#include <Wt/WAbstractItemDelegate>
Public Member Functions | |
WAbstractItemDelegate (WObject *parent=0) | |
Constructor. | |
virtual | ~WAbstractItemDelegate () |
Desturctor. | |
virtual WWidget * | update (WWidget *widget, const WModelIndex &index, WFlags< ViewItemRenderFlag > flags)=0 |
Create or update a widget that renders an item. | |
virtual void | updateModelIndex (WWidget *widget, const WModelIndex &index) |
Update the model index of a widget. |
Rendering of an item in a WTreeView is delegated to an implementation of this delegate class. The default implementation used by WTreeView is WItemDelegate. To provide specialized rendering support, you can reimplement this class, and indicate to the treeview to use this delegate for rendering items.
As a delegate is used for rendering multiple items, the class should not keep state about one specific item.
An example of a delegate that always renders the text in a line-edit, and saves the modified value back to the (editable) model.
// A custom delegate that uses an EditItem class EditItemDelegate : public WAbstractItemDelegate { class EditItem; public: EditItemDelegate(WObject *parent = 0) : WAbstractItemDelegate(parent) { } // Creates or updates an EditItem WWidget *update(WWidget *widget, const WModelIndex& index, WFlags<ViewItemRenderFlag> flags) { EditItem *item; if (widget) { item = dynamic_cast<EditItem *>(widget); } else { item = new EditItem(index); widget = item; } boost::any text = index.data(DisplayRole); item->edit()->setText(asString(text)); return widget; } // Updates the model index of the EditItem void updateModelIndex(WWidget *widget, const WModelIndex& index) { EditItem *item = dynamic_cast<EditItem *>(widget); item->setIndex(index); } private: // A custom item widget that contains only a WLineEdit class EditItem : public WContainerWidget { public: EditItem(const WModelIndex& index) : index_(index) { edit_ = new WLineEdit(this); edit_->changed().connect(SLOT(this, EditItem::onEdit)); setAttributeValue("style", "line-height: 1em;"); // Otherwise the line edit overflows the cell setSelectable(true); // WTreeView by default disables selection } // Updates the model index void setIndex(const WModelIndex& index) { index_ = index; } // Returns the editor WLineEdit *edit() const { return edit_; } private: WLineEdit *edit_; WModelIndex index_; // Updates the model with the edited value void onEdit() { WAbstractItemModel *model = const_cast<WAbstractItemModel *>(index_.model()); model->setData(index_, edit_->text()); } }; };
virtual WWidget* Wt::WAbstractItemDelegate::update | ( | WWidget * | widget, | |
const WModelIndex & | index, | |||
WFlags< ViewItemRenderFlag > | flags | |||
) | [pure virtual] |
Create or update a widget that renders an item.
The item is specified by its model index, which also indicates the model. If an existing widget already renders the item, but needs to be updated, it is passed as the widget parameter. You may decide to create a new widget, in which case you are responsible to delete the previous widget if it is not reused.
When widget is null
, a new widget needs to be created.
The flags parameter indicates options for rendering the item.
Implemented in Wt::WItemDelegate.
void Wt::WAbstractItemDelegate::updateModelIndex | ( | WWidget * | widget, | |
const WModelIndex & | index | |||
) | [virtual] |
Update the model index of a widget.
This method is invoked by the view when due to row/column insertions or removals, an index was modified for a widget.
You should reimplement this method if you are storing the model index (e.g. for editing purposes) in the widget, which you should update to the new index.
The default implementation does nothing.
Reimplemented in Wt::WItemDelegate.