M4.27: area type and rich text in SVG export

Every laid-out line of type is written at its own position (wraps,
indents, tabs, hyphenation and all caps as on the canvas): a positioned
tspan per style run and, on justified lines, per word. Centred and
right-aligned lines are anchored at their centre or right end, so they
stay aligned in a viewer whose font differs. Leading comes from the
layout's baselines, baseline shift is written as dy, horizontal scale as
textLength, vertical scale as the size, tracking and manual kerning as
letter-spacing. The fewerTspans option (engine and dialog) writes one
positioned tspan per line.

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

crates/engine/src/cmd/fileio/mod.rs

@@ -63,7 +63,7 @@ pub fn specs() -> Vec<CommandSpec> {
             "Export Document",
             [],
             None,
-            "{path?, format?: svg|pdf|png|jpg|webp|vectorcraft (default: from the path's extension, else png), artboard?: 0, artboards?: [i…], range?: \"1-3, 5\" | \"all\" (1-based; PDF writes one page per artboard, default all; SVG writes one file per artboard, {stem}-{artboard}.svg; raster formats write one artboard), scale?: 1 (raster), quality?: 90 (jpg), SVG options flat or as svg: {styling, outlineText, images, objectIds, decimals, minify, responsive, useArtboards, preserveEditing, metadata} (see document.formats), …the PDF options of document.exportPdf} → {path, format, bytes, warnings, files?: [path…] (several), linked?: [path…] (linked images)}; no path → {dataBase64, format, bytes, warnings, files?: [{name, dataBase64}], linked?: [{name, dataBase64}]}. Never changes the document's path",
+            "{path?, format?: svg|pdf|png|jpg|webp|vectorcraft (default: from the path's extension, else png), artboard?: 0, artboards?: [i…], range?: \"1-3, 5\" | \"all\" (1-based; PDF writes one page per artboard, default all; SVG writes one file per artboard, {stem}-{artboard}.svg; raster formats write one artboard), scale?: 1 (raster), quality?: 90 (jpg), SVG options flat or as svg: {styling, outlineText, images, objectIds, decimals, minify, responsive, useArtboards, preserveEditing, metadata, fewerTspans} (see document.formats), …the PDF options of document.exportPdf} → {path, format, bytes, warnings, files?: [path…] (several), linked?: [path…] (linked images)}; no path → {dataBase64, format, bytes, warnings, files?: [{name, dataBase64}], linked?: [{name, dataBase64}]}. Never changes the document's path",
             has_doc,
             export::export
         ),

crates/engine/src/cmd/fileio/svg.rs

@@ -55,6 +55,12 @@ pub const OPTIONS: &[FormatOption] = &[
         description: "embed the native document in <metadata> so VectorCraft reopens the SVG with nothing lost",
     },
     FormatOption { name: "metadata", ty: "boolean", default: "false", description: "write <metadata> with the title and format (Dublin Core)" },
+    FormatOption {
+        name: "fewerTspans",
+        ty: "boolean",
+        default: "false",
+        description: "type: one positioned <tspan> per line instead of one per style run, tab and justified word (smaller; viewers space the line themselves)",
+    },
     FormatOption {
         name: "svg",
         ty: "object",

crates/engine/src/cmd/fileio/tests_svg.rs

@@ -182,3 +182,13 @@ fn formats_list_the_svg_options_with_their_defaults() {
         assert!(svg["options"].get(k).is_some(), "{k}");
     }
 }
+
+#[test]
+fn fewer_tspans_reaches_the_writer() {
+    let mut s = Session::new();
+    let src = r##"<svg xmlns="http://www.w3.org/2000/svg" width="200" height="100"><text x="10" y="40" font-size="12">plain <tspan fill="#ff0000">red</tspan> plain</text></svg>"##;
+    s.execute("document.open", &json!({"name": "two-runs.svg", "dataBase64": vectorcraft_format::base64_encode(src.as_bytes())})).unwrap();
+    let placed = |svg: &str| svg.matches("<tspan x=").count();
+    assert_eq!(placed(&svg(&mut s, json!({}))), 3, "a tspan per style run");
+    assert_eq!(placed(&svg(&mut s, json!({"fewerTspans": true}))), 1, "a tspan per line");
+}