src/gui/kernel/qdrag.cpp
changeset 0 1918ee327afb
child 4 3b1da2848fc7
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/gui/kernel/qdrag.cpp	Mon Jan 11 14:00:40 2010 +0000
@@ -0,0 +1,357 @@
+/****************************************************************************
+**
+** 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 QtGui module 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.
+**
+**
+**
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <qwidget.h>
+#include <qdrag.h>
+#include <qpixmap.h>
+#include <qpoint.h>
+#include "qdnd_p.h"
+
+#ifndef QT_NO_DRAGANDDROP
+
+QT_BEGIN_NAMESPACE
+
+/*!
+    \class QDrag
+    \brief The QDrag class provides support for MIME-based drag and drop data
+    transfer.
+
+    Drag and drop is an intuitive way for users to copy or move data around in an
+    application, and is used in many desktop environments as a mechanism for copying
+    data between applications. Drag and drop support in Qt is centered around the
+    QDrag class that handles most of the details of a drag and drop operation.
+
+    The data to be transferred by the drag and drop operation is contained in a
+    QMimeData object. This is specified with the setMimeData() function in the
+    following way:
+
+    \snippet doc/src/snippets/dragging/mainwindow.cpp 1
+
+    Note that setMimeData() assigns ownership of the QMimeData object to the
+    QDrag object. The QDrag must be constructed on the heap with a parent QWidget
+    to ensure that Qt can clean up after the drag and drop operation has been
+    completed.
+
+    A pixmap can be used to represent the data while the drag is in
+    progress, and will move with the cursor to the drop target. This
+    pixmap typically shows an icon that represents the MIME type of
+    the data being transferred, but any pixmap can be set with
+    setPixmap(). The cursor's hot spot can be given a position
+    relative to the top-left corner of the pixmap with the
+    setHotSpot() function. The following code positions the pixmap so
+    that the cursor's hot spot points to the center of its bottom
+    edge:
+
+    \snippet doc/src/snippets/separations/finalwidget.cpp 2
+
+    \note On X11, the pixmap may not be able to keep up with the mouse
+    movements if the hot spot causes the pixmap to be displayed
+    directly under the cursor.
+
+    The source and target widgets can be found with source() and target().
+    These functions are often used to determine whether drag and drop operations
+    started and finished at the same widget, so that special behavior can be
+    implemented.
+
+    QDrag only deals with the drag and drop operation itself. It is up to the
+    developer to decide when a drag operation begins, and how a QDrag object should
+    be constructed and used. For a given widget, it is often necessary to
+    reimplement \l{QWidget::mousePressEvent()}{mousePressEvent()} to determine
+    whether the user has pressed a mouse button, and reimplement
+    \l{QWidget::mouseMoveEvent()}{mouseMoveEvent()} to check whether a QDrag is
+    required.
+
+    \sa {Drag and Drop}, QClipboard, QMimeData, QWindowsMime, QMacPasteboardMime,
+        {Draggable Icons Example}, {Draggable Text Example}, {Drop Site Example},
+	    {Fridge Magnets Example}
+*/
+
+/*!
+    Constructs a new drag object for the widget specified by \a dragSource.
+*/
+QDrag::QDrag(QWidget *dragSource)
+    : QObject(*new QDragPrivate, dragSource)
+{
+    Q_D(QDrag);
+    d->source = dragSource;
+    d->target = 0;
+    d->data = 0;
+    d->hotspot = QPoint(-10, -10);
+    d->possible_actions = Qt::CopyAction;
+    d->executed_action = Qt::IgnoreAction;
+    d->defaultDropAction = Qt::IgnoreAction;
+}
+
+/*!
+    Destroys the drag object.
+*/
+QDrag::~QDrag()
+{
+    Q_D(QDrag);
+    delete d->data;
+    QDragManager *manager = QDragManager::self();
+    if (manager && manager->object == this)
+        manager->cancel(false);
+}
+
+/*!
+    Sets the data to be sent to the given MIME \a data. Ownership of the data is
+    transferred to the QDrag object.
+*/
+void QDrag::setMimeData(QMimeData *data)
+{
+    Q_D(QDrag);
+    if (d->data == data)
+        return;
+    if (d->data != 0)
+        delete d->data;
+    d->data = data;
+}
+
+/*!
+    Returns the MIME data that is encapsulated by the drag object.
+*/
+QMimeData *QDrag::mimeData() const
+{
+    Q_D(const QDrag);
+    return d->data;
+}
+
+/*!
+    Sets \a pixmap as the pixmap used to represent the data in a drag
+    and drop operation. You can only set a pixmap before the drag is
+    started.
+*/
+void QDrag::setPixmap(const QPixmap &pixmap)
+{
+    Q_D(QDrag);
+    d->pixmap = pixmap;
+}
+
+/*!
+    Returns the pixmap used to represent the data in a drag and drop operation.
+*/
+QPixmap QDrag::pixmap() const
+{
+    Q_D(const QDrag);
+    return d->pixmap;
+}
+
+/*!
+    Sets the position of the hot spot relative to the top-left corner of the
+    pixmap used to the point specified by \a hotspot.
+
+    \bold{Note:} on X11, the pixmap may not be able to keep up with the mouse
+    movements if the hot spot causes the pixmap to be displayed
+    directly under the cursor.
