AutoFormat As You Type: optional "Add a period with double-space", and an AutoCorrect Options button in Options › Proofing (#2848) (#3318)

* AutoFormat As You Type: optional period with double-space, off by default (#2848)

* Test the double-space option through the AutoCorrect dialog (#2848)

* File > Options > Proofing: an AutoCorrect Options button opens the dialog (#476)

* #2848: report doubleSpacePeriod in tools.autocorrect's params doc and result

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Brandon Thomas <echelon@gmail.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

crates/engine/src/cmd/text.rs

@@ -101,6 +101,7 @@ fn insert(s: &mut Session, v: &Value) -> CmdResult {
     let raw = p::bool(v, "raw").unwrap_or(false);
     typing_options(s, text);
     let t = if raw { None } else { autoformat(s, text) };
+    let was_collapsed = s.sel.is_collapsed();
     type_text(s, t.as_deref().unwrap_or(text))?;
     let trigger = text.chars().count() == 1 && text.chars().all(|c| c == ' ' || ",.;:!?".contains(c));
     if raw || !trigger {
@@ -117,6 +118,9 @@ fn insert(s: &mut Session, v: &Value) -> CmdResult {
     if text == " " && !listed && s.prefs.autocorrect.enabled && s.prefs.autocorrect.dashes {
         dash_autoformat(s).inspect_err(|_| s.autocap = None)?;
     }
+    if text == " " && !listed && was_collapsed && s.prefs.autocorrect.enabled && s.prefs.autocorrect.double_space_period {
+        double_space_period(s)?;
+    }
     if let Some((para, sel)) = typed
         && s.doc.para_at(&f) != Some(&para)
     {
@@ -187,6 +191,27 @@ fn list_autoformat(s: &mut Session) -> Result<bool, CmdError> {
     Ok(true)
 }
 
+/// "word" + two spaces → "word. ": the second Space turns the first into a period, after a
+/// letter, a digit or a closing bracket or quote; not after other punctuation, at the start of a
+/// paragraph, after a tab, or for a third space (the text before them ends in a period by then).
+fn double_space_period(s: &mut Session) -> Result<(), CmdError> {
+    let f = s.sel.focus.clone();
+    let Some(para) = s.doc.para_at(&f) else { return Ok(()) };
+    let Some(before) = para.text.get(..f.off) else { return Ok(()) };
+    let Some(word) = before.strip_suffix("  ") else { return Ok(()) };
+    if !word.chars().next_back().is_some_and(|c| c.is_alphanumeric() || ")]}\"'\u{201D}\u{2019}\u{00BB}\u{203A}".contains(c)) {
+        return Ok(());
+    }
+    // The period takes the formatting of the space it replaces.
+    let at = word.len();
+    let p = s.doc.para_mut(f.story, &f.path)?;
+    let props = p.props_at(at + 1).clone().without_symbol();
+    p.delete(at, at + 1)?;
+    p.insert_text(at, ".", &props)?;
+    s.sel = Selection::caret(f);
+    Ok(())
+}
+
 /// "word -- word" → en dash, "word--word" → em dash (on the space after).
 fn dash_autoformat(s: &mut Session) -> Result<(), CmdError> {
     let f = s.sel.focus.clone();

