1 /****************************************************************************

     2 **

     3 ** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).

     4 ** All rights reserved.

     5 ** Contact: Nokia Corporation (qt-info@nokia.com)

     6 **

     7 ** This file is part of the QtGui module of the Qt Toolkit.

     8 **

     9 ** $QT_BEGIN_LICENSE:LGPL$

    10 ** No Commercial Usage

    11 ** This file contains pre-release code and may not be distributed.

    12 ** You may use this file in accordance with the terms and conditions

    13 ** contained in the Technology Preview License Agreement accompanying

    14 ** this package.

    15 **

    16 ** GNU Lesser General Public License Usage

    17 ** Alternatively, this file may be used under the terms of the GNU Lesser

    18 ** General Public License version 2.1 as published by the Free Software

    19 ** Foundation and appearing in the file LICENSE.LGPL included in the

    20 ** packaging of this file.  Please review the following information to

    21 ** ensure the GNU Lesser General Public License version 2.1 requirements

    22 ** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.

    23 **

    24 ** In addition, as a special exception, Nokia gives you certain additional

    25 ** rights.  These rights are described in the Nokia Qt LGPL Exception

    26 ** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.

    27 **

    28 ** If you have questions regarding the use of this file, please contact

    29 ** Nokia at qt-info@nokia.com.

    30 **

    31 **

    32 **

    33 **

    34 **

    35 **

    36 **

    37 **

    38 ** $QT_END_LICENSE$

    39 **

    40 ****************************************************************************/

    41 

    42 #include <qwidget.h>

    43 #include <qdrag.h>

    44 #include <qpixmap.h>

    45 #include <qpoint.h>

    46 #include "qdnd_p.h"

    47 

    48 #ifndef QT_NO_DRAGANDDROP

    49 

    50 QT_BEGIN_NAMESPACE

    51 

    52 /*!

    53     \class QDrag

    54     \brief The QDrag class provides support for MIME-based drag and drop data

    55     transfer.

    56 

    57     Drag and drop is an intuitive way for users to copy or move data around in an

    58     application, and is used in many desktop environments as a mechanism for copying

    59     data between applications. Drag and drop support in Qt is centered around the

    60     QDrag class that handles most of the details of a drag and drop operation.

    61 

    62     The data to be transferred by the drag and drop operation is contained in a

    63     QMimeData object. This is specified with the setMimeData() function in the

    64     following way:

    65 

    66     \snippet doc/src/snippets/dragging/mainwindow.cpp 1

    67 

    68     Note that setMimeData() assigns ownership of the QMimeData object to the

    69     QDrag object. The QDrag must be constructed on the heap with a parent QWidget

    70     to ensure that Qt can clean up after the drag and drop operation has been

    71     completed.

    72 

    73     A pixmap can be used to represent the data while the drag is in

    74     progress, and will move with the cursor to the drop target. This

    75     pixmap typically shows an icon that represents the MIME type of

    76     the data being transferred, but any pixmap can be set with

    77     setPixmap(). The cursor's hot spot can be given a position

    78     relative to the top-left corner of the pixmap with the

    79     setHotSpot() function. The following code positions the pixmap so

    80     that the cursor's hot spot points to the center of its bottom

    81     edge:

    82 

    83     \snippet doc/src/snippets/separations/finalwidget.cpp 2

    84 

    85     \note On X11, the pixmap may not be able to keep up with the mouse

    86     movements if the hot spot causes the pixmap to be displayed

    87     directly under the cursor.

    88 

    89     The source and target widgets can be found with source() and target().

    90     These functions are often used to determine whether drag and drop operations

    91     started and finished at the same widget, so that special behavior can be

    92     implemented.

    93 

    94     QDrag only deals with the drag and drop operation itself. It is up to the

    95     developer to decide when a drag operation begins, and how a QDrag object should

    96     be constructed and used. For a given widget, it is often necessary to

    97     reimplement \l{QWidget::mousePressEvent()}{mousePressEvent()} to determine

    98     whether the user has pressed a mouse button, and reimplement

    99     \l{QWidget::mouseMoveEvent()}{mouseMoveEvent()} to check whether a QDrag is

   100     required.

   101 

   102     \sa {Drag and Drop}, QClipboard, QMimeData, QWindowsMime, QMacPasteboardMime,

   103         {Draggable Icons Example}, {Draggable Text Example}, {Drop Site Example},

   104 	    {Fridge Magnets Example}

   105 */

   106 

   107 /*!

