Documents: soft breaks draw as lines; Reader::joined keeps GFM spaces

The screen keeps a single line break (Typora's default when writing);
outputs read with Reader::joined, which joins them as GFM does. Heading
titles read on one line.

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

src/documents/document/tests/point.rs

@@ -197,8 +197,9 @@ fn a_secondary_press_in_a_quote_lands_past_its_mark(cx: &mut TestAppContext) {
     let events = heard(&document, cx);
     let bounds = cx.debug_bounds("markdown-block-0").expect("drawn");
     let (body, _) = sizes(cx);
-    let x = bounds.left() + px(31.0) + body * 0.6 * 7.25;
-    press_at(x, bounds.top() + px(10.0), MouseButton::Right, cx);
+    // "beta" draws on its own line.
+    let x = bounds.left() + px(31.0) + body * 0.6 * 1.25;
+    press_at(x, bounds.top() + px(10.0) + body * 1.6, MouseButton::Right, cx);
     let at = source.find("eta").unwrap();
     assert_eq!(*events.borrow(), [target(at, TargetBlock::Quote)]);
 }

src/documents/tree/blocks.rs

@@ -194,7 +194,7 @@ mod tests {
         let bold = 2..3;
         assert_eq!(
             (line.text.as_str(), &line.styles[..]),
-            ("a b c", &[(bold, Style::Strong)][..])
+            ("a b\nc", &[(bold, Style::Strong)][..])
         );
     }
 

src/documents/tree/html_block.rs

@@ -197,7 +197,7 @@ mod tests {
                 other => panic!("a paragraph, not {other:?}"),
             })
             .collect();
-        assert_eq!(lines, ["<script> first", "second </script>"]);
+        assert_eq!(lines, ["<script> first", "second\n</script>"]);
         let inline = html("a <script>b</script> c").expect("text");
         assert_eq!(inline.text, "a <script>b</script> c");
         assert_eq!(html("<div>\na < b <i").expect("text").text, "a < b");

src/documents/tree/mod.rs

@@ -101,6 +101,8 @@ pub struct Reader<'a> {
     notes: HashMap<String, usize>,
     /// Every heading, as `[toc]` lists them.
     pub headings: Vec<DocumentHeading>,
+    /// Soft breaks as lines, as the screen draws them.
+    lines: bool,
 }
 
 /// An open element, as HTML names it.
@@ -122,6 +124,8 @@ struct Run {
     verbatim: bool,
     /// In a table cell, whose code reads `\|` as `|`.
     table: bool,
+    /// Soft breaks as lines, not spaces.
+    lines: bool,
     /// The current DOM text node's shortcodes.
     shortcodes: emoji::Shortcodes,
     /// White space owed, and the open elements before it.
@@ -159,8 +163,9 @@ impl Run {
     }
 
     fn push_plain(&mut self, shown: &str) {
-        let soft = shown.replace("\r\n", " ").replace(['\r', '\n'], " ");
-        self.text.text.push_str(&soft);
+        let soft = if self.lines { "\n" } else { " " };
+        let shown = shown.replace("\r\n", soft).replace(['\r', '\n'], soft);
+        self.text.text.push_str(&shown);
     }
 }
 
@@ -175,8 +180,17 @@ pub fn parse(markdown: &str) -> Vec<Node> {
 }
 
 impl<'a> Reader<'a> {
-    /// A reader of `root`, parsed from `source`.
+    /// A reader of `root`, parsed from `source`, as the screen draws it.
     pub fn new(source: &'a str, root: &mdast::Node) -> Self {
+        Self::reading(source, root, true)
+    }
+
+    /// The same, soft breaks joined as GFM output joins them.
+    pub fn joined(source: &'a str, root: &mdast::Node) -> Self {
+        Self::reading(source, root, false)
+    }
+
+    fn reading(source: &'a str, root: &mdast::Node, lines: bool) -> Self {
         let mut nodes = Vec::new();
         walk(root, &mut nodes);
         let (mut urls, mut notes, mut headings) = (HashMap::new(), HashMap::new(), Vec::new());
@@ -199,6 +213,7 @@ impl<'a> Reader<'a> {
             urls,
             notes,
             headings: Vec::new(),
+            lines: false,
         };
         reader.headings = headings
             .into_iter()
@@ -208,6 +223,8 @@ impl<'a> Reader<'a> {
                 at,
             })
             .collect();
+        // Titles read on one line; the body as asked.
+        reader.lines = lines;
         reader
     }
 
