Documents: a press in a table opens its cell alone

Visual mode opened a pressed table whole, as Markdown source. A press
in a table now opens only that cell, in place, as its source in a
one-line field; the rest of the table stays drawn. Tab and Shift-Tab
walk the cells, Up and Down move a row or leave the table, Enter and
Escape write back in one undo step, and a bare pipe typed in a cell is
escaped on write-back. The table drawing moves to render/table.rs and
presses on a cell's padding name the cell.

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

AGENTS.md

@@ -13,7 +13,7 @@ Ely GPUI Component. A component library for GPUI, in light and dark.
 - Web views: `wry` 0.57 (Apache-2.0 OR MIT, default features off, macOS only) lays a child WKWebView over the window.
 - Terminal: `alacritty_terminal` 0.26 (Apache-2.0, default features off, native only) for the grid, its parser and the pseudo-terminal; `futures` carries its events. `vte` 0.15 (Apache-2.0 OR MIT), the parser it re-exports, reads `AnsiText`'s codes alone, so colored output builds for wasm32.
 - Diffs: `similar` 3.2 (Apache-2.0) for line and word diffs and three-way merges; its `unicode` feature splits words at punctuation.
-- Markdown: `markdown` 1.0.0 (markdown-rs, MIT) reads GitHub's flavor and math into a syntax tree with byte positions for `MarkdownRenderer`, `MarkdownEditor`, the highlights, block ranges and outline. `MarkdownRenderer` draws display math through `typography::Latex`, a ```` ```mermaid ```` block through `documents::Diagram`, and pictures from the owner's folder (`base`) or `data:` addresses (`base64` 0.22, MIT OR Apache-2.0); web pictures stay unloaded. Inline math shows as TeX: gpui text carries no inline pictures. Inline it reads as Typora's defaults: `:shortcode:` turns to its emoji as GitHub reads it (the `emojis` crate's names, GitHub's today, so `:cricket:` is the insect; read after escapes and references, so `\:smile:` turns too; inside an autolink or `<code>` it stays text; within one DOM text node, which filtered tags do not split, the first `:name:`-shaped run decides for all: blank text or a space before it turns every shortcode, else none, so `x:smile: :smile:` stays), inline HTML's `u`, `b`/`strong`, `i`/`em`, `s`/`del`/`strike`, `code`/`kbd`, `mark`, `br` and `a href` draw as what they mean GFM's filtered tags (`script`, `style`, `title`, `textarea`, `iframe`, `xmp`, `noembed`, `noframes`, `plaintext`) show as text, and other tags, hyphenated names too, vanish, leaving their text; a tag's name runs to white space or `/`, as HTML5 reads it; attribute values split on ASCII whitespace alone and decode as HTML decodes them; each Markdown container is the element GitHub writes (`em`, `strong`, `del`, `a`), on one stack with the tags and repaired as HTML5 repairs: an end tag closes the innermost element of its name and all above it, of which only formatting elements (`a`, `b`, `code`, `em`, `i`, `s`, `strike`, `strong`, `u`) reopen, a new `a` ends the open one and an `a` without `href` links nothing; other tags are not tracked, and `</br>` breaks as `<br>` does; and a footnote reference is its number in superscript, numbered by first reference, as its definition is; one `~` still strikes. At the root, blocks read as GitHub shows them: a quote whose first line is plain text reading `[!NOTE]`, `[!TIP]`, `[!IMPORTANT]`, `[!WARNING]` or `[!CAUTION]` in any case, after escapes and references, spaces and tabs around it, with more after it, is an alert under its title (Important in the palette's violet, `syntax.keyword`, read at 4.5:1); a paragraph that is `[toc]` alone, as Typora reads it, lists every heading by depth, and a press on one reveals it as a link press does (`MarkdownDocument`'s `reveal`), the heading found where `CodeEditor` anchors carried it through each edit since the read, gone if an edit or an undo took it, and a secondary press acts on press, since a block writing back moves the list; front matter shows in a box without its fences; an HTML block shows its text with the inline tags above, white space collapsed and owed as a browser lays it, block elements breaking lines and closing what opened inside them, HTML5's start tags ending an open `p`, `fieldset` and `menu` too, and an `li` start an `li`, a `dd` or `dt` start either, as HTML5 ends them, comments dropped, the filtered tags shown as text, and an unclosed tag dropping the rest; a rule is a 2px `border_strong` line; bullets go •, ◦, ▪ by list depth, ordered lists counted. Exports read a tree as the drawing does through `MarkdownReader` (`block` gives its `MarkdownBlock`s, `inline` its text, `note` and `label` its footnotes, `headings` the `[toc]` list), one fresh stack per paragraph, heading or cell. `MarkdownDocument` holds a whole file in one `CodeEditor` (text and undo, colored by `CodeEditor::highlighter` with `markdown_highlights`): visual draws the file's top-level blocks in a gpui `list`, a pressed block opening as its source in a `TextInput` whose typing is the document's text at once and whose write-back is one undo step; source is the editor; preview draws without presses. A written-back block, a mode switch or a new text is read at once up to 128 KiB, longer ones on the background executor; typing in source or split reads 300 ms after the last key, off the main thread (markdown-rs grows with the square of its nodes, not its bytes: in release, 128 KiB of one-letter paragraphs takes 1.7 s, 16 KiB 42 ms, while 128 KiB of prose takes 20 ms; a block-heavy text under the cutoff can still hold the UI thread past 100 ms, a known limit). Texts past `LARGEST_READ` (2 MiB) are never read: no blocks, no outline. A new read keeps the list's blocks alike at both ends. One caret serves every mode: the editor's selection, which a written-back block moves; `set_caret` and `set_top_line` set caret and view apart; a top line asked (numbered, so a late frame callback finishes only its own ask; new text places it again, clamped to the text as it then is) waits for the read, lands on its block, then a frame later at its share of the block's height; `reveal` is such an ask with the caret at its line; a switch between source and the listLine truncated
