mesh_bsurfaces.py

                    vec_A = points_original[0] - points_original[1]
                    vec_B = points_target[0] - points_target[1]
                    # check for zero angles, not sure if it is a great fix
                    if vec_A.length != 0 and vec_B.length != 0:
                        angle = vec_A.angle(vec_B) / pi
                        edge_new_length = (Vector(verts_middle_position_co) - sp[1][i]).length
                    else:
                        angle = 0
                        edge_new_length = 0

                    # If after moving the verts to the middle point, the segment doesn't stretch too much
                    if edge_new_length <= loop_segment_dist * 1.5 * \
                       self.join_stretch_factor and angle < 0.25 * self.join_stretch_factor:

                        # Avoid joining when the actual loop must be merged with the original mesh
                        if not (self.selection_U_exists and i == 0) and \
                           not (self.selection_U2_exists and i == len(surface_splines_parsed[0]) - 1):

                            # Change the coords of both verts to the middle position
                            surface_splines_parsed[0][i] = verts_middle_position_co
                            surface_splines_parsed[len(surface_splines_parsed) - 1][i] = verts_middle_position_co

        # Delete object with control points and object from grease pencil conversion
        bpy.ops.object.delete({"selected_objects": [ob_ctrl_pts]})

        bpy.ops.object.delete({"selected_objects": splines_U_objects})

        # Generate surface

        # Get all verts coords
        all_surface_verts_co = []
        for i in range(0, len(surface_splines_parsed)):
            # Get coords of all verts and make a list with them
            for pt_co in surface_splines_parsed[i]:
                all_surface_verts_co.append(pt_co)

        # Define verts for each face
        all_surface_faces = []
        for i in range(0, len(all_surface_verts_co) - len(surface_splines_parsed[0])):
            if ((i + 1) / len(surface_splines_parsed[0]) != int((i + 1) / len(surface_splines_parsed[0]))):
                all_surface_faces.append(
                            [i + 1, i, i + len(surface_splines_parsed[0]),
                            i + len(surface_splines_parsed[0]) + 1]
                            )
        # Build the mesh
        surf_me_name = "SURFSKIO_surface"
        me_surf = bpy.data.meshes.new(surf_me_name)

        me_surf.from_pydata(all_surface_verts_co, [], all_surface_faces)

        me_surf.update()

        ob_surface = bpy.data.objects.new(surf_me_name, me_surf)
        bpy.context.collection.objects.link(ob_surface)

        # Select all the "unselected but participating" verts, from closed selection
        # or double selections with middle-vertex, for later join with remove doubles
        for v_idx in single_unselected_verts:
            self.main_object.data.vertices[v_idx].select = True

        # Join the new mesh to the main object
        ob_surface.select_set(True)
        self.main_object.select_set(True)
        bpy.context.view_layer.objects.active = self.main_object

        bpy.ops.object.join('INVOKE_REGION_WIN')

        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

        bpy.ops.mesh.remove_doubles('INVOKE_REGION_WIN', threshold=0.0001)
        bpy.ops.mesh.normals_make_consistent('INVOKE_REGION_WIN', inside=False)
        bpy.ops.mesh.select_all('INVOKE_REGION_WIN', action='DESELECT')

        return{'FINISHED'}

    def execute(self, context):

        if bpy.ops.object.mode_set.poll():
             bpy.ops.object.mode_set(mode='OBJECT')
        
        bsurfaces_props = bpy.context.scene.bsurfaces
        self.main_object = bsurfaces_props.SURFSK_object_with_retopology
        self.main_object.select_set(True)
        bpy.context.view_layer.objects.active = self.main_object

        if not self.is_fill_faces:
            bpy.ops.wm.context_set_value(data_path='tool_settings.mesh_select_mode',
                                         value='True, False, False')

            # Build splines from the "last saved splines".
            last_saved_curve = bpy.data.curves.new('SURFSKIO_last_crv', 'CURVE')
            self.main_splines = bpy.data.objects.new('SURFSKIO_last_crv', last_saved_curve)
            bpy.context.collection.objects.link(self.main_splines)

            last_saved_curve.dimensions = "3D"

            for sp in self.last_strokes_splines_coords:
                spline = self.main_splines.data.splines.new('BEZIER')
                # less one because one point is added when the spline is created
                spline.bezier_points.add(len(sp) - 1)
                for p in range(0, len(sp)):
                    spline.bezier_points[p].co = [sp[p][0], sp[p][1], sp[p][2]]

            #bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
            bpy.ops.object.mode_set(mode='OBJECT')

            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            self.main_splines.select_set(True)
            bpy.context.view_layer.objects.active = self.main_splines

            #bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
            bpy.ops.object.mode_set(mode='EDIT')

            bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='SELECT')
            # Important to make it vector first and then automatic, otherwise the
            # tips handles get too big and distort the shrinkwrap results later
            bpy.ops.curve.handle_type_set(type='VECTOR')
            bpy.ops.curve.handle_type_set('INVOKE_REGION_WIN', type='AUTOMATIC')
            bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

            self.main_splines.name = "SURFSKIO_temp_strokes"

            if self.is_crosshatch:
                strokes_for_crosshatch = True
                strokes_for_rectangular_surface = False
            else:
                strokes_for_rectangular_surface = True
                strokes_for_crosshatch = False