@@ -236,7 +253,7 @@ impl<'a> Reader<'a> {
         match node {
             mdast::Node::Paragraph(paragraph) => self.paragraph(node, &paragraph.children, out),
             mdast::Node::Heading(heading) => {
-                let (mut run, mut after) = (Run::default(), Vec::new());
+                let (mut run, mut after) = (self.run(), Vec::new());
                 for child in &heading.children {
                     self.inline_into(child, &mut run, &mut Images::After(&mut after));
                 }
@@ -310,7 +327,7 @@ impl<'a> Reader<'a> {
         }
         let mut run = Run {
             table: matches!(node, mdast::Node::TableCell(_)),
-            ..Run::default()
+            ..self.run()
         };
         for child in children {
             self.inline_into(child, &mut run, &mut Images::Split(out));
@@ -318,6 +335,13 @@ impl<'a> Reader<'a> {
         text_block(run.cut(), out);
     }
 
+    fn run(&self) -> Run {
+        Run {
+            lines: self.lines,
+            ..Run::default()
+        }
+    }
+
     /// A footnote's number, by its first reference.
     pub fn note(&self, identifier: &str) -> Option<usize> {
         self.notes.get(identifier).copied()
@@ -336,7 +360,7 @@ impl<'a> Reader<'a> {
 
     /// Inline text where images draw as their alt text.
     pub fn inline(&self, nodes: &[mdast::Node]) -> Inline {
-        let mut run = Run::default();
+        let mut run = self.run();
         for node in nodes {
             self.inline_into(node, &mut run, &mut Images::Alt);
         }

src/documents/tree/tests.rs

@@ -68,20 +68,27 @@ fn an_image_splits_its_paragraph_and_references_resolve() {
 }
 
 #[test]
-fn a_soft_break_reads_as_a_space_and_a_hard_one_as_a_line() {
-    for (source, shown) in [
-        ("one\ntwo  \nthree", "one two\nthree"),
-        ("one\r\ntwo  \r\nthree", "one two\nthree"),
-        ("one\rtwo  \rthree", "one two\nthree"),
-    ] {
+fn a_soft_break_draws_as_a_line_and_joins_for_output() {
+    for source in ["one\ntwo  \nthree", "one\r\ntwo  \r\nthree", "one\rtwo  \rthree"] {
         let nodes = parse(source);
         assert!(
-            matches!(&nodes[0], Node::Paragraph(text) if text.text == shown),
-            "{source:?} reads {nodes:?}"
+            matches!(&nodes[0], Node::Paragraph(text) if text.text == "one\ntwo\nthree"),
+            "{source:?} draws {nodes:?}"
         );
+        let root = super::super::markdown::tree(source);
+        let paragraph = &root.children().expect("blocks")[0];
+        let joined = Reader::joined(source, &root).inline(paragraph.children().expect("inlines"));
+        assert_eq!(joined.text, "one two\nthree", "{source:?} joins");
     }
 }
 
+#[test]
+fn a_heading_title_reads_on_one_line() {
+    let source = "one\ntwo\n===\n";
+    let root = super::super::markdown::tree(source);
+    assert_eq!(Reader::new(source, &root).headings[0].title, "one two");
+}
+
 #[test]
 fn definitions_nested_in_quotes_and_lists_resolve() {
     for source in [
@@ -385,9 +392,9 @@ fn the_first_shortcode_decides_its_text_node() {
         ("a.:x.y: :smile:", "a.:x.y: 😄"),
         ("x\t:smile: y:smile:", "x\t:smile: y:smile:"),
         ("x\u{a0}:smile: y:smile:", "x\u{a0}:smile: y:smile:"),
-        ("x\n:smile: y:smile:", "x :smile: y:smile:"),
+        ("x\n:smile: y:smile:", "x\n:smile: y:smile:"),
         ("*x*:smile: :smile:", "x😄 😄"),
-        ("*x*\n:smile: y:smile:", "x 😄 y😄"),
+        ("*x*\n:smile: y:smile:", "x\n😄 y😄"),
         ("x:smile: `c` :smile:", "x:smile: c 😄"),
         ("x:smile:<!-- c --> :smile:", "x:smile: 😄"),
         ("x:smile:<span>s</span> :smile:", "x:smile:s 😄"),