+- Markdown: `markdown` 1.0.0 (markdown-rs, MIT) reads GitHub's flavor and math into a syntax tree with byte positions for `MarkdownRenderer`, `MarkdownEditor`, the highlights, block ranges and outline. `MarkdownRenderer` draws display math through `typography::Latex`, a ```` ```mermaid ```` block through `documents::Diagram`, and pictures from the owner's folder (`base`) or `data:` addresses (`base64` 0.22, MIT OR Apache-2.0); web pictures stay unloaded. Inline math shows as TeX: gpui text carries no inline pictures. Inline it reads as Typora's defaults: `:shortcode:` turns to its emoji as GitHub reads it (the `emojis` crate's names, GitHub's today, so `:cricket:` is the insect; read after escapes and references, so `\:smile:` turns too; inside an autolink or `<code>` it stays text; within one DOM text node, which filtered tags do not split, the first `:name:`-shaped run decides for all: blank text or a space before it turns every shortcode, else none, so `x:smile: :smile:` stays), inline HTML's `u`, `b`/`strong`, `i`/`em`, `s`/`del`/`strike`, `code`/`kbd`, `mark`, `br` and `a href` draw as what they mean GFM's filtered tags (`script`, `style`, `title`, `textarea`, `iframe`, `xmp`, `noembed`, `noframes`, `plaintext`) show as text, and other tags, hyphenated names too, vanish, leaving their text; a tag's name runs to white space or `/`, as HTML5 reads it; attribute values split on ASCII whitespace alone and decode as HTML decodes them; each Markdown container is the element GitHub writes (`em`, `strong`, `del`, `a`), on one stack with the tags and repaired as HTML5 repairs: an end tag closes the innermost element of its name and all above it, of which only formatting elements (`a`, `b`, `code`, `em`, `i`, `s`, `strike`, `strong`, `u`) reopen, a new `a` ends the open one and an `a` without `href` links nothing; other tags are not tracked, and `</br>` breaks as `<br>` does; and a footnote reference is its number in superscript, numbered by first reference, as its definition is; one `~` still strikes. At the root, blocks read as GitHub shows them: a quote whose first line is plain text reading `[!NOTE]`, `[!TIP]`, `[!IMPORTANT]`, `[!WARNING]` or `[!CAUTION]` in any case, after escapes and references, spaces and tabs around it, with more after it, is an alert under its title (Important in the palette's violet, `syntax.keyword`, read at 4.5:1); a paragraph that is `[toc]` alone, as Typora reads it, lists every heading by depth, and a press on one reveals it as a link press does (`MarkdownDocument`'s `reveal`), the heading found where `CodeEditor` anchors carried it through each edit since the read, gone if an edit or an undo took it, and a secondary press acts on press, since a block writing back moves the list; front matter shows in a box without its fences; an HTML block shows its text with the inline tags above, white space collapsed and owed as a browser lays it, block elements breaking lines and closing what opened inside them, HTML5's start tags ending an open `p`, `fieldset` and `menu` too, and an `li` start an `li`, a `dd` or `dt` start either, as HTML5 ends them, comments dropped, the filtered tags shown as text, and an unclosed tag dropping the rest; a rule is a 2px `border_strong` line; bullets go •, ◦, ▪ by list depth, ordered lists counted. Exports read a tree as the drawing does through `MarkdownReader` (`block` gives its `MarkdownBlock`s, `inline` its text, `note` and `label` its footnotes, `headings` the `[toc]` list), one fresh stack per paragraph, heading or cell. `MarkdownDocument` holds a whole file in one `CodeEditor` (text and undo, colored by `CodeEditor::highlighter` with `markdown_highlights`): visual draws the file's top-level blocks in a gpui `list`, a pressed block opening as its source in a `TextInput` whose typing is the document's text at once and whose write-back is one undo step; a press in a table opens that cell alone, in place, as its source in a one-line field (a press on its text at the pressed character, past it at its end; a table block opened by its edge, the keyboard or a step from a neighbor opens its first or last cell), Tab and Shift-Tab going to the next and previous cell, Up and Down to the cell above and below or out of the table, Enter and Escape writing it back, a bare `|` typed in it escaped as the cell keeps it, and a table edit writing it back before it runs; source is the editor; preview draws without presses. A written-back block, a mode switch or a new text is read at once up to 128 KiB, longer ones on the background executor; typing in source or split reads 300 ms after the last key, off the main thread (markdown-rs grows with the square of its nodes, not its bytes: in release, 128 KiB of one-letter paragraphs takes 1.7 s, 16 KiB 42 ms, while 128 KiB of prose takes 20 ms; a block-heavy text under the cutoff can still hold the UI thread past 100 ms, a known limit). Texts past `LARGEST_READ` (2 MiB) are never read: no blocks, no outline. A new read keeLine truncated
 - Pictures: `image` 0.25 (MIT OR Apache-2.0), the crate gpui decodes with, default features off; it turns decoded frames and rims map tiles.
 - Math and diagrams: RaTeX 0.1.14 (`ratex-parser`, `ratex-layout`, `ratex-svg` with `embed-fonts`, `ratex-types`; MIT, KaTeX's fonts OFL) typesets `Latex` to SVG with outlined glyphs; `mermaid-rs-renderer` 0.3.1 (MIT, default features off) draws `Diagram`. Both go through gpui's `SvgRenderer` at the window's scale, loaded as gpui assets off the main thread; `usvg` 0.46, gpui's own, reads a diagram's size. A RaTeX or Mermaid panic on parsed input becomes the element's error. Each element holds its picture through `primitives::held`: a new source, or the element leaving the window, removes the old asset from gpui's cache and drops its image from the atlas after the frame.
 - Maps: Natural Earth's 110m countries (public domain). `assets/maps/countries.geojson`, trimmed by `scripts/countries.py` to an ISO code, a name and positions to 0.01°, backs `maps::WorldMap`; the gallery's tiles are cut from the same file, z0 to z3, by `scripts/tiles.py` with Pillow.

