 'Python 3.7', 'Python 3.8']

[belgort]

When using IDLE on OS X and scrolling to the bottom of a file you are not able to scroll using a mouse back up. You need to use the arrow keys.

[ned-deily]

I think I am able to reproduce that behavior (I'm using IDLE from a python.org 10.9+ installer). What I'm seeing is that if you scroll to the bottom of a file that exceeds the length of the open text window and then click on and try to move the position indicator in the scroll bar, the position indicator does not move nor does the file scroll. But if I then click elsewhere in the scroll bar and then try to grab and move the indicator, it works OK. So perhaps IDLE is overriding a text widget event or some such. FWIW a quick test in the wish8.6 text demo seems to work OK.

[terryjreedy]

There are 3 ways to scroll by key in each direction: Arrow Down/Up, Page Down/Up, and Cntl End/Home. There are 4 ways to scroll by mouse, in each direction: Mousewheel down/up, Scrollbar arrow bottom/top (== Arrow keys), Scrollbar trough below/above slider (= Page keys), and Scrollbar slider.

On Windows, if I Load Module idlelib.editor and go to the bottom, with the text cursor on the last line, all up methods work. Bruce, which of the four mouse up methods don't work for you? Just grabbing the slider, as Ned found? What happens is you move the slider down, and try to move up without releasing the button?

Cheryl or Tal, can one of you check on Linux?

In the text area, the mouse pointer, for me, is a vertical bar and the slider is a light gray. When I move the mouse over the scrollbar slider, the slider become active and ready to click on. The indication is that the mouse pointer becomes an arrow pointing up left and the slider turns dark gray. When the mouse is over the scrollbar trough or arrows, the slider only darkens to medium gray. When over an arrow, the arrow darkens. Bruce, do you see the 'activation' change when the slider is at the bottom and you mouse over it, but cannot grab it?

In May, we changed the 3.6+ editor text/mousewheel/scrollbar interaction a bit so that the text scrolled by lines, rather than by pixel. bpo-33664, PR 7351. There is always a complete line at the top -- unless one changes the window height to a non-integral number of lines and moves the cursor to the last line. (Then the complete lines are at the bottom until one moves the cursor to the top line -- Cheryl, we should try to fix this.)

The patch changed the command function that the scrollbar calls when it is clicked or the slider is moved to editor.EditorWindow.handle_yview. The new function has an extraneous "return 'break'" that can and should be removed. But I doubt that is the problem. It also has new code that is only executed for slider movements.

If only the slider has a problem and this slider code were to raise when at the bottom, we might have an explanation. I am dubious, as the only possible platform-specific calls are the tkinter calls text.index('end') and text.index('@0.0'). To check this anyway, please start IDLE in the Mac terminal with 'python3 -m idlelib' (correct on Mac?) and repeat the failing action and see if a traceback appears.

It might also help to know if 2.7 or 3.5- have the same problem.

[belgort]

2.7.15 scrolling is working just fine.

[terryjreedy]

1 down, but how about my other questions?
Is there only a problem if the slider is the first thing touched?
Is there still a problem if the line "return 'break'" in idlelib.editor.EditorWindow.handle_yview is deleted or disabled by prefixig it with '#'? (Are you allowed to edit stdlib files?)
Do you see any messages if you start IDLE in a terminal?

[belgort]

Terry,

Here is a video I made showing the problem I’m having. I have no clue about the other things you are asking about.

https://www.youtube.com/watch?v=BpyMhdjTNvQ <https://www.youtube.com/watch?v=BpyMhdjTNvQ\>

Bruce

On Jul 5, 2018, at 3:21 PM, Terry J. Reedy <report@bugs.python.org> wrote:

Change by Terry J. Reedy <tjreedy@udel.edu>:

----------
stage: -> test needed
title: Scrolling in IDLE for OS X is not working correctly when reaching end of file -> IDLE: on macOS, scroll slider 'sticks' at bottom of file

---

Python tracker <report@bugs.python.org>
<https://bugs.python.org/issue34047\>

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[taleinat]

Confirmed on latest master on OSX.

I'm also experiencing many other kinds of erratic scrolling behavior:

1. Dragging the scrollbar isn't possible immediately after opening the file Lib/idlelib/editor.py. Also later after scrolling to the top.
2. Scrolling via two-finger swipte on the trackpad scrolls down both when I scroll up and down.
3. Clicking in the trough slightly below the slider has no effect.

There's definitely something very broken!

Commenting out the return 'break' in handle_yview() doesn't appear to affect this.

In all cases I ran idle from a terminal via python -m idlelib and saw no errors.

[taleinat]

With Python 3.6.5 on OSX, I'm seeing all of the issues (including the originally reported one) except the issue with the scroll direction inversion on two-finger swipe.