crates/engine/src/cmd/tools.rs

@@ -114,6 +114,9 @@ pub struct AutoCorrectPrefs {
     /// letter or digit makes it Heading 1 (Heading 2 or 3 after one or two leading tabs).
     /// Off by default.
     pub heading_styles: bool,
+    /// A second Space after a word, number or closing bracket or quote turns the first into a
+    /// period (macOS's "Add period with double-space"); off by default.
+    pub double_space_period: bool,
     /// The user's entries: added, or replacing a built-in one.
     pub entries: Vec<(String, String)>,
     /// Built-in entries the user deleted.
@@ -152,6 +155,7 @@ impl Default for AutoCorrectPrefs {
             border_lines: true,
             tab_indent: false,
             heading_styles: false,
+            double_space_period: false,
             entries: Vec::new(),
             removed: Vec::new(),
             exceptions: Vec::new(),
@@ -344,6 +348,7 @@ fn autocorrect_options(s: &mut Session, v: &Value) -> CmdResult {
         ("borderLines", &mut ac.border_lines),
         ("tabIndent", &mut ac.tab_indent),
         ("headingStyles", &mut ac.heading_styles),
+        ("doubleSpacePeriod", &mut ac.double_space_period),
         ("autoAddFirstLetter", &mut ac.auto_add_first_letter),
         ("autoAddInitialCaps", &mut ac.auto_add_initial_caps),
     ] {
@@ -420,6 +425,7 @@ fn autocorrect_options(s: &mut Session, v: &Value) -> CmdResult {
         "borderLines": ac.border_lines,
         "tabIndent": ac.tab_indent,
         "headingStyles": ac.heading_styles,
+        "doubleSpacePeriod": ac.double_space_period,
         "autoAddFirstLetter": ac.auto_add_first_letter,
         "autoAddInitialCaps": ac.auto_add_initial_caps,
         "entries": ac.list().into_iter().map(|(a, b, builtin)| json!({"from": a, "to": b, "builtIn": builtin})).collect::<Vec<_>>(),
@@ -457,7 +463,7 @@ pub fn specs() -> Vec<CommandSpec> {
             .pure(),
         CommandSpec::new("tools.autocorrect", "AutoCorrect Options", "File › Options › Proofing", autocorrect_options)
             .params(
-                r#"{"enabled"?: bool (all of AutoCorrect), "replaceText"|"twoInitialCaps"|"capSentences"|"capCells"|"capDays"|"capsLock"|"smartQuotes"|"fractions"|"ordinals"|"dashes"|"links"|"bullets"|"numbering"|"borderLines"?: bool, "boldItalic"?: bool (*bold* and _italic_ with real formatting; default false), "tabIndent"?: bool (Set left- and first-indent with tabs and backspaces; default false), "headingStyles"?: bool (Built-in Heading styles; default false), "autoAddFirstLetter"|"autoAddInitialCaps"?: bool (Automatically add words to the exception lists when an automatic capital is undone; default true), "add"?: {"from": string, "to": string} (adds or replaces an entry), "delete"?: string (an entry's "from", built in or added), "addException"?: string, "deleteException"?: string, "addInitialCapsException"?: string (keeps TWo INitial CApitals, like "IDs"), "deleteInitialCapsException"?: string} → options, entries and exceptions"#,
+                r#"{"enabled"?: bool (all of AutoCorrect), "replaceText"|"twoInitialCaps"|"capSentences"|"capCells"|"capDays"|"capsLock"|"smartQuotes"|"fractions"|"ordinals"|"dashes"|"links"|"bullets"|"numbering"|"borderLines"?: bool, "boldItalic"?: bool (*bold* and _italic_ with real formatting; default false), "tabIndent"?: bool (Set left- and first-indent with tabs and backspaces; default false), "headingStyles"?: bool (Built-in Heading styles; default false), "doubleSpacePeriod"?: bool (Add a period with double-space; default false), "autoAddFirstLetter"|"autoAddInitialCaps"?: bool (Automatically add words to the exception lists when an automatic capital is undone; default true), "add"?: {"from": string, "to": string} (adds or replaces an entry), "delete"?: string (an entry's "from", built in or added), "addException"?: string, "deleteException"?: string, "addInitialCapsException"?: string (keeps TWo INitial CApitals, like "IDs"), "deleteInitialCapsException"?: string} → options, entries and exceptions"#,
             )
             .pure(),
         CommandSpec::new("tools.customizeKeyboard", "Customize Keyboard", "File › Options", customize_keyboard)

