--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/doc/src/examples/dropsite.qdoc Mon Jan 11 14:00:40 2010 +0000
@@ -0,0 +1,263 @@
+/****************************************************************************
+**
+** Copyright (C) 2009 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.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** 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 Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Nokia gives you certain additional
+** rights. These rights are described in the Nokia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** 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
+*/