animation_motion_trail.py

        for i, [f_ori, coords] in enumerate(locs_ori):
            if abs(frame_ori - f_ori) < 1e-4:
                if i == 0:
                    # first keyframe, nothing before it
                    direction = -1
                    range = [f_ori, locs_ori[i + 1][0]]
                elif i == len(locs_ori) - 1:
                    # last keyframe, nothing after it
                    range = [locs_ori[i - 1][0], f_ori]
                else:
                    current = mathutils.Vector(coords)
                    next = mathutils.Vector(locs_ori[i + 1][1])
                    previous = mathutils.Vector(locs_ori[i - 1][1])
                    angle_to_next = d.angle(next - current, 0)
                    angle_to_previous = d.angle(previous - current, 0)
                    if angle_to_previous < angle_to_next:
                        # mouse movement is in direction of previous keyframe
                        direction = -1
                    range = [locs_ori[i - 1][0], locs_ori[i + 1][0]]
                break
        direction *= -1  # feels more natural in 3d-view
        if not range:
            # keyframe not found, is impossible, but better safe than sorry
            return(active_keyframe, active_timebead, keyframes_ori)
        # calculate strength of movement
        d_screen = mathutils.Vector([event.mouse_region_x,
            event.mouse_region_y]) - drag_mouse_ori
        if d_screen.length != 0:
            d_screen = d_screen.length / (abs(d_screen[0]) / d_screen.length *
                      context.region.width + abs(d_screen[1]) / d_screen.length *
                      context.region.height)
            d_screen *= direction  # d_screen value ranges from -1.0 to 1.0
        else:
            d_screen = 0.0
        new_frame = d_screen * (range[1] - range[0]) + frame_ori
        max_frame = range[1]
        if max_frame == frame_ori:
            max_frame += 1
        min_frame = range[0]
        if min_frame == frame_ori:
            min_frame -= 1
        new_frame = min(max_frame - 1, max(min_frame + 1, new_frame))
        d_frame = new_frame - frame_ori
        curves = get_curves(action_ob, child)

        for i, curve in enumerate(curves):
            for kf in curve.keyframe_points:
                if abs(kf.co[0] - frame) < 1e-4:
                    kf.co[0] = new_frame
                    kf.handle_left[0] = handles_ori[objectname][frame_ori]["left"][i][0] + d_frame
                    kf.handle_right[0] = handles_ori[objectname][frame_ori]["right"][i][0] + d_frame
                    break
        active_keyframe = [objectname, new_frame, frame_ori, action_ob, child]

    # change position of active timebead on the timeline, thus altering speed
    elif context.window_manager.motion_trail.mode == 'speed' and \
    active_timebead:
        objectname, frame, frame_ori, action_ob, child = active_timebead
        if child:
            mat = action_ob.matrix_world.copy().inverted() * \
                edit_bones[child.name].copy().to_4x4()
        else:
            mat = 1

        mouse_ori_world = screen_to_world(context, drag_mouse_ori[0],
            drag_mouse_ori[1]) * mat
        vector = screen_to_world(context, event.mouse_region_x,
            event.mouse_region_y) * mat
        d = vector - mouse_ori_world

        # determine direction (to next or previous keyframe)
        curves = get_curves(action_ob, child)
        fcx, fcy, fcz = curves
        locx = fcx.evaluate(frame_ori)
        locy = fcy.evaluate(frame_ori)
        locz = fcz.evaluate(frame_ori)
        loc_ori = mathutils.Vector([locx, locy, locz])  # bonespace
        keyframes = [kf for kf in keyframes_ori[objectname]]
        keyframes.append(frame_ori)
        keyframes.sort()
        frame_index = keyframes.index(frame_ori)
        kf_prev = keyframes[frame_index - 1]
        kf_next = keyframes[frame_index + 1]
        vec_prev = (
                mathutils.Vector(keyframes_ori[objectname][kf_prev][1]) *
                mat - loc_ori
                ).normalized()
        vec_next = (mathutils.Vector(keyframes_ori[objectname][kf_next][1]) *
                mat - loc_ori
                ).normalized()
        d_normal = d.copy().normalized()
        dist_to_next = (d_normal - vec_next).length
        dist_to_prev = (d_normal - vec_prev).length
        if dist_to_prev < dist_to_next:
            direction = 1
        else:
            direction = -1

