// Given a multi data trigger and associated context information,
// evaluate the old and new states of the trigger.
// The short-circuit logic of multi property trigger applies here too.
// we bail if any of the "other" conditions evaluate to false.
private static void EvaluateOldNewStates( MultiDataTrigger multiDataTrigger,
DependencyObject triggerContainer,
BindingBase binding, BindingValueChangedEventArgs changedArgs, UncommonField<HybridDictionary[]> dataField,
Style style, FrameworkTemplate frameworkTemplate,
out bool oldState, out bool newState )
{
BindingBase evaluationBinding = null;
object evaluationValue = null;
TriggerCondition[] conditions = multiDataTrigger.TriggerConditions;
// Set up the default condition: A trigger with no conditions will never evaluate to true.
oldState = false;
newState = false;
for( int i = 0; i < multiDataTrigger.Conditions.Count; i++ )
{
evaluationBinding = conditions[i].Binding;
Debug.Assert( evaluationBinding != null,
"A null binding was encountered in a MultiDataTrigger conditions collection - this is invalid input and should have been caught earlier.");
if( evaluationBinding == binding )
{
// The binding that changed belonged to the current condition.
oldState = conditions[i].ConvertAndMatch(changedArgs.OldValue);
newState = conditions[i].ConvertAndMatch(changedArgs.NewValue);
if( oldState == newState )
{
// There couldn't possibly be a transition here, abort. The
// returned values here aren't necessarily the state of the
// triggers, but we only care about a transition today. If
// we care about actual values, we'll need to continue evaluation.
return;
}
}
else
{
evaluationValue = GetDataTriggerValue(dataField, triggerContainer, evaluationBinding);
if( !conditions[i].ConvertAndMatch(evaluationValue) )
{
// A condition other than the one changed has evaluated to false.
// There couldn't possibly be a transition here, short-circuit and abort.
oldState = false;
newState = false;
return;
}
}
}
// We should only get this far only if the binding change causes
// a true->false (or vice versa) transition in one of the conditions,
// AND that every other condition evaluated to true.
return;
}
// Given a Style/Template and a Binding whose value has changed, look for
// any data triggers that have trigger actions (EnterAction/ExitAction)
// and see if any of those actions need to run as a response to this change.
private static void InvokeApplicableDataTriggerActions(
Style style,
FrameworkTemplate frameworkTemplate,
DependencyObject container,
BindingBase binding,
BindingValueChangedEventArgs e,
UncommonField<HybridDictionary[]> dataField)
{
HybridDictionary dataTriggersWithActions;
if( style != null )
{
dataTriggersWithActions = style.DataTriggersWithActions;
}
else if( frameworkTemplate != null )
{
dataTriggersWithActions = frameworkTemplate.DataTriggersWithActions;
}
else
{
dataTriggersWithActions = null;
}
if( dataTriggersWithActions != null )
{
object candidateTrigger = dataTriggersWithActions[binding];
if( candidateTrigger != null )
{
// One or more trigger objects need to be evaluated. The candidateTrigger
// object may be a single trigger or a collection of them.
TriggerBase triggerBase = candidateTrigger as TriggerBase;
if( triggerBase != null )
{
InvokeDataTriggerActions( triggerBase, container, binding, e,
style, frameworkTemplate, dataField);
}
else
{
Debug.Assert(candidateTrigger is List<TriggerBase>, "Internal data structure error: The HybridDictionary [Style/Template].DataTriggersWithActions " +
"is expected to hold a single TriggerBase or a List<T> of them. An object of type " +
candidateTrigger.GetType().ToString() + " is not expected. Where did this object come from?");
List<TriggerBase> triggerList = (List<TriggerBase>)candidateTrigger;
for( int i = 0; i < triggerList.Count; i++ )
{
InvokeDataTriggerActions( triggerList[i], container, binding, e,
style, frameworkTemplate, dataField);
}
}
}
}
}
//
// This method
// 1. Is Invoked when a binding in a condition of a data trigger changes its value.
// 2. When this happens we must invalidate all its dependents
//
private static void OnBindingValueInThemeStyleChanged(object sender, BindingValueChangedEventArgs e)
{
BindingExpressionBase bindingExpr = (BindingExpressionBase)sender;
BindingBase binding = bindingExpr.ParentBindingBase;
DependencyObject container = bindingExpr.TargetElement;
FrameworkElement fe;
FrameworkContentElement fce;
Helper.DowncastToFEorFCE(container, out fe, out fce, false);
Style style = (fe != null) ? fe.ThemeStyle : fce.ThemeStyle;
// Look for data trigger Setter information - invalidate the associated
// properties if found.
HybridDictionary dataTriggerRecordFromBinding = style._dataTriggerRecordFromBinding;
if( dataTriggerRecordFromBinding != null &&
!bindingExpr.IsAttaching ) // Don't invalidate in the middle of attaching - effective value will be updated elsewhere in Style application code.
{
DataTriggerRecord record = (DataTriggerRecord)dataTriggerRecordFromBinding[binding];
if (record != null) // triggers with no setters (only actions) don't appear in the table
{
InvalidateDependents(style, null, container, null, ref record.Dependents, false);
}
}
// Look for any applicable trigger EnterAction or ExitAction
InvokeApplicableDataTriggerActions(style, null, container, binding, e, ThemeStyleDataField);
}
// Given a single data trigger and associated context information,
// evaluate the old and new states of the trigger.
private static void EvaluateOldNewStates( DataTrigger dataTrigger,
DependencyObject triggerContainer,
BindingBase binding, BindingValueChangedEventArgs bindingChangedArgs, UncommonField<HybridDictionary[]> dataField,
Style style, FrameworkTemplate frameworkTemplate,
out bool oldState, out bool newState )
{
TriggerCondition[] conditions = dataTrigger.TriggerConditions;
Debug.Assert( conditions != null && conditions.Length == 1,
"This method assumes there is exactly one TriggerCondition." );
oldState = conditions[0].ConvertAndMatch(bindingChangedArgs.OldValue);
newState = conditions[0].ConvertAndMatch(bindingChangedArgs.NewValue);
}
// This is expected to be called when a Binding for a DataTrigger has
// changed and we need to look for true/false transitions. If found,
// invoke EnterAction (or ExitAction) as needed.
private static void InvokeDataTriggerActions( TriggerBase triggerBase,
DependencyObject triggerContainer, BindingBase binding, BindingValueChangedEventArgs bindingChangedArgs,
Style style, FrameworkTemplate frameworkTemplate,
UncommonField<HybridDictionary[]> dataField)
{
bool oldState;
bool newState;
DataTrigger dataTrigger = triggerBase as DataTrigger;
if( dataTrigger != null )
{
EvaluateOldNewStates( dataTrigger, triggerContainer,
binding, bindingChangedArgs, dataField,
style, frameworkTemplate,
out oldState, out newState );
}
else
{
Debug.Assert( triggerBase is MultiDataTrigger,
"This method only handles DataTrigger and MultiDataTrigger. Other types should have been handled elsewhere." );
EvaluateOldNewStates( (MultiDataTrigger)triggerBase, triggerContainer,
binding, bindingChangedArgs, dataField,
style, frameworkTemplate,
out oldState, out newState );
}
InvokeEnterOrExitActions( triggerBase, oldState, newState, triggerContainer,
style, frameworkTemplate );
}
