Wt  4.11.0
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Public Member Functions | Protected Member Functions | List of all members
Wt::WItemDelegate Class Reference

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

#include <Wt/WItemDelegate.h>

Inheritance diagram for Wt::WItemDelegate:
[legend]

Public Member Functions

 WItemDelegate ()
 Create an item delegate.
 
virtual std::unique_ptr< WWidgetupdate (WWidget *widget, const WModelIndex &index, WFlags< ViewItemRenderFlag > flags) override
 Creates or updates a widget that renders an item.
 
virtual void updateModelIndex (WWidget *widget, const WModelIndex &index) override
 Updates the model index of a widget.
 
void setTextFormat (const WString &format)
 Sets the text format string.
 
const WStringtextFormat () const
 Returns the text format string.
 
virtual void setModelData (const cpp17::any &editState, WAbstractItemModel *model, const WModelIndex &index) const override
 Saves the edited data to the model.
 
virtual cpp17::any editState (WWidget *editor, const WModelIndex &index) const override
 Returns the current edit state.
 
virtual void setEditState (WWidget *editor, const WModelIndex &index, const cpp17::any &value) const override
 Sets the editor data from the editor state.
 
- 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.
 
Signal< WWidget *, bool > & closeEditor ()
 Signal which indicates that an editor needs to be closed.
 
const Signal< WWidget *, bool > & closeEditor () const
 Signal which indicates that an editor needs to be closed.
 
- 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 >
ChildaddChild (std::unique_ptr< Child > child)
 Add a child WObject, returning a raw pointer.
 
std::unique_ptr< WObjectremoveChild (WObject *child)
 Remove a child WObject, so its lifetime is no longer determined by this WObject.
 
template<typename Child >
std::unique_ptr< ChildremoveChild (Child *child)
 Remove a child WObject, so its lifetime is no longer determined by this WObject.
 
virtual const std::string id () const
 Returns the (unique) identifier for this object.
 
virtual void setObjectName (const std::string &name)
 Sets an object name.
 
virtual std::string objectName () const
 Returns the object name.
 
void resetLearnedSlots ()
 Resets learned stateless slot implementations.
 
template<class T >
void resetLearnedSlot (void(T::*method)())
 Resets a learned stateless slot implementation.
 
template<class T >
WStatelessSlot * implementStateless (void(T::*method)())
 Declares a slot to be stateless and learn client-side behaviour on first invocation.
 
template<class T >
WStatelessSlot * implementStateless (void(T::*method)(), void(T::*undoMethod)())
 Declares a slot to be stateless and learn client-side behaviour in advance.
 
void isNotStateless ()
 Marks the current function as not stateless.
 
template<class T >
WStatelessSlot * implementJavaScript (void(T::*method)(), const std::string &jsCode)
 Provides a JavaScript implementation for a method.
 
- Public Member Functions inherited from Wt::Core::observable
 observable () noexcept
 Default constructor.
 
virtual ~observable ()
 Destructor.
 
template<typename... Args, typename C >
auto bindSafe (void(C::*method)(Args...)) noexcept
 Protects a method call against object destruction.
 
template<typename... Args, typename C >
auto bindSafe (void(C::*method)(Args...) const) const noexcept
 Protects a const method call against object destruction.
 
template<typename Function >
auto bindSafe (const Function &function) noexcept
 Protects a function against object destruction.
 

Protected Member Functions

virtual std::unique_ptr< WWidgetcreateEditor (const WModelIndex &index, WFlags< ViewItemRenderFlag > flags) const
 Creates an editor for a data item.
 
- Protected Member Functions inherited from Wt::WObject
virtual WStatelessSlot * getStateless (Method method)
 On-demand stateless slot implementation.
 

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
{
}
A signal that conveys user-interface events.
Definition WSignal.h:558
void emit(E e=NoClass()) const
Emits the signal.
Definition WSignal.h:898
static constexpr const int Edit
Role for the edited value.
Definition WModelIndex.h:152
Signal< WWidget *, bool > & closeEditor()
Signal which indicates that an editor needs to be closed.
Definition WAbstractItemDelegate.h:177
virtual std::unique_ptr< WWidget > createEditor(const WModelIndex &index, WFlags< ViewItemRenderFlag > flags) const
Creates an editor for a data item.
Definition WItemDelegate.C:418
A value class that describes an index to an item in a data model.
Definition WModelIndex.h:292
cpp17::any data(ItemDataRole role=ItemDataRole::Display) const
Returns data in the model at this index.
Definition WModelIndex.C:44
The abstract base class for a user-interface component.
Definition WWidget.h:66
WString asString(const cpp17::any &v, const WString &format)
Interprets a cpp17::any as a string value.
Definition WAny.C:368
@ Focused
Render (the editor) focused

◆ 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:

{
Wt::WLineEdit *lineEdit = dynamic_cast<Wt::WLineEdit *>(w->widget(0));
return cpp17::any(lineEdit->text());
}
A widget that holds and manages child widgets.
Definition WContainerWidget.h:135
virtual WWidget * widget(int index) const
Returns the widget at index
Definition WContainerWidget.C:235
virtual cpp17::any editState(WWidget *editor, const WModelIndex &index) const override
Returns the current edit state.
Definition WItemDelegate.C:448
A widget that provides a single line edit.
Definition WLineEdit.h:76
const WString & text() const
Returns the current content.
Definition WLineEdit.h:115
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::WLineEdit *lineEdit = dynamic_cast<Wt::WLineEdit *>(w->widget(0));
lineEdit->setText(cpp17::any_cast<Wt::WString>(value));
}
virtual void setEditState(WWidget *editor, const WModelIndex &index, const cpp17::any &value) const override
Sets the editor data from the editor state.
Definition WItemDelegate.C:458
virtual void setText(const WString &text)
Sets the content of the line edit.
Definition WLineEdit.C:55
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,
const Wt::WModelIndex& index) const
{
}
An abstract model for use with Wt's view classes.
Definition WAbstractItemModel.h:175
virtual bool setData(const WModelIndex &index, const cpp17::any &value, ItemDataRole role=ItemDataRole::Edit)
Sets data at the given model index.
virtual void setModelData(const cpp17::any &editState, WAbstractItemModel *model, const WModelIndex &index) const override
Saves the edited data to the model.
Definition WItemDelegate.C:468
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:

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.