simvx.core.undo

Undo/redo system using the Command pattern.

Provides an UndoStack that tracks reversible operations, with pre-built command types for property changes, arbitrary callables, and batched operations.

Example: stack = UndoStack() cmd = PropertyCommand(node, “position”, (0, 0, 0), (1, 2, 3), description=”Move node”) stack.push(cmd) # executes + records stack.undo() # reverts to (0, 0, 0) stack.redo() # re-applies (1, 2, 3)

Module Contents

Classes

Command	Interface for undoable operations.
PropertyCommand	Sets obj.attr to new_value; undoes by restoring old_value.
CallableCommand	Wraps a do_fn / undo_fn pair as a command.
BatchCommand	Groups several commands into a single undo step.
AddChildCommand	Add child under parent. Undo removes the child.
RemoveChildCommand	Remove child from parent. Undo re-adds at the original index.
ReparentCommand	Move node from old_parent to new_parent. Undo restores both the original parent and the original sibling order via old_index.
UndoStack	Maintains undo and redo history with an optional size limit.

Data

log

API

simvx.core.undo.log

‘getLogger(…)’

class simvx.core.undo.Command

Bases: typing.Protocol

Interface for undoable operations.

property description: str

execute() → None

undo() → None

__slots__

()

classmethod __init_subclass__(*args, **kwargs)

classmethod __class_getitem__(item)

class simvx.core.undo.PropertyCommand(obj: Any, attr: str, old_value: Any, new_value: Any, description: str = '')

Sets obj.attr to new_value; undoes by restoring old_value.

Initialization

property description: str

execute() → None

undo() → None

class simvx.core.undo.CallableCommand(do_fn: collections.abc.Callable[[], None], undo_fn: collections.abc.Callable[[], None], description: str = '')

Wraps a do_fn / undo_fn pair as a command.

Initialization

property description: str

execute() → None

undo() → None

class simvx.core.undo.BatchCommand(commands: collections.abc.Sequence[simvx.core.undo.Command], description: str = '')

Groups several commands into a single undo step.

Commands are executed in order and undone in reverse order.

Initialization

property description: str

execute() → None

undo() → None

class simvx.core.undo.AddChildCommand(parent: Any, child: Any, index: int = -1, description: str = '')

Add child under parent. Undo removes the child.

If index is provided (>= 0), the child is moved to that slot after the append so order is preserved on redo.

Initialization

property description: str

execute() → None

undo() → None

class simvx.core.undo.RemoveChildCommand(parent: Any, child: Any, description: str = '')

Remove child from parent. Undo re-adds at the original index.

The original index is captured at construction so the undo always restores the exact slot: even if siblings have shifted by the time the undo runs.

Initialization

property description: str

execute() → None

undo() → None

class simvx.core.undo.ReparentCommand(node: Any, new_parent: Any, old_parent: Any, old_index: int, description: str = '')

Move node from old_parent to new_parent. Undo restores both the original parent and the original sibling order via old_index.

Initialization

property description: str

execute() → None

undo() → None

class simvx.core.undo.UndoStack(max_size: int = 100)

Maintains undo and redo history with an optional size limit.

Parameters

max_size: Maximum number of commands kept in the undo history. When exceeded the oldest entry is silently dropped. Defaults to 100.

Initialization

push(command: simvx.core.undo.Command) → None

Execute command and record it on the undo stack.

push_without_execute(command: simvx.core.undo.Command) → None

Record command on the undo stack without executing it.

Use for operations whose effect has already been applied directly (e.g. gizmo drag, where intermediate frames mutated state). The command’s undo() must still restore the pre-operation state.

undo() → bool

Undo the most recent command. Returns True if an action was undone.

redo() → bool

Redo the most recently undone command. Returns True if an action was redone.

clear() → None

Discard all undo and redo history.

property can_undo: bool

property can_redo: bool

property undo_description: str | None

Description of the next action that would be undone, or None.

property redo_description: str | None

Description of the next action that would be redone, or None.

property max_size: int