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Diffstat (limited to 'doc/python_api/rst/info_gotcha.rst')
| -rw-r--r-- | doc/python_api/rst/info_gotcha.rst | 26 |
1 files changed, 24 insertions, 2 deletions
diff --git a/doc/python_api/rst/info_gotcha.rst b/doc/python_api/rst/info_gotcha.rst index 0713ffa54a1..eb5cc143a2c 100644 --- a/doc/python_api/rst/info_gotcha.rst +++ b/doc/python_api/rst/info_gotcha.rst @@ -677,7 +677,8 @@ Here are some general hints to avoid running into these problems: Undo/Redo --------- -Undo invalidates all :class:`bpy.types.ID` instances (Object, Scene, Mesh, Light, etc.). +For safety, you should assume that undo and redo always invalidates all :class:`bpy.types.ID` +instances (Object, Scene, Mesh, Light, etc.), as weel obviously as all of their sub-data. This example shows how you can tell undo changes the memory locations: @@ -686,7 +687,7 @@ This example shows how you can tell undo changes the memory locations: >>> hash(bpy.context.object) -9223372036849950810 -Move the active object, then undo: +Delete the active object, then undo: >>> hash(bpy.context.object) -9223372036849951740 @@ -695,6 +696,16 @@ As suggested above, simply not holding references to data when Blender is used interactively by the user is the only way to make sure that the script doesn't become unstable. +.. note:: + + Modern undo/redo system does not systematically invalidate all pointers anymore. + Some data (in fact, most data, in typical cases), which were detected as unchanged for a + particular history step, may remain unchanged and hence their pointers may remain valid. + + Be aware that if you want to take advantage of this behavior for some reason, there is no + guarantee of any kind that it will be safe and consistent. Use it at your own risk. + + Undo & Library Data ^^^^^^^^^^^^^^^^^^^ @@ -712,6 +723,17 @@ So it's best to consider modifying library data an advanced usage of the API and only to use it when you know what you're doing. +Abusing RNA property callbacks +------------------------------ + +Python-defined RNA properties can have custom callbacks. Trying to perform complex operations +from there, like calling an operator, may work, but is not officialy recommended nor supported. + +Main reason is that those callback should be very fast, but additionally, it may for example +create issues with undo/redo system (most operators store an history step, and editing an RNA +property does so as well), trigger infinite update loops, and so on. + + Edit-Mode / Memory Access ------------------------- |