Fix #3233: dimensions are redrawn in the colour mode after Document Color Mode and on open

Follow-up to #3702 (CodeRabbit): dimensions are only redrawn when their
recipe changes. Document Color Mode converted their art through the colour
profile, so black became a four-ink C67 M67 Y67 K100 again, and CMYK files
saved before #3702 kept RGB dimension art.

dimension::refresh now also redraws when the document's colour mode
changes. dimension::conform, run when a document is opened or reverted
(Session::add_document, replace_document), redraws a dimension whose art
has colours in the wrong model; one that can't be redrawn keeps its art.

dimension_colours_follow_the_document_colour_model covers RGB to CMYK and
back, and a CMYK document with RGB dimension art being opened. Without the
change it finds C0.67 M0.67 Y0.67 K1 after Document Color Mode.

crates/engine/src/cmd/dimension.rs

@@ -227,13 +227,45 @@ pub(crate) fn refresh(before: &Document, doc: &mut Document) -> Result<()> {
                 next.moved = None;
             }
         }
-        if next != old || before.node(id).and_then(|n| n.extras().dimension.as_deref()).is_some_and(|d| d != &next) {
+        // A new document colour mode (Document Color Mode) redraws every dimension in it.
+        if next != old
+            || before.color_mode != doc.color_mode
+            || before.node(id).and_then(|n| n.extras().dimension.as_deref()).is_some_and(|d| d != &next)
+        {
             replace(doc, id, next)?;
         }
     }
     Ok(())
 }
 
+/// Redraw the dimensions of an opened document whose art isn't in its colour mode: files saved
+/// before dimensions followed the colour mode have RGB dimensions in CMYK documents. A dimension
+/// that can't be redrawn keeps the art it has.
+pub(crate) fn conform(doc: &mut Document) {
+    if !doc.dimensions {
+        return;
+    }
+    let mode = doc.color_mode;
+    let off_mode = |c: &Color| match mode {
+        ColorMode::Rgb => matches!(c, Color::Cmyk { .. }),
+        ColorMode::Cmyk => matches!(c, Color::Rgb { .. }),
+    };
+    let mut stale = Vec::new();
+    doc.walk(|n| {
+        if let Some(d) = &n.extras().dimension {
+            let mut off = false;
+            n.walk(&mut |c| off |= [c.appearance.fill_paint(), c.appearance.stroke_paint()].iter().filter_map(|p| p.color()).any(|c| off_mode(&c)));
+            if off {
+                stale.push((n.id, (**d).clone()));
+            }
+        }
+    });
+    for (id, d) in stale {
+        // An error leaves this dimension as it was; the others are still redrawn.
+        let _ = replace(doc, id, d);
+    }
+}
+
 /// Option colour `c` as a paint in the document's colour model: in a CMYK document black is K
 /// only (a rich four-ink black would print a black dimension in every plate) and other colours
 /// convert through the active colour settings.

crates/engine/src/lib.rs

@@ -1587,6 +1587,7 @@ impl Session {
         Self::refresh_text_bounds(&mut doc);
         // Guides from files saved before guides had layers go on a layer.
         doc.adopt_guides();
+        cmd::dimension::conform(&mut doc);
         self.reset_tool_for_doc_switch();
         let mut st = DocState::new(doc, path);
         st.history.limit = self.prefs.history_states as usize;
@@ -1604,6 +1605,7 @@ impl Session {
         doc.limit_depth();
         Self::refresh_text_bounds(&mut doc);
         doc.adopt_guides();
+        cmd::dimension::conform(&mut doc);
         if self.active == Some(index) {
             // Pending tool work (typing, a drag) belongs to the content being thrown away.
             self.reset_tool_for_doc_switch();

crates/engine/tests/dimensions.rs

@@ -505,4 +505,19 @@ fn dimension_colours_follow_the_document_colour_model() {
     let line = edge(&mut s);
     let id = dim(&mut s, line);
     assert!(colours(&s, id).iter().all(|c| *c == vectorcraft_color::Color::rgb8(0, 0, 0)));
+    // Document Color Mode redraws dimensions in the new mode: K-only black in CMYK, RGB black back
+    // in RGB (not a profile conversion of the old art).
+    let k = vectorcraft_color::Color::cmyk(0.0, 0.0, 0.0, 1.0);
+    run(&mut s, "file.documentColorMode", json!({"mode":"cmyk"}));
+    let after = colours(&s, id);
+    assert!(!after.is_empty() && after.iter().all(|c| *c == k), "{after:?}");
+    run(&mut s, "file.documentColorMode", json!({"mode":"rgb"}));
+    assert!(colours(&s, id).iter().all(|c| *c == vectorcraft_color::Color::rgb8(0, 0, 0)), "{:?}", colours(&s, id));
+    // A CMYK file saved with RGB dimension art (before dimensions followed the colour mode) opens
+    // with its dimensions redrawn in CMYK.
+    let mut old = (*s.doc().unwrap().doc).clone();
+    old.color_mode = vectorcraft_doc::ColorMode::Cmyk;
+    s.add_document(old, None);
+    let opened = colours(&s, id);
+    assert!(!opened.is_empty() && opened.iter().all(|c| *c == k), "{opened:?}");
 }