crates/engine/src/tests_typing.rs

@@ -3320,3 +3320,48 @@ fn tab_with_a_partial_selection_still_inserts_a_tab() {
     run(&mut s, "text.tab", json!({}));
     assert_eq!(paras(&s), vec![para("H\t world", None)]);
 }
+
+/// #2848: "Add a period with double-space" (an AutoFormat As You Type switch, off by default):
+/// a second Space after a word, a number or a closing bracket or quote turns the first into a
+/// period. Undo puts the two spaces back; other punctuation, a lone space and a run of three
+/// spaces are left as typed.
+#[test]
+fn double_space_adds_a_period_when_asked() {
+    let with_option = |keys: &str| {
+        let mut s = s();
+        run(&mut s, "tools.autocorrect", json!({"doubleSpacePeriod": true}));
+        typ(&mut s, keys);
+        s
+    };
+    let text = |s: &Session| s.doc.plain_text(StoryRef::Body);
+    // Off unless asked for.
+    assert_eq!(text(&typed("Hello  world")), "Hello  world");
+    assert!(!s().prefs.autocorrect.double_space_period);
+    // On: the second space makes the period, and the next sentence starts with a capital.
+    assert_eq!(text(&with_option("Hello  world")), "Hello. world");
+    assert_eq!(text(&with_option("Hello  world ")), "Hello. World ");
+    assert_eq!(text(&with_option("See page 5  Then")), "See page 5. Then");
+    assert_eq!(text(&with_option("(it is done)  Next")), "(it is done). Next");
+    assert_eq!(text(&with_option("He said \"stop\"  Next")), "He said “stop”. Next");
+    // Undo brings the two spaces back, in one step.
+    let mut t = with_option("Hello  ");
+    assert_eq!(text(&t), "Hello. ");
+    run(&mut t, "edit.undo", json!({}));
+    assert_eq!(text(&t), "Hello  ");
+    // Left alone: other punctuation before the spaces, a lone space, spaces at the start of a
+    // paragraph or after a tab, and a third space.
+    for keys in ["Hello.  x", "Hello,  x", "Hello?  x", "Hello;  x", "Hello:  x", "Hello x", "  x", "\n  x", "a\t  x"] {
+        let want = typed(keys);
+        assert_eq!(text(&with_option(keys)), text(&want), "{keys:?}");
+    }
+    assert_eq!(text(&with_option("Hello   x")), "Hello.  x");
+    // A selection typed over, and the master switch.
+    let mut t = with_option("Hello world");
+    run(&mut t, "select.all", json!({}));
+    run(&mut t, "text.insert", json!({"text": " "}));
+    assert_eq!(text(&t), " ");
+    let mut t = s();
+    run(&mut t, "tools.autocorrect", json!({"doubleSpacePeriod": true, "enabled": false}));
+    typ(&mut t, "Hello  world");
+    assert_eq!(text(&t), "Hello  world");
+}

crates/ui-egui/src/dialogs_review.rs

@@ -356,6 +356,7 @@ impl AutoCorrectForm {
             "borderLines": o.border_lines,
             "tabIndent": o.tab_indent,
             "headingStyles": o.heading_styles,
+            "doubleSpacePeriod": o.double_space_period,
             "autoAddFirstLetter": o.auto_add_first_letter,
             "autoAddInitialCaps": o.auto_add_initial_caps,
         })
@@ -401,6 +402,7 @@ fn autocorrect_ui(app: &mut WordApp, ui: &mut Ui, f: &mut AutoCorrectForm) -> bo
             ui.checkbox(&mut o.bold_italic, tl!("*Bold* and _italic_ as real formatting"));
             ui.checkbox(&mut o.dashes, tl!("Hyphens (--) as dashes (—)"));
             ui.checkbox(&mut o.links, tl!("Internet addresses as links"));
+            ui.checkbox(&mut o.double_space_period, tl!("Add a period with double-space"));
             heading(ui, "Apply as you type");
             ui.checkbox(&mut o.bullets, tl!("Automatic bulleted lists"));
             ui.checkbox(&mut o.numbering, tl!("Automatic numbered lists"));
@@ -897,4 +899,44 @@ mod tests {
         }
         assert!(texts(&h).iter().any(|t| t.contains("(none)")), "no matches: the hint shows");
     }
+
+    /// #2848 through the real dialog: tick "Add a period with double-space" on the AutoFormat As
+    /// You Type tab, press OK, and a double Space typed in the page makes a period.
+    #[test]
+    fn the_double_space_option_is_set_in_the_dialog_and_works_when_typing() {
+        use egui_kittest::kittest::Queryable;
+        let mut app = app("");
+        app.run("tools.autocorrect", json!({})).unwrap();
+        let mut h = egui_kittest::Harness::builder().with_size(vec2(1440.0, 900.0)).build_ui_state(
+            |ui, app: &mut WordApp| {
+                let ctx = ui.ctx().clone();
+                app.logic(&ctx);
+                app.ui(ui);
+            },
+            app,
+        );
+        for _ in 0..4 {
+            h.step();
+        }
+        h.get_by_label("AutoFormat As You Type").click();
+        for _ in 0..3 {
+            h.step();
+        }
+        h.get_by_label("Add a period with double-space").click();
+        for _ in 0..3 {
+            h.step();
+        }
+        h.get_by_label("OK").click();
+        for _ in 0..4 {
+            h.step();
+        }
+        assert!(h.state().dialog.is_none(), "OK closes the dialog");
+        assert!(h.state().session.prefs.autocorrect.double_space_period, "the option is on");
+        h.state_mut().canvas.focused = true;
+        for t in ["Hello", " ", " ", "world"] {
+            h.event(egui::Event::Text(t.to_string()));
+            h.step();
+        }
+        assert_eq!(h.state().session.doc.plain_text(wordcraft_doc::StoryRef::Body), "Hello. world");
+    }
 }

