qdrag.cpp

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33 -

34 #include <qdrag.h> -

35 #include "private/qguiapplication_p.h" -

36 #include <qpixmap.h> -

37 #include <qpoint.h> -

38 #include "qdnd_p.h" -

39 -

40 #ifndef QT_NO_DRAGANDDROP -

41 -

42 QT_BEGIN_NAMESPACE -

43 -

44 /*! -

45 \class QDrag -

46 \inmodule QtGui -

47 \ingroup draganddrop -

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

49 transfer. -

50 -

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

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

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

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

55 -

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

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

58 following way: -

59 -

60 \snippet dragging/mainwindow.cpp 1 -

61 -

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

63 QDrag object. The QDrag must be constructed on the heap with a parent QObject -

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

65 completed. -

66 -

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

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

69 pixmap typically shows an icon that represents the MIME type of -

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

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

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

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

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

75 edge: -

76 -

77 \snippet separations/finalwidget.cpp 2 -

78 -

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

80 movements if the hot spot causes the pixmap to be displayed -

81 directly under the cursor. -

82 -

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

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

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

86 implemented. -

87 -

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

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

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

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

92 whether the user has pressed a mouse button, and reimplement -

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

94 required. -

95 -

96 \sa {Drag and Drop}, QClipboard, QMimeData, QMacPasteboardMime, -

97 {Draggable Icons Example}, {Draggable Text Example}, {Drop Site Example}, -

98 {Fridge Magnets Example} -

99 */ -

100 -

101 /*! -

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

103 */ -

104 QDrag::QDrag(QObject *dragSource) -

105 : QObject(*new QDragPrivate, dragSource) -

106 { -

107 Q_D(QDrag); -

108 d->source = dragSource; -

109 d->target = 0; -

110 d->data = 0; -

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

112 d->executed_action = Qt::IgnoreAction; -

113 d->supported_actions = Qt::IgnoreAction; -

114 d->default_action = Qt::IgnoreAction; -

115

}

never executed: end of block

116 -

117 /*! -

118 Destroys the drag object. -

119 */ -

120 QDrag::~QDrag() -

121 { -

122 Q_D(QDrag); -

123 delete d->data; -

124

}

never executed: end of block

125 -

126 /*! -

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

128 transferred to the QDrag object. -

129 */ -

130 void QDrag::setMimeData(QMimeData *data) -

131 { -

132 Q_D(QDrag); -

133

if (d->data == data)

d->data == data	Description
TRUE	never evaluated
FALSE	never evaluated

134

return;

never executed: return;

135

if (d->data != 0)

d->data != 0	Description
TRUE	never evaluated
FALSE	never evaluated

136

delete d->data;

never executed: delete d->data;

137 d->data = data; -

138

}

never executed: end of block

139 -

140 /*! -

141 Returns the MIME data that is encapsulated by the drag object. -

142 */ -

143 QMimeData *QDrag::mimeData() const -

144 { -

145 Q_D(const QDrag); -

146

return d->data;

never executed: return d->data;

147 } -

148 -

149 /*! -

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

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

152 started. -

153 */ -

154 void QDrag::setPixmap(const QPixmap &pixmap) -

155 { -

156 Q_D(QDrag); -

157 d->pixmap = pixmap; -

158

}

never executed: end of block

159 -

160 /*! -

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

162 */ -

163 QPixmap QDrag::pixmap() const -

164 { -

165 Q_D(const QDrag); -

166

return d->pixmap;

never executed: return d->pixmap;

167 } -

168 -

169 /*! -

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

171 pixmap used to the point specified by \a hotspot. -

172 -

173 \b{Note:} on X11, the pixmap may not be able to keep up with the mouse -

174 movements if the hot spot causes the pixmap to be displayed -

175 directly under the cursor. -

176 */ -

177 void QDrag::setHotSpot(const QPoint& hotspot) -

178 { -

179 Q_D(QDrag); -

180 d->hotspot = hotspot; -

181

}

never executed: end of block

182 -

183 /*! -

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

185 cursor. -

186 */ -

187 QPoint QDrag::hotSpot() const -

188 { -

189 Q_D(const QDrag); -

190

return d->hotspot;

never executed: return d->hotspot;

