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diff --git a/doc/src/examples/dropsite.qdoc b/doc/src/examples/dropsite.qdoc new file mode 100644 index 0000000000..d8c17e1793 --- /dev/null +++ b/doc/src/examples/dropsite.qdoc @@ -0,0 +1,249 @@ +/**************************************************************************** +** +** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies). +** All rights reserved. +** Contact: Nokia Corporation (qt-info@nokia.com) +** +** This file is part of the documentation of the Qt Toolkit. +** +** $QT_BEGIN_LICENSE:FDL$ +** No Commercial Usage +** This file contains pre-release code and may not be distributed. +** You may use this file in accordance with the terms and conditions +** contained in the Technology Preview License Agreement accompanying +** this package. +** +** GNU Free Documentation License +** Alternatively, this file may be used under the terms of the GNU Free +** Documentation License version 1.3 as published by the Free Software +** Foundation and appearing in the file included in the packaging of this +** file. +** +** If you have questions regarding the use of this file, please contact +** Nokia at qt-info@nokia.com. +** $QT_END_LICENSE$ +** +****************************************************************************/ + +/*! + \example draganddrop/dropsite + \title Drop Site Example + + The example shows how to distinguish the various MIME formats available + in a drag and drop operation. + + \image dropsite-example.png Screenshot of the Drop Site example + + The Drop Site example accepts drops from other applications, and displays + the MIME formats provided by the drag object. + + There are two classes, \c DropArea and \c DropSiteWindow, and a \c main() + function in this example. A \c DropArea object is instantiated in + \c DropSiteWindow; a \c DropSiteWindow object is then invoked in the + \c main() function. + + \section1 DropArea Class Definition + + The \c DropArea class is a subclass of QLabel with a public slot, + \c clear(), and a \c changed() signal. + + \snippet draganddrop/dropsite/droparea.h DropArea header part1 + + In addition, \c DropArea also contains a private instance of QLabel and + reimplementations of four \l{QWidget} event handlers: + + \list 1 + \o \l{QWidget::dragEnterEvent()}{dragEnterEvent()} + \o \l{QWidget::dragMoveEvent()}{dragMoveEvent()} + \o \l{QWidget::dragLeaveEvent()}{dragLeaveEvent()} + \o \l{QWidget::dropEvent()}{dropEvent()} + \endlist + + These event handlers are further explained in the implementation of the + \c DropArea class. + + \snippet draganddrop/dropsite/droparea.h DropArea header part2 + + \section1 DropArea Class Implementation + + In the \c DropArea constructor, we set the \l{QWidget::setMinimumSize()} + {minimum size} to 200x200 pixels, the \l{QFrame::setFrameStyle()} + {frame style} to both QFrame::Sunken and QFrame::StyledPanel, and we align + its contents to the center. + + \snippet draganddrop/dropsite/droparea.cpp DropArea constructor + + Also, we enable drop events in \c DropArea by setting the + \l{QWidget::acceptDrops()}{acceptDrops} property to \c true. Then, + we enable the \l{QWidget::autoFillBackground()}{autoFillBackground} + property and invoke the \c clear() function. + + The \l{QWidget::dragEnterEvent()}{dragEnterEvent()} event handler is + called when a drag is in progress and the mouse enters the \c DropArea + object. For the \c DropSite example, when the mouse enters \c DropArea, + we set its text to "<drop content>" and highlight its background. + + \snippet draganddrop/dropsite/droparea.cpp dragEnterEvent() function + + Then, we invoke \l{QDropEvent::acceptProposedAction()} + {acceptProposedAction()} on \a event, setting the drop action to the one + proposed. Lastly, we emit the \c changed() signal, with the data that was + dropped and its MIME type information as a parameter. + + For \l{QWidget::dragMoveEvent()}{dragMoveEvent()}, we just accept the + proposed QDragMoveEvent object, \a event, with + \l{QDropEvent::acceptProposedAction()}{acceptProposedAction()}. + + \snippet draganddrop/dropsite/droparea.cpp dragMoveEvent() function + + The \c DropArea class's implementation of \l{QWidget::dropEvent()} + {dropEvent()} extracts the \a{event}'s mime data and displays it + accordingly. + + \snippet draganddrop/dropsite/droparea.cpp dropEvent() function part1 + + The \c mimeData object can contain one of the following objects: an image, + HTML text, plain text, or a list of URLs. + + \snippet draganddrop/dropsite/droparea.cpp dropEvent() function part2 + + \list + \o If \c mimeData contains an image, we display it in \c DropArea with + \l{QLabel::setPixmap()}{setPixmap()}. + \o If \c mimeData contains HTML, we display it with + \l{QLabel::setText()}{setText()} and set \c{DropArea}'s text format + as Qt::RichText. + \o If \c mimeData contains plain text, we display it with + \l{QLabel::setText()}{setText()} and set \c{DropArea}'s text format + as Qt::PlainText. In the event that \c mimeData contains URLs, we + iterate through the list of URLs to display them on individual + lines. + \o If \c mimeData contains other types of objects, we set + \c{DropArea}'s text, with \l{QLabel::setText()}{setText()} to + "Cannot display data" to inform the user. + \endlist + + We then set \c{DropArea}'s \l{QWidget::backgroundRole()}{backgroundRole} to + QPalette::Dark and we