crates/ui-egui/src/options.rs

@@ -292,7 +292,11 @@ fn display(app: &mut WordApp, ui: &mut Ui) {
 }
 
 fn proofing(app: &mut WordApp, ui: &mut Ui) {
-    // #476 (AutoCorrect Options…) goes here, at the top.
+    section(ui, "AutoCorrect");
+    if ui.button(tl!("AutoCorrect Options")).clicked() {
+        let _ = app.run("tools.autocorrect", json!({}));
+    }
+    ui.add_space(8.0);
     section(ui, "Spelling");
     let pr = app.session.prefs.clone();
     flag(app, ui, "Ignore words in capitals", "ignoreUppercase", pr.ignore_uppercase);
@@ -1089,6 +1093,13 @@ mod tests {
         h.get_by_label("Ignore words in capitals").click();
         h.run_steps(2);
         assert!(!h.state().session.prefs.ignore_uppercase);
+        // The AutoCorrect Options dialog opens from this pane.
+        assert!(h.state().dialog.is_none());
+        h.get_by_label("AutoCorrect Options").click();
+        h.run_steps(3);
+        assert_eq!(h.state().dialog.as_ref().map(|d| d.name()), Some("autoCorrect"));
+        h.state_mut().dialog = None;
+        h.run_steps(2);
         // #1063: the dictionaries folder and the dictionary each language found.
         assert!(h.query_by_label("Dictionaries folder:").is_some());
         assert!(h.query_by_label_contains("Polish: ").is_some(), "the Polish dictionary's line");

docs/typing-parity.md

@@ -156,6 +156,13 @@ ideographic space (`autocorrect_finds_the_word_after_a_wide_space`):
   is “ (U+201C) even though it shows on the right of the word, after a letter ” (U+201D); in an
   acronym (`צה"ל`) it becomes ” as in Word for Mac 16.113.4, not gershayim (״); `'` after a letter
   (`ג'ירפה`) is ’ as after any letter, with no geresh conversion (not yet checked in Word; `smart_quotes_in_hebrew_use_logical_order`, #1670).
+- Add a period with double-space (File › Options › Proofing › AutoCorrect Options › AutoFormat As
+  You Type, `tools.autocorrect {"doubleSpacePeriod"}`; **off by default**, as macOS's system switch
+  is a per-user choice): a second Space after a letter, a digit or a closing bracket or quote turns
+  the first into a period (`Hello  world`→`Hello. world`). Other punctuation before the spaces,
+  a lone space, the start of a paragraph, a tab, a selection typed over and a third space are left
+  as typed; Undo puts the two spaces back (`double_space_adds_a_period_when_asked`, #2848). Not
+  observed in Word; Word for Mac follows the macOS setting.
 - Correct TWo INitial CApitals: a finished word of three or more letters with two capitals and
   the rest lowercase loses its second capital (`WOrd`→`Word`, `TEh`→`The`); not the exceptions
   (`IDs`, `CDs`, `PCs`, `TVs`, … plus the user's, `tools.autocorrect {"addInitialCapsException"}`)
@@ -427,6 +434,7 @@ again.
 | 2026-10-19 | trivial | Delete on whole selected cells (rows, columns, the table, a cell) leaves one empty paragraph in each, with the cell's last paragraph's formatting; nested tables go too (#2802) |
 | 2026-10-19 | trivial | Ctrl+Tab (⌥Tab on macOS) types a tab character in a table cell (#3137) |
 | 2026-10-16 | trivial | AltGr on Linux (Wayland) types ś, ł, ż… instead of opening KeyTips: the modifiers event without Alt that follows the Right Alt key no longer reads as Alt let go, and a bare AltGr tap doesn't open KeyTips (#2388) |
+| 2026-10-20 | trivial | AutoFormat As You Type: optional "Add a period with double-space" (off by default), undoable (#2848) |
 | 2026-10-18 | trivial | Typing over a selection takes the first selected character's formatting, also when the selection was made right to left (#2879) |
 | 2026-10-17 | trivial | A table inserted in a right-to-left paragraph is a right-to-left table, so Tab moves to the cell on the left (#2634) |
 | 2026-10-15 | trivial | Backspace after a section break and Delete before it remove the break, also one on the last paragraph's mark; the text takes the following section's setup and keeps the headers it showed (#2127) |