qgraphicslayout.cpp

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39 -

40 #include "qapplication.h" -

41 -

42 #ifndef QT_NO_GRAPHICSVIEW -

43 #include "qgraphicslayout.h" -

44 #include "qgraphicslayout_p.h" -

45 #include "qgraphicslayoutitem.h" -

46 #include "qgraphicslayoutitem_p.h" -

47 #include "qgraphicswidget.h" -

48 #include "qgraphicswidget_p.h" -

49 #include "qgraphicsscene.h" -

50 -

51 QT_BEGIN_NAMESPACE -

52 -

53 /*! -

54 \class QGraphicsLayout -

55 \brief The QGraphicsLayout class provides the base class for all layouts -

56 in Graphics View. -

57 \since 4.4 -

58 \ingroup graphicsview-api -

59 \inmodule QtWidgets -

60 -

61 QGraphicsLayout is an abstract class that defines a virtual API for -

62 arranging QGraphicsWidget children and other QGraphicsLayoutItem objects -

63 for a QGraphicsWidget. QGraphicsWidget assigns responsibility to a -

64 QGraphicsLayout through QGraphicsWidget::setLayout(). As the widget -

65 is resized, the layout will automatically arrange the widget's children. -

66 QGraphicsLayout inherits QGraphicsLayoutItem, so, it can be managed by -

67 any layout, including its own subclasses. -

68 -

69 \section1 Writing a Custom Layout -

70 -

71 You can use QGraphicsLayout as a base to write your own custom layout -

72 (e.g., a flowlayout), but it is more common to use one of its subclasses -

73 instead - QGraphicsLinearLayout or QGraphicsGridLayout. When creating -

74 a custom layout, the following functions must be reimplemented as a bare -

75 minimum: -

76 -

77 \table -

78 \header \li Function \li Description -

79 \row \li QGraphicsLayoutItem::setGeometry() -

80 \li Notifies you when the geometry of the layout is set. You can -

81 store the geometry in your own layout class in a reimplementation -

82 of this function. -

83 \row \li QGraphicsLayoutItem::sizeHint() -

84 \li Returns the layout's size hints. -

85 \row \li QGraphicsLayout::count() -

86 \li Returns the number of items in your layout. -

87 \row \li QGraphicsLayout::itemAt() -

88 \li Returns a pointer to an item in your layout. -

89 \row \li QGraphicsLayout::removeAt() -

90 \li Removes an item from your layout without destroying it. -

91 \endtable -

92 -

93 For more details on how to implement each function, refer to the individual -

94 function documentation. -

95 -

96 Each layout defines its own API for arranging widgets and layout items. -

97 For example, with a grid layout, you require a row and a -

98 column index with optional row and column spans, alignment, spacing, and more. -

99 A linear layout, however, requires a single row or column index to position its -

100 items. For a grid layout, the order of insertion does not affect the layout in -

101 any way, but for a linear layout, the order is essential. When writing your own -

102 layout subclass, you are free to choose the API that best suits your layout. -

103 -

104 QGraphicsLayout provides the addChildLayoutItem() convenience function to add -

105 layout items to a custom layout. The function will automatically reparent -

106 graphics items, if required. -

107 -

108 \section1 Activating the Layout -

109 -

110 When the layout's geometry changes, QGraphicsLayout immediately rearranges -

111 all of its managed items by calling setGeometry() on each item. This -

112 rearrangement is called \e activating the layout. -

113 -

114 QGraphicsLayout updates its own geometry to match the contentsRect() of the -

115 QGraphicsLayoutItem it is managing. Thus, it will automatically rearrange all -

116 its items when the widget is resized. QGraphicsLayout caches the sizes of all -

117 its managed items to avoid calling setGeometry() too often. -

118 -

119 \note A QGraphicsLayout will have the same geometry as the contentsRect() -

120 of the widget (not the layout) it is assigned to. -

121 -

122 \section2 Activating the Layout Implicitly -

123 -

124 The layout can be activated implicitly using one of two ways: by calling -

125 activate() or by calling invalidate(). Calling activate() activates the layout -