+*/
+void QDrag::setHotSpot(const QPoint& hotspot)
+{
+    Q_D(QDrag);
+    d->hotspot = hotspot;
+}
+
+/*!
+    Returns the position of the hot spot relative to the top-left corner of the
+    cursor.
+*/
+QPoint QDrag::hotSpot() const
+{
+    Q_D(const QDrag);
+    return d->hotspot;
+}
+
+/*!
+    Returns the source of the drag object. This is the widget where the drag
+    and drop operation originated.
+*/
+QWidget *QDrag::source() const
+{
+    Q_D(const QDrag);
+    return d->source;
+}
+
+/*!
+    Returns the target of the drag and drop operation. This is the widget where
+    the drag object was dropped.
+*/
+QWidget *QDrag::target() const
+{
+    Q_D(const QDrag);
+    return d->target;
+}
+
+/*!
+    \since 4.3
+
+    Starts the drag and drop operation and returns a value indicating the requested
+    drop action when it is completed. The drop actions that the user can choose
+    from are specified in \a supportedActions. The default proposed action will be selected
+    among the allowed actions in the following order: Move, Copy and Link.
+
+    \bold{Note:} On Linux and Mac OS X, the drag and drop operation
+    can take some time, but this function does not block the event
+    loop. Other events are still delivered to the application while
+    the operation is performed. On Windows, the Qt event loop is
+    blocked while during the operation.
+*/
+
+Qt::DropAction QDrag::exec(Qt::DropActions supportedActions)
+{
+    return exec(supportedActions, Qt::IgnoreAction);
+}
+
+/*!
+    \since 4.3
+
+    Starts the drag and drop operation and returns a value indicating the requested
+    drop action when it is completed. The drop actions that the user can choose
+    from are specified in \a supportedActions.
+
+    The \a defaultDropAction determines which action will be proposed when the user performs a
+    drag without using modifier keys.
+
+    \bold{Note:} On Linux and Mac OS X, the drag and drop operation
+    can take some time, but this function does not block the event
+    loop. Other events are still delivered to the application while
+    the operation is performed. On Windows, the Qt event loop is
+    blocked while during the operation.
+*/
+
+Qt::DropAction QDrag::exec(Qt::DropActions supportedActions, Qt::DropAction defaultDropAction)
+{
+    Q_D(QDrag);
+    if (!d->data) {
+        qWarning("QDrag: No mimedata set before starting the drag");
+        return d->executed_action;
+    }
+    QDragManager *manager = QDragManager::self();
+    d->defaultDropAction = Qt::IgnoreAction;
+    d->possible_actions = supportedActions;
+
+    if (manager) {
+        if (defaultDropAction == Qt::IgnoreAction) {
+            if (supportedActions & Qt::MoveAction) {
+                d->defaultDropAction = Qt::MoveAction;
+            } else if (supportedActions & Qt::CopyAction) {
+                d->defaultDropAction = Qt::CopyAction;
+            } else if (supportedActions & Qt::LinkAction) {
+                d->defaultDropAction = Qt::LinkAction;
+            }
+        } else {
+            d->defaultDropAction = defaultDropAction;
+        }
+        d->executed_action = manager->drag(this);
+    }
+
+    return d->executed_action;
+}
+
+/*!
+    \obsolete
+
+    \bold{Note:} It is recommended to use exec() instead of this function.
+
+    Starts the drag and drop operation and returns a value indicating the requested
+    drop action when it is completed. The drop actions that the user can choose
+    from are specified in \a request. Qt::CopyAction is always allowed.
+
+    \bold{Note:} Although the drag and drop operation can take some time, this function
+    does not block the event loop. Other events are still delivered to the application
+    while the operation is performed.
+
+    \sa exec()
+*/
+Qt::DropAction QDrag::start(Qt::DropActions request)
+{
+    Q_D(QDrag);
+    if (!d->data) {
+        qWarning("QDrag: No mimedata set before starting the drag");
+        return d->executed_action;
+    }
+    QDragManager *manager = QDragManager::self();
+    d->defaultDropAction = Qt::IgnoreAction;
+    d->possible_actions = request | Qt::CopyAction;
+    if (manager)
+        d->executed_action = manager->drag(this);
+    return d->executed_action;
+}
+
+/*!
+    Sets the drag \a cursor for the \a action. This allows you
+    to override the default native cursors. To revert to using the
+    native cursor for \a action pass in a null QPixmap as \a cursor.
+
+    The \a action can only be CopyAction, MoveAction or LinkAction.
+    All other values of DropAction are ignored.
+*/
+void QDrag::setDragCursor(const QPixmap &cursor, Qt::DropAction action)
+{
+    Q_D(QDrag);
+    if (action != Qt::CopyAction && action != Qt::MoveAction && action != Qt::LinkAction)
+        return;
+    if (cursor.isNull())
+        d->customCursors.remove(action);
+    else
+        d->customCursors[action] = cursor;
+}
+
+/*!
+    \fn void QDrag::actionChanged(Qt::DropAction action)
+
+    This signal is emitted when the \a action associated with the
+    drag changes.
+
+    \sa targetChanged()
+*/
+
+/*!
+    \fn void QDrag::targetChanged(QWidget *newTarget)
+
+    This signal is emitted when the target of the drag and drop
+    operation changes, with \a newTarget the new target.
+
+    \sa target(), actionChanged()
+*/
+
+QT_END_NAMESPACE
+
+#endif // QT_NO_DRAGANDDROP