blender bpy监听数值变化的4种方法

适用于blender≥4.5.0

bpy.app.handlers

https://docs.blender.org/api/current/bpy.app.handlers.html#bpy.app.handlers.depsgraph_update_post
如加载文件等hooks可以用这个。

def on_update(scene, depsgraph): ... # 监听依赖图更新
def register():
    bpy.app.handlers.depsgraph_update_post.append(on_update)
def unregister():
    bpy.app.handlers.depsgraph_update_post.remove(on_update)

消息总线 bpy.msgbus.subscribe_rna

https://docs.blender.org/api/current/bpy.msgbus.html#bpy.msgbus.subscribe_rna
当app.handers无效时使用。频繁会变动的属性（如当前选择的物体active_obj）就会用到这个。

OWNER = object()
def on_change(): ...
@bpy.app.handlers.persistent
def register_msgbus():
    bpy.msgbus.clear_by_owner(OWNER)
    bpy.msgbus.subscribe_rna(
        key=(bpy.types.LayerObjects, "active"),
        owner=OWNER,
        args=(),
        notify=on_change
    )
def register():
    bpy.app.handlers.load_post.append(register_msgbus)
def unregister():
    bpy.app.handlers.load_post.remove(register_msgbus)

UI更改 bl_ui.space_toolsystem_common.item_from_id.handlers.set.append

https://archive.blender.org/developer/D10635

modal()

最复杂，最灵活，且modal在持续运行时会禁用自动保存。我用modal()+yield Gernator实现了一个暂停可恢复的Operator，用于耗时操作（如fk转ik)

class Operator(bpy.types.Operator):
    def modal(self, context):
        ...