126 immediately. In contrast, calling invalidate() is delayed, as it posts a -

127 \l{QEvent::LayoutRequest}{LayoutRequest} event to the managed widget. Due -

128 to event compression, the activate() will only be called once after control has -

129 returned to the event loop. This is referred to as \e invalidating the layout. -

130 Invalidating the layout also invalidates any cached information. Also, the -

131 invalidate() function is a virtual function. So, you can invalidate your own -

132 cache in a subclass of QGraphicsLayout by reimplementing this function. -

133 -

134 \section1 Event Handling -

135 -

136 QGraphicsLayout listens to events for the widget it manages through the -

137 virtual widgetEvent() event handler. When the layout is assigned to a -

138 widget, all events delivered to the widget are first processed by -

139 widgetEvent(). This allows the layout to be aware of any relevant state -

140 changes on the widget such as visibility changes or layout direction changes. -

141 -

142 \section1 Margin Handling -

143 -

144 The margins of a QGraphicsLayout can be modified by reimplementing -

145 setContentsMargins() and getContentsMargins(). -

146 -

147 */ -

148 -

149 /*! -

150 Contructs a QGraphicsLayout object. -

151 -

152 \a parent is passed to QGraphicsLayoutItem's constructor and the -

153 QGraphicsLayoutItem's isLayout argument is set to \e true. -

154 -

155 If \a parent is a QGraphicsWidget the layout will be installed -

156 on that widget. (Note that installing a layout will delete the old one -

157 installed.) -

158 */ -

159 QGraphicsLayout::QGraphicsLayout(QGraphicsLayoutItem *parent) -

160 : QGraphicsLayoutItem(*new QGraphicsLayoutPrivate) -

161 { -

162 setParentLayoutItem(parent); -

163

if (parent && !parent->isLayout()) {

parent	Description
TRUE	never evaluated
FALSE	never evaluated

!parent->isLayout()	Description
TRUE	never evaluated
FALSE	never evaluated

164 // If a layout has a parent that is not a layout it must be a QGraphicsWidget. -

165 QGraphicsItem *itemParent = parent->graphicsItem(); -

166

if (itemParent && itemParent->isWidget()) {

itemParent	Description
TRUE	never evaluated
FALSE	never evaluated

itemParent->isWidget()	Description
TRUE	never evaluated
FALSE	never evaluated

167 static_cast<QGraphicsWidget *>(itemParent)->d_func()->setLayout_helper(this); -

168

} else {

never executed: end of block

169 qWarning("QGraphicsLayout::QGraphicsLayout: Attempt to create a layout with a parent that is" -

170 " neither a QGraphicsWidget nor QGraphicsLayout"); -

171

}

never executed: end of block

172 } -

173 d_func()->sizePolicy = QSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding, QSizePolicy::DefaultType); -

174 setOwnedByLayout(true); -

175

}

never executed: end of block

176 -

177 /*! -

178 \internal -

179 */ -

180 QGraphicsLayout::QGraphicsLayout(QGraphicsLayoutPrivate &dd, QGraphicsLayoutItem *parent) -

181 : QGraphicsLayoutItem(dd) -

182 { -

183 setParentLayoutItem(parent); -

184

if (parent && !parent->isLayout()) {

parent	Description
TRUE	never evaluated
FALSE	never evaluated

!parent->isLayout()	Description
TRUE	never evaluated
FALSE	never evaluated

185 // If a layout has a parent that is not a layout it must be a QGraphicsWidget. -

186 QGraphicsItem *itemParent = parent->graphicsItem(); -

187

if (itemParent && itemParent->isWidget()) {

itemParent	Description
TRUE	never evaluated
FALSE	never evaluated

itemParent->isWidget()	Description
TRUE	never evaluated
FALSE	never evaluated

188 static_cast<QGraphicsWidget *>(itemParent)->d_func()->setLayout_helper(this); -

