13.3: Composing Morphs

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One way of creating new graphical representations is by placing one morph inside another. This is called composition; morphs can be composed to any depth.

You can place a morph inside another by sending the message addMorph: to the container morph.

Try adding a morph to another one:

balloon := BalloonMorph new color: Color yellow.
joe addMorph: balloon.
balloon position: joe position.

The last line positions the balloon at the same coordinates as joe. Notice that the coordinates of the contained morph are still relative to the screen, not to the containing morph. There are many methods available to position a morph; browse the geometry protocol of class Morph to see for yourself. For example, to center the balloon inside joe, execute balloon center: joe center.

If you now try to grab the balloon with the mouse, you will find that you actually grab joe, and the two morphs move together: the balloon is embedded inside joe. It is possible to embed more morphs inside joe. In addition to doing this programmatically, you can also embed morphs by direct manipulation.

The balloon inside the joe morph. — Figure \(\PageIndex{1}\): The balloon is contained inside joe, the translucent orange morph.