        if (kf_next - frame_ori) < (frame_ori - kf_prev):
            kf_bead = kf_next
            side = "left"
        else:
            kf_bead = kf_prev
            side = "right"
        d_frame = d.length * direction * 2  # * 2 to make it more sensitive

        angles = []
        for i, curve in enumerate(curves):
            for kf in curve.keyframe_points:
                if abs(kf.co[0] - kf_bead) < 1e-4:
                    if side == "left":
                        # left side
                        kf.handle_left[0] = min(
                                            handles_ori[objectname][kf_bead]["left"][i][0] +
                                            d_frame, kf_bead - 1
                                            )
                        angle = mathutils.Vector([-1, 0]).angle(
                                            mathutils.Vector(kf.handle_left) -
                                            mathutils.Vector(kf.co), 0
                                            )
                        if angle != 0:
                            angles.append(angle)
                    else:
                        # right side
                        kf.handle_right[0] = max(
                                            handles_ori[objectname][kf_bead]["right"][i][0] +
                                            d_frame, kf_bead + 1
                                            )
                        angle = mathutils.Vector([1, 0]).angle(
                                            mathutils.Vector(kf.handle_right) -
                                            mathutils.Vector(kf.co), 0
                                            )
                        if angle != 0:
                            angles.append(angle)
                    break

        # update frame of active_timebead
        perc = (sum(angles) / len(angles)) / (math.pi / 2)
        perc = max(0.4, min(1, perc * 5))
        if side == "left":
            bead_frame = kf_bead - perc * ((kf_bead - kf_prev - 2) / 2)
        else:
            bead_frame = kf_bead + perc * ((kf_next - kf_bead - 2) / 2)
        active_timebead = [objectname, bead_frame, frame_ori, action_ob, child]

    return(active_keyframe, active_timebead, keyframes_ori)


# revert changes made by dragging
def cancel_drag(context, active_keyframe, active_handle, active_timebead,
keyframes_ori, handles_ori, edit_bones):
    # revert change in 3d-location of active keyframe and its handles
    if context.window_manager.motion_trail.mode == 'location' and \
    active_keyframe:
        objectname, frame, frame_ori, active_ob, child = active_keyframe
        curves = get_curves(active_ob, child)
        loc_ori = keyframes_ori[objectname][frame][1]
        if child:
            loc_ori = loc_ori * edit_bones[child.name] * \
                active_ob.matrix_world.copy().inverted()
        for i, curve in enumerate(curves):
            for kf in curve.keyframe_points:
                if kf.co[0] == frame:
                    kf.co[1] = loc_ori[i]
                    kf.handle_left[1] = handles_ori[objectname][frame]["left"][i][1]
                    kf.handle_right[1] = handles_ori[objectname][frame]["right"][i][1]
                    break

    # revert change in 3d-location of active handle
    elif context.window_manager.motion_trail.mode == 'location' and \
    active_handle:
        objectname, frame, side, active_ob, child = active_handle
        curves = get_curves(active_ob, child)
        for i, curve in enumerate(curves):
            for kf in curve.keyframe_points:
                if kf.co[0] == frame:
                    kf.handle_left[1] = handles_ori[objectname][frame]["left"][i][1]
                    kf.handle_right[1] = handles_ori[objectname][frame]["right"][i][1]
                    break