            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            self.main_object.select_set(True)
            bpy.context.view_layer.objects.active = self.main_object

            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

            if strokes_for_rectangular_surface:
                self.rectangular_surface()
            elif strokes_for_crosshatch:
                self.crosshatch_surface_execute()

            # Delete main splines
            #bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
            bpy.ops.object.mode_set(mode='OBJECT')
            if self.keep_strokes:
                self.main_splines.name = "keep_strokes"
                self.main_splines.data.bevel_depth = 0.001
                if "keep_strokes_material" in bpy.data.materials :
                    self.main_splines.data.materials.append(bpy.data.materials["keep_strokes_material"])
                else:
                    mat = bpy.data.materials.new("keep_strokes_material")
                    mat.diffuse_color = (1, 0, 0, 0)
                    mat.specular_color = (1, 0, 0)
                    mat.specular_intensity = 0.0
                    mat.roughness = 0.0
                    self.main_splines.data.materials.append(mat)
            else:
                bpy.ops.object.delete({"selected_objects": [self.main_splines]})
            
            # Delete grease pencil strokes
            if self.strokes_type == "GP_STROKES" and not self.stopping_errors:
                try:
                    bpy.context.scene.bsurfaces.SURFSK_object_with_strokes.data.layers.active.clear()
                except:
                    pass
                
            # Delete annotations
            if self.strokes_type == "GP_ANNOTATION" and not self.stopping_errors:
                try:
                    bpy.data.grease_pencils[0].layers.active.clear()
                except:
                    pass

            bsurfaces_props.SURFSK_edges_U = self.edges_U
            bsurfaces_props.SURFSK_edges_V = self.edges_V
            bsurfaces_props.SURFSK_cyclic_cross = self.cyclic_cross
            bsurfaces_props.SURFSK_cyclic_follow = self.cyclic_follow
            bsurfaces_props.SURFSK_automatic_join = self.automatic_join
            bsurfaces_props.SURFSK_loops_on_strokes = self.loops_on_strokes
            bsurfaces_props.SURFSK_keep_strokes = self.keep_strokes
            
            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            self.main_object.select_set(True)
            bpy.context.view_layer.objects.active = self.main_object

            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

        return{'FINISHED'}

    def invoke(self, context, event):
        if bpy.ops.object.mode_set.poll():
             bpy.ops.object.mode_set(mode='OBJECT')

        bsurfaces_props = bpy.context.scene.bsurfaces
        self.cyclic_cross = bsurfaces_props.SURFSK_cyclic_cross
        self.cyclic_follow = bsurfaces_props.SURFSK_cyclic_follow
        self.automatic_join = bsurfaces_props.SURFSK_automatic_join
        self.loops_on_strokes = bsurfaces_props.SURFSK_loops_on_strokes
        self.keep_strokes = bsurfaces_props.SURFSK_keep_strokes
        self.main_object = bsurfaces_props.SURFSK_object_with_retopology
        try:
            self.main_object.select_set(True)
        except:
            self.report({'WARNING'}, "Specify the name of the object with retopology")
            return{"CANCELLED"}
        bpy.context.view_layer.objects.active = self.main_object

        self.main_object_selected_verts_count = len([v for v in self.main_object.data.vertices if v.select])

        bpy.ops.wm.context_set_value(data_path='tool_settings.mesh_select_mode',
                                     value='True, False, False')

        #if self.loops_on_strokes:
        #    self.edges_V = 1
        #else:
        #    self.edges_V = bsurfaces_props.SURFSK_edges_V
        self.edges_U = bsurfaces_props.SURFSK_edges_U
        self.edges_V = bsurfaces_props.SURFSK_edges_V

        self.is_fill_faces = False
        self.stopping_errors = False
        self.last_strokes_splines_coords = []

        # Determine the type of the strokes
        self.strokes_type = get_strokes_type(context)

        # Check if it will be used grease pencil strokes or curves
        # If there are strokes to be used
        if self.strokes_type == "GP_STROKES" or self.strokes_type == "EXTERNAL_CURVE" or self.strokes_type == "GP_ANNOTATION":
            if self.strokes_type == "GP_STROKES":
                # Convert grease pencil strokes to curve
                gp = bsurfaces_props.SURFSK_object_with_strokes
                #bpy.ops.gpencil.convert(type='CURVE', use_link_strokes=False)
                self.original_curve = conver_gpencil_to_curve(self, context, gp, 'GPensil')
                # XXX gpencil.convert now keep org object as active/selected, *not* newly created curve!
                # XXX This is far from perfect, but should work in most cases...
                # self.original_curve = bpy.context.object
                gplayer_prefix_translated = bpy.app.translations.pgettext_data('GP_Layer')
                for ob in bpy.context.selected_objects:
                    if ob != bpy.context.view_layer.objects.active and \
                       ob.name.startswith((gplayer_prefix_translated, 'GP_Layer')):
                        self.original_curve = ob
                self.using_external_curves = False
                
