DataTable: Switching focus is slow when table contains lots of data

[ihabunek]

I have a use case where I put data from a database into the data table and i noticed that if cells contain a lot of text, switching focus to and from the data table is very slow.

In the following example, when tab is pressed, it takes ~2 seconds to switch focus from the Input to the DataTable. Scrolling is reasonably fast once focused.

from textual.app import App
from textual.widgets import DataTable, Input

NUM_LINES = 100
NUM_COLS = 20
NUM_ROWS = 50

COLS = [f"col {n}" for n in range(NUM_COLS)]
# Each cell contains a bunch of text with line breaks
CELL = "\n".join("much data wow" for _ in range(NUM_LINES))
ROW = [CELL for _ in range(NUM_COLS)]
ROWS = [ROW for _ in range(NUM_ROWS)]


class ReproApp(App):
    CSS = "DataTable { height: 80%; }"

    def compose(self):
        yield Input("Pressing TAB to switch focus is slow!")
        dt = DataTable()
        dt.add_columns(*COLS)
        dt.add_rows(ROWS)
        yield dt


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

Textual Diagnostics

Versions

Name	Value
Textual	0.72.0
Rich	13.7.1

Python

Name	Value
Version	3.12.3
Implementation	CPython
Compiler	GCC 14.0.1 20240411 (Red Hat 14.0.1-0)
Executable	/home/ihabunek/.virtualenvs/pgtui/bin/python

Operating System

Name	Value
System	Linux
Release	6.9.5-200.fc40.x86_64
Version	#1 SMP PREEMPT_DYNAMIC Sun Jun 16 15:47:09 UTC 2024

Terminal

Name	Value
Terminal Application	Kitty
TERM	xterm-kitty
COLORTERM	truecolor
FORCE_COLOR	Not set
NO_COLOR	Not set

Rich Console options

Name	Value
size	width=182, height=48
legacy_windows	False
min_width	1
max_width	182
is_terminal	False
encoding	utf-8
max_height	48
justify	None
overflow	None
no_wrap	False
highlight	None
markup	None
height	None

[darrenburns]

Confirmed 👍

[github-actions]

Don't forget to star the repository!

Follow @textualizeio for Textual updates.

[darrenburns]

@ihabunek Should be resolved in the next release (I'm guessing this week) for cases where cells contain text (str or rich.Text) content that spans multiple lines and only a portion of it is visible.

Load time of the DataTable should be much faster in those cases too, and focus/blur should be instant.

[ihabunek]

@darrenburns I have tested on main and it seems much better. Thanks for your work!