src/documents/document/apart.rs

@@ -7,6 +7,7 @@ use gpui::{AppContext as _, Context};
 use super::{
     DocumentEvent, LARGEST_READ, MarkdownDocument,
     block::{self, BlockCommand, settled},
+    cells,
     format::{Change, EditRefusal, InlineFormat, drop_image, toggle},
     tables::{self, TableEdit},
 };
@@ -127,9 +128,18 @@ impl MarkdownDocument {
                 &text[open.range.end..],
             ),
         };
-        let picked = input.selection();
+        let (typed, mut picked) = (input.text(), input.selection());
+        // A cell reads as it writes back.
+        let typed = match open.cell {
+            Some(_) => {
+                let shift = |at: usize| cells::guarded(&typed[..at]).len();
+                picked = shift(picked.start)..shift(picked.end);
+                cells::guarded(typed)
+            }
+            None => typed.to_string(),
+        };
         let offset = before.len();
-        let full = format!("{before}{}{after}", input.text());
+        let full = format!("{before}{typed}{after}");
         settle((full, offset, offset + picked.start..offset + picked.end))
     }
 
@@ -144,12 +154,16 @@ impl MarkdownDocument {
     ) -> Result<(), EditRefusal> {
         log::info!("markdown document: {name}");
         if let Some(open) = &self.open {
-            let end = offset + open.input.read(cx).text().len();
+            let typed = open.input.read(cx).text();
+            // Offsets read the escaped cell; its field holds it raw.
+            let raw = open.cell.is_some() && cells::guarded(typed) != typed;
+            let end = offset + typed.len();
             let grown = (edits.iter().map(|(_, with)| with.len()).sum::<usize>() + end)
                 .checked_sub(edits.iter().map(|(range, _)| range.len()).sum::<usize>());
-            let inside = edits
-                .iter()
-                .all(|(range, _)| offset <= range.start && range.end <= end)
+            let inside = !raw
+                && edits
+                    .iter()
+                    .all(|(range, _)| offset <= range.start && range.end <= end)
                 && grown.is_some_and(|grown| offset <= selected.start && selected.end <= grown);
             if inside {
                 let (Some(from), Some(to)) = (

src/documents/document/cells.rs

@@ -0,0 +1,221 @@
+//! A table cell opens alone, as Typora edits tables.
+
+use std::ops::Range;
+
+use markdown::mdast::Node;
+
+use crate::documents::{
+    markdown::{file_tree, span, walk},
+    render::CellAt,
+};
+
+/// A cell of the text: which, its source, the caret in it.
+#[derive(Debug, PartialEq, Eq)]
+pub(super) struct Cell {
+    pub at: CellAt,
+    pub range: Range<usize>,
+    pub caret: usize,
+}
+
+/// What names a cell in a block.
+#[derive(Clone, Copy, Debug)]
+pub(super) enum Aim {
+    /// The cell holding this byte of the text.
+    Byte(usize),
+    /// This cell, its caret at the end.
+    At(CellAt),
+    First,
+    Last,
+}
+
+/// A way out of a cell.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub(super) enum Move {
+    Next,
+    Previous,
+    Up,
+    Down,
+}
+
+/// The rows of each table in `root`, in drawing order.
+fn tables(root: &Node) -> Vec<Vec<&Node>> {
+    let mut nodes = Vec::new();
+    walk(root, &mut nodes);
+    nodes
+        .into_iter()
+        .filter(|node| matches!(node, Node::Table(_)))
+        .map(|table| {
+            table
+                .children()
+                .expect("a table holds rows")
+                .iter()
+                .collect()
+        })
+        .collect()
+}
+
+fn cells(row: &Node) -> &[Node] {
+    row.children().expect("a row holds cells")
+}
+
+/// The cell `aim` names in `block` of `text`.
+pub(super) fn find(text: &str, block: Range<usize>, aim: Aim) -> Option<Cell> {
+    let root = file_tree(&text[block.clone()]);
+    let tables = tables(&root);
+    let at = match aim {
+        Aim::At(at) => at,
+        Aim::First if !tables.is_empty() => CellAt {
+            table: 0,
+            row: 0,
+            column: 0,
+        },
+        Aim::Last => {
+            let table = tables.len().checked_sub(1)?;
+            let row = tables[table].len() - 1;
+            let column = cells(tables[table][row]).len().checked_sub(1)?;
+            CellAt { table, row, column }
+        }
+        Aim::First => return None,
+        Aim::Byte(byte) => {
+            let byte = byte.checked_sub(block.start)?;
+            let table = (tables.iter()).position(|rows| {
+                let (first, last) = (rows[0], rows[rows.len() - 1]);
+                (span(first).start..=span(last).end).contains(&byte)
+            })?;
+            let rows = &tables[table];
+            let row = rows.iter().rposition(|row| span(row).start <= byte)?;