            elif self.strokes_type == "GP_ANNOTATION":
                # Convert grease pencil strokes to curve
                gp = bpy.data.grease_pencils["Annotations"]
                #bpy.ops.gpencil.convert(type='CURVE', use_link_strokes=False)
                self.original_curve = conver_gpencil_to_curve(self, context, gp, 'Annotation')
                # XXX gpencil.convert now keep org object as active/selected, *not* newly created curve!
                # XXX This is far from perfect, but should work in most cases...
                # self.original_curve = bpy.context.object
                gplayer_prefix_translated = bpy.app.translations.pgettext_data('GP_Layer')
                for ob in bpy.context.selected_objects:
                    if ob != bpy.context.view_layer.objects.active and \
                       ob.name.startswith((gplayer_prefix_translated, 'GP_Layer')):
                        self.original_curve = ob
                self.using_external_curves = False
                
            elif self.strokes_type == "EXTERNAL_CURVE":
                self.original_curve = bsurfaces_props.SURFSK_object_with_strokes
                self.using_external_curves = True

                bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

            # Make sure there are no objects left from erroneous
            # executions of this operator, with the reserved names used here
            for o in bpy.data.objects:
                if o.name.find("SURFSKIO_") != -1:
                    bpy.ops.object.delete({"selected_objects": [o]})

            #bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            self.original_curve.select_set(True)
            bpy.context.view_layer.objects.active = self.original_curve

            bpy.ops.object.duplicate('INVOKE_REGION_WIN')

            self.temporary_curve = bpy.context.view_layer.objects.active

            # Deselect all points of the curve
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
            bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

            # Delete splines with only a single isolated point
            for i in range(len(self.temporary_curve.data.splines)):
                sp = self.temporary_curve.data.splines[i]

                if len(sp.bezier_points) == 1:
                    sp.bezier_points[0].select_control_point = True

            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
            bpy.ops.curve.delete(type='VERT')
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            self.temporary_curve.select_set(True)
            bpy.context.view_layer.objects.active = self.temporary_curve

            # Set a minimum number of points for crosshatch
            minimum_points_num = 15

            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
            # Check if the number of points of each curve has at least the number of points
            # of minimum_points_num, which is a bit more than the face-loops limit.
            # If not, subdivide to reach at least that number of points
            for i in range(len(self.temporary_curve.data.splines)):
                sp = self.temporary_curve.data.splines[i]

                if len(sp.bezier_points) < minimum_points_num:
                    for bp in sp.bezier_points:
                        bp.select_control_point = True

                    if (len(sp.bezier_points) - 1) != 0:
                        # Formula to get the number of cuts that will make a curve
                        # of N number of points have near to "minimum_points_num"
                        # points, when subdividing with this number of cuts
                        subdivide_cuts = int(
                                    (minimum_points_num - len(sp.bezier_points)) /
                                    (len(sp.bezier_points) - 1)
                                    ) + 1
                    else:
                        subdivide_cuts = 0

                    bpy.ops.curve.subdivide('INVOKE_REGION_WIN', number_cuts=subdivide_cuts)
                    bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='DESELECT')

            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

            # Detect if the strokes are a crosshatch and do it if it is
            self.crosshatch_surface_invoke(self.temporary_curve)

            if not self.is_crosshatch:
                bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
                self.temporary_curve.select_set(True)
                bpy.context.view_layer.objects.active = self.temporary_curve

                bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

                # Set a minimum number of points for rectangular surfaces
                minimum_points_num = 60

                # Check if the number of points of each curve has at least the number of points
                # of minimum_points_num, which is a bit more than the face-loops limit.
                # If not, subdivide to reach at least that number of points
                for i in range(len(self.temporary_curve.data.splines)):
                    sp = self.temporary_curve.data.splines[i]

                    if len(sp.bezier_points) < minimum_points_num:
                        for bp in sp.bezier_points:
                            bp.select_control_point = True

                        if (len(sp.bezier_points) - 1) != 0:
                            # Formula to get the number of cuts that will make a curve of
                            # N number of points have near to "minimum_points_num" points,
                            # when subdividing with this number of cuts
                            subdivide_cuts = int(
                                        (minimum_points_num - len(sp.bezier_points)) /
                                        (len(sp.bezier_points) - 1)
                                        ) + 1
                        else:
                            subdivide_cuts = 0

                        bpy.ops.curve.subdivide('INVOKE_REGION_WIN', number_cuts=subdivide_cuts)
                        bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='DESELECT')

                bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

            # Save coordinates of the actual strokes (as the "last saved splines")
            for sp_idx in range(len(self.temporary_curve.data.splines)):
                self.last_strokes_splines_coords.append([])
                for bp_idx in range(len(self.temporary_curve.data.splines[sp_idx].bezier_points)):
                    coords = self.temporary_curve.matrix_world @ \
                             self.temporary_curve.data.splines[sp_idx].bezier_points[bp_idx].co
                    self.last_strokes_splines_coords[sp_idx].append([coords[0], coords[1], coords[2]])

