CoshML

Introduction

CoshML is a small BBCode-style markup language for styling parts of a string. It's parsed by RichLabel, letting you mix multiple fonts, colors, weights, and other styles within a single block of text.

Basic Usage

cui.RichLabel(id="my_label", text="Welcome [bold]back[/], friend!")

Tags open with [tag] and close with [/]. Tags can be nested, and inner tags inherit whatever style is currently active — only overriding what they explicitly set.

Nesting

cui.RichLabel(id="my_label", text="[font=Courier]Hello [bold]World[/][/]")

Here, World is bold and stays in Courier, since [bold] doesn't touch the active font — it only adds bold on top of it.

Keyword Tags

These are single-word tags that don't take a value:

Tag	Effect
`[bold]`	Bold weight
`[italic]`	Italic style
`[underline]`	Underlines the text
`[strikethrough]`	Strikes through the text
`[red]` / `[green]` / `[blue]` / `[white]`	Sets text color

Keyword tags

cui.RichLabel(id="my_label", text="[bold][red]Warning:[/] please read carefully[/]")

Attribute Tags

These take a value with tag=value syntax:

Tag	Value	Example
`color`	`(r, g, b)` string	`[color=(255, 0, 0)]`
`font`	Registered font name	`[font=Courier]`
`font_size`	Integer	`[font_size=24]`

Attribute tags

cui.RichLabel(id="my_label", text="[color=(0, 200, 255)][font_size=24]Big blue text[/][/]")

Fonts referenced here must already be registered via add_font() — see Fonts.

Custom Text Classes — `add_class()`

For styles you reuse often, register a named TextStyle once with add_class(), then reference it by name as a tag:

add_class() with TextStyle

cui.add_class("warning", cui.TextStyle(color=(255, 80, 80), bold=True))

cui.RichLabel(id="my_label", text="[warning]Careful, this can't be undone.[/]")

TextStyle accepts the same properties as the attribute tags above (color, font, font_size, bold, italic, underline, strikethrough). A class name can't collide with an existing tag name or another registered class — both raise a CoshUIError.

Note: add_class() is also used to register CoshStyling classes for general Node styling (background color, border, etc.) — passing a CoshStyling instead of a TextStyle registers a class usable via a Node's classes property instead of a CoshML tag. The two are separate registries, so a name can be reused as both a Node style class and a text style class.

Error Handling

Malformed CoshML raises a CoshMLError rather than failing silently — unclosed tags, unknown tags/attributes (with a suggestion via typo-matching), and invalid values (e.g. a non-3-tuple color) are all caught at parse time.