189

} else {

never executed: end of block

190 qWarning("QGraphicsLayout::QGraphicsLayout: Attempt to create a layout with a parent that is" -

191 " neither a QGraphicsWidget nor QGraphicsLayout"); -

192

}

never executed: end of block

193 } -

194 d_func()->sizePolicy = QSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding, QSizePolicy::DefaultType); -

195 setOwnedByLayout(true); -

196

}

never executed: end of block

197 -

198 /*! -

199 Destroys the QGraphicsLayout object. -

200 */ -

201 QGraphicsLayout::~QGraphicsLayout() -

202 { -

203 } -

204 -

205 /*! -

206 Sets the contents margins to \a left, \a top, \a right and \a bottom. The -

207 default contents margins for toplevel layouts are style dependent -

208 (by querying the pixelMetric for QStyle::PM_LayoutLeftMargin, -

209 QStyle::PM_LayoutTopMargin, QStyle::PM_LayoutRightMargin and -

210 QStyle::PM_LayoutBottomMargin). -

211 -

212 For sublayouts the default margins are 0. -

213 -

214 Changing the contents margins automatically invalidates the layout. -

215 -

216 \sa invalidate() -

217 */ -

218 void QGraphicsLayout::setContentsMargins(qreal left, qreal top, qreal right, qreal bottom) -

219 { -

220 Q_D(QGraphicsLayout); -

221

if (d->left == left && d->top == top && d->right == right && d->bottom == bottom)

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

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

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

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

222

return;

never executed: return;

223 d->left = left; -

224 d->right = right; -

225 d->top = top; -

226 d->bottom = bottom; -

227 invalidate(); -

228

}

never executed: end of block

229 -

230 /*! -

231 \reimp -

232 */ -

233 void QGraphicsLayout::getContentsMargins(qreal *left, qreal *top, qreal *right, qreal *bottom) const -

234 { -

235 Q_D(const QGraphicsLayout); -

236 d->getMargin(left, d->left, QStyle::PM_LayoutLeftMargin); -

237 d->getMargin(top, d->top, QStyle::PM_LayoutTopMargin); -

238 d->getMargin(right, d->right, QStyle::PM_LayoutRightMargin); -

239 d->getMargin(bottom, d->bottom, QStyle::PM_LayoutBottomMargin); -

240

}

never executed: end of block

241 -

242 /*! -

243 Activates the layout, causing all items in the layout to be immediately -

244 rearranged. This function is based on calling count() and itemAt(), and -

245 then calling setGeometry() on all items sequentially. When activated, -

246 the layout will adjust its geometry to its parent's contentsRect(). -

247 The parent will then invalidate any layout of its own. -

248 -

249 If called in sequence or recursively, e.g., by one of the arranged items -

250 in response to being resized, this function will do nothing. -

251 -

252 Note that the layout is free to use geometry caching to optimize this -

253 process. To forcefully invalidate any such cache, you can call -

254 invalidate() before calling activate(). -

255 -

256 \sa invalidate() -

257 */ -

258 void QGraphicsLayout::activate() -

259 { -

260 Q_D(QGraphicsLayout); -

261

if (d->activated)

d->activated	Description
TRUE	never evaluated
FALSE	never evaluated

262

return;

never executed: return;

263 -

264 d->activateRecursive(this); -

265 -

266 // we don't call activate on a sublayout, but somebody might. -

267 // Therefore, we walk to the parentitem of the toplevel layout. -

268 QGraphicsLayoutItem *parentItem = this; -

269

while (parentItem && parentItem->isLayout())

parentItem	Description
TRUE	never evaluated
FALSE	never evaluated

parentItem->isLayout()	Description
TRUE	never evaluated
FALSE	never evaluated

270

parentItem = parentItem->parentLayoutItem();

never executed: parentItem = parentItem->parentLayoutItem();

271

if (!parentItem)

!parentItem	Description
TRUE	never evaluated
FALSE	never evaluated

272

return;

never executed: return;

273 Q_ASSERT(!parentItem->isLayout()); -

274 -

275

if (QGraphicsLayout::instantInvalidatePropagation()) {

QGraphicsLayou...ePropagation()	Description
TRUE	never evaluated
FALSE	never evaluated

276 QGraphicsWidget *parentWidget = static_cast<QGraphicsWidget*>(parentItem); -

277

if (!parentWidget->parentLayoutItem()) {

!parentWidget-...ntLayoutItem()	Description
TRUE	never evaluated
FALSE	never evaluated

278 // we've reached the topmost widget, resize it -

279 bool wasResized = parentWidget->testAttribute(Qt::WA_Resized); -

280 parentWidget->resize(parentWidget->size()); -

281 parentWidget->setAttribute(Qt::WA_Resized, wasResized); -

282

}

never executed: end of block

283 -

284 setGeometry(parentItem->contentsRect()); // relayout children -

285

} else {

never executed: end of block

286 setGeometry(parentItem->contentsRect()); // relayout children -

287 parentLayoutItem()->updateGeometry(); -

288

}

never executed: end of block

289 } -

290 -

291 /*! -

292 Returns \c true if the layout is currently being activated; otherwise, -

293 returns \c false. If the layout is being activated, this means that it is -

294 currently in the process of rearranging its items (i.e., the activate() -

295 function has been called, and has not yet returned). -

296 -

297 \sa activate(), invalidate() -

298 */ -

299 bool QGraphicsLayout::isActivated() const -

300 { -

301 Q_D(const QGraphicsLayout); -

302

return d->activated;

never executed: return d->activated;

303 } -

304 -

305 /*! -

306 Clears any cached geometry and size hint information in the layout, and -

307 posts a \l{QEvent::LayoutRequest}{LayoutRequest} event to the managed -

308 parent QGraphicsLayoutItem. -

309 -

310 \sa activate(), setGeometry() -

311 */ -

312 void QGraphicsLayout::invalidate() -

313 { -

314

if (QGraphicsLayout::instantInvalidatePropagation()) {

QGraphicsLayou...ePropagation()	Description
TRUE	never evaluated
FALSE	never evaluated

315 updateGeometry(); -

316

} else {

never executed: end of block

317 // only mark layouts as invalid (activated = false) if we can post a LayoutRequest event. -

318 QGraphicsLayoutItem *layoutItem = this; -

319

while (layoutItem && layoutItem->isLayout()) {

layoutItem	Description
TRUE	never evaluated
FALSE	never evaluated

layoutItem->isLayout()	Description
TRUE	never evaluated
FALSE	never evaluated

320 // we could call updateGeometry(), but what if that method -

321 // does not call the base implementation? In addition, updateGeometry() -

322 // does more than we need. -

323 layoutItem->d_func()->sizeHintCacheDirty = true; -

324 layoutItem->d_func()->sizeHintWithConstraintCacheDirty = true; -

325 layoutItem = layoutItem->parentLayoutItem(); -

326

}

never executed: end of block

327

if (layoutItem) {

layoutItem	Description
TRUE	never evaluated
FALSE	never evaluated

328 layoutItem->d_func()->sizeHintCacheDirty = true; -

329 layoutItem->d_func()->sizeHintWithConstraintCacheDirty = true; -

330

}

never executed: end of block

331 -

332

bool postIt = layoutItem ? !layoutItem->isLayout() : false;

layoutItem	Description
TRUE	never evaluated
FALSE	never evaluated

333

if (postIt) {

postIt	Description
TRUE	never evaluated
FALSE	never evaluated

334 layoutItem = this; -

335

while (layoutItem && layoutItem->isLayout()

layoutItem	Description
TRUE	never evaluated
FALSE	never evaluated

layoutItem->isLayout()	Description
TRUE	never evaluated
FALSE	never evaluated

336

&& static_cast<QGraphicsLayout*>(layoutItem)->d_func()->activated) {

static_cast<QG...c()->activated	Description
TRUE	never evaluated
FALSE	never evaluated