            # Check for cyclic splines, put the first and last points in the middle of their actual positions
            for sp_idx in range(len(self.temporary_curve.data.splines)):
                if self.temporary_curve.data.splines[sp_idx].use_cyclic_u is True:
                    first_p_co = self.last_strokes_splines_coords[sp_idx][0]
                    last_p_co = self.last_strokes_splines_coords[sp_idx][
                                                            len(self.last_strokes_splines_coords[sp_idx]) - 1
                                                            ]
                    target_co = [
                            (first_p_co[0] + last_p_co[0]) / 2,
                            (first_p_co[1] + last_p_co[1]) / 2,
                            (first_p_co[2] + last_p_co[2]) / 2
                            ]

                    self.last_strokes_splines_coords[sp_idx][0] = target_co
                    self.last_strokes_splines_coords[sp_idx][
                                                            len(self.last_strokes_splines_coords[sp_idx]) - 1
                                                            ] = target_co
            tuple(self.last_strokes_splines_coords)

            # Estimation of the average length of the segments between
            # each point of the grease pencil strokes.
            # Will be useful to determine whether a curve should be made "Cyclic"
            segments_lengths_sum = 0
            segments_count = 0
            random_spline = self.temporary_curve.data.splines[0].bezier_points
            for i in range(0, len(random_spline)):
                if i != 0 and len(random_spline) - 1 >= i:
                    segments_lengths_sum += (random_spline[i - 1].co - random_spline[i].co).length
                    segments_count += 1

            self.average_gp_segment_length = segments_lengths_sum / segments_count

            # Delete temporary strokes curve object
            bpy.ops.object.delete({"selected_objects": [self.temporary_curve]})
            
            # If "Keep strokes" option is not active, delete original strokes curve object
            if not self.stopping_errors or self.is_crosshatch:
                bpy.ops.object.delete({"selected_objects": [self.original_curve]})

            # Delete grease pencil strokes
            if self.strokes_type == "GP_STROKES" and not self.stopping_errors:
                try:
                    bpy.context.scene.bsurfaces.SURFSK_object_with_strokes.data.layers.active.clear()
                except:
                    pass
                
            # Delete grease pencil strokes
            if self.strokes_type == "GP_ANNOTATION" and not self.stopping_errors:
                try:
                    bpy.data.grease_pencils[0].layers.active.clear()
                except:
                    pass
            
            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            self.main_object.select_set(True)
            bpy.context.view_layer.objects.active = self.main_object
            
            # Set again since "execute()" will turn it again to its initial value
            self.execute(context)

            if not self.stopping_errors:
                return {"FINISHED"}
            else:
                return{"CANCELLED"}

        elif self.strokes_type == "SELECTION_ALONE":
            self.is_fill_faces = True
            created_faces_count = self.fill_with_faces(self.main_object)

            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

            if created_faces_count == 0:
                self.report({'WARNING'}, "There aren't any strokes attached to the object")
                return {"CANCELLED"}
            else:
                return {"FINISHED"}

        if self.strokes_type == "EXTERNAL_NO_CURVE":
            self.report({'WARNING'}, "The secondary object is not a Curve.")
            return{"CANCELLED"}

        elif self.strokes_type == "MORE_THAN_ONE_EXTERNAL":
            self.report({'WARNING'}, "There shouldn't be more than one secondary object selected.")
            return{"CANCELLED"}

        elif self.strokes_type == "SINGLE_GP_STROKE_NO_SELECTION" or \
             self.strokes_type == "SINGLE_CURVE_STROKE_NO_SELECTION":

            self.report({'WARNING'}, "It's needed at least one stroke and one selection, or two strokes.")
            return{"CANCELLED"}

        elif self.strokes_type == "NO_STROKES":
            self.report({'WARNING'}, "There aren't any strokes attached to the object")
            return{"CANCELLED"}

        elif self.strokes_type == "CURVE_WITH_NON_BEZIER_SPLINES":
            self.report({'WARNING'}, "All splines must be Bezier.")
            return{"CANCELLED"}

        else:
            return{"CANCELLED"}

# Edit strokes operator
class GPENCIL_OT_SURFSK_init(Operator):
    bl_idname = "gpencil.surfsk_init"
    bl_label = "Bsurfaces initialize"
    bl_description = "Bsurfaces initialize"

    active_object: PointerProperty(type=bpy.types.Object)

    def execute(self, context):
    
        bs = bpy.context.scene.bsurfaces
    
        if bpy.ops.object.mode_set.poll():
             bpy.ops.object.mode_set(mode='OBJECT')
        
