Composite morphs
- Any morph may have or be a submorph.
- Can only be a submorph of one morph ± forms a tree.
- All morphs on the screen are submorphs of a worldMorph.
- The hand is represented by a handMorph
Composite Morphs
A composite morph is a morph that contains other morphs known as submorphs. Note that the terms "composite" and "submorph" refer to roles that can be played by any morph. Submorphs can be added to any kind of morph-even morphs such as circleMorphs or labelMorphs that are atomic in some other systems. Copying, deleting, moving, drawing, and layout operations are applied to the composite morph as a whole.The structure of a composite morph forms a tree. When morph B is a submorph of morph A, B's owner is A and B appears in A's submorphs list. A morph can only be a submorph of at most one morph at a time, so its owner is a single value, not a collection. A window containing a collection of morphs is itself just a morph known as a worldMorph. Each user's cursor is represented by a handMorph. Grabbing a morph with the mouse is implemented by removing the target morph from the worldMorph and adding it to the handMorph. Dropping a morph when the mouse is released is implemented by reversing this process. A handMorph is itself a submorph of its world. The message root can be sent to a morph to get the topmost owner of a composite morph (stopping just short of the worldMorph or handMorph that contains it). If a morph is not a submorph of any morph, its owner is nil.