    # revert position of all keyframes and handles on timeline
    elif context.window_manager.motion_trail.mode == 'timing' and \
    active_timebead:
        objectname, frame, frame_ori, active_ob, child = active_timebead
        curves = get_curves(active_ob, child)
        for i, curve in enumerate(curves):
            for kf in curve.keyframe_points:
                for kf_ori, [frame_ori, loc] in keyframes_ori[objectname].\
                items():
                    if abs(kf.co[0] - kf_ori) < 1e-4:
                        kf.co[0] = frame_ori
                        kf.handle_left[0] = handles_ori[objectname][frame_ori]["left"][i][0]
                        kf.handle_right[0] = handles_ori[objectname][frame_ori]["right"][i][0]
                        break

    # revert position of active keyframe and its handles on the timeline
    elif context.window_manager.motion_trail.mode == 'timing' and \
    active_keyframe:
        objectname, frame, frame_ori, active_ob, child = active_keyframe
        curves = get_curves(active_ob, child)
        for i, curve in enumerate(curves):
            for kf in curve.keyframe_points:
                if abs(kf.co[0] - frame) < 1e-4:
                    kf.co[0] = keyframes_ori[objectname][frame_ori][0]
                    kf.handle_left[0] = handles_ori[objectname][frame_ori]["left"][i][0]
                    kf.handle_right[0] = handles_ori[objectname][frame_ori]["right"][i][0]
                    break
        active_keyframe = [objectname, frame_ori, frame_ori, active_ob, child]

    # revert position of handles on the timeline
    elif context.window_manager.motion_trail.mode == 'speed' and \
    active_timebead:
        objectname, frame, frame_ori, active_ob, child = active_timebead
        curves = get_curves(active_ob, child)
        keyframes = [kf for kf in keyframes_ori[objectname]]
        keyframes.append(frame_ori)
        keyframes.sort()
        frame_index = keyframes.index(frame_ori)
        kf_prev = keyframes[frame_index - 1]
        kf_next = keyframes[frame_index + 1]
        if (kf_next - frame_ori) < (frame_ori - kf_prev):
            kf_frame = kf_next
        else:
            kf_frame = kf_prev
        for i, curve in enumerate(curves):
            for kf in curve.keyframe_points:
                if kf.co[0] == kf_frame:
                    kf.handle_left[0] = handles_ori[objectname][kf_frame]["left"][i][0]
                    kf.handle_right[0] = handles_ori[objectname][kf_frame]["right"][i][0]
                    break
        active_timebead = [objectname, frame_ori, frame_ori, active_ob, child]

    return(active_keyframe, active_timebead)


# return the handle type of the active selection
def get_handle_type(active_keyframe, active_handle):
    if active_keyframe:
        objectname, frame, side, action_ob, child = active_keyframe
        side = "both"
    elif active_handle:
        objectname, frame, side, action_ob, child = active_handle
    else:
        # no active handle(s)
        return(False)

    # properties used when changing handle type
    bpy.context.window_manager.motion_trail.handle_type_frame = frame
    bpy.context.window_manager.motion_trail.handle_type_side = side
    bpy.context.window_manager.motion_trail.handle_type_action_ob = \
        action_ob.name
    if child:
        bpy.context.window_manager.motion_trail.handle_type_child = child.name
    else:
        bpy.context.window_manager.motion_trail.handle_type_child = ""

    curves = get_curves(action_ob, child=child)
    for c in curves:
        for kf in c.keyframe_points:
            if kf.co[0] == frame:
                if side in ("left", "both"):
                    return(kf.handle_left_type)
                else:
                    return(kf.handle_right_type)

    return("AUTO")


# turn the given frame into a keyframe
def insert_keyframe(self, context, frame):
    objectname, frame, frame, action_ob, child = frame
    curves = get_curves(action_ob, child)
    for c in curves:
        y = c.evaluate(frame)
        if c.keyframe_points:
            c.keyframe_points.insert(frame, y)

    bpy.context.window_manager.motion_trail.force_update = True
    calc_callback(self, context)