        if bs.SURFSK_object_with_retopology == None:
            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            mesh = bpy.data.meshes.new('BSurfaceMesh')
            mesh_object = object_utils.object_data_add(context, mesh, operator=None)
            mesh_object.select_set(True)
            mesh_object.show_all_edges = True
            mesh_object.show_in_front = True
            mesh_object.display_type = 'SOLID'
            mesh_object.show_wire = True
            bpy.context.view_layer.objects.active = mesh_object
            bpy.ops.object.modifier_add(type='SHRINKWRAP')
            modifier = mesh_object.modifiers["Shrinkwrap"]
            if self.active_object is not None:
                modifier.target = self.active_object
                modifier.wrap_method = 'TARGET_PROJECT'
                modifier.wrap_mode = 'OUTSIDE_SURFACE'
                #modifier.offset = 0.05
            
            bpy.context.scene.bsurfaces.SURFSK_object_with_retopology = mesh_object
        
        if context.scene.bsurfaces.SURFSK_guide == 'GPencil' and bs.SURFSK_object_with_strokes == None:
            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.ops.object.gpencil_add(radius=1.0, align='WORLD', location=(0.0, 0.0, 0.0), rotation=(0.0, 0.0, 0.0), type='EMPTY')
            bpy.context.scene.tool_settings.gpencil_stroke_placement_view3d = 'SURFACE'
            gpencil_object = bpy.context.scene.objects[bpy.context.scene.objects[-1].name]
            gpencil_object.select_set(True)
            bpy.context.view_layer.objects.active = gpencil_object
            bpy.ops.object.mode_set(mode='PAINT_GPENCIL')
            bpy.context.scene.bsurfaces.SURFSK_object_with_strokes = gpencil_object
            gpencil_object.data.stroke_depth_order = '3D'
        
        if context.scene.bsurfaces.SURFSK_guide == 'Annotation':
            bpy.ops.wm.tool_set_by_id(name="builtin.annotate")
            bpy.context.scene.tool_settings.annotation_stroke_placement_view3d = 'SURFACE'

        return {"FINISHED"}

    def invoke(self, context, event):
        if bpy.context.active_object:
            self.active_object = bpy.context.active_object
        else:
            self.active_object = None
        
        self.execute(context)

        return {"FINISHED"}
        
# Edit strokes operator
class GPENCIL_OT_SURFSK_add_modifiers(Operator):
    bl_idname = "gpencil.surfsk_add_modifiers"
    bl_label = "Add Mirror and others modifiers"
    bl_description = "Add modifiers: Mirror, Shrinkwrap, Subdivision, Solidify "

    active_object: PointerProperty(type=bpy.types.Object)

    def execute(self, context):
    
        bs = bpy.context.scene.bsurfaces
    
        if bpy.ops.object.mode_set.poll():
             bpy.ops.object.mode_set(mode='OBJECT')
        
        if bs.SURFSK_object_with_retopology == None:
            self.report({'ERROR_INVALID_INPUT'}, "Please select Mesh of BSurface or click Initialize")
        else:
            mesh_object = bs.SURFSK_object_with_retopology
            
            try:
                mesh_object.select_set(True)
            except:
                self.report({'ERROR_INVALID_INPUT'}, "Mesh of BSurface does not exist")
                return {"CANCEL"}
            
            bpy.context.view_layer.objects.active = mesh_object
            
            try:
                shrinkwrap = mesh_object.modifiers["Shrinkwrap"]
                if self.active_object is not None and self.active_object != mesh_object:
                    shrinkwrap.target = self.active_object
                    shrinkwrap.wrap_method = 'TARGET_PROJECT'
                    shrinkwrap.wrap_mode = 'OUTSIDE_SURFACE'
            except:
                bpy.ops.object.modifier_add(type='SHRINKWRAP')
                shrinkwrap = mesh_object.modifiers["Shrinkwrap"]
                if self.active_object is not None and self.active_object != mesh_object:
                    shrinkwrap.target = self.active_object
                    shrinkwrap.wrap_method = 'TARGET_PROJECT'
                    shrinkwrap.wrap_mode = 'OUTSIDE_SURFACE'
            
            try:
                mirror = mesh_object.modifiers["Mirror"]
                mirror.use_clip = True
            except:
                bpy.ops.object.modifier_add(type='MIRROR')
                mirror = mesh_object.modifiers["Mirror"]
                mirror.use_clip = True
            
            try:
                subsurf = mesh_object.modifiers["Subdivision"]
            except:
                bpy.ops.object.modifier_add(type='SUBSURF')
                subsurf = mesh_object.modifiers["Subdivision"]
            
            try:
                solidify = mesh_object.modifiers["Solidify"]
                solidify.thickness = 0.01
            except:
                bpy.ops.object.modifier_add(type='SOLIDIFY')
                solidify = mesh_object.modifiers["Solidify"]
                solidify.thickness = 0.01

        return {"FINISHED"}

    def invoke(self, context, event):
        if bpy.context.active_object:
            self.active_object = bpy.context.active_object
        else:
            self.active_object = None
        
