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"""Lektor Markdown figures with arbitrary CSS classes and Markdown captions.
Syntax::
:::figure right w50
Caption with *Markdown* and [links](https://example.com/).
:::
The first non-empty content line must be a Markdown image. Every remaining
line is treated as the optional caption.
"""
from __future__ import annotations
import html
import re
from typing import Any
import mistune
from lektor.pluginsystem import Plugin
FIGURE_PATTERN = re.compile(
r" {0,3}:::figure(?:[ \t]+(?P<classes>[^\n]*?))?[ \t]*\n"
r"(?P<body>[\s\S]*?)"
r"\n {0,3}:::[ \t]*(?:\n+|$)"
)
# Mistune 0.8 renders this marker as inline HTML. The renderer mixin removes
# it and, at the same time, avoids wrapping the figure image in a paragraph.
_FIGURE_IMAGE_MARKER = "<!--lektor-markdown-figure:image-->"
def _normalise_classes(value: str | None) -> str:
"""Return whitespace-normalised, otherwise unrestricted CSS classes."""
return " ".join((value or "").split())
def _class_attribute(classes: str) -> str:
if not classes:
return ""
return f' class="{html.escape(classes, quote=True)}"'
def _split_figure(match: re.Match[str]) -> tuple[str, str, str]:
"""Extract classes, the image line, and the optional caption source."""
classes = _normalise_classes(match.group("classes"))
lines = match.group("body").splitlines()
while lines and not lines[0].strip():
lines.pop(0)
while lines and not lines[-1].strip():
lines.pop()
if not lines:
raise ValueError("A figure directive must contain a Markdown image.")
image_source = lines.pop(0).strip()
if not image_source.startswith("!["):
raise ValueError(
"The first non-empty line in a figure directive must be a Markdown image."
)
caption_source = "\n".join(lines).strip()
return classes, image_source, caption_source
# ---------------------------------------------------------------------------
# Mistune 0.8 support (used by Lektor 3.3.x)
# ---------------------------------------------------------------------------
if hasattr(mistune, "BlockGrammar"):
class FigureBlockGrammar(mistune.BlockGrammar): # type: ignore[misc]
figure = FIGURE_PATTERN
class FigureBlockLexer(mistune.BlockLexer): # type: ignore[misc]
grammar_class = FigureBlockGrammar
default_rules = list(mistune.BlockLexer.default_rules)
default_rules.insert(default_rules.index("fences"), "figure")
caption_rules = [rule for rule in default_rules if rule != "figure"]
def parse_figure(self, match: re.Match[str]) -> None:
classes, image_source, caption_source = _split_figure(match)
class_attribute = _class_attribute(classes)
# ``close_html`` is Mistune 0.8's raw block-HTML output token.
self.tokens.append(
{
"type": "close_html",
"text": f"<figure{class_attribute}>\n",
}
)
# The marker lets FigureRendererMixin remove the otherwise
# automatic <p> wrapper while retaining Lektor's normal inline
# image renderer and attachment-relative URL resolution.
self.tokens.append(
{
"type": "paragraph",
"text": _FIGURE_IMAGE_MARKER + image_source,
}
)
if caption_source:
self.tokens.append({"type": "close_html", "text": "<figcaption>\n"})
self.parse(caption_source, self.caption_rules)
self.tokens.append({"type": "close_html", "text": "</figcaption>\n"})
self.tokens.append({"type": "close_html", "text": "</figure>\n"})
class FigureRendererMixin:
"""Remove the paragraph wrapper from the directive's image only."""
def paragraph(self, text: str) -> str:
if text.startswith(_FIGURE_IMAGE_MARKER):
return text[len(_FIGURE_IMAGE_MARKER) :] + "\n"
return super().paragraph(text) # type: ignore[misc]
else:
FigureBlockLexer = None # type: ignore[assignment,misc]
FigureRendererMixin = None # type: ignore[assignment,misc]
# ---------------------------------------------------------------------------
# Mistune 2 support (used by Lektor's newer Markdown controller)
# ---------------------------------------------------------------------------
def _render_figure(text: str, classes: str) -> str:
return f"<figure{_class_attribute(classes)}>\n{text}</figure>\n"
def _render_figure_image(text: str) -> str:
return text + "\n"
def _render_figure_caption(text: str) -> str:
return f"<figcaption>\n{text}</figcaption>\n"
def _render_ast_figure(children: list[dict[str, Any]], classes: str) -> dict[str, Any]:
return {"type": "figure", "classes": classes.split(), "children": children}
def _render_ast_figure_image(children: list[dict[str, Any]]) -> dict[str, Any]:
return {"type": "figure_image", "children": children}
def _render_ast_figure_caption(children: list[dict[str, Any]]) -> dict[str, Any]:
return {"type": "figure_caption", "children": children}
def mistune_figure_plugin(md: Any) -> None:
"""Register the figure block with Mistune 2."""
def parse_figure(
block: Any, match: re.Match[str], state: dict[str, Any]
) -> dict[str, Any]:
classes, image_source, caption_source = _split_figure(match)
children: list[dict[str, Any]] = [
{"type": "figure_image", "text": image_source}
]
if caption_source:
caption_rules = [rule for rule in block.rules if rule != "figure"]
caption_children = block.parse(caption_source, state, caption_rules)
children.append({"type": "figure_caption", "children": caption_children})
return {
"type": "figure",
"children": children,
"params": (classes,),
}
md.block.register_rule("figure", FIGURE_PATTERN, parse_figure)
if "figure" not in md.block.rules:
md.block.rules.insert(0, "figure")
if md.renderer.NAME == "html":
md.renderer.register("figure", _render_figure)
md.renderer.register("figure_image", _render_figure_image)
md.renderer.register("figure_caption", _render_figure_caption)
elif md.renderer.NAME == "ast":
md.renderer.register("figure", _render_ast_figure)
md.renderer.register("figure_image", _render_ast_figure_image)
md.renderer.register("figure_caption", _render_ast_figure_caption)
class MarkdownFigurePlugin(Plugin):
name = "Markdown Figure"
description = (
"Adds :::figure blocks with arbitrary CSS classes and optional "
"Markdown captions."
)
def on_markdown_config(self, config: Any, **extra: Any) -> None:
# Newer Lektor controller using Mistune 2.
if hasattr(config, "parser_options"):
print("Using mistune 2")
plugins = config.parser_options.setdefault("plugins", [])
if mistune_figure_plugin not in plugins:
plugins.append(mistune_figure_plugin)
return
print("Not using mistune 2")
# Stable Lektor 3.3 controller using Mistune 0.8.
if FigureBlockLexer is None or FigureRendererMixin is None:
raise RuntimeError("Unsupported Mistune version for Markdown Figure.")
existing_block = config.options.get("block")
if existing_block not in (None, FigureBlockLexer):
raise RuntimeError(
"Markdown Figure cannot be combined with another plugin "
"that replaces Mistune's block lexer."
)
config.options["block"] = FigureBlockLexer
if FigureRendererMixin not in config.renderer_mixins:
config.renderer_mixins.insert(0, FigureRendererMixin)
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