# change the handle type of the active selection
def set_handle_type(self, context):
    if not context.window_manager.motion_trail.handle_type_enabled:
        return
    if context.window_manager.motion_trail.handle_type_old == \
    context.window_manager.motion_trail.handle_type:
        # function called because of selection change, not change in type
        return
    context.window_manager.motion_trail.handle_type_old = \
        context.window_manager.motion_trail.handle_type

    frame = bpy.context.window_manager.motion_trail.handle_type_frame
    side = bpy.context.window_manager.motion_trail.handle_type_side
    action_ob = bpy.context.window_manager.motion_trail.handle_type_action_ob
    action_ob = bpy.data.objects[action_ob]
    child = bpy.context.window_manager.motion_trail.handle_type_child
    if child:
        child = action_ob.pose.bones[child]
    new_type = context.window_manager.motion_trail.handle_type

    curves = get_curves(action_ob, child=child)
    for c in curves:
        for kf in c.keyframe_points:
            if kf.co[0] == frame:
                # align if necessary
                if side in ("right", "both") and new_type in (
                            "AUTO", "AUTO_CLAMPED", "ALIGNED"):
                    # change right handle
                    normal = (kf.co - kf.handle_left).normalized()
                    size = (kf.handle_right[0] - kf.co[0]) / normal[0]
                    normal = normal * size + kf.co
                    kf.handle_right[1] = normal[1]
                elif side == "left" and new_type in (
                            "AUTO", "AUTO_CLAMPED", "ALIGNED"):
                    # change left handle
                    normal = (kf.co - kf.handle_right).normalized()
                    size = (kf.handle_left[0] - kf.co[0]) / normal[0]
                    normal = normal * size + kf.co
                    kf.handle_left[1] = normal[1]
                # change type
                if side in ("left", "both"):
                    kf.handle_left_type = new_type
                if side in ("right", "both"):
                    kf.handle_right_type = new_type

    context.window_manager.motion_trail.force_update = True


class MotionTrailOperator(bpy.types.Operator):
    bl_idname = "view3d.motion_trail"
    bl_label = "Motion Trail"
    bl_description = "Edit motion trails in 3d-view"

    _handle_calc = None
    _handle_draw = None

    @staticmethod
    def handle_add(self, context):
        MotionTrailOperator._handle_calc = bpy.types.SpaceView3D.draw_handler_add(
            calc_callback, (self, context), 'WINDOW', 'POST_VIEW')
        MotionTrailOperator._handle_draw = bpy.types.SpaceView3D.draw_handler_add(
            draw_callback, (self, context), 'WINDOW', 'POST_PIXEL')

    @staticmethod
    def handle_remove():
        if MotionTrailOperator._handle_calc is not None:
            bpy.types.SpaceView3D.draw_handler_remove(MotionTrailOperator._handle_calc, 'WINDOW')
        if MotionTrailOperator._handle_draw is not None:
            bpy.types.SpaceView3D.draw_handler_remove(MotionTrailOperator._handle_draw, 'WINDOW')
        MotionTrailOperator._handle_calc = None
        MotionTrailOperator._handle_draw = None

    def modal(self, context, event):
        # XXX Required, or custom transform.translate will break!
        # XXX If one disables and re-enables motion trail, modal op will still be running,
        # XXX default translate op will unintentionally get called, followed by custom translate.
        if not context.window_manager.motion_trail.enabled:
            MotionTrailOperator.handle_remove()
            context.area.tag_redraw()
            return {'FINISHED'}

        if not context.area or not context.region or event.type == 'NONE':
            context.area.tag_redraw()
            return {'PASS_THROUGH'}

        wm = context.window_manager
        keyconfig = wm.keyconfigs.active
        select = getattr(keyconfig.preferences, "select_mouse", "LEFT")