        self.execute(context)

        return {"FINISHED"}

# Edit surface operator
class GPENCIL_OT_SURFSK_edit_surface(Operator):
    bl_idname = "gpencil.surfsk_edit_surface"
    bl_label = "Bsurfaces edit surface"
    bl_description = "Edit surface mesh"

    def execute(self, context):
        bpy.context.scene.bsurfaces.SURFSK_object_with_retopology.select_set(True)
        bpy.context.view_layer.objects.active = bpy.context.scene.bsurfaces.SURFSK_object_with_retopology
        bpy.ops.object.mode_set(mode='EDIT')
        
    def invoke(self, context, event):
        try:
            bpy.context.scene.bsurfaces.SURFSK_object_with_retopology.select_set(True)
        except:
            self.report({'WARNING'}, "Specify the name of the object with retopology")
            return{"CANCELLED"}
        
        self.execute(context)

        return {"FINISHED"}

# Add strokes operator
class GPENCIL_OT_SURFSK_add_strokes(Operator):
    bl_idname = "gpencil.surfsk_add_strokes"
    bl_label = "Bsurfaces add strokes"
    bl_description = "Add the grease pencil strokes"

    def execute(self, context):
        # Determine the type of the strokes
        self.strokes_type = get_strokes_type(context)
        # Check if strokes are grease pencil strokes or a curves object
        selected_objs = bpy.context.selected_objects
        if self.strokes_type == "EXTERNAL_CURVE" or self.strokes_type == "SINGLE_CURVE_STROKE_NO_SELECTION":
            for ob in selected_objs:
                if ob != bpy.context.view_layer.objects.active:
                    curve_ob = ob

            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            curve_ob.select_set(True)
            bpy.context.view_layer.objects.active = curve_ob

            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
        else:
            bpy.context.scene.bsurfaces.SURFSK_object_with_strokes.select_set(True)
            bpy.context.view_layer.objects.active = bpy.context.scene.bsurfaces.SURFSK_object_with_strokes
            bpy.ops.object.mode_set(mode='PAINT_GPENCIL')

            return{"FINISHED"}

    def invoke(self, context, event):
        try:
            bpy.context.scene.bsurfaces.SURFSK_object_with_strokes.select_set(True)
        except:
            self.report({'WARNING'}, "Specify the name of the object with strokes")
            return{"CANCELLED"}
        
        self.execute(context)

        return {"FINISHED"}

# Edit strokes operator
class GPENCIL_OT_SURFSK_edit_strokes(Operator):
    bl_idname = "gpencil.surfsk_edit_strokes"
    bl_label = "Bsurfaces edit strokes"
    bl_description = "Edit the grease pencil strokes or curves used"

    def execute(self, context):
        # Determine the type of the strokes
        self.strokes_type = get_strokes_type(context)
        # Check if strokes are grease pencil strokes or a curves object
        selected_objs = bpy.context.selected_objects
        if self.strokes_type == "EXTERNAL_CURVE" or self.strokes_type == "SINGLE_CURVE_STROKE_NO_SELECTION":
            for ob in selected_objs:
                if ob != bpy.context.view_layer.objects.active:
                    curve_ob = ob

            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            curve_ob.select_set(True)
            bpy.context.view_layer.objects.active = curve_ob

            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
        elif self.strokes_type == "GP_STROKES" or self.strokes_type == "SINGLE_GP_STROKE_NO_SELECTION":
            # Convert grease pencil strokes to curve
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
            #bpy.ops.gpencil.convert('INVOKE_REGION_WIN', type='CURVE', use_link_strokes=False)
            gp = bpy.context.scene.bsurfaces.SURFSK_object_with_strokes
            conver_gpencil_to_curve(self, context, gp, 'GPensil')
            for ob in bpy.context.selected_objects:
                    if ob != bpy.context.view_layer.objects.active and ob.name.startswith("GP_Layer"):
                        ob_gp_strokes = ob

            ob_gp_strokes = bpy.context.object

            # Delete grease pencil strokes
            try:
                bpy.context.scene.bsurfaces.SURFSK_object_with_strokes.data.layers.active.clear()
            except:
                pass

            # Clean up curves
            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            ob_gp_strokes.select_set(True)
            bpy.context.view_layer.objects.active = ob_gp_strokes

            curve_crv = ob_gp_strokes.data
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
            bpy.ops.curve.spline_type_set('INVOKE_REGION_WIN', type="BEZIER")
            bpy.ops.curve.handle_type_set('INVOKE_REGION_WIN', type="AUTOMATIC")
            #curve_crv.show_handles = False
            #curve_crv.show_normal_face = False

        elif self.strokes_type == "EXTERNAL_NO_CURVE":
            self.report({'WARNING'}, "The secondary object is not a Curve.")
            return{"CANCELLED"}

        elif self.strokes_type == "MORE_THAN_ONE_EXTERNAL":
            self.report({'WARNING'}, "There shouldn't be more than one secondary object selected.")
            return{"CANCELLED"}

