ScrollView/RichLog: Page Up / Page Down off by one with horizontal scrollbar

[xavierog]

I noticed this issue while using the RichLog widget but it may actually stem from ScrollView.

Assuming a 25-line high RichLog widget:

• When there is a horizontal scrollbar, Page Up and Page Down move e.g. from lines 1-25 to lines 26-50, which is the expected behaviour.
  This can be confirmed by running the MRE below this way: SUFFIX= ./richlogtest.py
• When there is a horizontal scrollbar, Page Up and Page Down move e.g. from lines 1-24 to lines 26-49, thus hiding line 25, hence this report.
  This can be confirmed by running the MRE below this way: ./richlogtest.py

MRE:

#!/usr/bin/env python3
import os
from textual.app import App
from textual.widgets import RichLog

class RichLogTest(App):
	def compose(self):
		ri = RichLog(auto_scroll=False)
		suffix = os.environ.get('SUFFIX', 'A'*1000)
		for i in range(1, 1000):
			ri.write(f"This is line number {i} {suffix}")
		yield ri

if __name__ == "__main__":
	app = RichLogTest()
	app.run()

Textual Diagnostics

Versions

Name	Value
Textual	0.76.0
Rich	13.7.1

Python

Name	Value
Version	3.12.5
Implementation	CPython
Compiler	GCC 14.2.0
Executable	/path/to/venv/bin/python3

Operating System

Name	Value
System	Linux
Release	6.10.4-amd64
Version	#1 SMP PREEMPT_DYNAMIC Debian 6.10.4-1 (2024-08-12)

Terminal

Name	Value
Terminal Application	tmux (3.4)
TERM	tmux-256color
COLORTERM	truecolor
FORCE_COLOR	Not set
NO_COLOR	Not set

Rich Console options

Name	Value
size	width=196, height=25
legacy_windows	False
min_width	1
max_width	196
is_terminal	False
encoding	utf-8
max_height	25
justify	None
overflow	None
no_wrap	False
highlight	None
markup	None
height	None

[github-actions]

We found the following entry in the FAQ which you may find helpful:

• How do I center a widget in a screen?

Feel free to close this issue if you found an answer in the FAQ. Otherwise, please give us a little time to review.

This is an automated reply, generated by FAQtory

[TomJGooding]

I think this is the expected behaviour, otherwise the RichLog size would need to grow?

EDIT: Sorry never mind, I should have read the issue more carefully. Currently page down will "skip" the line obscured by the horizontal scrollbar.

[willmcgugan]

Confirmed. It actually goes all the way back to widget.py, so this would impact anything that scrolls.

Fortunately looks like an easy fix.

[github-actions]

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