accept \c{event}'s proposed action. + + \snippet draganddrop/dropsite/droparea.cpp dropEvent() function part3 + + The \l{QWidget::dragLeaveEvent()}{dragLeaveEvent()} event handler is + called when a drag is in progress and the mouse leaves the widget. + + \snippet draganddrop/dropsite/droparea.cpp dragLeaveEvent() function + + For \c{DropArea}'s implementation, we clear invoke \c clear() and then + accept the proposed event. + + The \c clear() function sets the text in \c DropArea to "<drop content>" + and sets the \l{QWidget::backgroundRole()}{backgroundRole} to + QPalette::Dark. Lastly, it emits the \c changed() signal. + + \snippet draganddrop/dropsite/droparea.cpp clear() function + + \section1 DropSiteWindow Class Definition + + The \c DropSiteWindow class contains a constructor and a public slot, + \c updateFormatsTable(). + + \snippet draganddrop/dropsite/dropsitewindow.h DropSiteWindow header + + The class also contains a private instance of \c DropArea, \c dropArea, + QLabel, \c abstractLabel, QTableWidget, \c formatsTable, QDialogButtonBox, + \c buttonBox, and two QPushButton objects, \c clearButton and + \c quitButton. + + \section1 DropSiteWindow Class Implementation + + In the constructor of \c DropSiteWindow, we instantiate \c abstractLabel + and set its \l{QLabel::setWordWrap()}{wordWrap} property to \c true. We + also call the \l{QLabel::adjustSize()}{adjustSize()} function to adjust + \c{abstractLabel}'s size according to its contents. + + \snippet draganddrop/dropsite/dropsitewindow.cpp constructor part1 + + Then we instantiate \c dropArea and connect its \c changed() signal to + \c{DropSiteWindow}'s \c updateFormatsTable() slot. + + \snippet draganddrop/dropsite/dropsitewindow.cpp constructor part2 + + We now set up the QTableWidget object, \c formatsTable. Its + horizontal header is set using a QStringList object, \c labels. The number + of columms are set to two and the table is not editable. Also, the + \c{formatTable}'s horizontal header is formatted to ensure that its second + column stretches to occupy additional space available. + + \snippet draganddrop/dropsite/dropsitewindow.cpp constructor part3 + + Two QPushButton objects, \c clearButton and \c quitButton, are instantiated + and added to \c buttonBox - a QDialogButtonBox object. We use + QDialogButtonBox here to ensure that the push buttons are presented in a + layout that conforms to the platform's style. + + \snippet draganddrop/dropsite/dropsitewindow.cpp constructor part4 + + The \l{QPushButton::clicked()}{clicked()} signals for \c quitButton and + \c clearButton are connected to \l{QWidget::close()}{close()} and + \c clear(), respectively. + + For the layout, we use a QVBoxLayout, \c mainLayout, to arrange our widgets + vertically. We also set the window title to "Drop Site" and the minimum + size to 350x500 pixels. + + \snippet draganddrop/dropsite/dropsitewindow.cpp constructor part5 + + We move on to the \c updateFormatsTable() function. This function updates + the \c formatsTable, displaying the MIME formats of the object dropped onto + the \c DropArea object. First, we set \l{QTableWidget}'s + \l{QTableWidget::setRowCount()}{rowCount} property to 0. Then, we validate + to ensure that the QMimeData object passed in is a valid object. + + \snippet draganddrop/dropsite/dropsitewindow.cpp updateFormatsTable() part1 + + Once we are sure that \c mimeData is valid, we iterate through its + supported formats using the \l{The foreach Keyword}{foreach keyword}. + This keyword has the following format: + + \snippet doc/src/snippets/code/doc_src_examples_dropsite.qdoc 0 + + In our example, \c format is the \a variable and the \a container is a + QStringList, obtained from \c mimeData->formats(). + + \note The \l{QMimeData::formats()}{formats()} function returns a + QStringList object, containing all the formats supported by the + \c mimeData. + + \snippet draganddrop/dropsite/dropsitewindow.cpp updateFormatsTable() part2 + + Within each iteration, we create a QTableWidgetItem, \c formatItem and we + set its \l{QTableWidgetItem::setFlags()}{flags} to Qt::ItemIsEnabled, and + its \l{QTableWidgetItem::setTextAlignment()}{text alignment} to Qt::AlignTop + and Qt::AlignLeft. + + A QString object, \c text, is customized to display data according to the + contents of \c format. We invoke {QString}'s \l{QString::simplified()} + {simplified()} function on \c text, to obtain a string that has no + additional space before, after or in between words. + + \snippet draganddrop/dropsite/dropsitewindow.cpp updateFormatsTable() part3 + + If \c format contains a list of URLs, we iterate through them, using spaces + to separate them. On the other hand, if \c format contains an image, we + display the data by converting the text to hexadecimal. + + \snippet draganddrop/dropsite/dropsitewindow.cpp updateFormatsTable() part4 + + Once \c text has been customized to contain the appropriate data, we insert + both \c format and \c text into \c formatsTable with + \l{QTableWidget::setItem()}{setItem()}. Lastly, we invoke + \l{QTableView::resizeColumnToContents()}{resizeColumnToContents()} on + \c{formatsTable}'s first column. + + \section1 The main() Function + + Within the \c main() function, we instantiate \c DropSiteWindow and invoke + its \l{QWidget::show()}{show()} function. + + \snippet draganddrop/dropsite/main.cpp main() function +*/ |