191 } -

192 -

193 /*! -

194 Returns the source of the drag object. This is the widget where the drag -

195 and drop operation originated. -

196 */ -

197 QObject *QDrag::source() const -

198 { -

199 Q_D(const QDrag); -

200

return d->source;

never executed: return d->source;

201 } -

202 -

203 /*! -

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

205 the drag object was dropped. -

206 */ -

207 QObject *QDrag::target() const -

208 { -

209 Q_D(const QDrag); -

210

return d->target;

never executed: return d->target;

211 } -

212 -

213 /*! -

214 \since 4.3 -

215 -

216 Starts the drag and drop operation and returns a value indicating the requested -

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

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

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

220 -

221 \b{Note:} On Linux and \macos, the drag and drop operation -

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

223 loop. Other events are still delivered to the application while -

224 the operation is performed. On Windows, the Qt event loop is -

225 blocked during the operation. -

226 */ -

227 -

228 Qt::DropAction QDrag::exec(Qt::DropActions supportedActions) -

229 { -

230

return exec(supportedActions, Qt::IgnoreAction);

never executed: return exec(supportedActions, Qt::IgnoreAction);

231 } -

232 -

233 /*! -

234 \since 4.3 -

235 -

236 Starts the drag and drop operation and returns a value indicating the requested -

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

238 from are specified in \a supportedActions. -

239 -

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

241 drag without using modifier keys. -

242 -

243 \b{Note:} On Linux and \macos, the drag and drop operation -

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

245 loop. Other events are still delivered to the application while -

246 the operation is performed. On Windows, the Qt event loop is -

247 blocked during the operation. However, QDrag::exec() on -

248 Windows causes processEvents() to be called frequently to keep the GUI responsive. -

249 If any loops or operations are called while a drag operation is active, it will block the drag operation. -

250 */ -

251 -

252 Qt::DropAction QDrag::exec(Qt::DropActions supportedActions, Qt::DropAction defaultDropAction) -

253 { -

254 Q_D(QDrag); -

255

if (!d->data) {

!d->data	Description
TRUE	never evaluated
FALSE	never evaluated

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

257

return d->executed_action;

never executed: return d->executed_action;

258 } -

259 Qt::DropAction transformedDefaultDropAction = Qt::IgnoreAction; -

260 -

261

if (defaultDropAction == Qt::IgnoreAction) {

defaultDropAct...::IgnoreAction	Description
TRUE	never evaluated
FALSE	never evaluated

262

if (supportedActions & Qt::MoveAction) {

supportedActio...Qt::MoveAction	Description
TRUE	never evaluated
FALSE	never evaluated

263 transformedDefaultDropAction = Qt::MoveAction; -

264

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

never executed: end of block

supportedActio...Qt::CopyAction	Description
TRUE	never evaluated
FALSE	never evaluated

265 transformedDefaultDropAction = Qt::CopyAction; -

266

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

never executed: end of block

supportedActio...Qt::LinkAction	Description
TRUE	never evaluated
FALSE	never evaluated

267 transformedDefaultDropAction = Qt::LinkAction; -

268

}

never executed: end of block

269

} else {

never executed: end of block

270 transformedDefaultDropAction = defaultDropAction; -

271

}

never executed: end of block

272 d->supported_actions = supportedActions; -

273 d->default_action = transformedDefaultDropAction; -

274 d->executed_action = QDragManager::self()->drag(this); -

275 -

276

return d->executed_action;

never executed: return d->executed_action;

277 } -

278 -

279 /*! -

280 \obsolete -

281 -

282 \b{Note:} It is recommended to use exec() instead of this function. -

283 -

284 Starts the drag and drop operation and returns a value indicating the requested -

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

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

287 -

288 \b{Note:} Although the drag and drop operation can take some time, this function -

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

290 while the operation is performed. -

291 -

292 \sa exec() -

293 */ -

294 Qt::DropAction QDrag::start(Qt::DropActions request) -

295 { -

296 Q_D(QDrag); -

297

if (!d->data) {

!d->data	Description
TRUE	never evaluated
FALSE	never evaluated

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

299

return d->executed_action;

never executed: return d->executed_action;

