UsdLayerManager/openspec/changes/undo-redo-scene-editing/specs/undoable-scene-edits/spec.md

ADDED Requirements

Requirement: Prim creation is undoable

The system SHALL push a CreatePrimCommand to CommandHistory when a prim is created via the scene hierarchy context menu. Undo() SHALL remove the created prim from the stage. Redo() SHALL re-create the prim with the same path and type.

Scenario: Undo removes created prim

• WHEN the user creates a Sphere prim and then presses Ctrl+Z
• THEN the Sphere prim no longer appears in the scene hierarchy

Scenario: Redo re-creates the prim

• WHEN the user undoes a prim creation and then presses Ctrl+Y
• THEN the Sphere prim reappears at the same path with the same type

Requirement: Prim deletion is undoable

The system SHALL push a DeletePrimCommand to CommandHistory when a prim is deleted via the scene hierarchy confirm modal. Before deletion, the command SHALL serialize the prim spec (including all authored opinions on the edit-target layer) to an in-memory string. Undo() SHALL restore the serialized spec to the layer.

Scenario: Undo restores deleted prim

• WHEN the user deletes a prim and then presses Ctrl+Z
• THEN the prim reappears in the scene hierarchy with all its authored attributes intact

Scenario: Redo re-deletes the prim

• WHEN the user undoes a deletion and then presses Ctrl+Y
• THEN the prim is deleted again

Requirement: Add-reference is undoable

The system SHALL push an AddReferenceCommand to CommandHistory when an external USD file is added as a reference. Undo() SHALL remove the reference (and the wrapping Xform prim if it was created by the add-reference operation). Redo() SHALL re-add the reference.

Scenario: Undo removes added reference

• WHEN the user adds a reference to an external file and then presses Ctrl+Z
• THEN the reference prim is removed from the scene hierarchy

Requirement: Replace-reference is undoable

The system SHALL push a ReplaceReferenceCommand to CommandHistory when an existing reference is replaced via the scene hierarchy. Undo() SHALL restore the previous SdfReference. Redo() SHALL apply the replacement again.

Scenario: Undo restores previous reference path

• WHEN the user replaces a reference and then presses Ctrl+Z
• THEN the prim points back to the original reference file