+            let column = (cells(rows[row]).iter()).rposition(|cell| span(cell).start <= byte)?;
+            CellAt { table, row, column }
+        }
+    };
+    let cell = cells(tables.get(at.table)?.get(at.row)?).get(at.column)?;
+    let range = written(&text[block.clone()], cell);
+    let caret = match aim {
+        Aim::Byte(byte) => (byte - block.start).clamp(range.start, range.end) - range.start,
+        _ => range.len(),
+    };
+    Some(Cell {
+        at,
+        range: block.start + range.start..block.start + range.end,
+        caret,
+    })
+}
+
+/// The cell `by` reaches from `at`; none past the table's edge.
+pub(super) fn beside(text: &str, block: Range<usize>, at: CellAt, by: Move) -> Option<CellAt> {
+    let root = file_tree(&text[block]);
+    let tables = tables(&root);
+    let rows = tables.get(at.table)?;
+    let width = |row: usize| rows.get(row).map_or(0, |row| cells(row).len());
+    let (row, column) = match by {
+        Move::Next if at.column + 1 < width(at.row) => (at.row, at.column + 1),
+        Move::Next => (at.row + 1, 0),
+        Move::Previous if at.column > 0 => (at.row, at.column - 1),
+        Move::Previous => {
+            let row = at.row.checked_sub(1)?;
+            (row, width(row).checked_sub(1)?)
+        }
+        Move::Up => (at.row.checked_sub(1)?, at.column),
+        Move::Down => (at.row + 1, at.column),
+    };
+    let column = column.min(width(row).checked_sub(1)?);
+    Some(CellAt {
+        table: at.table,
+        row,
+        column,
+    })
+}
+
+/// A cell's source between its pipes; empty, a place after the opening one.
+fn written(text: &str, cell: &Node) -> Range<usize> {
+    let inside = cell.children().expect("a cell holds inlines");
+    if let (Some(first), Some(last)) = (inside.first(), inside.last()) {
+        return span(first).start..span(last).end;
+    }
+    let span = span(cell);
+    let mut at = span.start;
+    if text[at..span.end].starts_with('|') {
+        at += 1;
+    }
+    if text[at..span.end].starts_with([' ', '\t']) {
+        at += 1;
+    }
+    at..at
+}
+
+/// `typed` with each bare `|` escaped, as a cell keeps it.
+pub(super) fn guarded(typed: &str) -> String {
+    let mut out = String::with_capacity(typed.len());
+    let mut slashes = 0;
+    for ch in typed.chars() {
+        if ch == '|' && slashes % 2 == 0 {
+            out.push('\\');
+        }
+        slashes = if ch == '\\' { slashes + 1 } else { 0 };
+        out.push(ch);
+    }
+    out
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{Aim, CellAt, Move, beside, find, guarded};
+
+    const TABLE: &str = "intro\n\n| a | **b** |\n| --- | --- |\n| c |  |\n| d | e |\n";
+
+    fn block() -> std::ops::Range<usize> {
+        7..TABLE.len() - 1
+    }
+
+    fn at(row: usize, column: usize) -> CellAt {
+        CellAt {
+            table: 0,
+            row,
+            column,
+        }
+    }
+
+    #[test]
+    fn a_byte_opens_its_cell_with_the_caret_there() {
+        let byte = TABLE.find("**b**").expect("in the table") + 2;
+        let cell = find(TABLE, block(), Aim::Byte(byte)).expect("a cell");
+        assert_eq!(cell.at, at(0, 1));
+        assert_eq!(&TABLE[cell.range.clone()], "**b**");
+        assert_eq!(cell.caret, 2);
+    }
+
+    #[test]
+    fn an_empty_cell_opens_between_its_pipes() {
+        let cell = find(TABLE, block(), Aim::At(at(1, 1))).expect("a cell");
+        assert!(cell.range.is_empty());
+        let written = [&TABLE[..cell.range.start], "x", &TABLE[cell.range.end..]].concat();
+        assert!(written.contains("| c | x |"), "{written:?}");
+    }
+
+    #[test]
+    fn ends_open_the_first_and_last_cells() {
+        let first = find(TABLE, block(), Aim::First).expect("a cell");
+        assert_eq!((first.at, &TABLE[first.range]), (at(0, 0), "a"));
+        let last = find(TABLE, block(), Aim::Last).expect("a cell");
+        assert_eq!((last.at, &TABLE[last.range]), (at(2, 1), "e"));
+        assert_eq!(find("plain\n", 0..5, Aim::First), None);
+    }
+
+    #[test]
+    fn moves_wrap_rows_and_stop_at_edges() {
+        let to = |from, by| beside(TABLE, block(), from, by);
+        assert_eq!(to(at(0, 1), Move::Next), Some(at(1, 0)));
+        assert_eq!(to(at(1, 0), Move::Previous), Some(at(0, 1)));
+        assert_eq!(to(at(0, 0), Move::Previous), None);
+        assert_eq!(to(at(2, 1), Move::Next), None);
+        assert_eq!(to(at(1, 1), Move::Up), Some(at(0, 1)));
+        assert_eq!(to(at(2, 0), Move::Down), None);
+    }
+
+    #[test]
+    fn bare_pipes_escape_and_escaped_stay() {
+        assert_eq!(guarded("a|b"), "a\\|b");
+        assert_eq!(guarded("a\\|b"), "a\\|b");
+        assert_eq!(guarded("a\\\\|b"), "a\\\\\\|b");
+    }
+}