        if (not context.active_object or
                context.active_object.mode not in ('OBJECT', 'POSE')):
            if self.drag:
                self.drag = False
                self.lock = True
                context.window_manager.motion_trail.force_update = True
            # default hotkeys should still work
            if event.type == self.transform_key and event.value == 'PRESS':
                if bpy.ops.transform.translate.poll():
                    bpy.ops.transform.translate('INVOKE_DEFAULT')
            elif event.type == select + 'MOUSE' and event.value == 'PRESS' \
            and not self.drag and not event.shift and not event.alt \
            and not event.ctrl:
                if bpy.ops.view3d.select.poll():
                    bpy.ops.view3d.select('INVOKE_DEFAULT')
            elif event.type == 'LEFTMOUSE' and event.value == 'PRESS' and not\
            event.alt and not event.ctrl and not event.shift:
                if eval("bpy.ops." + self.left_action + ".poll()"):
                    eval("bpy.ops." + self.left_action + "('INVOKE_DEFAULT')")
            return {'PASS_THROUGH'}
        # check if event was generated within 3d-window, dragging is exception
        if not self.drag:
            if not (0 < event.mouse_region_x < context.region.width) or \
            not (0 < event.mouse_region_y < context.region.height):
                return {'PASS_THROUGH'}

        if (event.type == self.transform_key and event.value == 'PRESS' and
               (self.active_keyframe or
                self.active_handle or
                self.active_timebead or
                self.active_frame)):
            # override default translate()
            if not self.drag:
                # start drag
                if self.active_frame:
                    insert_keyframe(self, context, self.active_frame)
                    self.active_keyframe = self.active_frame
                    self.active_frame = False
                self.keyframes_ori, self.handles_ori = \
                    get_original_animation_data(context, self.keyframes)
                self.drag_mouse_ori = mathutils.Vector([event.mouse_region_x,
                    event.mouse_region_y])
                self.drag = True
                self.lock = False
            else:
                # stop drag
                self.drag = False
                self.lock = True
                context.window_manager.motion_trail.force_update = True
        elif event.type == self.transform_key and event.value == 'PRESS':
            # call default translate()
            if bpy.ops.transform.translate.poll():
                bpy.ops.transform.translate('INVOKE_DEFAULT')
        elif (event.type == 'ESC' and self.drag and event.value == 'PRESS') or \
             (event.type == 'RIGHTMOUSE' and self.drag and event.value == 'PRESS'):
            # cancel drag
            self.drag = False
            self.lock = True
            context.window_manager.motion_trail.force_update = True
            self.active_keyframe, self.active_timebead = cancel_drag(context,
                self.active_keyframe, self.active_handle,
                self.active_timebead, self.keyframes_ori, self.handles_ori,
                self.edit_bones)
        elif event.type == 'MOUSEMOVE' and self.drag:
            # drag
            self.active_keyframe, self.active_timebead, self.keyframes_ori = \
                drag(context, event, self.drag_mouse_ori,
                self.active_keyframe, self.active_handle,
                self.active_timebead, self.keyframes_ori, self.handles_ori,
                self.edit_bones)
        elif event.type == select + 'MOUSE' and event.value == 'PRESS' and \
        not self.drag and not event.shift and not event.alt and not \
        event.ctrl:
            # select
            treshold = 10
            clicked = mathutils.Vector([event.mouse_region_x,
                event.mouse_region_y])
            self.active_keyframe = False
            self.active_handle = False
            self.active_timebead = False
            self.active_frame = False
            context.window_manager.motion_trail.force_update = True
            context.window_manager.motion_trail.handle_type_enabled = True
            found = False

            if context.window_manager.motion_trail.path_before == 0:
                frame_min = context.scene.frame_start
            else:
                frame_min = max(
                            context.scene.frame_start,
                            context.scene.frame_current -
                            context.window_manager.motion_trail.path_before
                            )
            if context.window_manager.motion_trail.path_after == 0:
                frame_max = context.scene.frame_end
            else:
                frame_max = min(
                            context.scene.frame_end,
                            context.scene.frame_current +
                            context.window_manager.motion_trail.path_after
                            )

