Overcome a limitation of binding data variables to checkboxes

Source/Core/DataControllerDefault.cpp

@@ -35,18 +35,17 @@
 
 namespace Rml {
 
-DataControllerValue::DataControllerValue(Element* element) : DataController(element)
+DataControllerAttributeBased::DataControllerAttributeBased(Element* element, String attribute)
+	: DataController(element), attribute(std::move(attribute))
 {}
 
-DataControllerValue::~DataControllerValue()
+DataControllerAttributeBased::~DataControllerAttributeBased()
 {
 	if (Element* element = GetElement())
-	{
 		element->RemoveEventListener(EventId::Change, this);
-	}
 }
 
-bool DataControllerValue::Initialize(DataModel& model, Element* element, const String& variable_name, const String& /*modifier*/)
+bool DataControllerAttributeBased::Initialize(DataModel& model, Element* element, const String& variable_name, const String& /*modifier*/)
 {
 	RMLUI_ASSERT(element);
 
@@ -62,74 +61,40 @@ bool DataControllerValue::Initialize(DataModel& model, Element* element, const S
 	return true;
 }
 
-void DataControllerValue::ProcessEvent(Event& event)
+void DataControllerAttributeBased::ProcessEvent(Event& event)
 {
-	if (Element* element = GetElement())
+	if (const Element* element = GetElement())
 	{
 		const auto& parameters = event.GetParameters();
-
-		auto it = parameters.find("value");
-		if (it == parameters.end())
+		const auto it = parameters.find(attribute);
+		if (it == parameters.cend())
 		{
-			Log::Message(Log::LT_WARNING, "A 'change' event was received, but it did not contain a value. During processing of 'data-value' in %s", element->GetAddress().c_str());
+			Log::Message(Log::LT_WARNING, "A 'change' event was received, but it did not contain the attribute '%s' when processing 'data-%s' in %s",
+				attribute.c_str(), attribute.c_str(), element->GetAddress().c_str());
 			return;
 		}
 
+		const auto affected_it = parameters.find("should_affect_data_binding");
+		if (affected_it != parameters.cend() && !affected_it->second.Get<bool>())
+			return;
+
 		DataModel* model = element->GetDataModel();
 		if (!model)
 			return;
 
 		if (DataVariable variable = model->GetVariable(address))
 		{
-			if (SetValue(it->second, variable))
+			if (variable.Set(it->second))
 				model->DirtyVariable(address.front().name);
 		}
 	}
 }
 
-void DataControllerValue::Release()
+void DataControllerAttributeBased::Release()
 {
 	delete this;
 }
 
-bool DataControllerValue::SetValue(const Variant& value, DataVariable variable)
-{
-	return variable.Set(value);
-}
-
-
-DataControllerChecked::DataControllerChecked(Element* element) : DataControllerValue(element)
-{}
-
-
-bool DataControllerChecked::SetValue(const Variant& value, DataVariable variable)
-{
-	bool result = false;
-	Variant old_value;
-
-	if (variable.Get(old_value))
-	{
-		// Value will be empty if the button was just unchecked, otherwise it will take the 'value' attribute.
-		const String new_value = value.Get<String>();
-
-		if (old_value.GetType() == Variant::BOOL)
-		{
-			// If the client variable is a boolean type, we assume the button acts like a checkbox, and set the new checked state.
-			result = variable.Set(Variant(!new_value.empty()));
-		}
-		else
-		{
-			// Otherwise, we assume the button acts like a radio box. Then, we do nothing if the box was unchecked,
-			// and instead let only the newly checked box set the new value.
-			if (!new_value.empty())
-				result = variable.Set(value);
-		}
-	}
-
-	return result;
-}
-
-
 
 DataControllerEvent::DataControllerEvent(Element* element) : DataController(element)
 {}

Source/Core/DataControllerDefault.h

@@ -42,33 +42,37 @@ class DataModel;
 class DataExpression;
 using DataExpressionPtr = UniquePtr<DataExpression>;
 
-
-class DataControllerValue : public DataController, private EventListener {
+class DataControllerAttributeBased : public DataController, private EventListener {
 public:
-    DataControllerValue(Element* element);
-    ~DataControllerValue();
+    DataControllerAttributeBased(Element* element, String attribute);
+    ~DataControllerAttributeBased();
 
     bool Initialize(DataModel& model, Element* element, const String& expression, const String& modifier) override;
 
-protected:
+private:
     // Responds to 'Change' events.
     void ProcessEvent(Event& event) override;
 
     // Delete this.
     void Release() override;
 
-    // Set the new value on the variable, returns true if it should be dirtied.
-    virtual bool SetValue(const Variant& new_value, DataVariable variable);
-
     DataAddress address;
+    String attribute;
 };
 