src/documents/document/edit.rs

@@ -2,7 +2,10 @@ use std::ops::Range;
 
 use gpui::{AppContext as _, Context, Focusable as _, Window};
 
-use super::{DocumentEvent, MarkdownDocument, Open};
+use super::{
+    DocumentEvent, MarkdownDocument, Open, TargetBlock,
+    cells::{self, Aim, Move},
+};
 use crate::{
     documents::{
         MarkdownMode,
@@ -20,6 +23,8 @@ pub(super) enum Landing {
     End,
     /// A source byte of the drawn read.
     At(usize),
+    /// A table cell, by byte or place.
+    Cell(Aim),
 }
 
 /// Where byte `at` lies after `edit`, if it survives.
@@ -76,8 +81,8 @@ impl MarkdownDocument {
             return log::warn!("markdown document: pressed while the text is read again");
         }
         let text = self.editor.read(cx).text();
-        let (range, append) = match pressed {
-            None => (text.len()..text.len(), true),
+        let (range, append, cell) = match pressed {
+            None => (text.len()..text.len(), true, None),
             Some(start) => {
                 let found = moved(start, &written).and_then(|start| {
                     self.parsed
@@ -88,12 +93,36 @@ impl MarkdownDocument {
                 let Some(block) = found else {
                     return log::warn!("markdown document: the pressed block changed as one wrote");
                 };
-                (block.range.clone(), false)
+                let table = block.kind == TargetBlock::Table;
+                let aim = match landing {
+                    Landing::Cell(Aim::Byte(at)) => match moved(at, &written) {
+                        Some(at) => Some(Aim::Byte(at)),
+                        None => {
+                            return log::warn!(
+                                "markdown document: the pressed cell was written over"
+                            );
+                        }
+                    },
+                    Landing::Cell(aim) => Some(aim),
+                    Landing::Start if table => Some(Aim::First),
+                    Landing::End if table => Some(Aim::Last),
+                    _ => None,
+                };
+                match aim {
+                    None => (block.range.clone(), false, None),
+                    Some(aim) => match cells::find(text, block.range.clone(), aim) {
+                        Some(cell) => (cell.range, false, Some((cell.at, cell.caret))),
+                        None => {
+                            return log::warn!("markdown document: no cell {aim:?} in the block");
+                        }
+                    },
+                }
             }
         };
         let caret = match landing {
+            _ if cell.is_some() => cell.map(|(_, caret)| caret),
             Landing::Start => Some(0),
-            Landing::End => None,
+            Landing::End | Landing::Cell(_) => None,
             Landing::At(at) => match moved(at, &written) {
                 Some(at) if range.contains(&at) || at == range.end => Some(at - range.start),
                 _ => {
@@ -104,9 +133,11 @@ impl MarkdownDocument {
         };
         let source = text[range.clone()].to_string();
         let input = cx.new(|cx| {
-            TextInput::new(window, cx)
-                .multi_line(1, usize::MAX)
-                .highlighter(markdown_highlights)
+            let input = TextInput::new(window, cx).highlighter(markdown_highlights);
+            match cell {
+                Some(_) => input,
+                None => input.multi_line(1, usize::MAX),
+            }
         });
         input.update(cx, |input, cx| {
             input.set_text(source, cx);
@@ -118,23 +149,39 @@ impl MarkdownDocument {
         let subscriptions = vec![cx.subscribe_in(
             &input,
             window,
-            |document, _, event: &InputEvent, window, cx| match event {
-                InputEvent::Blur if lent(window, cx) => document.lend(window, cx),
-                InputEvent::Blur => {
-                    document.commit(cx);
+            |document, _, event: &InputEvent, window, cx| {
+                match event {
+                    InputEvent::Blur if lent(window, cx) => document.lend(window, cx),
+                    InputEvent::Blur => {
+                        document.commit(cx);
+                    }
+                    InputEvent::Changed => {
+                        document.typed += 1;
+                        cx.emit(DocumentEvent::Changed)
+                    }
+                    // Enter in a cell writes it back.
+                    InputEvent::Submit
+                        if document
+                            .open
+                            .as_ref()
+                            .is_some_and(|open| open.cell.is_some()) =>
+                    {
+                        document.commit(cx);
+                        window.focus(&document.focus, cx);
+                    }
+                    _ => {}
                 }
-                InputEvent::Changed => {
-                    document.typed += 1;
-                    cx.emit(DocumentEvent::Changed)
-                }
-                _ => {}
             },
         )];
-        log::info!("markdown document: block {range:?} opens");
+        match cell {
+            Some((at, _)) => log::info!("markdown document: cell {at:?} at {range:?} opens"),
+            None => log::info!("markdown document: block {range:?} opens"),
+        }
         self.open = Some(Open {
             range,
             input,
             append,
+            cell: cell.map(|(at, _)| at),
             lent: None,
             _subscriptions: subscriptions,
         });
@@ -187,7 +234,12 @@ impl MarkdownDocument {
         let (lead, written) = match open.append {
             true if typed.is_empty() => return None,
             true => (joint(text).len(), format!("{}{typed}", joint(text))),
-            false => (0, typed),
+            false if open.cell.is_some() => (0, cells::guarded(&typed)),
+            false => (0, typed.clone()),
+        };
+        let caret = match open.cell {
+            Some(_) => cells::guarded(&typed[..caret]).len(),
+            None => caret,
         };
         let at = open.range.start + lead + caret;
         let edit = (text[open.range.clone()] != written).then(|| {
@@ -222,6 +274,15 @@ impl MarkdownDocument {
             return false;
         }
         let here = self.block_at(open.range.start);
+        if let Some(at) = open.cell {
+            let block = self.parsed.blocks[here].range.clone();
+            let by = if down { Move::Down } else { Move::Up };
+            let text = self.editor.read(cx).text();
+            if let Some(to) = cells::beside(text, block, at, by) {
+                self.open(Some(here), Landing::Cell(Aim::At(to)), window, cx);
+                return true;
+            }
+        }
         let next = match down {
             true => Some(here + 1).filter(|next| *next < self.parsed.blocks.len()),
             false => here.checked_sub(1),

src/documents/document/lists.rs

@@ -5,7 +5,11 @@ use std::ops::Range;
 use gpui::{Context, Window};
 use markdown::mdast;
 
-use super::MarkdownDocument;
+use super::{
+    MarkdownDocument,
+    cells::{Aim, Move, beside},
+    edit::Landing,
+};
 use crate::documents::markdown::{span, tree, walk};
 
 /// Spaces one indent step adds.
@@ -196,7 +200,7 @@ impl MarkdownDocument {
 
     /// Enter on a block list line; false leaves it.
     pub(super) fn block_newline(&mut self, cx: &mut Context<Self>) -> bool {
-        let Some(open) = &self.open else {
+        let Some(open) = self.open.as_ref().filter(|open| open.cell.is_none()) else {
             return false;
         };
         let input = open.input.clone();
@@ -218,11 +222,27 @@ impl MarkdownDocument {
         true
     }
 
-    /// Tab or Shift-Tab in the open block.
-    pub(super) fn block_shift(&mut self, deeper: bool, _: &mut Window, cx: &mut Context<Self>) {
+    /// Tab or Shift-Tab in the open block; in a cell, the next or previous.
+    pub(super) fn block_shift(
+        &mut self,
+        deeper: bool,
+        window: &mut Window,
+        cx: &mut Context<Self>,
+    ) {
         let Some(open) = &self.open else {
             return;
         };
+        if let Some(at) = open.cell {
+            let here = self.block_at(open.range.start);
+            let block = self.parsed.blocks[here].range.clone();
+            let by = if deeper { Move::Next } else { Move::Previous };
+            let text = self.editor.read(cx).text();
+            match beside(text, block, at, by) {
+                Some(to) => self.open(Some(here), Landing::Cell(Aim::At(to)), window, cx),
+                None => log::info!("markdown document: no cell {by:?} of {at:?}"),
+            }
+            return;
+        }
         let input = open.input.clone();
         let (text, selection) = {
             let input = input.read(cx);

src/documents/document/mod.rs

@@ -1,6 +1,7 @@
 mod apart;
 mod attach;
 mod block;
+mod cells;
 mod edit;
 mod finding;
 mod format;
@@ -36,7 +37,7 @@ use super::{
     MarkdownMode,
     markdown::markdown_highlights,
     modes::joint,
-    render::{OnHeading, OnLink},
+    render::{CellAt, OnHeading, OnLink},
 };
 use crate::{
     editor::{CodeEditor, EditorEvent, LineNumbers},
@@ -80,6 +81,8 @@ struct Open {
     input: Entity<TextInput>,
     /// Opened past the end, to add a block.
     append: bool,
+    /// A table cell alone; its bare pipes escape.
+    cell: Option<CellAt>,
     /// Watches an overlay that borrowed focus.
     lent: Option<Subscription>,
     _subscriptions: Vec<Subscription>,
@@ -243,6 +246,7 @@ impl MarkdownDocument {
         let written = match open.append {
             true if typed.is_empty() => String::new(),
             true => format!("{}{typed}", joint(text)),
+            false if open.cell.is_some() => cells::guarded(typed),
             false => typed.to_string(),
         };
         [&text[..open.range.start], &written, &text[open.range.end..]].concat()

src/documents/document/point.rs

@@ -3,7 +3,9 @@ use std::rc::Rc;
 use gpui::{AppContext as _, Context, MouseButton, Pixels, Point, Window};
 use markdown::mdast;
 
