Node selection

Node selection is always enabled in FWTreeView but it is not always shown. The CSS that comes with FWTreeView provides for checkboxes to show selection. The developer may choose to show them in a different manner. To make them visible, the container should have the CSS class name `yui3-fw-treeview-checkbox`, like:

The example above uses the same code as the basic example to show the tree but the class name on the container makes the selection checkboxes visible.

Clicking on the checkboxes or pressing the space bar when the a node has the focus changes the selected state of the node.

FWTreeView optionally supports propagation of selection. Selecting a node may select all its descendants while, at the same time, it may affect its ancestors. This is controlled by the `propagateUp` and `propagateDown` attributes and to see it at work, the example has two checkboxes below the tree to change the state of these two attributes.

When `propagateUp` is enabled, changing the selected state of a node will make the parent recalculate its selected state. If all its children are selected, it will become selected. If none of its children is selected, it will not be selected. If there is a mix of selected and unselected nodes, it will become partially selected.

The `Show Selected` button shows the labels of the nodes that are fully or partially selected with the value of the `selected` attribute. It will be 1 for those partially selected and 2 for fully selected. The `selected` attribute can return three values, 0, 1 or 2 while when setting however, the developer cannot force a node to have a 1 state, it can only be the result of propagation. On setting the `selected` attribute, any falsy value will make it 0, any thruthy value will make it 2.

See the basic example for the code to draw the tree. This extra code has been added to respond to the changes in setting propagation and showing the data from the tree: