Select null-selection badly broken

[Marc Englund]

setNullSelectionItemId() is not sufficient for handling all cases, or even the most usual ones.

AFAIK:

• there is no easy/sane way to make a (dropdown) single select that does not have a null selection ("-") <- major problem!!!
• setNullSelectionItemId() is supposed to make it possible to select null (no selection) even if the datasource has no null - but this implicitly makes the nullselectionitem unselectable

Thoughts:

• Add setNullSelectionAllowed(Boolean allowed) and setNullSelection(String caption, Resource icon) to Select.
• The nullselection -item is only added to the select, not the datasource.
• Null selection is not allowed if setNullSelectionAllowed() is not set.
• setNullSelectionAllowed() might not be needed since setNullSelection() implies this. However, this might be weird in some cases (table has no visible null-item).
• Some singleselects (dropdown,optiongroup) should render the caption (and icon) specified, or a default "-" if no caption is specified.
• Some singleselects should not render the caption (table allows deselecting row instead).
• Multiselects should dissallow deselecting the last item when null selection is not allowed (or always allow null selection). No special null-selection-item should be added (in either case).
• The value of the select should never be null if null selection is not allowed - it should autoselect first item if needed, when needed.
• remove setNullSelectionItemId() - it should not be needed.

This is potentially controversial - requires API change, but is imo sufficiently broken to warrant this.

[Marc Englund]

Also see #427 (might be a container problem, however - please check)

[Marc Englund]

IMPORTANT: inform -removed- team when this is fixed; renderSelect is overridden in -removed- theme - it autoselects first item if nothing is selected, and does not render "-" automatically.

[Jani Laakso]

Known issue suggestion: There is afaik no sane way to make a dropdown-select that does not allow null selection.

[Jani Laakso]

Marc, use cc field if you wish to inform others (e.g. -removed- team) of the progress of this ticket.

[Jani Laakso]

Milestone 4.0 Candidates for next release deleted

[Matti Tahvonen]

These issues ought to be resolved for first 5.0 release.

[Matti Tahvonen]

(last issue was fixed in trees at [2719]