feat: save body and occurrence visibility with the design (#531) (#592)

Hidden bodies, occurrence placements, sketches and origin items are saved with the design and come back when it is reopened. Visibility is still not an undo step, but hiding or showing something now counts as an unsaved change. Additive field under format 16. Fixes #531.

Co-authored-by: jonaswre <jonas.wrede@beyondit.gmbh>

crates/doc/src/document.rs

@@ -1765,6 +1765,38 @@ pub struct Document {
     /// Named views: saved cameras.
     #[serde(default, skip_serializing_if = "Vec::is_empty")]
     pub named_views: Vec<NamedView>,
+    /// What was hidden when the design was saved. A session takes it from here when the design
+    /// opens and keeps the live state itself (`browser.visibility`: saved, not an undo step), so
+    /// a document in a session leaves this empty; the session puts it back when it saves.
+    #[serde(default, skip_serializing_if = "Visibility::is_empty")]
+    pub visibility: Visibility,
+}
+
+/// Items hidden or shown one by one. Saved with the design, but not an undo step.
+#[derive(Clone, Debug, Default, PartialEq, Serialize, Deserialize)]
+#[serde(default)]
+pub struct Visibility {
+    /// Bodies by name.
+    pub hidden_bodies: Vec<String>,
+    /// Exact occurrence placements hidden with all descendants.
+    pub hidden_occurrences: Vec<Vec<u64>>,
+    /// Origin items (O, X, Y, Z, XY, XZ, YZ) and construction geometry, by name.
+    pub hidden_origin: Vec<String>,
+    /// Sketches by feature id.
+    pub hidden_sketches: Vec<u64>,
+    /// Finished sketches shown although a feature uses them.
+    pub shown_sketches: Vec<u64>,
+}
+
+impl Visibility {
+    /// Nothing hidden or shown one by one (the default view).
+    pub fn is_empty(&self) -> bool {
+        self.hidden_bodies.is_empty()
+            && self.hidden_occurrences.is_empty()
+            && self.hidden_origin.is_empty()
+            && self.hidden_sketches.is_empty()
+            && self.shown_sketches.is_empty()
+    }
 }
 
 /// A saved camera (orbit camera: target, yaw, pitch, distance; `fov` 0 for orthographic).
@@ -1833,6 +1865,7 @@ impl Document {
             browser_groups: Vec::new(),
             browser_order: Default::default(),
             named_views: Vec::new(),
+            visibility: Visibility::default(),
         }
     }