MarkdownDocument: a Markdown file in one CodeEditor, shown visual, source, split or preview

Visual draws the top-level blocks in a gpui list; a pressed block opens as
its source and its typing is the text at once, written back as one undo
step. CodeEditor takes the owner's line colors, resets with a fresh
history and keeps at most 64 MiB of undo text. MarkdownMode gains Preview.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/documents/render.rs

@@ -8,6 +8,7 @@ use gpui::{
 use markdown::mdast::AlignKind;
 
 use super::{
+    contents::anchor,
     diagram::Diagram,
     picture::Picture,
     tree::{Inline, Node, Style, parse},
@@ -20,7 +21,7 @@ use crate::{
     typography::{Latex, failed},
 };
 
-type OnLink = Rc<dyn Fn(&str, &mut Window, &mut App)>;
+pub(crate) type OnLink = Rc<dyn Fn(&str, &mut Window, &mut App)>;
 type DrawCode = Rc<dyn Fn(ElementId, Option<SharedString>, SharedString) -> AnyElement>;
 
 /// Markdown as a document: headings, prose with its styles and links, lists and tasks, quotes, code colored as code, tables, rules, math and footnotes. A press on a link opens it, or hands it to the host.
@@ -401,37 +402,24 @@ fn open_link(on_link: &Option<OnLink>, url: &str, window: &mut Window, cx: &mut
     }
 }
 
-/// The anchor of the document's `ordinal`th heading.
-fn anchor(ordinal: usize) -> SharedString {
-    format!("heading-{ordinal}").into()
-}
-
-/// The headings of `markdown` in order, as a table of contents takes them: anchor, text and depth from 0.
-pub fn outline(markdown: &str) -> Vec<(SharedString, SharedString, usize)> {
-    fn walk(nodes: &[Node], out: &mut Vec<(SharedString, SharedString, usize)>) {
-        for node in nodes {
-            match node {
-                Node::Heading(level, inline) => {
-                    let ordinal = out.len();
-                    out.push((
-                        anchor(ordinal),
-                        inline.text.clone().into(),
-                        *level as usize - 1,
-                    ));
-                }
-                Node::Quote(inner) | Node::Footnote { body: inner, .. } => walk(inner, out),
-                Node::List { items, .. } => {
-                    for (_, body) in items {
-                        walk(body, out);
-                    }
-                }
-                _ => {}
-            }
-        }
-    }
-    let mut out = Vec::new();
-    walk(&parse(markdown), &mut out);
-    out
+/// Parsed `nodes` drawn under `id`; pictures read from `base`.
+pub(crate) fn draw_nodes(
+    id: &ElementId,
+    nodes: &[Node],
+    base: &Option<Arc<Path>>,
+    on_link: &Option<OnLink>,
+    cx: &App,
+) -> Vec<AnyElement> {
+    let draw = Draw {
+        id,
+        on_link,
+        next: std::cell::Cell::new(0),
+        sections: &None,
+        headings: std::cell::Cell::new(0),
+        code: &None,
+        base,
+    };
+    draw.nodes(nodes, cx)
 }
 
 impl RenderOnce for MarkdownRenderer {
@@ -456,28 +444,3 @@ impl RenderOnce for MarkdownRenderer {
             .children(draw.nodes(&nodes, cx))
     }
 }
-
-#[cfg(test)]
-mod tests {
-    use super::outline;
-
-    #[test]
-    fn the_outline_numbers_headings_in_order_with_their_depth() {
-        let found =
-            outline("# Lift\n\ntext\n\n## In light\n\n> ### Quoted\n\n- #### Listed\n\n## In dark");
-        let shape: Vec<(&str, &str, usize)> = found
-            .iter()
-            .map(|(anchor, text, depth)| (anchor.as_ref(), text.as_ref(), *depth))
-            .collect();
-        assert_eq!(
-            shape,
-            [
-                ("heading-0", "Lift", 0),
-                ("heading-1", "In light", 1),
-                ("heading-2", "Quoted", 2),
-                ("heading-3", "Listed", 3),
-                ("heading-4", "In dark", 1),
-            ]
-        );
-    }
-}