Standard delegate class for rendering a view item. More...

#include <Wt/WItemDelegate.h>

Inheritance diagram for Wt::WItemDelegate:

Public Member Functions
	WItemDelegate ()
	Create an item delegate.

virtual std::unique_ptr< WWidget >	update (WWidget *widget, const WModelIndex &index, WFlags< ViewItemRenderFlag > flags) override
	Creates or updates a widget that renders an item. More...

virtual void	updateModelIndex (WWidget *widget, const WModelIndex &index) override
	Updates the model index of a widget. More...

void	setTextFormat (const WString &format)
	Sets the text format string. More...

const WString &	textFormat () const
	Returns the text format string. More...

virtual void	setModelData (const cpp17::any &editState, WAbstractItemModel *model, const WModelIndex &index) const override
	Saves the edited data to the model. More...

virtual cpp17::any	editState (WWidget *editor, const WModelIndex &index) const override
	Returns the current edit state. More...

virtual void	setEditState (WWidget *editor, const WModelIndex &index, const cpp17::any &value) const override
	Sets the editor data from the editor state. More...

Public Member Functions inherited from Wt::WAbstractItemDelegate
	WAbstractItemDelegate ()
	Constructor.

virtual	~WAbstractItemDelegate ()
	Destructor.

virtual ValidationState	validate (const WModelIndex &index, const cpp17::any &editState) const
	Returns whether the edited value is valid. More...

Signal< WWidget *, bool > &	closeEditor ()
	Signal which indicates that an editor needs to be closed. More...

const Signal< WWidget *, bool > &	closeEditor () const
	Signal which indicates that an editor needs to be closed. More...

Public Member Functions inherited from Wt::WObject
void	addChild (std::unique_ptr< WObject > child)
	Add a child WObject whose lifetime is determined by this WObject.

template<typename Child >
Child *	addChild (std::unique_ptr< Child > child)
	Add a child WObject, returning a raw pointer. More...

std::unique_ptr< WObject >	removeChild (WObject *child)
	Remove a child WObject, so its lifetime is no longer determined by this WObject.

template<typename Child >
std::unique_ptr< Child >	removeChild (Child *child)
	Remove a child WObject, so its lifetime is no longer determined by this WObject. More...

virtual const std::string	id () const
	Returns the (unique) identifier for this object. More...

virtual void	setObjectName (const std::string &name)
	Sets an object name. More...

virtual std::string	objectName () const
	Returns the object name. More...

void	resetLearnedSlots ()
	Resets learned stateless slot implementations. More...

template<class T >
void	resetLearnedSlot (void(T::*method)())
	Resets a learned stateless slot implementation. More...

template<class T >
WStatelessSlot *	implementStateless (void(T::*method)())
	Declares a slot to be stateless and learn client-side behaviour on first invocation. More...

template<class T >
WStatelessSlot *	implementStateless (void(T::method)(), void(T::undoMethod)())
	Declares a slot to be stateless and learn client-side behaviour in advance. More...

void	isNotStateless ()
	Marks the current function as not stateless. More...

template<class T >
WStatelessSlot *	implementJavaScript (void(T::*method)(), const std::string &jsCode)
	Provides a JavaScript implementation for a method. More...

Public Member Functions inherited from Wt::Core::observable
	observable () noexcept
	Default constructor.

virtual	~observable ()
	Destructor. More...

template<typename... Args, typename C >
auto	bindSafe (void(C::*method)(Args...)) noexcept
	Protects a method call against object destruction. More...

template<typename... Args, typename C >
auto	bindSafe (void(C::*method)(Args...) const) const noexcept
	Protects a const method call against object destruction. More...

template<typename Function >
auto	bindSafe (const Function &function) noexcept
	Protects a function against object destruction. More...

Protected Member Functions
virtual std::unique_ptr< WWidget >	createEditor (const WModelIndex &index, WFlags< ViewItemRenderFlag > flags) const
	Creates an editor for a data item. More...

Protected Member Functions inherited from Wt::WObject
virtual WStatelessSlot *	getStateless (Method method)
	On-demand stateless slot implementation. More...

Additional Inherited Members
Public Types inherited from Wt::WObject
typedef void(WObject::*	Method) ()
	Typedef for a WObject method without arguments.

Detailed Description

Standard delegate class for rendering a view item.

This class provides the standard implementation for rendering an item (as in a WAbstractItemView), and renders data provided by the standard data roles (see ItemDataRole). It also provides default editing support using a line edit.

You may provide special editing support for an item by specializing the widget and reimplement createEditor(), setModelData(), editState(), and setEditState().

Member Function Documentation

◆ createEditor()

std::unique_ptr< WWidget > Wt::WItemDelegate::createEditor	(	const WModelIndex &	index,
		WFlags< ViewItemRenderFlag >	flags
	)		const

protectedvirtual

Creates an editor for a data item.

The default implementation returns a WLineEdit which edits the item's Wt::ItemDataRole::Edit value.

You may reimplement this method to provide a suitable editor, or to attach a custom validator. In that case, you will probably also want to reimplement editState(), setEditState(), and setModelData().

The editor should not keep a reference to the model index (it does not need to since setModelData() will provide the proper model index to save the data to the model). Otherwise, because model indexes may shift because of row or column insertions, you should reimplement updateModelIndex().

