3 files changed, 69 insertions, 4 deletions
diff --git a/release/scripts/modules/bpy_extras/bmesh_utils.py b/release/scripts/modules/bpy_extras/bmesh_utils.py
new file mode 100644
index 00000000000..a24ea253f51
--- /dev/null
+++ b/release/scripts/modules/bpy_extras/bmesh_utils.py
@@ -0,0 +1,56 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+__all__ = (
+    "bmesh_linked_uv_islands",
+)
+
+import bmesh
+
+
+def match_uv(face, vert, uv, uv_layer):
+    for loop in face.loops:
+        if loop.vert == vert:
+            return uv == loop[uv_layer].uv
+    return False
+
+
+def bmesh_linked_uv_islands(bm, uv_layer):
+    """
+    Returns lists of faces connected by UV islands.
+
+    For meshes use :class:`bpy.types.Mesh.mesh_linked_uv_islands` instead.
+
+    :arg bm: the bmesh used to group with.
+    :type bmesh: :class:`BMesh`
+    :arg uv_layer: the UV layer to source UVs from.
+    :type bmesh: :class:`BMLayerItem`
+    :return: list of lists containing polygon indices
+    :rtype: list
+    """
+
+    result = []
+    used = set()
+    for seed_face in bm.faces:
+        if seed_face in used:
+            continue  # Face has already been processed.
+        used.add(seed_face)
+        island = [seed_face]
+        stack = [seed_face]  # Faces still to consider on this island.
+        while stack:
+            current_face = stack.pop()
+            for loop in current_face.loops:
+                v = loop.vert
+                uv = loop[uv_layer].uv
+                for f in v.link_faces:
+                    if f is current_face or f in used:
+                        continue
+                    if not match_uv(f, v, uv, uv_layer):
+                        continue
+
+                    # `f` is part of island, add to island and stack
+                    used.add(f)
+                    island.append(f)
+                    stack.append(f)
+        result.append(island)
+
+    return result
diff --git a/release/scripts/modules/bpy_extras/io_utils.py b/release/scripts/modules/bpy_extras/io_utils.py
index 0497d69162e..35b7d564a5e 100644
--- a/release/scripts/modules/bpy_extras/io_utils.py
+++ b/release/scripts/modules/bpy_extras/io_utils.py
@@ -21,6 +21,7 @@ from bpy.props import (
     EnumProperty,
     StringProperty,
 )
+from bpy.app.translations import pgettext_data as data_
 
 
 def _check_axis_conversion(op):
@@ -56,7 +57,7 @@ class ExportHelper:
         if not self.filepath:
             blend_filepath = context.blend_data.filepath
             if not blend_filepath:
-                blend_filepath = "untitled"
+                blend_filepath = data_("untitled")
             else:
                 blend_filepath = os.path.splitext(blend_filepath)[0]
 
diff --git a/release/scripts/modules/bpy_extras/mesh_utils.py b/release/scripts/modules/bpy_extras/mesh_utils.py
index f6dc33e4f02..d593ce6a1e4 100644
--- a/release/scripts/modules/bpy_extras/mesh_utils.py
+++ b/release/scripts/modules/bpy_extras/mesh_utils.py
@@ -13,14 +13,22 @@ __all__ = (
 
 def mesh_linked_uv_islands(mesh):
     """
-    Splits the mesh into connected polygons, use this for separating cubes from
-    other mesh elements within 1 mesh datablock.
+    Returns lists of polygon indices connected by UV islands.
 
     :arg mesh: the mesh used to group with.
     :type mesh: :class:`bpy.types.Mesh`
-    :return: lists of lists containing polygon indices
+    :return: list of lists containing polygon indices
     :rtype: list
     """
+
+    if mesh.polygons and not mesh.uv_layers.active.data:
+        # Currently, when in edit mode, UV Layer data will always be empty
+        # when accessed though RNA. This may change in the future.
+        raise ValueError(
+            "UV Layers are not currently available from python in Edit Mode. "
+            "Use bmesh and bpy_extras.bmesh_utils.bmesh_linked_uv_islands instead."
+        )
+
     uv_loops = [luv.uv[:] for luv in mesh.uv_layers.active.data]
     poly_loops = [poly.loop_indices for poly in mesh.polygons]
     luv_hash = {}