-use super::{DocumentEvent, MarkdownDocument, edit::Landing, edit::moved, parse::Block};
+use super::{
+    DocumentEvent, MarkdownDocument, cells::Aim, edit::Landing, edit::moved, parse::Block,
+};
 use crate::documents::{
     markdown::{file_tree, span, walk},
     render::{OnPoint, Place, Pointed},
@@ -80,15 +82,20 @@ impl MarkdownDocument {
                     Some(lines_at(&parsed.text[start..], *from, text, *at).unwrap_or(*from))
                 }
                 Place::At(at) => Some(*at),
-                Place::Block => None,
+                Place::Cell(_) | Place::Block => None,
             }
             .map(|at| start + at);
+            // A press in a table opens only its cell.
+            let landing = match (&pointed.place, at) {
+                (Place::Cell(cell), _) => Landing::Cell(Aim::At(*cell)),
+                (_, Some(at)) if pointed.table => Landing::Cell(Aim::Byte(at)),
+                (_, Some(at)) => Landing::At(at),
+                (_, None) => Landing::End,
+            };
             let ix = Some(ix);
             document
                 .update(cx, |document, cx| match button {
-                    MouseButton::Left => {
-                        document.open(ix, at.map_or(Landing::End, Landing::At), window, cx)
-                    }
+                    MouseButton::Left => document.open(ix, landing, window, cx),
                     MouseButton::Right => document.point(ix, at, pointed, window, cx),
                     _ => {}
                 })

src/documents/document/tests/cells.rs

@@ -0,0 +1,58 @@
+//! A press in a table opens only its cell (R6.1).
+
+use gpui::{Modifiers, MouseButton, TestAppContext, VisualTestContext, point, px};
+
+use super::{open, opened, text};
+use crate::documents::MarkdownMode;
+
+const TABLE: &str = "| a | **bold** |\n| --- | --- |\n| c |  |\n";
+
+/// Presses cell `row`, `column` of the first table near its left.
+fn press_cell(row: usize, column: usize, cx: &mut VisualTestContext) {
+    let name = format!("markdown-cell-0-{row}-{column}");
+    let bounds = cx
+        .debug_bounds(Box::leak(name.into_boxed_str()))
+        .expect("the cell is drawn");
+    let at = point(bounds.left() + px(2.0), bounds.top() + px(2.0));
+    cx.simulate_mouse_down(at, MouseButton::Left, Modifiers::none());
+    cx.simulate_mouse_up(at, MouseButton::Left, Modifiers::none());
+    cx.run_until_parked();
+}
+
+#[gpui::test]
+fn a_press_opens_its_cell_and_writes_one_undo_step(cx: &mut TestAppContext) {
+    let (document, cx) = open(TABLE, MarkdownMode::Visual, cx);
+    press_cell(0, 1, cx);
+    assert_eq!(opened(&document, cx), "**bold**");
+    assert!(
+        cx.debug_bounds("markdown-cell-0-0-0").is_some(),
+        "the rest stays drawn"
+    );
+    press_cell(1, 1, cx);
+    assert_eq!(opened(&document, cx), "");
+    cx.simulate_input("x|y");
+    assert_eq!(
+        text(&document, cx),
+        "| a | **bold** |\n| --- | --- |\n| c | x\\|y |\n"
+    );
+    cx.simulate_keystrokes("escape");
+    let editor = document.read_with(cx, |document, _| document.editor().clone());
+    editor.update(cx, |editor, cx| editor.undo(cx));
+    assert_eq!(text(&document, cx), TABLE);
+}
+
+#[gpui::test]
+fn tab_and_arrows_walk_the_cells(cx: &mut TestAppContext) {
+    let (document, cx) = open(TABLE, MarkdownMode::Visual, cx);
+    press_cell(0, 0, cx);
+    assert_eq!(opened(&document, cx), "a");
+    cx.simulate_keystrokes("tab");
+    assert_eq!(opened(&document, cx), "**bold**");
+    cx.simulate_keystrokes("shift-tab");
+    assert_eq!(opened(&document, cx), "a");
+    cx.simulate_keystrokes("down");
+    assert_eq!(opened(&document, cx), "c");
+    cx.simulate_keystrokes("enter");
+    assert!(document.read_with(cx, |document, _| document.open.is_none()));
+    assert_eq!(text(&document, cx), TABLE);
+}

src/documents/document/tests/mod.rs

@@ -368,6 +368,7 @@ fn a_press_after_a_write_back_waits_for_the_long_read(cx: &mut TestAppContext) {
 mod attach;
 mod block;
 mod block_edges;
+mod cells;
 mod format;
 mod history;
 mod lend;

src/documents/document/tests/tools.rs

@@ -341,9 +341,10 @@ fn a_new_table_takes_the_texts_line_ending(cx: &mut TestAppContext) {
 }
 
 #[gpui::test]
-fn tidy_in_an_open_table_keeps_it_open(cx: &mut TestAppContext) {
+fn tidy_in_an_open_cell_writes_it_and_tidies(cx: &mut TestAppContext) {
     let (document, cx) = open(SMALL, MarkdownMode::Visual, cx);
     press(0, Modifiers::none(), cx);
+    assert_eq!(opened(&document, cx), "2");
     document.update(cx, |document, cx| {
         document
             .edit_table(crate::documents::TableEdit::Tidy, cx)
@@ -351,8 +352,8 @@ fn tidy_in_an_open_table_keeps_it_open(cx: &mut TestAppContext) {
     });
     cx.run_until_parked();
     assert_eq!(
-        opened(&document, cx),
-        "| A    | B    |\n| ---- | ---- |\n| 1    | 2    |"
+        text(&document, cx),
+        "| A    | B    |\n| ---- | ---- |\n| 1    | 2    |\n"
     );
 }
 

