Part of #394: Preferences for snapping, handles, rubber bands, pattern tiles, tints and type

Fourteen more Preferences options that were stored but read by nothing now
act, for the mouse and for agents (prefs.set, then pointer_gesture,
press_key or the commands):

- Selection & Anchor Display: Snap to Point and its distance (with Smart
  Guides off, View > Snap to Point lands a dragged selection's grabbed
  point, drawn points and reference points on anchors and ruler guides);
  Move Locked and Hidden Artwork with Artboard (artboard.move, the Artboard
  tool and Rearrange; off, hidden art now stays too); Enable Rubber Band for
  the Pen and Curvature tools; Handles (solid, hollow, large);
  Show handles when multiple anchors are selected (canvas and Direct
  Selection's handle picking); Hide Corner Widget for angles greater than.
- General: Transform Pattern Tiles is the default of a new `patterns`
  param on object.transform/move/rotate/scale/reflect/shear/transformEach
  (journalled when the art uses a pattern), and the transform dialogs get a
  Transform Patterns checkbox; Select Same Tint % (off, Select > Same
  Fill/Stroke Color takes every tint of a global or spot swatch).
- Type: new type.step {attribute, by} steps size, leading, tracking, kerning
  and baseline shift by the Size/Leading, Tracking and Baseline Shift
  increments; Increase/Decrease Font Size (Cmd+Shift+. and Cmd+Shift+,);
  the Type tool's Alt+arrows (kerning at a caret or tracking, leading,
  Shift for baseline shift, Cmd/Ctrl for five steps). Enable Missing Glyph
  Protection keeps characters a new font lacks in the font that had them
  (text.setStyle, text.setRangeStyle). Fill New Type Objects With
  Placeholder Text: type the Type tools place starts with placeholder text,
  selected (text.create / text.createInPath take `placeholder`).

Units > General, Stroke and Type were already the single source of truth
(units.rs). Auto Size New Area Type, Show Font Names in English and
Highlight Alternate Glyphs need subsystems the app doesn't have yet and
stay open with the rest of #394.

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

crates/engine/src/cmd/textedit.rs

@@ -45,7 +45,7 @@ pub fn specs() -> Vec<CommandSpec> {
             "Area / Path Type",
             [],
             None,
-            "{path: id, mode: \"area\"|\"onPath\", text?: \"\", vertical?: bool = false, at?: [x, y] (on-path start: nearest point), size?, font?} turn a path into an area-type frame or a type-on-a-path baseline (the path's paint is dropped) → {id}",
+            "{path: id, mode: \"area\"|\"onPath\", text?: \"\", vertical?: bool = false, at?: [x, y] (on-path start: nearest point), size?, font?, placeholder?: bool (placeholder text instead, as text.create)} turn a path into an area-type frame or a type-on-a-path baseline (the path's paint is dropped) → {id}",
             has_doc,
             create_in_path
         ),
@@ -58,6 +58,33 @@ pub fn specs() -> Vec<CommandSpec> {
             has_selection,
             fit_headline
         ),
+        cmd!(
+            "type.step",
+            "Step Type",
+            [],
+            None,
+            "{attribute: \"size\"|\"leading\"|\"tracking\"|\"kerning\"|\"baselineShift\", by?: steps (1; negative steps down), id?, start?: byte, end?: byte} step type by the Preferences › Type increments (size and leading: typeSizeIncrement, pt; tracking and kerning: trackingIncrement, 1/1000 em; baseline shift: baselineShiftIncrement, pt), what the Type tool's Alt+arrows do (Cmd/Ctrl too: five steps; ←/→ kerning at the caret or tracking of the selection, ↑/↓ leading, Shift+↑/↓ baseline shift). The range of `id`, else the text the Type tool has selected (at a caret: kerning steps the character before it, leading its paragraph), else every selected type object → {ids}",
+            has_doc,
+            type_step
+        ),
+        cmd!(
+            "type.size.increase",
+            "Increase Font Size",
+            [],
+            Some("Cmd+Shift+."),
+            "{by?: steps (1)} type.step {attribute: size}",
+            has_selection,
+            |s, p| type_step(s, &json!({"attribute": "size", "by": f64_or(p, "by", 1.0)}))
+        ),
+        cmd!(
+            "type.size.decrease",
+            "Decrease Font Size",
+            [],
+            Some("Cmd+Shift+,"),
+            "{by?: steps (1)} type.step {attribute: size, by: -by}",
+            has_selection,
+            |s, p| type_step(s, &json!({"attribute": "size", "by": -f64_or(p, "by", 1.0)}))
+        ),
         cmd!(
             "text.discardEmpty",
             "Discard Empty Type",
@@ -332,6 +359,45 @@ impl CharChange {
     }
 }
 
