Add a temporary modifier class for convenience

Author: greisane

helpers.py

@@ -283,7 +283,7 @@ def wrapper(*args, **kwargs):
             logd(f"Couldn't patch {self.module_name}.{self.function_name}, module not found")
         return self
 
-    def __exit__(self, type, value, traceback):
+    def __exit__(self, exc_type, exc_value, exc_traceback):
         module = sys.modules.get(self.module_name)
         if module:
             wrapper = getattr(module, self.function_name, None)

mesh/graft.py

@@ -3,7 +3,7 @@
 import bmesh
 import bpy
 
-from .helpers import new_vgroup, new_modifier, edit_mesh_elements, bmesh_vertex_group_bleed
+from .helpers import new_vgroup, new_modifier, TempModifier, edit_mesh_elements, bmesh_vertex_group_bleed
 from ..helpers import get_context, link_properties, load_selection, save_selection
 
 class GRET_OT_graft(bpy.types.Operator):
@@ -206,39 +206,38 @@ def _execute(self, context):
 
             ctx = get_context(obj)
             if self.transfer_normals:
-                mod = new_modifier(obj, type='DATA_TRANSFER', at_top=True)
-                mod.object = dst_obj
-                mod.vertex_group = boundary_vg.name
-                mod.use_object_transform = True
-                mod.use_loop_data = True
-                mod.data_types_loops = {'CUSTOM_NORMAL'}
-                mod.loop_mapping = 'POLYINTERP_NEAREST'
                 obj.data.use_auto_smooth = True
                 obj.data.auto_smooth_angle = pi
                 bpy.ops.mesh.customdata_custom_splitnormals_clear(ctx)
-                bpy.ops.object.modifier_apply(ctx, modifier=mod.name)
+
+                with TempModifier(obj, type='DATA_TRANSFER') as data_mod:
+                    data_mod.object = dst_obj
+                    data_mod.vertex_group = boundary_vg.name
+                    data_mod.use_object_transform = True
+                    data_mod.use_loop_data = True
+                    data_mod.data_types_loops = {'CUSTOM_NORMAL'}
+                    data_mod.loop_mapping = 'POLYINTERP_NEAREST'
 
             if self.transfer_vertex_groups or self.transfer_uv:
-                mod = new_modifier(obj, type='DATA_TRANSFER', at_top=True)
-                mod.object = dst_obj
-                mod.use_object_transform = True
-                if self.transfer_vertex_groups:
-                    mod.use_vert_data = True
-                    mod.data_types_verts = {'VGROUP_WEIGHTS'}
-                    mod.vert_mapping = 'EDGEINTERP_NEAREST'
-                if self.transfer_uv:
-                    mod.use_loop_data = True
-                    mod.data_types_loops = {'UV'}  # Automatically turns on use_poly_data
-                    mod.loop_mapping = 'POLYINTERP_NEAREST'
-                bpy.ops.object.datalayout_transfer(ctx, modifier=mod.name)
-                bpy.ops.object.modifier_apply(ctx, modifier=mod.name)
+                with TempModifier(obj, type='DATA_TRANSFER') as data_mod:
+                    data_mod.object = dst_obj
+                    data_mod.use_object_transform = True
+                    if self.transfer_vertex_groups:
+                        data_mod.use_vert_data = True
+                        data_mod.data_types_verts = {'VGROUP_WEIGHTS'}
+                        data_mod.vert_mapping = 'EDGEINTERP_NEAREST'
+                    if self.transfer_uv:
+                        data_mod.use_loop_data = True
+                        data_mod.data_types_loops = {'UV'}  # Automatically turns on use_poly_data
+                        data_mod.loop_mapping = 'POLYINTERP_NEAREST'
+                    bpy.ops.object.datalayout_transfer(ctx, modifier=data_mod.name)
 
             # If requested, create a mask modifier that will hide the intersection's inner verts
             if self.create_mask:
                 mask_vg = new_vgroup(orig_dst_obj, f"_mask_{obj.name}")
                 intersecting_verts = (dst_mesh.vertices[i] for i in intersecting_vert_indices)
                 mask_vg.add([v.index for v in intersecting_verts if not v.select], 1.0, 'REPLACE')
-                mask_mod = new_modifier(orig_dst_obj, type='MASK', name=mask_vg.name, at_top=True)
+                mask_mod = new_modifier(orig_dst_obj, type='MASK', name=mask_vg.name)
                 mask_mod.vertex_group = mask_vg.name
                 mask_mod.invert_vertex_group = True
                 mod_dp = f'modifiers["{mask_mod.name}"]'

mesh/helpers.py

@@ -23,17 +23,33 @@ def new_vgroup(obj, name):
         vgroup = obj.vertex_groups.new(name=name)
     return vgroup
 
-def new_modifier(obj, type, name="", at_top=False):
-    """Ensures that a modifier with the given name exists. Moved first to avoid warnings on applying."""
+def new_modifier(obj, type, name=""):
+    """Ensures that a modifier with the given name exists."""
+    # Should it clear an existing modifier?
 
     modifier = obj.modifiers.get(name) if name else None
     if not modifier or modifier.type != type:
         modifier = obj.modifiers.new(type=type, name=name)
-    if at_top:
-        ctx = get_context(obj)
-        bpy.ops.object.modifier_move_to_index(ctx, modifier=modifier.name, index=0)
     return modifier
 
+class TempModifier:
+    """Convenient modifier wrapper to use in a `with` block to be automatically applied at the end."""
+
+    def __init__(self, obj, type):
+        self.obj = obj
+        self.type = type
+
+    def __enter__(self):
+        self.modifier = self.obj.modifiers.new(type=self.type, name="")
+        # Move first to avoid the warning on applying
+        ctx = get_context(self.obj)
+        bpy.ops.object.modifier_move_to_index(ctx, modifier=self.modifier.name, index=0)
+        return self.modifier
+
+    def __exit__(self, exc_type, exc_value, exc_traceback):
+        ctx = get_context(self.obj)
+        bpy.ops.object.modifier_apply(ctx, modifier=self.modifier.name)
+
 def edit_mesh_elements(obj, type='VERT', indices=None, key=None):
     """
     Enters edit mode and selects elements of a mesh to be operated on.