Just Java

There are several misunderstandings related to bounds. (Amy Fowler tried to explain the layout mechanisms some days ago)

There are three bounds that can be used:

• layoutBounds – represent the *logical* bounds used to layout the node
• boundsInLocal – represent the *real* bounds used to paint the node
• boundsInParent – the boundsInLocal transformed to the coordinates of the parent.

And now there is simple stuff you should remember:

layoutBounds are used for layouting (only). They do not have anything to do with boundsInLocal. They are just a logical concept. Sometimes they are the same as the boundsInLocal. Sometimes they are smaller, sometimes larger.

Some examples

layoutBounds == boundsInLocal

This is the case for many very simple nodes. For example a rectangle without any effects like drop shadows.

layoutBounds < boundsInLocal

This is the case for nodes that have some type of effect – for example a drop shadow. That shadow must not be included into the layout. If the layout algorithm used the boundsInLocal (including the drop shadow) the nodes would look misaligned to the human eye.

Aligned using the layoutBounds:

Aligned using the boundsInLocal:

layoutBounds > boundsInLocal

This is the case if some parts of the node are (yet) invisible, but the human eye interpolates them:

If those Pacman like circles are aligned using the boundsInLocal this will result in:

While the human eye expects the alignment to be more like that:

Disclamier:

I know that this post does not contain many (if any) new informations. It is just a little bit shorter. And therefore might be helpful for somebody.