Control models usually have some kind of value property, which reflects the very current
content of the controls associated with this model. For instance, for an
::com::sun::star::form::component::TextField, this would be the
::com::sun::star::awt::UnoControlEditModel::Text property of the base
service. Similarily, a ::com::sun::star::form::component::CheckBox has
a property ::com::sun::star::awt::UnoControlCheckBoxModel::State, which
reflects the current check state.
Usual ::com::sun::star::form::DataAwareControlModels can be bound to
a column of a ::com::sun::star::form::component::DataForm, and exchange
their content with such a column.
In particular, when the ::com::sun::star::form::component::DataForm
is moved to a different record, then the bound control model is updated with the value of
it's column in this particular row.
On the other hand, when any change in the control model (e.g. resulting from a user entering
data in a control associated with the control model) is committed
(::com::sun::star::form::XBoundComponent::commit), then the actual
data of the control model is written into the associated
::com::sun::star::form::component::DataForm column.
BindableDataAwareControlModel's additionally support an alternative value
binding, which forces them to exchange their value with another foreign instance.
In some sense, they are an abstraction of the data aware control models, which only
support a specialized, hard-coded value binding (namely the binding to a
::com::sun::star::form::component::DataForm column).
For this, they provide the XBindableValue interface which allows to
set an external component to exchange the value with.
The following rules apply when a data aware control model is bound to an external value binding:
- Priority
External value bindings overrule any active SQL-column binding. If an external
component is bound to a control model which currently has an active SQL binding,
this SQL binding is suspended, until the external binding is revoked.
- Activation
An external value binding becomes effective as soon as it is set. This is a
difference to SQL bindings, which only are effective when the parent form
of the control model is loaded (::com::sun::star::form::XLoadable).
- Immediacy
When a BindableDataAwareControlModel is bound to an external value,
then every change in the control model's value is immediately reflected
in the external binding. This is a difference to SQL bindings of most
::com::sun::star::form::DataAwareControlModel's, where changes
in the control model's value are only propagated to the bound column upon explicit
request via ::com::sun::star::form::XBoundComponent::commit.
Note that this restriction is inherited from the BindableControlModel.
- Cloning
::com::sun::star::form::FormControlModels support cloning themself
via the ::com::sun::star::util::XCloneable interface which they
inherit from the ::com::sun::star::awt::UnoControlModel service.
When a BindableDataAwareControlModel is cloned while it has an active
external value binding, then the clone is also bound to the same binding instance.
Note that this restriction is inherited from the BindableControlModel.
When a BindableDataAwareControlModel is being bound to an external value,
using XBindableValue::setValueBinding,
then the control model (it's value property, respectively) and the external value are
initially synchronized by setting the external value (XValueBinding::getValue)
at the control model.