+/// Type › Enable Missing Glyph Protection: after a font change, the characters of `runs` their new
+/// font has no glyph for, but their font `before` the change had, keep that font.
+pub(crate) fn protect_missing_glyphs(before: &[TextRun], runs: &mut Vec<TextRun>) {
+    fn chars(runs: &[TextRun]) -> impl Iterator<Item = (usize, char, &CharStyle)> {
+        runs.iter()
+            .scan(0, |at, r| {
+                let start = *at;
+                *at += r.text.len();
+                Some(r.text.char_indices().map(move |(i, c)| (start + i, c, &r.style)))
+            })
+            .flatten()
+    }
+    let db = vectorcraft_text::FontDb::global();
+    let mut faces = std::collections::HashMap::new();
+    let mut covers = |st: &CharStyle, c: char| {
+        let face = faces.entry((st.font_family.clone(), st.font_style.clone())).or_insert_with(|| db.face(&st.font_family, &st.font_style));
+        face.as_ref().map(|f| f.covers(c))
+    };
+    // Byte ranges that keep a font (family, style).
+    let mut keep: Vec<(usize, usize, &CharStyle)> = vec![];
+    for ((at, c, old), (_, _, new)) in chars(before).zip(chars(runs)) {
+        let changed = (&old.font_family, &old.font_style) != (&new.font_family, &new.font_style);
+        if !changed || c.is_whitespace() || c.is_control() || covers(new, c) != Some(false) || covers(old, c) != Some(true) {
+            continue;
+        }
+        let end = at + c.len_utf8();
+        match keep.last_mut() {
+            Some((_, e, st)) if *e == at && (&st.font_family, &st.font_style) == (&old.font_family, &old.font_style) => *e = end,
+            _ => keep.push((at, end, old)),
+        }
+    }
+    for (a, b, old) in keep {
+        edit::style_range(runs, a, b, |st| {
+            st.font_family.clone_from(&old.font_family);
+            st.font_style.clone_from(&old.font_style);
+        });
+    }
+}
+
 fn set_range_style(s: &mut Session, p: &Value) -> Result<Value> {
     const C: &str = "text.setRangeStyle";
     let id = id_param(p, "id").ok_or_else(|| bad(C, "missing `id`"))?;
@@ -339,6 +405,7 @@ fn set_range_style(s: &mut Session, p: &Value) -> Result<Value> {
     if change.is_empty() {
         return Err(bad(C, "nothing to change"));
     }
+    let protect = s.prefs.missing_glyph_protection && (change.font.is_some() || change.style.is_some());
     let t = text_ref(s, id)?;
     let (a, b) = range_of(p, edit::runs_len(&t.runs));
     let n = s.edit("Character", |d, _| {
@@ -347,7 +414,11 @@ fn set_range_style(s: &mut Session, p: &Value) -> Result<Value> {
             // An empty range inside text styles nothing (Illustrator keeps it for the next typing).
             return Ok(t.runs.len());
         }
+        let before = protect.then(|| t.runs.clone());
         edit::style_range(&mut t.runs, a, b, |st| change.apply(st));
+        if let Some(before) = before {
+            protect_missing_glyphs(&before, &mut t.runs);
+        }
         refresh_bounds(t);
         Ok(t.runs.len())
     })?;
@@ -397,7 +468,11 @@ fn create_in_path(s: &mut Session, p: &Value) -> Result<Value> {
         wrap: Vec::new(),
         cached_bounds: None,
     };
-    refresh_bounds(&mut t);
+    if bool_or(p, "placeholder", false) {
+        super::typemenu::fill_with_placeholder(&mut t);
+    } else {
+        refresh_bounds(&mut t);
+    }
     let id = s.edit(if on_path { "Type on a Path" } else { "Area Type" }, |d, sel| {
         let (par, idx, _) = d.position(pid).ok_or(EngineError::NoNode(pid))?;
         d.remove(pid)?;
@@ -413,6 +488,95 @@ fn create_in_path(s: &mut Session, p: &Value) -> Result<Value> {
     Ok(json!({"id": id.0}))
 }
 
+/// What `type.step` changes.
+#[derive(Clone, Copy, PartialEq)]
+enum Step {
+    Size,
+    Leading,
+    Tracking,
+    Kerning,
+    BaselineShift,
+}
+
+/// The Type tool's selected text while it edits (its typing session ends first: one undo step).
+fn editing_range(s: &mut Session) -> Result<Option<(NodeId, usize, usize)>> {
+    let o = s.tool_options();
+    let Some(id) = o.get("editing").and_then(Value::as_u64).map(NodeId) else { return Ok(None) };
+    if super::edit::typing_in_progress(s) {
+        s.set_tool_option("commitTyping", &Value::Bool(true));
+        s.commit_interaction()?;
+    }
+    let at = |k: &str| byte_param(&o, k).unwrap_or(0);
+    Ok(Some((id, at("start"), at("end"))))
+}
+
+fn type_step(s: &mut Session, p: &Value) -> Result<Value> {
+    const C: &str = "type.step";
+    let step = match str_param(p, "attribute") {
+        Some("size") => Step::Size,
+        Some("leading") => Step::Leading,
+        Some("tracking") => Step::Tracking,
+        Some("kerning") => Step::Kerning,
+        Some("baselineShift") => Step::BaselineShift,
+        _ => return Err(bad(C, "attribute must be size|leading|tracking|kerning|baselineShift")),
+    };
+    let by = f64_or(p, "by", 1.0);
+    if !by.is_finite() {
+        return Err(bad(C, "by must be a number"));
+    }
+    let prefs = &s.prefs;
+    let inc = by.clamp(-1000.0, 1000.0)
+        * match step {
+            Step::Size | Step::Leading => prefs.type_size_increment,
+            Step::Tracking | Step::Kerning => prefs.tracking_increment,
+            Step::BaselineShift => prefs.baseline_shift_increment,
+        };
+    // (text, its range; None: all of it).
+    let targets: Vec<(NodeId, Option<(usize, usize)>)> = match id_param(p, "id") {
+        Some(id) => vec![(id, Some(range_of(p, edit::runs_len(&text_ref(s, id)?.runs))))],
+        None => match editing_range(s)? {
+            Some((id, a, b)) => vec![(id, Some((a.min(b), a.max(b))))],
+            None => super::typecmd::text_targets(s, p, C)?.into_iter().map(|id| (id, None)).collect(),
+        },
+    };
+    // The ranges stepped. At a caret: kerning is the space after the character before it, leading
+    // the paragraph's; the rest wait for a selection.
+    let mut ranges = vec![];
+    for (id, range) in targets {
+        let text = text_ref(s, id)?.plain_text();
+        let (a, b) = range.map_or((0, text.len()), |(a, b)| (a.min(text.len()), b.min(text.len())));
+        let (a, b) = match step {
+            _ if a < b => (a, b),
+            Step::Kerning => (edit::prev_char(&text, a), a),
+            Step::Leading => {
+                let para = edit::paragraph_at(&text, a);
+                (para.start, para.end)
+            }
+            _ => continue,
+        };
+        if a < b {
+            ranges.push((id, a, b));
+        }
+    }
+    if !ranges.is_empty() {
+        s.edit("Character", |d, _| {
+            for &(id, a, b) in &ranges {
+                let t = text_mut(d, id).ok_or(EngineError::NoNode(id))?;
+                edit::style_range(&mut t.runs, a, b, |st| match step {
+                    Step::Size => st.size = (st.size + inc).clamp(0.1, 1296.0),
+                    Step::Leading => st.leading = Some((st.effective_leading() + inc).clamp(0.1, 5000.0)),
+                    Step::Tracking => st.tracking = (st.tracking + inc).clamp(-1000.0, 10000.0),
+                    Step::Kerning => st.kerning = Some((st.kerning.unwrap_or(0.0) + inc).clamp(-1000.0, 10000.0)),
+                    Step::BaselineShift => st.baseline_shift = (st.baseline_shift + inc).clamp(-1296.0, 1296.0),
+                });
+                refresh_bounds(t);
+            }
+            Ok(())
+        })?;
+    }
+    Ok(json!({ "ids": ranges.iter().map(|(id, ..)| id.0).collect::<Vec<_>>() }))
+}
+
 /// Tracking (1/1000 em) that makes the first paragraph of `t` exactly `target` wide, if it fits
 /// on one line at all.
 fn headline_tracking(t: &TextObject, target: f64) -> Option<f64> {