Fix hidden features refusing to show again after their body's feature was hidden

src/libslic3r/CAD/CadDocument.cpp

@@ -2197,11 +2197,16 @@ static void stage_history_change(std::vector<CadFeature>& features,
             ref = nn >= 0 ? 3 + nn : 3 + int(after.size()) + 1000;
         });
         if (f.body_ref_ids.size() != size_t(kBodyRefCount)) continue;   // never resolved: nothing to follow
+        // A feature hidden after the change is not replayed, so a hidden source is no reason to
+        // drop its body: it keeps following it and re-points when shown. Shown while the source
+        // is still hidden, it is staged as replayed and loses the body then. Only deleting the
+        // source drops a hidden feature's body.
+        const bool replayed = enabled_after(j);
         int k = 0;
         for_each_body_ref(f, [&](int& ref, bool) {
             CadFeature::BodyId& id = f.body_ref_ids[k++];
             if (ref < 0 || id.src < 0) return;
-            if (!alive(id.src)) { ref = kBodyGone; id = {}; return; }
+            if (replayed ? !alive(id.src) : map_feature(id.src) < 0) { ref = kBodyGone; id = {}; return; }
             id.src = map_feature(id.src);
         });
         f.body_refs_pending = true;

tests/libslic3r/test_caddocument.cpp

@@ -8801,6 +8801,29 @@ TEST_CASE("Hiding a body-making feature keeps later features on their body", "[C
     CHECK(doc.features[lift].target_body == 1);
 }
 
+TEST_CASE("A hidden feature can be shown again once the feature that made its body is shown",
+          "[CadDocument][history]")
+{
+    CadDocument doc;
+    const int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 0, "S");
+    const int ex = doc.add_extrude(sk, 5, false, BooleanMode::New, "E");
+    const int ch = doc.add_chamfer(1.0, FaceGroup::All, "C");
+    doc.features[ch].target_body = 0;   // as the Design tab sets it from picked edges; -1 has no body to follow
+    REQUIRE(doc.recompute());
+    const double chamfered = double(doc.display_mesh.volume());
+
+    REQUIRE(doc.set_feature_enabled(ch, false));
+    REQUIRE(doc.set_feature_enabled(ex, false));
+    // The chamfer has no body while the extrude is hidden...
+    CHECK_FALSE(doc.set_feature_enabled(ch, true));
+    CHECK_FALSE(doc.features[ch].enabled);
+    // ...and gets it back once the extrude is shown.
+    REQUIRE(doc.set_feature_enabled(ex, true));
+    REQUIRE(doc.set_feature_enabled(ch, true));
+    CHECK(doc.features[ch].target_body == 0);
+    CHECK_THAT(double(doc.display_mesh.volume()), Catch::Matchers::WithinRel(chamfered, 1e-6));
+}
+
 TEST_CASE("Datum-plane references follow their plane when an earlier plane is deleted",
           "[CadDocument][history]")
 {