   108     Constructs a new drag object for the widget specified by \a dragSource.

   109 */

   110 QDrag::QDrag(QWidget *dragSource)

   111     : QObject(*new QDragPrivate, dragSource)

   112 {

   113     Q_D(QDrag);

   114     d->source = dragSource;

   115     d->target = 0;

   116     d->data = 0;

   117     d->hotspot = QPoint(-10, -10);

   118     d->possible_actions = Qt::CopyAction;

   119     d->executed_action = Qt::IgnoreAction;

   120     d->defaultDropAction = Qt::IgnoreAction;

   121 }

   122 

   123 /*!

   124     Destroys the drag object.

   125 */

   126 QDrag::~QDrag()

   127 {

   128     Q_D(QDrag);

   129     delete d->data;

   130     QDragManager *manager = QDragManager::self();

   131     if (manager && manager->object == this)

   132         manager->cancel(false);

   133 }

   134 

   135 /*!

   136     Sets the data to be sent to the given MIME \a data. Ownership of the data is

   137     transferred to the QDrag object.

   138 */

   139 void QDrag::setMimeData(QMimeData *data)

   140 {

   141     Q_D(QDrag);

   142     if (d->data == data)

   143         return;

   144     if (d->data != 0)

   145         delete d->data;

   146     d->data = data;

   147 }

   148 

   149 /*!

   150     Returns the MIME data that is encapsulated by the drag object.

   151 */

   152 QMimeData *QDrag::mimeData() const

   153 {

   154     Q_D(const QDrag);

   155     return d->data;

   156 }

   157 

   158 /*!

   159     Sets \a pixmap as the pixmap used to represent the data in a drag

   160     and drop operation. You can only set a pixmap before the drag is

   161     started.

   162 */

   163 void QDrag::setPixmap(const QPixmap &pixmap)

   164 {

   165     Q_D(QDrag);

   166     d->pixmap = pixmap;

   167 }

   168 

   169 /*!

   170     Returns the pixmap used to represent the data in a drag and drop operation.

   171 */

   172 QPixmap QDrag::pixmap() const

   173 {

   174     Q_D(const QDrag);

   175     return d->pixmap;

   176 }

   177 

   178 /*!

   179     Sets the position of the hot spot relative to the top-left corner of the

   180     pixmap used to the point specified by \a hotspot.

   181 

   182     \bold{Note:} on X11, the pixmap may not be able to keep up with the mouse

   183     movements if the hot spot causes the pixmap to be displayed

   184     directly under the cursor.

   185 */

   186 void QDrag::setHotSpot(const QPoint& hotspot)

   187 {

   188     Q_D(QDrag);

   189     d->hotspot = hotspot;

   190 }

   191 

   192 /*!

   193     Returns the position of the hot spot relative to the top-left corner of the

   194     cursor.

   195 */

   196 QPoint QDrag::hotSpot() const

   197 {

   198     Q_D(const QDrag);

   199     return d->hotspot;

   200 }

   201 

   202 /*!

   203     Returns the source of the drag object. This is the widget where the drag

   204     and drop operation originated.

   205 */

   206 QWidget *QDrag::source() const

   207 {

   208     Q_D(const QDrag);

   209     return d->source;

   210 }

   211 

   212 /*!

   213     Returns the target of the drag and drop operation. This is the widget where

   214     the drag object was dropped.

   215 */

   216 QWidget *QDrag::target() const

   217 {

   218     Q_D(const QDrag);

   219     return d->target;

   220 }

   221 

   222 /*!

   223     \since 4.3

   224 

   225     Starts the drag and drop operation and returns a value indicating the requested

   226     drop action when it is completed. The drop actions that the user can choose

   227     from are specified in \a supportedActions. The default proposed action will be selected

   228     among the allowed actions in the following order: Move, Copy and Link.

   229 

   230     \bold{Note:} On Linux and Mac OS X, the drag and drop operation

   231     can take some time, but this function does not block the event

   232     loop. Other events are still delivered to the application while

   233     the operation is performed. On Windows, the Qt event loop is

   234     blocked while during the operation.

   235 */

   236 

   237 Qt::DropAction QDrag::exec(Qt::DropActions supportedActions)

   238 {

   239     return exec(supportedActions, Qt::IgnoreAction);

   240 }

   241 

   242 /*!

