Allow Sparkline to be of any height

[uriyyo]

Make Sparkline be able to use not only 1 as a height value.

Demo app:

import random
from statistics import mean

from textual.containers import Grid

from textual.app import App, ComposeResult
from textual.widgets import Sparkline

random.seed(73)
data = [random.expovariate(1 / 3) for _ in range(1000)]


class SparklineAnyHeightApp(App[None]):
    DEFAULT_CSS = """
    SparklineAnyHeightApp {
        Sparkline {
            height: 1fr;
            border: round white;
        }
    }
    """

    def compose(self) -> ComposeResult:
        with Grid():
            yield Sparkline(data, summary_function=max)
            yield Sparkline(data, summary_function=mean)
            yield Sparkline(data, summary_function=min)
            yield Sparkline([*range(len(data))])
            yield Sparkline([1])
            yield Sparkline([])


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

Result:

Please review the following checklist.

• Docstrings on all new or modified functions / classes
• Updated documentation
• Updated CHANGELOG.md (where appropriate)

[willmcgugan]

Nice.

Can I request a snapshot test?

See test_snapshots.py for examples. Can be very simple, just a single sparkline is all that is needed.

[Copilot]

Pull Request Overview

This PR enhances the Sparkline widget to support multi-line rendering at any height, not just a single line. The implementation adds a height parameter that controls how many terminal lines the sparkline uses, with taller sparklines providing more granular vertical resolution for data visualization.

Key Changes:

• Added height parameter to Sparkline renderable with appropriate default of None (defaulting to 1)
• Updated rendering logic to distribute bar segments across multiple lines
• Modified edge case handling (empty data, single datapoint) to respect the height parameter

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
src/textual/renderables/sparkline.py	Core implementation: added height parameter, updated rendering algorithm to distribute bar segments across multiple lines, and fixed edge cases
src/textual/widgets/_sparkline.py	Widget integration: passes widget height to the sparkline renderable
tests/renderables/test_sparkline.py	Test coverage: added parametrized tests for heights 1, 2, and 3
CHANGELOG.md	Documentation: added changelog entry for the new feature

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[uriyyo]

@willmcgugan Added snapshot test, hope I did it right 🙏