            for objectname, values in self.click.items():
                if found:
                    break
                for frame, type, coord, action_ob, child in values:
                    if frame < frame_min or frame > frame_max:
                        continue
                    if (coord - clicked).length <= treshold:
                        found = True
                        if type == "keyframe":
                            self.active_keyframe = [objectname, frame, frame,
                                action_ob, child]
                        elif type == "handle_left":
                            self.active_handle = [objectname, frame, "left",
                                action_ob, child]
                        elif type == "handle_right":
                            self.active_handle = [objectname, frame, "right",
                                action_ob, child]
                        elif type == "timebead":
                            self.active_timebead = [objectname, frame, frame,
                                action_ob, child]
                        elif type == "frame":
                            self.active_frame = [objectname, frame, frame,
                                action_ob, child]
                        break
            if not found:
                context.window_manager.motion_trail.handle_type_enabled = False
                # no motion trail selections, so pass on to normal select()
                if bpy.ops.view3d.select.poll():
                    bpy.ops.view3d.select('INVOKE_DEFAULT')
            else:
                handle_type = get_handle_type(self.active_keyframe,
                    self.active_handle)
                if handle_type:
                    context.window_manager.motion_trail.handle_type_old = \
                        handle_type
                    context.window_manager.motion_trail.handle_type = \
                        handle_type
                else:
                    context.window_manager.motion_trail.handle_type_enabled = \
                        False
        elif event.type == 'LEFTMOUSE' and event.value == 'PRESS' and \
        self.drag:
            # stop drag
            self.drag = False
            self.lock = True
            context.window_manager.motion_trail.force_update = True
        elif event.type == 'LEFTMOUSE' and event.value == 'PRESS' and not\
        event.alt and not event.ctrl and not event.shift:
            if eval("bpy.ops." + self.left_action + ".poll()"):
                eval("bpy.ops." + self.left_action + "('INVOKE_DEFAULT')")

        if context.area:  # not available if other window-type is fullscreen
            context.area.tag_redraw()

        return {'PASS_THROUGH'}

    def invoke(self, context, event):
        if context.area.type != 'VIEW_3D':
            self.report({'WARNING'}, "View3D not found, cannot run operator")
            return {'CANCELLED'}

        # get clashing keymap items
        wm = context.window_manager
        keyconfig = wm.keyconfigs.active
        select = getattr(keyconfig.preferences, "select_mouse", "LEFT")
        kms = [
            bpy.context.window_manager.keyconfigs.active.keymaps['3D View'],
            bpy.context.window_manager.keyconfigs.active.keymaps['Object Mode']
            ]
        kmis = []
        self.left_action = None
        self.right_action = None
        for km in kms:
            for kmi in km.keymap_items:
                if kmi.idname == "transform.translate" and \
                kmi.map_type == 'KEYBOARD' and not \
                kmi.properties.texture_space:
                    kmis.append(kmi)
                    self.transform_key = kmi.type
                elif (kmi.type == 'ACTIONMOUSE' and select == 'RIGHT') \
                and not kmi.alt and not kmi.any and not kmi.ctrl \
                and not kmi.shift:
                    kmis.append(kmi)
                    self.left_action = kmi.idname
                elif kmi.type == 'SELECTMOUSE' and not kmi.alt and not \
                kmi.any and not kmi.ctrl and not kmi.shift:
                    kmis.append(kmi)
                    if select == 'RIGHT':
                        self.right_action = kmi.idname
                    else:
                        self.left_action = kmi.idname
                elif kmi.type == 'LEFTMOUSE' and not kmi.alt and not \
                kmi.any and not kmi.ctrl and not kmi.shift:
                    kmis.append(kmi)
                    self.left_action = kmi.idname