 
-class DataControllerChecked final : public DataControllerValue {
+class DataControllerAttributeBasedInstancer final : public DataControllerInstancer {
 public:
-    DataControllerChecked(Element* element);
+    DataControllerAttributeBasedInstancer(String attribute)
+        : attribute(std::move(attribute))
+    {}
+
+    DataControllerPtr InstanceController(Element* element) override {
+        return DataControllerPtr(new DataControllerAttributeBased(element, attribute));
+    }
 
-    bool SetValue(const Variant& new_value, DataVariable variable) override;
+private:
+    String attribute;
 };
 
 

Source/Core/Elements/InputTypeCheckbox.cpp

@@ -48,15 +48,16 @@ bool InputTypeCheckbox::IsSubmitted()
 // Checks for necessary functional changes in the control as a result of changed attributes.
 bool InputTypeCheckbox::OnAttributeChange(const ElementAttributes& changed_attributes)
 {
-	// Check if maxlength has been defined.
-	if (changed_attributes.find("checked") != changed_attributes.end())
+	if (changed_attributes.count("checked"))
 	{
-		bool checked = element->HasAttribute("checked");
+		const bool checked = element->HasAttribute("checked");
 		element->SetPseudoClass("checked", checked);
 
-		Dictionary parameters;
-		parameters["value"] = String(checked ? GetValue() : "");
-		element->DispatchEvent(EventId::Change, parameters);
+		const auto value = GetValue();
+		element->DispatchEvent(EventId::Change, {
+			{ "checked", Variant(checked) },
+			{ "value", Variant(checked ? (value.empty() ? "on" : value) : "") }
+		});
 	}
 
 	return true;
@@ -65,8 +66,7 @@ bool InputTypeCheckbox::OnAttributeChange(const ElementAttributes& changed_attri
 // Checks for necessary functional changes in the control as a result of the event.
 void InputTypeCheckbox::ProcessDefaultAction(Event& event)
 {
-	if (event == EventId::Click &&
-		!element->IsDisabled())
+	if (event == EventId::Click && !element->IsDisabled())
 	{
 		if (element->HasAttribute("checked"))
 			element->RemoveAttribute("checked");

Source/Core/Elements/InputTypeRadio.cpp

@@ -52,18 +52,20 @@ bool InputTypeRadio::IsSubmitted()
 // Checks for necessary functional changes in the control as a result of changed attributes.
 bool InputTypeRadio::OnAttributeChange(const ElementAttributes& changed_attributes)
 {
-	// Check if maxlength has been defined.
-	if (changed_attributes.find("checked") != changed_attributes.end())
+	if (changed_attributes.count("checked"))
 	{
 		bool checked = element->HasAttribute("checked");
 		element->SetPseudoClass("checked", checked);
 
 		if (checked)
 			PopRadioSet();
 
-		Dictionary parameters;
-		parameters["value"] = String(checked ? GetValue() : "");
-		element->DispatchEvent(EventId::Change, parameters);
+		const auto perceived_value = Variant(checked ? GetValue() : "");
+		element->DispatchEvent(EventId::Change, {
+			{ "checked", perceived_value },
+			{ "should_affect_data_binding", Variant(checked) },
+			{ "value", perceived_value }
+		});
 	}
 
 	return true;
@@ -79,8 +81,7 @@ void InputTypeRadio::OnChildAdd()
 // Checks for necessary functional changes in the control as a result of the event.
 void InputTypeRadio::ProcessDefaultAction(Event& event)
 {
-	if (event == EventId::Click &&
-		!element->IsDisabled())
+	if (event == EventId::Click && !element->IsDisabled())
 		element->SetAttribute("checked", "");
 }
 

Source/Core/Factory.cpp

@@ -186,9 +186,9 @@ struct DefaultInstancers {
 	DataViewInstancerDefault<DataViewFor> structural_data_view_for;
 
 	// Data binding controllers
-	DataControllerInstancerDefault<DataControllerValue> data_controller_value;
+	DataControllerAttributeBasedInstancer data_controller_checked { "checked" };
 	DataControllerInstancerDefault<DataControllerEvent> data_controller_event;
-	DataControllerInstancerDefault<DataControllerChecked> data_controller_checked;
+	DataControllerAttributeBasedInstancer data_controller_value { "value" };
 };
 
 static UniquePtr<DefaultInstancers> default_instancers;
@@ -279,9 +279,9 @@ bool Factory::Initialise()
 	RegisterDataViewInstancer(&default_instancers->structural_data_view_for, "for",     true );
 
 	// Data binding controllers
-	RegisterDataControllerInstancer(&default_instancers->data_controller_value, "value");
-	RegisterDataControllerInstancer(&default_instancers->data_controller_event, "event");
 	RegisterDataControllerInstancer(&default_instancers->data_controller_checked, "checked");
+	RegisterDataControllerInstancer(&default_instancers->data_controller_event, "event");
+	RegisterDataControllerInstancer(&default_instancers->data_controller_value, "value");
 
 	// XML node handlers
 	XMLParser::RegisterNodeHandler("", MakeShared<XMLNodeHandlerDefault>());