IDLE: Scrolling issues with code context shown

GitHub fields:

assignee = 'https://github.com/terryjreedy'
closed_at = None
created_at = <Date 2019-07-11.10:00:19.089>
labels = ['3.8', 'expert-IDLE', 'type-bug', '3.7', '3.9']
title = 'IDLE: Scrolling issues with code context shown'
updated_at = <Date 2019-07-16.05:42:43.716>
user = 'https://github.com/taleinat'

bugs.python.org fields:

activity = <Date 2019-07-16.05:42:43.716>
actor = 'terry.reedy'
assignee = 'terry.reedy'
closed = False
closed_date = None
closer = None
components = ['IDLE']
creation = <Date 2019-07-11.10:00:19.089>
creator = 'taleinat'
dependencies = []
files = ['48469']
hgrepos = []
issue_num = 37559
keywords = ['patch']
message_count = 7.0
messages = ['347666', '347855', '347890', '347893', '347931', '347954', '348003']
nosy_count = 3.0
nosy_names = ['terry.reedy', 'taleinat', 'cheryl.sabella']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'needs patch'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue37559'
versions = ['Python 3.7', 'Python 3.8', 'Python 3.9']