As an example of how to provide a specialized editor, consider the default implementation, which returns a WLineEdit:

std::unique_ptr<Wt::WWidget> WItemDelegate::createEditor(const Wt::WModelIndex& index, WFlags<ViewItemRenderFlag> flags) const
{
  auto result = std::make_unique<Wt::WContainerWidget>();
  result->setSelectable(true);
 
  auto lineEdit = std::make_unique<Wt::WLineEdit>();
  lineEdit->setText(asString(index.data(ItemDataRole::Edit), textFormat_));
  lineEdit->enterPressed().connect(std::bind(&WItemDelegate::doCloseEditor, this, result, true));
  lineEdit->escapePressed().connect(std::bind(&WItemDelegate::doCloseEditor, this, result, false));
 
  if (flags.test(ViewItemRenderFlag::Focused))
    lineEdit->setFocus();
 
  // We use a layout so that the line edit fills the entire cell.
  result->setLayout(std::make_unique<WHBoxLayout>());
  result->layout()->setContentsMargins(1, 1, 1, 1);
  result->layout()->addWidget(std::move(lineEdit));
 
  return result;
}
 
void WItemDelegate::doCloseEditor(Wt::WWidget *editor, bool save) const
{
  closeEditor().emit(editor, save);
}

◆ editState()

cpp17::any Wt::WItemDelegate::editState	(	WWidget *	editor,
		const WModelIndex &	index
	)		const

overridevirtual

Returns the current edit state.

The default implementation returns the current text in the line edit. You will need to reimplement this method for a custom editor.

As an example of how to deal with a specialized editor, consider the default implementation:

cpp17::any WItemDelegate::editState(Wt::WWidget *editor) const
{
  Wt::WContainerWidget *w = dynamic_cast<Wt::WContainerWidget *>(editor);
  Wt::WLineEdit *lineEdit = dynamic_cast<Wt::WLineEdit *>(w->widget(0));
 
  return cpp17::any(lineEdit->text());
}

See also: createEditor(), setEditState(), setModelData()

Reimplemented from Wt::WAbstractItemDelegate.

◆ setEditState()

void Wt::WItemDelegate::setEditState	(	WWidget *	editor,
		const WModelIndex &	index,
		const cpp17::any &	value
	)		const

overridevirtual

Sets the editor data from the editor state.

The default implementation resets the text in the line edit. You will need to reimplement this method if for a custom editor.

As an example of how to deal with a specialized editor, consider the default implementation:

void WItemDelegate::setEditState(Wt::WWidget *editor, const WModelIndex& index, const cpp17::any& value) const
{
  Wt::WContainerWidget *w = dynamic_cast<Wt::WContainerWidget *>(editor);
  Wt::WLineEdit *lineEdit = dynamic_cast<Wt::WLineEdit *>(w->widget(0));
 
  lineEdit->setText(cpp17::any_cast<Wt::WString>(value));
}

See also: createEditor()

Reimplemented from Wt::WAbstractItemDelegate.

◆ setModelData()

void Wt::WItemDelegate::setModelData	(	const cpp17::any &	editState,
		WAbstractItemModel *	model,
		const WModelIndex &	index
	)		const

overridevirtual

Saves the edited data to the model.

The default implementation saves the current edit value to the model. You will need to reimplement this method for a custom editor.

As an example of how to deal with a specialized editor, consider the default implementation:

void WItemDelegate::setModelData(const Wt::cpp17::any& editState,
                                 Wt::WAbstractItemModel *model,
                                 const Wt::WModelIndex& index) const
{
  model->setData(index, editState, ItemDataRole::Edit);
}

See also: createEditor(), editState()

Reimplemented from Wt::WAbstractItemDelegate.

◆ setTextFormat()

void Wt::WItemDelegate::setTextFormat ( const WString & format )

Sets the text format string.

The ItemDataRole::Display data is converted to a string using asString() by passing the given format.

The default value is "".

◆ textFormat()

const WString& Wt::WItemDelegate::textFormat ( ) const

Returns the text format string.

See also: setTextFormat()

◆ update()

std::unique_ptr< WWidget > Wt::WItemDelegate::update	(	WWidget *	widget,
		const WModelIndex &	index,
		WFlags< ViewItemRenderFlag >	flags
	)

overridevirtual

Creates or updates a widget that renders an item.

The following properties of an item are rendered:

text using the Wt::ItemDataRole::Display data, with the format specified by setTextFormat()
a check box depending on the Wt::ItemFlag::UserCheckable flag and Wt::ItemDataRole::Checked data
an anchor depending on the value of Wt::ItemDataRole::Link
an icon depending on the value of Wt::ItemDataRole::Decoration
a tooltip depending on the value of Wt::ItemDataRole::ToolTip
a custom style class depending on the value of Wt::ItemDataRole::StyleClass

When the flags indicates Wt::ViewItemRenderFlag::Editing, then createEditor() is called to create a suitable editor for editing the item.

Implements Wt::WAbstractItemDelegate.

◆ updateModelIndex()

void Wt::WItemDelegate::updateModelIndex	(	WWidget *	widget,
		const WModelIndex &	index
	)

overridevirtual

Updates the model index of a widget.

This method is invoked by the view when due to row/column insertions or removals, the index has shifted.

You should reimplement this method only if you are storing the model index in the widget, to update the stored model index.

The default implementation does nothing.

Reimplemented from Wt::WAbstractItemDelegate.

Public Member Functions

Protected Member Functions

Additional Inherited Members

Detailed Description

Member Function Documentation

◆ createEditor()

◆ editState()

◆ setEditState()

◆ setModelData()

◆ setTextFormat()

◆ textFormat()

◆ update()

◆ updateModelIndex()