        elif self.strokes_type == "NO_STROKES" or self.strokes_type == "SELECTION_ALONE":
            self.report({'WARNING'}, "There aren't any strokes attached to the object")
            return{"CANCELLED"}

        else:
            return{"CANCELLED"}

    def invoke(self, context, event):
        try:
           bpy.context.scene.bsurfaces.SURFSK_object_with_strokes.select_set(True)
        except:
            self.report({'WARNING'}, "Specify the name of the object with strokes")
            return{"CANCELLED"}

        self.execute(context)

        return {"FINISHED"}

# Add annotation
class GPENCIL_OT_SURFSK_add_annotation(Operator):
    bl_idname = "gpencil.surfsk_add_annotation"
    bl_label = "Bsurfaces add annotation"
    bl_description = "Add annotation"

    def execute(self, context):
        bpy.ops.wm.tool_set_by_id(name="builtin.annotate")
        bpy.context.scene.tool_settings.annotation_stroke_placement_view3d = 'SURFACE'

        return{"FINISHED"}

    def invoke(self, context, event):
        
        self.execute(context)

        return {"FINISHED"}

class CURVE_OT_SURFSK_reorder_splines(Operator):
    bl_idname = "curve.surfsk_reorder_splines"
    bl_label = "Bsurfaces reorder splines"
    bl_description = "Defines the order of the splines by using grease pencil strokes"
    bl_options = {'REGISTER', 'UNDO'}

    def execute(self, context):
        objects_to_delete = []
        # Convert grease pencil strokes to curve.
        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
        bpy.ops.gpencil.convert('INVOKE_REGION_WIN', type='CURVE', use_link_strokes=False)
        for ob in bpy.context.selected_objects:
            if ob != bpy.context.view_layer.objects.active and ob.name.startswith("GP_Layer"):
                GP_strokes_curve = ob

        # GP_strokes_curve = bpy.context.object
        objects_to_delete.append(GP_strokes_curve)

        bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
        GP_strokes_curve.select_set(True)
        bpy.context.view_layer.objects.active = GP_strokes_curve

        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
        bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='SELECT')
        bpy.ops.curve.subdivide('INVOKE_REGION_WIN', number_cuts=100)
        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

        bpy.ops.object.duplicate('INVOKE_REGION_WIN')
        GP_strokes_mesh = bpy.context.object
        objects_to_delete.append(GP_strokes_mesh)

        GP_strokes_mesh.data.resolution_u = 1
        bpy.ops.object.convert(target='MESH', keep_original=False)

        bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
        self.main_curve.select_set(True)
        bpy.context.view_layer.objects.active = self.main_curve

        bpy.ops.object.duplicate('INVOKE_REGION_WIN')
        curves_duplicate_1 = bpy.context.object
        objects_to_delete.append(curves_duplicate_1)

        minimum_points_num = 500

        # Some iterations since the subdivision operator
        # has a limit of 100 subdivisions per iteration
        for x in range(round(minimum_points_num / 100)):
            # Check if the number of points of each curve has at least the number of points
            # of minimum_points_num. If not, subdivide to reach at least that number of points
            for i in range(len(curves_duplicate_1.data.splines)):
                sp = curves_duplicate_1.data.splines[i]

                if len(sp.bezier_points) < minimum_points_num:
                    for bp in sp.bezier_points:
                        bp.select_control_point = True

                    if (len(sp.bezier_points) - 1) != 0:
                        # Formula to get the number of cuts that will make a curve of N
                        # number of points have near to "minimum_points_num" points,
                        # when subdividing with this number of cuts
                        subdivide_cuts = int(
                                (minimum_points_num - len(sp.bezier_points)) /
                                (len(sp.bezier_points) - 1)
                                ) + 1
                    else:
                        subdivide_cuts = 0

                    bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
                    bpy.ops.curve.subdivide('INVOKE_REGION_WIN', number_cuts=subdivide_cuts)
                    bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='DESELECT')
                    bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

        bpy.ops.object.duplicate('INVOKE_REGION_WIN')
        curves_duplicate_2 = bpy.context.object
        objects_to_delete.append(curves_duplicate_2)

        # Duplicate the duplicate and add Shrinkwrap to it, with the grease pencil strokes curve as target
        bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
        curves_duplicate_2.select_set(True)
        bpy.context.view_layer.objects.active = curves_duplicate_2

        bpy.ops.object.modifier_add('INVOKE_REGION_WIN', type='SHRINKWRAP')
        curves_duplicate_2.modifiers["Shrinkwrap"].wrap_method = "NEAREST_VERTEX"
        curves_duplicate_2.modifiers["Shrinkwrap"].target = GP_strokes_mesh
        bpy.ops.object.modifier_apply('INVOKE_REGION_WIN', apply_as='DATA', modifier='Shrinkwrap')