   243     \since 4.3

   244 

   245     Starts the drag and drop operation and returns a value indicating the requested

   246     drop action when it is completed. The drop actions that the user can choose

   247     from are specified in \a supportedActions.

   248 

   249     The \a defaultDropAction determines which action will be proposed when the user performs a

   250     drag without using modifier keys.

   251 

   252     \bold{Note:} On Linux and Mac OS X, the drag and drop operation

   253     can take some time, but this function does not block the event

   254     loop. Other events are still delivered to the application while

   255     the operation is performed. On Windows, the Qt event loop is

   256     blocked while during the operation.

   257 */

   258 

   259 Qt::DropAction QDrag::exec(Qt::DropActions supportedActions, Qt::DropAction defaultDropAction)

   260 {

   261     Q_D(QDrag);

   262     if (!d->data) {

   263         qWarning("QDrag: No mimedata set before starting the drag");

   264         return d->executed_action;

   265     }

   266     QDragManager *manager = QDragManager::self();

   267     d->defaultDropAction = Qt::IgnoreAction;

   268     d->possible_actions = supportedActions;

   269 

   270     if (manager) {

   271         if (defaultDropAction == Qt::IgnoreAction) {

   272             if (supportedActions & Qt::MoveAction) {

   273                 d->defaultDropAction = Qt::MoveAction;

   274             } else if (supportedActions & Qt::CopyAction) {

   275                 d->defaultDropAction = Qt::CopyAction;

   276             } else if (supportedActions & Qt::LinkAction) {

   277                 d->defaultDropAction = Qt::LinkAction;

   278             }

   279         } else {

   280             d->defaultDropAction = defaultDropAction;

   281         }

   282         d->executed_action = manager->drag(this);

   283     }

   284 

   285     return d->executed_action;

   286 }

   287 

   288 /*!

   289     \obsolete

   290 

   291     \bold{Note:} It is recommended to use exec() instead of this function.

   292 

   293     Starts the drag and drop operation and returns a value indicating the requested

   294     drop action when it is completed. The drop actions that the user can choose

   295     from are specified in \a request. Qt::CopyAction is always allowed.

   296 

   297     \bold{Note:} Although the drag and drop operation can take some time, this function

   298     does not block the event loop. Other events are still delivered to the application

   299     while the operation is performed.

   300 

   301     \sa exec()

   302 */

   303 Qt::DropAction QDrag::start(Qt::DropActions request)

   304 {

   305     Q_D(QDrag);

   306     if (!d->data) {

   307         qWarning("QDrag: No mimedata set before starting the drag");

   308         return d->executed_action;

   309     }

   310     QDragManager *manager = QDragManager::self();

   311     d->defaultDropAction = Qt::IgnoreAction;

   312     d->possible_actions = request | Qt::CopyAction;

   313     if (manager)

   314         d->executed_action = manager->drag(this);

   315     return d->executed_action;

   316 }

   317 

   318 /*!

   319     Sets the drag \a cursor for the \a action. This allows you

   320     to override the default native cursors. To revert to using the

   321     native cursor for \a action pass in a null QPixmap as \a cursor.

   322 

   323     The \a action can only be CopyAction, MoveAction or LinkAction.

   324     All other values of DropAction are ignored.

   325 */

   326 void QDrag::setDragCursor(const QPixmap &cursor, Qt::DropAction action)

   327 {

   328     Q_D(QDrag);

   329     if (action != Qt::CopyAction && action != Qt::MoveAction && action != Qt::LinkAction)

   330         return;

   331     if (cursor.isNull())

   332         d->customCursors.remove(action);

   333     else

   334         d->customCursors[action] = cursor;

   335 }

   336 

   337 /*!

   338     \fn void QDrag::actionChanged(Qt::DropAction action)

   339 

   340     This signal is emitted when the \a action associated with the

   341     drag changes.

   342 

   343     \sa targetChanged()

   344 */

   345 

   346 /*!

   347     \fn void QDrag::targetChanged(QWidget *newTarget)

   348 

   349     This signal is emitted when the target of the drag and drop

   350     operation changes, with \a newTarget the new target.

   351 

   352     \sa target(), actionChanged()

   353 */

   354 

   355 QT_END_NAMESPACE

   356 

   357 #endif // QT_NO_DRAGANDDROP