        if not context.window_manager.motion_trail.enabled:
            # enable
            self.active_keyframe = False
            self.active_handle = False
            self.active_timebead = False
            self.active_frame = False
            self.click = {}
            self.drag = False
            self.lock = True
            self.perspective = context.region_data.perspective_matrix
            self.displayed = []
            context.window_manager.motion_trail.force_update = True
            context.window_manager.motion_trail.handle_type_enabled = False
            self.cached = {
                    "path": {}, "keyframes": {},
                    "timebeads_timing": {}, "timebeads_speed": {}
                    }

            for kmi in kmis:
                kmi.active = False

            MotionTrailOperator.handle_add(self, context)
            context.window_manager.motion_trail.enabled = True

            if context.area:
                context.area.tag_redraw()

            context.window_manager.modal_handler_add(self)
            return {'RUNNING_MODAL'}

        else:
            # disable
            for kmi in kmis:
                kmi.active = True
            MotionTrailOperator.handle_remove()
            context.window_manager.motion_trail.enabled = False

            if context.area:
                context.area.tag_redraw()

            return {'FINISHED'}


class MotionTrailPanel(bpy.types.Panel):
    bl_idname = "VIEW3D_PT_motion_trail"
    bl_category = "Animation"
    bl_space_type = 'VIEW_3D'
    bl_region_type = 'UI'
    bl_label = "Motion Trail"
    bl_options = {'DEFAULT_CLOSED'}

    @classmethod
    def poll(cls, context):
        if context.active_object is None:
            return False
        return context.active_object.mode in ('OBJECT', 'POSE')

    def draw(self, context):
        col = self.layout.column()
        if not context.window_manager.motion_trail.enabled:
            col.operator("view3d.motion_trail", text="Enable motion trail")
        else:
            col.operator("view3d.motion_trail", text="Disable motion trail")

        box = self.layout.box()
        box.prop(context.window_manager.motion_trail, "mode")
        # box.prop(context.window_manager.motion_trail, "calculate")
        if context.window_manager.motion_trail.mode == 'timing':
            box.prop(context.window_manager.motion_trail, "timebeads")

        box = self.layout.box()
        col = box.column()
        row = col.row()

        if context.window_manager.motion_trail.path_display:
            row.prop(context.window_manager.motion_trail, "path_display",
                icon="DOWNARROW_HLT", text="", emboss=False)
        else:
            row.prop(context.window_manager.motion_trail, "path_display",
                icon="RIGHTARROW", text="", emboss=False)

        row.label(text="Path options")

        if context.window_manager.motion_trail.path_display:
            col.prop(context.window_manager.motion_trail, "path_style",
                text="Style")
            grouped = col.column(align=True)
            grouped.prop(context.window_manager.motion_trail, "path_width",
                text="Width")
            grouped.prop(context.window_manager.motion_trail,
                "path_transparency", text="Transparency")
            grouped.prop(context.window_manager.motion_trail,
                "path_resolution")
            row = grouped.row(align=True)
            row.prop(context.window_manager.motion_trail, "path_before")
            row.prop(context.window_manager.motion_trail, "path_after")
            col = col.column(align=True)
            col.prop(context.window_manager.motion_trail, "keyframe_numbers")
            col.prop(context.window_manager.motion_trail, "frame_display")

        if context.window_manager.motion_trail.mode == 'location':
            box = self.layout.box()
            col = box.column(align=True)
            col.prop(context.window_manager.motion_trail, "handle_display",
                text="Handles")
            if context.window_manager.motion_trail.handle_display:
                row = col.row()
                row.enabled = context.window_manager.motion_trail.\
                    handle_type_enabled
                row.prop(context.window_manager.motion_trail, "handle_type")


class MotionTrailProps(bpy.types.PropertyGroup):
    def internal_update(self, context):
        context.window_manager.motion_trail.force_update = True
        if context.area:
            context.area.tag_redraw()