        # Get the distance of each vert from its original position to its position with Shrinkwrap
        nearest_points_coords = {}
        for st_idx in range(len(curves_duplicate_1.data.splines)):
            for bp_idx in range(len(curves_duplicate_1.data.splines[st_idx].bezier_points)):
                bp_1_co = curves_duplicate_1.matrix_world @ \
                          curves_duplicate_1.data.splines[st_idx].bezier_points[bp_idx].co

                bp_2_co = curves_duplicate_2.matrix_world @ \
                          curves_duplicate_2.data.splines[st_idx].bezier_points[bp_idx].co

                if bp_idx == 0:
                    shortest_dist = (bp_1_co - bp_2_co).length
                    nearest_points_coords[st_idx] = ("%.4f" % bp_2_co[0],
                                                     "%.4f" % bp_2_co[1],
                                                     "%.4f" % bp_2_co[2])

                dist = (bp_1_co - bp_2_co).length

                if dist < shortest_dist:
                    nearest_points_coords[st_idx] = ("%.4f" % bp_2_co[0],
                                                     "%.4f" % bp_2_co[1],
                                                     "%.4f" % bp_2_co[2])
                    shortest_dist = dist

        # Get all coords of GP strokes points, for comparison
        GP_strokes_coords = []
        for st_idx in range(len(GP_strokes_curve.data.splines)):
            GP_strokes_coords.append(
                    [("%.4f" % x if "%.4f" % x != "-0.00" else "0.00",
                    "%.4f" % y if "%.4f" % y != "-0.00" else "0.00",
                    "%.4f" % z if "%.4f" % z != "-0.00" else "0.00") for
                    x, y, z in [bp.co for bp in GP_strokes_curve.data.splines[st_idx].bezier_points]]
                    )

        # Check the point of the GP strokes with the same coords as
        # the nearest points of the curves (with shrinkwrap)

        # Dictionary with GP stroke index as index, and a list as value.
        # The list has as index the point index of the GP stroke
        # nearest to the spline, and as value the spline index
        GP_connection_points = {}
        for gp_st_idx in range(len(GP_strokes_coords)):
            GPvert_spline_relationship = {}

            for splines_st_idx in range(len(nearest_points_coords)):
                if nearest_points_coords[splines_st_idx] in GP_strokes_coords[gp_st_idx]:
                    GPvert_spline_relationship[
                        GP_strokes_coords[gp_st_idx].index(nearest_points_coords[splines_st_idx])
                        ] = splines_st_idx

            GP_connection_points[gp_st_idx] = GPvert_spline_relationship

        # Get the splines new order
        splines_new_order = []
        for i in GP_connection_points:
            dict_keys = sorted(GP_connection_points[i].keys())  # Sort dictionaries by key

            for k in dict_keys:
                splines_new_order.append(GP_connection_points[i][k])

        # Reorder
        curve_original_name = self.main_curve.name

        bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
        self.main_curve.select_set(True)
        bpy.context.view_layer.objects.active = self.main_curve

        self.main_curve.name = "SURFSKIO_CRV_ORD"

        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
        bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='DESELECT')
        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

        for sp_idx in range(len(self.main_curve.data.splines)):
            self.main_curve.data.splines[0].bezier_points[0].select_control_point = True

            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
            bpy.ops.curve.separate('EXEC_REGION_WIN')
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

        # Get the names of the separated splines objects in the original order
        splines_unordered = {}
        for o in bpy.data.objects:
            if o.name.find("SURFSKIO_CRV_ORD") != -1:
                spline_order_string = o.name.partition(".")[2]

                if spline_order_string != "" and int(spline_order_string) > 0:
                    spline_order_index = int(spline_order_string) - 1
                    splines_unordered[spline_order_index] = o.name

        # Join all splines objects in final order
        for order_idx in splines_new_order:
            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.data.objects[splines_unordered[order_idx]].select_set(True)
            bpy.data.objects["SURFSKIO_CRV_ORD"].select_set(True)
            bpy.context.view_layer.objects.active = bpy.data.objects["SURFSKIO_CRV_ORD"]

            bpy.ops.object.join('INVOKE_REGION_WIN')

        # Go back to the original name of the curves object.
        bpy.context.object.name = curve_original_name

        # Delete all unused objects
        bpy.ops.object.delete({"selected_objects": objects_to_delete})

        bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
        bpy.data.objects[curve_original_name].select_set(True)
        bpy.context.view_layer.objects.active = bpy.data.objects[curve_original_name]

        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
        bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='DESELECT')

        try:
            bpy.context.scene.bsurfaces.SURFSK_object_with_strokes.data.layers.active.clear()
        except:
            pass
        

        return {"FINISHED"}

    def invoke(self, context, event):
        self.main_curve = bpy.context.object
        there_are_GP_strokes = False

        try:
            # Get the active grease pencil layer
            strokes_num = len(self.main_curve.grease_pencil.layers.active.active_frame.strokes)

            if strokes_num > 0:
                there_are_GP_strokes = True
        except:
            pass

        if there_are_GP_strokes:
            self.execute(context)
            self.report({'INFO'}, "Splines have been reordered")
        else: