qdrag.cpp

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39 -

40 #include <qdrag.h> -

41 #include "private/qguiapplication_p.h" -

42 #include "qpa/qplatformintegration.h" -

43 #include "qpa/qplatformdrag.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 \inmodule QtGui -

55 \ingroup draganddrop -

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

57 transfer. -

58 -

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

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

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

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

63 -

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

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

66 following way: -

67 -

68 \snippet dragging/mainwindow.cpp 1 -

69 -

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

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

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

73 completed. -

74 -

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

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

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

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

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

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

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

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

83 edge: -

84 -

85 \snippet separations/finalwidget.cpp 2 -

86 -

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

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

89 directly under the cursor. -

90 -

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

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

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

94 implemented. -

95 -

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

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

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

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

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

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

102 required. -

103 -

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

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

106 {Fridge Magnets Example} -

107 */ -

108 -

109 /*! -

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

111 */ -

112 QDrag::QDrag(QObject *dragSource) -

113 : QObject(*new QDragPrivate, dragSource) -

114 { -

115 Q_D(QDrag); -

116 d->source = dragSource; -

117 d->target = 0; -

118 d->data = 0; -

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

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

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

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

123 } -

124 -

125 /*! -

126 Destroys the drag object. -

127 */ -

128 QDrag::~QDrag() -

129 { -

130 Q_D(QDrag); -

131 delete d->data; -

132 } -

133 -

134 /*! -

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

136 transferred to the QDrag object. -

137 */ -

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

139 { -

140 Q_D(QDrag); -

141 if (d->data == data) -

142 return; -

143 if (d->data != 0) -

144 delete d->data; -

145 d->data = data; -

146 } -

147 -

148 /*! -

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

150 */ -

151 QMimeData *QDrag::mimeData() const -

152 { -

153 Q_D(const QDrag); -

154 return d->data; -

155 } -

156 -

157 /*! -

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

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

160 started. -

161 */ -

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

163 { -

164 Q_D(QDrag); -

165 d->pixmap = pixmap; -

166 } -

167 -

168 /*! -

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

170 */ -

171 QPixmap QDrag::pixmap() const -

172 { -

173 Q_D(const QDrag); -

174 return d->pixmap; -

175 } -

176 -

177 /*! -

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

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

180 -

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

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

183 directly under the cursor. -

184 */ -

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

186 { -

187 Q_D(QDrag); -

188 d->hotspot = hotspot; -

189 } -

190 -

191 /*! -

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

193 cursor. -

194 */ -

195 QPoint QDrag::hotSpot() const -

196 { -

197 Q_D(const QDrag); -

198 return d->hotspot; -

199 } -

200 -

201 /*! -

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

203 and drop operation originated. -

204 */ -

205 QObject *QDrag::source() const -

206 { -

207 Q_D(const QDrag); -

208 return d->source; -

209 } -

210 -

211 /*! -

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

213 the drag object was dropped. -

214 */ -

215 QObject *QDrag::target() const -

216 { -

217 Q_D(const QDrag); -

218 return d->target; -

219 } -

220 -

221 /*! -

222 \since 4.3 -

223 -

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

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

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

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

228 -

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

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

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

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

233 blocked during the operation. -

234 -

235 \sa cancel() -

236 */ -

237 -

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

239 { -

240 return exec(supportedActions, Qt::IgnoreAction); -

241 } -

242 -

243 /*! -

244 \since 4.3 -

245 -

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

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

248 from are specified in \a supportedActions. -

249 -

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

251 drag without using modifier keys. -

252 -

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

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

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

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

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

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

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

260 */ -

261 -

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

263 { -

264 Q_D(QDrag); -

265 if (!d->data) { -

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

267 return d->executed_action; -

268 } -

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

270 -

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

272 if (supportedActions & Qt::MoveAction) { -

273 transformedDefaultDropAction = Qt::MoveAction; -

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

275 transformedDefaultDropAction = Qt::CopyAction; -

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

277 transformedDefaultDropAction = Qt::LinkAction; -

278 } -

279 } else { -

280 transformedDefaultDropAction = defaultDropAction; -

281 } -

282 d->supported_actions = supportedActions; -

283 d->default_action = transformedDefaultDropAction; -

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

285 -

286 return d->executed_action; -

287 } -

288 -

289 /*! -

290 \obsolete -

291 -

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

293 -

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

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

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

297 -

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

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

300 while the operation is performed. -

301 -

302 \sa exec() -

303 */ -

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

305 { -

306 Q_D(QDrag); -

307 if (!d->data) { -

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

309 return d->executed_action; -

310 } -

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

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

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

314 return d->executed_action; -

315 } -

316 -

317 /*! -

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

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

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

321 -

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

323 All other values of DropAction are ignored. -

324 */ -

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

326 { -

327 Q_D(QDrag); -

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

329 return; -

330 if (cursor.isNull()) -

331 d->customCursors.remove(action); -

332 else -

333 d->customCursors[action] = cursor; -

334 } -

335 -

336 /*! -

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

338 -

339 \since 5.0 -

340 */ -

341 -

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

343 { -

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

345 -

346 Q_D(const QDrag); -

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

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

349 return it.value(); -

350 -

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

352 switch (action) { -

353 case Qt::MoveAction: -

354 shape = Qt::DragMoveCursor; -

355 break; -

356 case Qt::CopyAction: -

357 shape = Qt::DragCopyCursor; -

358 break; -

359 case Qt::LinkAction: -

360 shape = Qt::DragLinkCursor; -

361 break; -

362 default: -

363 shape = Qt::ForbiddenCursor; -

364 } -

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

366 } -

367 -

368 /*! -

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

370 -

371 \sa exec(), defaultAction() -

372 */ -

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

374 { -

375 Q_D(const QDrag); -

376 return d->supported_actions; -

377 } -

378 -

379 -

380 /*! -

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

382 -

383 \sa exec(), supportedActions() -

384 */ -

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

386 { -

387 Q_D(const QDrag); -

388 return d->default_action; -

389 } -

390 -

391 /*! -

392 Cancels a drag operation initiated by Qt. -

393 -

394 \note This is currently implemented on Windows and X11. -

395 -

396 \since 5.6 -

397 \sa exec() -

398 */ -

399 void QDrag::cancel() -

400 { -

401

if (QPlatformDrag *platformDrag = QGuiApplicationPrivate::platformIntegration()->drag())

QPlatformDrag ...tion()->drag()	Description
TRUE	never evaluated
FALSE	never evaluated

402

platformDrag->cancelDrag();

never executed: platformDrag->cancelDrag();

403

}

never executed: end of block

404 -

405 /*! -

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

407 -

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

409 drag changes. -

410 -

411 \sa targetChanged() -

412 */ -

413 -

414 /*! -

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

416 -

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

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

419 -

420 \sa target(), actionChanged() -

421 */ -

422 -

423 QT_END_NAMESPACE -

424 -

425 #endif // QT_NO_DRAGANDDROP -

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