    # internal use
    enabled: BoolProperty(default=False)

    force_update: BoolProperty(name="internal use",
        description="Force calc_callback to fully execute",
        default=False)

    handle_type_enabled: BoolProperty(default=False)
    handle_type_frame: FloatProperty()
    handle_type_side: StringProperty()
    handle_type_action_ob: StringProperty()
    handle_type_child: StringProperty()

    handle_type_old: EnumProperty(
            items=(
                ("AUTO", "", ""),
                ("AUTO_CLAMPED", "", ""),
                ("VECTOR", "", ""),
                ("ALIGNED", "", ""),
                ("FREE", "", "")),
            default='AUTO'
            )
    # visible in user interface
    calculate: EnumProperty(name="Calculate", items=(
            ("fast", "Fast", "Recommended setting, change if the "
                             "motion path is positioned incorrectly"),
            ("full", "Full", "Takes parenting and modifiers into account, "
                             "but can be very slow on complicated scenes")),
            description="Calculation method for determining locations",
            default='full',
            update=internal_update
            )
    frame_display: BoolProperty(name="Frames",
            description="Display frames, \n test",
            default=True,
            update=internal_update
            )
    handle_display: BoolProperty(name="Display",
            description="Display handles",
            default=True,
            update=internal_update
            )
    handle_type: EnumProperty(name="Type", items=(
            ("AUTO", "Automatic", ""),
            ("AUTO_CLAMPED", "Auto Clamped", ""),
            ("VECTOR", "Vector", ""),
            ("ALIGNED", "Aligned", ""),
            ("FREE", "Free", "")),
            description="Set handle type for the selected handle",
            default='AUTO',
            update=set_handle_type
            )
    keyframe_numbers: BoolProperty(name="Keyframe numbers",
            description="Display keyframe numbers",
            default=False,
            update=internal_update
            )
    mode: EnumProperty(name="Mode", items=(
            ("location", "Location", "Change path that is followed"),
            ("speed", "Speed", "Change speed between keyframes"),
            ("timing", "Timing", "Change position of keyframes on timeline")),
            description="Enable editing of certain properties in the 3d-view",
            default='location',
            update=internal_update
            )
    path_after: IntProperty(name="After",
            description="Number of frames to show after the current frame, "
                        "0 = display all",
            default=50,
            min=0,
            update=internal_update
            )
    path_before: IntProperty(name="Before",
            description="Number of frames to show before the current frame, "
                        "0 = display all",
            default=50,
            min=0,
            update=internal_update
            )
    path_display: BoolProperty(name="Path options",
            description="Display path options",
            default=True
            )
    path_resolution: IntProperty(name="Resolution",
            description="10 is smoothest, but could be "
                        "slow when adjusting keyframes, handles or timebeads",
            default=10,
            min=1,
            max=10,
            update=internal_update
            )
    path_style: EnumProperty(name="Path style", items=(
            ("acceleration", "Acceleration", "Gradient based on relative acceleration"),
            ("simple", "Simple", "Black line"),
            ("speed", "Speed", "Gradient based on relative speed")),
            description="Information conveyed by path color",
            default='simple',
            update=internal_update
            )
    path_transparency: IntProperty(name="Path transparency",
            description="Determines visibility of path",
            default=0,
            min=0,
            max=100,
            subtype='PERCENTAGE',
            update=internal_update
            )
    path_width: IntProperty(name="Path width",
            description="Width in pixels",
            default=1,
            min=1,
            soft_max=5,
            update=internal_update
            )
    timebeads: IntProperty(name="Time beads",
            description="Number of time beads to display per segment",
            default=5,
            min=1,
            soft_max=10,
            update=internal_update
            )


classes = (
        MotionTrailProps,
        MotionTrailOperator,
        MotionTrailPanel,
        )


def register():
    for cls in classes:
        bpy.utils.register_class(cls)

    bpy.types.WindowManager.motion_trail = PointerProperty(
                                                type=MotionTrailProps
                                                )


def unregister():
    MotionTrailOperator.handle_remove()
    for cls in classes:
        bpy.utils.unregister_class(cls)

    del bpy.types.WindowManager.motion_trail


if __name__ == "__main__":
    register()