300 } -

301 d->supported_actions = request | Qt::CopyAction; -

302 d->default_action = Qt::IgnoreAction; -

303 d->executed_action = QDragManager::self()->drag(this); -

304

return d->executed_action;

never executed: return d->executed_action;

305 } -

306 -

307 /*! -

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

309 to override the default native cursors. To revert to using the -

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

311 -

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

313 All other values of DropAction are ignored. -

314 */ -

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

316 { -

317 Q_D(QDrag); -

318

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

action != Qt::CopyAction	Description
TRUE	never evaluated
FALSE	never evaluated

action != Qt::MoveAction	Description
TRUE	never evaluated
FALSE	never evaluated

action != Qt::LinkAction	Description
TRUE	never evaluated
FALSE	never evaluated

319

return;

never executed: return;

320

if (cursor.isNull())

cursor.isNull()	Description
TRUE	never evaluated
FALSE	never evaluated

321

d->customCursors.remove(action);

never executed: d->customCursors.remove(action);

322 else -

323

d->customCursors[action] = cursor;

never executed: d->customCursors[action] = cursor;

324 } -

325 -

326 /*! -

327 Returns the drag cursor for the \a action. -

328 -

329 \since 5.0 -

330 */ -

331 -

332 QPixmap QDrag::dragCursor(Qt::DropAction action) const -

333 { -

334 typedef QMap<Qt::DropAction, QPixmap>::const_iterator Iterator; -

335 -

336 Q_D(const QDrag); -

337 const Iterator it = d->customCursors.constFind(action); -

338

if (it != d->customCursors.constEnd())

it != d->custo...ors.constEnd()	Description
TRUE	never evaluated
FALSE	never evaluated

339

return it.value();

never executed: return it.value();

340 -

341 Qt::CursorShape shape = Qt::ForbiddenCursor; -

342 switch (action) { -

343

case Qt::MoveAction:

never executed: case Qt::MoveAction:

344 shape = Qt::DragMoveCursor; -

345

break;

never executed: break;

346

case Qt::CopyAction:

never executed: case Qt::CopyAction:

347 shape = Qt::DragCopyCursor; -

348

break;

never executed: break;

349

case Qt::LinkAction:

never executed: case Qt::LinkAction:

350 shape = Qt::DragLinkCursor; -

351

break;

never executed: break;

352

default:

never executed: default:

353 shape = Qt::ForbiddenCursor; -

354

}

never executed: end of block

355

return QGuiApplicationPrivate::instance()->getPixmapCursor(shape);

never executed: return QGuiApplicationPrivate::instance()->getPixmapCursor(shape);

356 } -

357 -

358 /*! -

359 Returns the set of possible drop actions for this drag operation. -

360 -

361 \sa exec(), defaultAction() -

362 */ -

363 Qt::DropActions QDrag::supportedActions() const -

364 { -

365 Q_D(const QDrag); -

366

return d->supported_actions;

never executed: return d->supported_actions;

367 } -

368 -

369 -

370 /*! -

371 Returns the default proposed drop action for this drag operation. -

372 -

373 \sa exec(), supportedActions() -

374 */ -

375 Qt::DropAction QDrag::defaultAction() const -

376 { -

377 Q_D(const QDrag); -

378

return d->default_action;

never executed: return d->default_action;

379 } -

380 /*! -

381 \fn void QDrag::actionChanged(Qt::DropAction action) -

382 -

383 This signal is emitted when the \a action associated with the -

384 drag changes. -

385 -

386 \sa targetChanged() -

387 */ -

388 -

389 /*! -

390 \fn void QDrag::targetChanged(QObject *newTarget) -

391 -

392 This signal is emitted when the target of the drag and drop -

393 operation changes, with \a newTarget the new target. -

394 -

395 \sa target(), actionChanged() -

396 */ -

397 -

398 QT_END_NAMESPACE -

399 -

400 #endif // QT_NO_DRAGANDDROP -

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