src/documents/document/visual.rs

@@ -9,7 +9,7 @@ use super::{MarkdownDocument, edit::Landing};
 use crate::{
     documents::{
         MarkdownMode,
-        render::{Hooks, Pointed, draw_nodes, point_lines},
+        render::{Hooks, OpenCell, Pointed, draw_nodes, point_lines},
     },
     forms::{self, Down, Up},
     primitives::FocusRing as _,
@@ -72,11 +72,7 @@ impl MarkdownDocument {
         // Focus fades all but the reader's block.
         let faded = self.look.focus && editing_mode(self.mode) && ix != self.current_block(cx);
         let open = self.open.as_ref();
-        let point = cx.listener(|document, event: &MouseDownEvent, window, cx| {
-            window.prevent_default();
-            cx.stop_propagation();
-            document.point_open(event.position, cx);
-        });
+        let point = Self::point_in_open(cx);
         let field = |open: &super::Open| {
             div()
                 .debug_selector(|| "markdown-open".to_string())
@@ -98,9 +94,25 @@ impl MarkdownDocument {
                 (_, false) => div().into_any_element(),
             };
         };
-        if let Some(open) = open.filter(|open| open.range == block.range) {
+        if let Some(open) = open.filter(|open| open.cell.is_none() && open.range == block.range) {
             return field(open);
         }
+        // A cell open in this block, typed in place.
+        let cell = open.and_then(|open| {
+            let inside = block.range.start <= open.range.start && open.range.end <= block.range.end;
+            Some(OpenCell {
+                at: open.cell.filter(|_| inside)?,
+                field: std::cell::RefCell::new(Some(
+                    div()
+                        .debug_selector(|| "markdown-open-cell".to_string())
+                        .on_mouse_down(MouseButton::Right, Self::point_in_open(cx))
+                        .rounded(radius)
+                        .bg(colors.sunken)
+                        .child(open.input.clone())
+                        .into_any_element(),
+                )),
+            })
+        });
         let shown = match &block.nodes {
             Some(nodes) => div()
                 .flex()
@@ -117,6 +129,7 @@ impl MarkdownDocument {
                         on_link: &self.on_link,
                         on_heading: &self.on_heading,
                         on_point: &on_point,
+                        cell: cell.as_ref(),
                     },
                     self.look.scale,
                     cx,
@@ -155,6 +168,17 @@ impl MarkdownDocument {
         }
     }
 
+    /// A right press in the open field points there.
+    fn point_in_open(
+        cx: &mut Context<Self>,
+    ) -> impl Fn(&MouseDownEvent, &mut Window, &mut App) + 'static {
+        cx.listener(|document, event: &MouseDownEvent, window, cx| {
+            window.prevent_default();
+            cx.stop_propagation();
+            document.point_open(event.position, cx);
+        })
+    }
+
     /// `element` opens block `ix`; a right press points.
     fn pressable(
         &self,

src/documents/render.rs

@@ -5,7 +5,6 @@ use gpui::{
     IntoElement, ParentElement, RenderOnce, SharedString, StrikethroughStyle, Styled, StyledText,
     UnderlineStyle, Window, div, prelude::*,
 };
-use markdown::mdast::AlignKind;
 
 use super::{
     contents::anchor,
@@ -23,8 +22,10 @@ use crate::{
 
 mod blocks;
 mod point;
+mod table;
 
 pub(crate) use point::{OnPoint, Place, Pointed, point_lines};
+pub(crate) use table::{CellAt, OpenCell};
 
 pub(crate) type OnLink = Rc<dyn Fn(&str, &mut Window, &mut App)>;
 /// Reveals the heading whose source starts at a byte.
@@ -96,6 +97,8 @@ pub(crate) struct Hooks<'a> {
     pub on_link: &'a Option<OnLink>,
     pub on_heading: &'a Option<OnHeading>,
     pub on_point: &'a Option<OnPoint>,
+    /// The cell typed in, drawn in its place.
+    pub cell: Option<&'a OpenCell>,
 }
 
 /// Draws nodes under one owner's ids and hooks.
@@ -112,6 +115,8 @@ struct Draw<'a> {
     lists: std::cell::Cell<usize>,
     /// Drawing a table's cells.
     table: std::cell::Cell<bool>,
+    /// Tables drawn so far.
+    tables: std::cell::Cell<usize>,
 }
 
 impl Draw<'_> {
@@ -302,60 +307,7 @@ impl Draw<'_> {
                 self.point_code(block, Some(layout), text, *from)
             }
             Node::List { start, items } => self.list(start, items, cx),
-            Node::Table { aligns, head, rows } => {
-                let cell = |blocks: &[Node], column: usize, header: bool, cx: &App| {
-                    div()
-                        .flex_1()
-                        .min_w_0()
-                        .flex()
-                        .px_3()
-                        .py_1p5()
-                        .when(aligns.get(column) == Some(&AlignKind::Right), |cell| {
-                            cell.justify_end()
-                        })
-                        .when(aligns.get(column) == Some(&AlignKind::Center), |cell| {
-                            cell.justify_center()
-                        })
-                        .when(header, |cell| {
-                            cell.font_weight(FontWeight::MEDIUM)
-                                .text_color(colors.fg_muted)
-                        })
-                        .child(
-                            div()
-                                .max_w_full()
-                                .flex()
-                                .flex_col()
-                                .gap_1()
-                                .children(self.nodes(blocks, cx)),
-                        )
-                };
-                div()
-                    .flex()
-                    .flex_col()
-                    .rounded(theme.radius(Radius::Md))
-                    .border_1()
-                    .border_color(colors.border)
-                    .overflow_hidden()
-                    .child(
-                        div().flex().bg(colors.hover).children(
-                            head.iter()
-                                .enumerate()
-                                .map(|(column, blocks)| cell(blocks, column, true, cx)),
-                        ),
-                    )
-                    .children(rows.iter().map(|row| {
-                        div()
-                            .flex()
-                            .border_t_1()
-                            .border_color(colors.border)
-                            .children(
-                                row.iter()
-                                    .enumerate()
-                                    .map(|(column, blocks)| cell(blocks, column, false, cx)),
-                            )
-                    }))
-                    .into_any_element()
-            }
+            Node::Table { aligns, head, rows } => self.table(aligns, head, rows, cx),
             Node::Rule => div()
                 .debug_selector(|| "markdown-rule".into())
                 .my_2()
@@ -443,6 +395,7 @@ pub(crate) fn draw_nodes(
         scale,
         lists: std::cell::Cell::new(0),
         table: std::cell::Cell::new(false),
+        tables: std::cell::Cell::new(0),
     };
     draw.nodes(nodes, cx)
 }
@@ -458,6 +411,7 @@ impl RenderOnce for MarkdownRenderer {
                 on_link: &self.on_link,
                 on_heading: &None,
                 on_point: &None,
+                cell: None,
             },
             next: std::cell::Cell::new(0),
             sections: &self.sections,
@@ -466,6 +420,7 @@ impl RenderOnce for MarkdownRenderer {
             scale: 1.0,
             lists: std::cell::Cell::new(0),
             table: std::cell::Cell::new(false),
+            tables: std::cell::Cell::new(0),
         };
         div()
             .flex()

src/documents/render/point.rs

@@ -1,11 +1,11 @@
 use std::rc::Rc;
 
 use gpui::{
-    AnyElement, App, InteractiveElement as _, IntoElement as _, MouseButton, MouseDownEvent,
+    AnyElement, App, Div, InteractiveElement, IntoElement as _, MouseButton, MouseDownEvent,
     ParentElement as _, TextLayout, Window, div,
 };
 
-use super::Draw;
+use super::{Draw, table::CellAt};
 use crate::documents::tree::Inline;
 
 /// Where a press fell, as the drawing knows it.
@@ -20,6 +20,8 @@ pub(crate) enum Place {
         from: usize,
         at: usize,
     },
+    /// A table cell, pressed past its text.
+    Cell(CellAt),
     /// Somewhere the block holds no byte for.
     Block,
 }
@@ -61,6 +63,19 @@ fn pointable(
     table: bool,
     point: impl Fn(&MouseDownEvent) -> Pointed + 'static,
 ) -> AnyElement {
+    match on_point {
+        Some(_) => pressed(div().child(element), on_point, table, point).into_any_element(),
+        None => element,
+    }
+}
+
+/// `element` itself takes the presses `pointable` hands on.
+fn pressed<E: InteractiveElement>(
+    element: E,
+    on_point: &Option<OnPoint>,
+    table: bool,
+    point: impl Fn(&MouseDownEvent) -> Pointed + 'static,
+) -> E {
     let Some(on_point) = on_point.clone() else {
         return element;
     };
@@ -79,11 +94,9 @@ fn pointable(
             on_point(pointed, button, window, cx);
         }
     };
-    div()
+    element
         .on_mouse_down(MouseButton::Left, press(MouseButton::Left))
         .on_mouse_down(MouseButton::Right, press(MouseButton::Right))
-        .child(element)
-        .into_any_element()
 }
 
 /// Drawn `text`, its lines written from source byte `from`.
@@ -120,6 +133,13 @@ impl Draw<'_> {
         pointable(element, self.hooks.on_point, self.table.get(), point)
     }
 
+    /// A table cell taking its presses, past its text too.
+    pub(super) fn pressed_cell(&self, cell: Div, at: CellAt) -> Div {
+        pressed(cell, self.hooks.on_point, true, move |_| {
+            Pointed::at(Place::Cell(at))
+        })
+    }
+
     /// Drawn `inline`; a press finds its byte through `layout`.
     pub(super) fn point_text(
         &self,

src/documents/render/table.rs

@@ -0,0 +1,99 @@
+use std::cell::RefCell;
+
+use gpui::{AnyElement, App, FontWeight, IntoElement, ParentElement, Styled, div, prelude::*};
+use markdown::mdast::AlignKind;
+
+use super::Draw;
+use crate::{
+    documents::tree::Node,
+    theme::{ActiveTheme, Radius},
+};
+
+/// A cell: its table in drawing order, row from the head, column.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub(crate) struct CellAt {
+    pub table: usize,
+    pub row: usize,
+    pub column: usize,
+}
+
+/// The cell open for typing and its field, drawn once.
+pub(crate) struct OpenCell {
+    pub at: CellAt,
+    pub field: RefCell<Option<AnyElement>>,
+}
+
+impl Draw<'_> {
+    pub(super) fn table(
+        &self,
+        aligns: &[AlignKind],
+        head: &[Vec<Node>],
+        rows: &[Vec<Vec<Node>>],
+        cx: &App,
+    ) -> AnyElement {
+        let theme = cx.theme();
+        let colors = theme.colors.clone();
+        let table = self.tables.get();
+        self.tables.set(table + 1);
+        let cell = |blocks: &[Node], row: usize, column: usize, cx: &App| {
+            let at = CellAt { table, row, column };
+            let open = (self.hooks.cell)
+                .filter(|open| open.at == at)
+                .and_then(|open| open.field.borrow_mut().take());
+            let drawn = div()
+                .debug_selector(move || format!("markdown-cell-{table}-{row}-{column}"))
+                .flex_1()
+                .min_w_0()
+                .flex()
+                .px_3()
+                .py_1p5()
+                .when(aligns.get(column) == Some(&AlignKind::Right), |cell| {
+                    cell.justify_end()
+                })
+                .when(aligns.get(column) == Some(&AlignKind::Center), |cell| {
+                    cell.justify_center()
+                })
+                .when(row == 0, |cell| {
+                    cell.font_weight(FontWeight::MEDIUM)
+                        .text_color(colors.fg_muted)
+                })
+                .child(match open {
+                    Some(field) => div().w_full().child(field),
+                    None => div()
+                        .max_w_full()
+                        .flex()
+                        .flex_col()
+                        .gap_1()
+                        .children(self.nodes(blocks, cx)),
+                });
+            self.pressed_cell(drawn, at)
+        };
+        div()
+            .flex()
+            .flex_col()
+            .rounded(theme.radius(Radius::Md))
+            .border_1()
+            .border_color(colors.border)
+            .overflow_hidden()
+            .child(
+                div().flex().bg(colors.hover).children(
+                    head.iter()
+                        .enumerate()
+                        .map(|(column, blocks)| cell(blocks, 0, column, cx)),
+                ),
+            )
+            .children(rows.iter().enumerate().map(|(row, cells)| {
+                div()
+                    .flex()
+                    .border_t_1()
+                    .border_color(colors.border)
+                    .children(
+                        cells
+                            .iter()
+                            .enumerate()
+                            .map(|(column, blocks)| cell(blocks, row + 1, column, cx)),
+                    )
+            }))
+            .into_any_element()
+    }
+}