Fix Collada exporter skipping App::Link geometry (#27974)

* Fix Collada exporter skipping App::Link geometry

Resolve App::Link objects recursively during export so referenced
geometry is included in the .dae output while preserving link placement.

* Arch: Fix Collada export for App::Link objects

The Collada exporter skipped geometry for App::Link instances because
it only handled objects directly present in the document.

This change resolves Link objects using getLinkedObject() and exports
their referenced geometry while applying the placement of the exporting
instance.

The original App::Part expansion behavior is preserved.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* Arch: fix placement handling for App::Link and primitives in Collada export

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* final change

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

src/Mod/BIM/importers/importDAE.py

@@ -169,6 +169,23 @@ def read(filename):
         FreeCAD.Gui.SendMsgToActiveView("ViewFit")
 
 
+def get_global_placement(obj):
+    """
+    Compute the global placement of an object by accumulating
+    placements from its parent containers.
+    """
+    pl = obj.Placement
+
+    parent = obj.getParentGeoFeatureGroup()
+
+    while parent:
+        if hasattr(parent, "Placement"):
+            pl = parent.Placement.multiply(pl)
+        parent = parent.getParentGeoFeatureGroup()
+
+    return pl
+
+
 def export(
     exports: list[FreeCAD.DocumentObject],
     filename: str,
@@ -219,21 +236,34 @@ def export(
         addgroups=True,
     )
     objects = Arch.pruneIncluded(objects, strict=True)
+
     for obj in objects:
+        is_link = obj.isDerivedFrom("App::Link")
+        if is_link:
+            real_obj = obj.getLinkedObject(True)
+        else:
+            real_obj = obj
+        if is_link:
+            global_pl = get_global_placement(obj)
+        elif hasattr(obj, "getGlobalPlacement"):
+            global_pl = obj.getGlobalPlacement()
+        else:
+            global_pl = obj.Placement
         findex = np.array([])
         m: Optional[Mesh.Mesh] = None
-        if obj.isDerivedFrom("Part::Feature"):
+        if real_obj.isDerivedFrom("Part::Feature"):
             FreeCAD.Console.PrintMessage(
                 f'Exporting shape of object {obj.Name} ("{obj.Label}")' + "\n"
             )
-            new_shape = obj.Shape.copy()
-            new_shape.Placement = obj.getGlobalPlacement()
-            m = Mesh.Mesh(triangulate(new_shape))
-        elif obj.isDerivedFrom("Mesh::Feature"):
+            shape = real_obj.Shape.copy()
+            shape.Placement = global_pl
+            m = Mesh.Mesh(triangulate(shape))
+        elif real_obj.isDerivedFrom("Mesh::Feature"):
             FreeCAD.Console.PrintMessage(
                 f'Exporting mesh of object {obj.Name} ("{obj.Label}")' + "\n"
             )
-            m = obj.Mesh
+            m = real_obj.Mesh.copy()
+            m.transform(global_pl.toMatrix())
         elif obj.isDerivedFrom("App::Part"):
             for child in obj.OutList:
                 objects.append(child)