72106832e4
Add a slot copying the QMimeData contents as text. Task-number: QTBUG-60635 Change-Id: Ided14fccd8a49029ff1aff64969454ed2232dbeb Reviewed-by: Paul Wicking <paul.wicking@qt.io> Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
244 lines
11 KiB
Plaintext
244 lines
11 KiB
Plaintext
/****************************************************************************
|
|
**
|
|
** Copyright (C) 2016 The Qt Company Ltd.
|
|
** Contact: https://www.qt.io/licensing/
|
|
**
|
|
** This file is part of the documentation of the Qt Toolkit.
|
|
**
|
|
** $QT_BEGIN_LICENSE:FDL$
|
|
** Commercial License Usage
|
|
** Licensees holding valid commercial Qt licenses may use this file in
|
|
** accordance with the commercial license agreement provided with the
|
|
** Software or, alternatively, in accordance with the terms contained in
|
|
** a written agreement between you and The Qt Company. For licensing terms
|
|
** and conditions see https://www.qt.io/terms-conditions. For further
|
|
** information use the contact form at https://www.qt.io/contact-us.
|
|
**
|
|
** GNU Free Documentation License Usage
|
|
** 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. Please review the following information to ensure
|
|
** the GNU Free Documentation License version 1.3 requirements
|
|
** will be met: https://www.gnu.org/licenses/fdl-1.3.html.
|
|
** $QT_END_LICENSE$
|
|
**
|
|
****************************************************************************/
|
|
|
|
/*!
|
|
\example draganddrop/dropsite
|
|
\title Drop Site Example
|
|
|
|
\brief 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
|
|
\li \l{QWidget::dragEnterEvent()}{dragEnterEvent()}
|
|
\li \l{QWidget::dragMoveEvent()}{dragMoveEvent()}
|
|
\li \l{QWidget::dragLeaveEvent()}{dragLeaveEvent()}
|
|
\li \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
|
|
\li If \c mimeData contains an image, we display it in \c DropArea with
|
|
\l{QLabel::setPixmap()}{setPixmap()}.
|
|
\li If \c mimeData contains HTML, we display it with
|
|
\l{QLabel::setText()}{setText()} and set \c{DropArea}'s text format
|
|
as Qt::RichText.
|
|
\li 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.
|
|
\li 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
|
|
|
|
Three QPushButton objects, \c clearButton, \c copyButton, 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 copyButton,
|
|
\c clearButton, and \c quitButton are connected to \c copy(),
|
|
\c clear() and \l{QWidget::close()}{close()}, 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.
|
|
|
|
\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 \l{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
|
|
*/
|