TBackend.Assign

procedure Assign(Source: TPersistent); override;

Description

Handles copying the source surface defined by the Source parameter to the current instance.
Internally it calls ChangeSize on the current back-end instance to set the new size. Then it copies the content of the source surface to the allocated surface via MoveLongword.
This method is used during switching of the back-end classes in TCustomBitmap32.