Omitting TextArea theme doesn't highlight

[davidbrochart]

It seems that passing a theme to a TextArea is mandatory to get syntax highlighting, is it intended?

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

TEXT = """\
def hello(name):
    print("hello" + name)

def goodbye(name):
    print("goodbye" + name)
"""


class TextAreaExample(App):
    def compose(self) -> ComposeResult:
        # doesn't highlight
        yield TextArea(TEXT, language="python")
        # does highlight
        yield TextArea(TEXT, language="python", theme="monokai")


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

Textual Diagnostics

Versions

Name	Value
Textual	0.50.1
Rich	13.7.0

Python

Name	Value
Version	3.12.1
Implementation	CPython
Compiler	GCC 12.3.0
Executable	/home/david/.local/share/hatch/env/virtual/jpterm/-V8cnvgI/dev/bin/python

Operating System

Name	Value
System	Linux
Release	5.15.0-94-generic
Version	#104-Ubuntu SMP Tue Jan 9 15:25:40 UTC 2024

Terminal

Name	Value
Terminal Application	Unknown
TERM	xterm-256color
COLORTERM	truecolor
FORCE_COLOR	Not set
NO_COLOR	Not set

Rich Console options

Name	Value
size	width=136, height=35
legacy_windows	False
min_width	1
max_width	136
is_terminal	True
encoding	utf-8
max_height	35
justify	None
overflow	None
no_wrap	False
highlight	None
markup	None
height	None

[davep]

If your intention is to create a TextArea that is intended for code editing, complete with syntax highlighting and the like, you should probably be looking at using TextArea.code_editor.

Note that this approach is new as of 0.48.0.

[davidbrochart]

Thanks, yes that's what I saw, but still it feels weird that TextArea accepts a language parameter which is ignored if no theme is passed. Maybe there should be a runtime check that sets a default theme if a language was passed without a theme?

[davep]

If using code_editor to make a code-oriented editor (which would make sense, as there's a number of other things that aren't code-friendly about TextArea "out of the box") it will default the theme.

[darrenburns]

Yeah this was mentioned elsewhere and I agree. The default CSS theme just has no syntax highlighting mapping on it at the moment, but it probably should have at least the basic highlighting. The language parameter isn't ignored - by specifying a language it means tree-sitter is parsing the content behind the scenes and returning syntax tree nodes to us, but because the CSS theme doesn't have a mapping defined, you don't see any colours.

[darrenburns]

I've made this PR in relation to this: #4149

[davidbrochart]

Thanks!