The QDragObject encapsulates MIME-based drag-and-drop interaction. More...
#include <qdragobject.h>
Inherits QObject.
Inherited by QImageDrag and QStoredDrag.
Drag-and-drop in Qt uses the MIME open standard, to allow independently developers applications to exchange information.
To start a drag, for example in a mouse motion event, create an object of the QDragObject subclass appropriate for your media, such as QTextDrag for text and QImageDrag for images. Then call the drag() method. This is all you need for simple dragging of existing types.
To be able to receive media dropped on a widget, multiply-inherit the QDropSite class and override the dragEnterEvent(), dragMoveEvent(), dragLeaveEvent(), and dropEvent() event handler methods.
Support for specific media types is provided by subclasses of QDragObject. For example, QTextDrag provides support for the "text/plain" MIME type (ordinary unformated text), QImageDrag provides for "image/*", where * is all the image formats that Qt supports, and the QUrlDrag subclass provides "url/url", a standard format for transfering a list of filenames.
To implement drag-and-drop of some type of media for which there is no available QDragObject subclass, the first and most important step is to look for existing formats that are appropriate - the Internet Assigned Numbers Authority (IANA) provides a hierarchical list of MIME media types at the Information Sciences Institute (ISI). This maximizes inter-operability of your software.
To support an additional media type, subclass either QDragObject or QStoredDrag. Subclass QDragObject when you need to provide support for multiple media types. Subclass the simpler QStoredDrag when one type is sufficient.
Subclasses of QDragObject will override the format() and encodedData() members, and provide a set-method to encode the media data and static members canDecode() and decode() to decode incoming data. QImageDrag is an example of such a class in Qt. Of course, you can provide drag-only or drop-only support for a media type by omitting some of these methods.
Subclasses of QStoredDrag provide a set-method to encode the media data and static members canDecode() and decode() to decode incoming data. QTextDrag in Qt 1.x is an example of such a class in Qt.
Creates a drag object which is a child of dragSource and named name.
Note that the drag object will be deleted when dragSource is.
Deletes the drag object and frees up the storage used.
Starts a drag operation using the contents of this object, using DragDefault mode.
See drag(DragMove) for important further information.
[virtual protected]Starts a drag operation using the contents of this object.
At this point, the object becomes owned by Qt, not the application. You should not delete the drag object nor anything it references. The actual transfer of data to the target application will be done during future event processing - after that time the drag object will be deleted.
Returns TRUE if the dragged data was dragged as a move, indicating that the caller should remove the original source of the data (the drag object must continue to have a copy).
The mode is one of:
DragDefault - the mode is determined heuristically.
DragCopy - the data is copied, never moved.
DragMove - the data is moved, if dragged at all.
DragCopyOrMove - the user chooses the mode
by using control key to switch from the default.
Normally one of simpler drag(), dragMove(), or dragCopy() functions would be used instead.
Starts a drag operation using the contents of this object, using DragCopy mode.
See drag(DragMove) for important further information.
Starts a drag operation using the contents of this object, using DragMove mode.
See drag(DragMove) for important further information.
[virtual]Returns the encoded payload of this object. The drag manager calls this when the recipient needs to see the content of the drag; this generally doesn't happen until the actual drop.
Subclasses must override this function.
[virtual]Returns the ith format, or NULL.
Returns the currently set pixmap (which isNull() if none is set).
Returns the currently set pixmap hitspot.
[virtual]Returns TRUE if the drag object can provide the data in format mimeType. The default implementation iterates over format().
Set the pixmap pm to display while dragging the object. The platform-specific implementation will use this in a loose fashion - so provide a small masked pixmap, but do not require that the user ever sees it in all its splendour. In particular, cursors on Windows 95 are of limited size.
The hotspot is the point on (or off) the pixmap that should be under the cursor as it is dragged. It is relative to the top-left pixel of the pixmap.
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
Uses a hotspot that positions the pixmap below and to the right of the mouse pointer. This allows the user to clearly see the point on the window which they are dragging the data onto.
Returns a pointer to the drag source where this object originated.
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