337 static_cast<QGraphicsLayout*>(layoutItem)->d_func()->activated = false; -

338 layoutItem = layoutItem->parentLayoutItem(); -

339

}

never executed: end of block

340

if (layoutItem && !layoutItem->isLayout()) {

layoutItem	Description
TRUE	never evaluated
FALSE	never evaluated

!layoutItem->isLayout()	Description
TRUE	never evaluated
FALSE	never evaluated

341 // If a layout has a parent that is not a layout it must be a QGraphicsWidget. -

342 QApplication::postEvent(static_cast<QGraphicsWidget *>(layoutItem), new QEvent(QEvent::LayoutRequest)); -

343

}

never executed: end of block

344

}

never executed: end of block

345

}

never executed: end of block

346 } -

347 -

348 /*! -

349 \reimp -

350 */ -

351 void QGraphicsLayout::updateGeometry() -

352 { -

353 Q_D(QGraphicsLayout); -

354

if (QGraphicsLayout::instantInvalidatePropagation()) {

QGraphicsLayou...ePropagation()	Description
TRUE	never evaluated
FALSE	never evaluated

355 d->activated = false; -

356 QGraphicsLayoutItem::updateGeometry(); -

357 -

358 QGraphicsLayoutItem *parentItem = parentLayoutItem(); -

359

if (!parentItem)

!parentItem	Description
TRUE	never evaluated
FALSE	never evaluated

360

return;

never executed: return;

361 -

362

if (parentItem->isLayout())

parentItem->isLayout()	Description
TRUE	never evaluated
FALSE	never evaluated

363

static_cast<QGraphicsLayout *>(parentItem)->invalidate();

never executed: static_cast<QGraphicsLayout *>(parentItem)->invalidate();

364 else -

365

parentItem->updateGeometry();

never executed: parentItem->updateGeometry();

366 } else { -

367 QGraphicsLayoutItem::updateGeometry(); -

368

if (QGraphicsLayoutItem *parentItem = parentLayoutItem()) {

QGraphicsLayou...ntLayoutItem()	Description
TRUE	never evaluated
FALSE	never evaluated

369

if (parentItem->isLayout()) {

parentItem->isLayout()	Description
TRUE	never evaluated
FALSE	never evaluated

370 parentItem->updateGeometry(); -

371

} else {

never executed: end of block

372 invalidate(); -

373

}

never executed: end of block

374 } -

375

}

never executed: end of block

376 } -

377 -

378 /*! -

379 This virtual event handler receives all events for the managed -

380 widget. QGraphicsLayout uses this event handler to listen for layout -

381 related events such as geometry changes, layout changes or layout -

382 direction changes. -

383 -

384 \a e is a pointer to the event. -

385 -

386 You can reimplement this event handler to track similar events for your -

387 own custom layout. -

388 -

389 \sa QGraphicsWidget::event(), QGraphicsItem::sceneEvent() -

390 */ -

391 void QGraphicsLayout::widgetEvent(QEvent *e) -

392 { -

393 switch (e->type()) { -

394

case QEvent::GraphicsSceneResize:

never executed: case QEvent::GraphicsSceneResize:

395

if (isActivated()) {

isActivated()	Description
TRUE	never evaluated
FALSE	never evaluated

396 setGeometry(parentLayoutItem()->contentsRect()); -

397

} else {

never executed: end of block

398 activate(); // relies on that activate() will call updateGeometry() -

399

}

never executed: end of block

400

break;

never executed: break;

401

case QEvent::LayoutRequest:

never executed: case QEvent::LayoutRequest:

402 activate(); -

403

break;

never executed: break;

404

case QEvent::LayoutDirectionChange:

never executed: case QEvent::LayoutDirectionChange:

405 invalidate(); -

406

break;

never executed: break;

407

default:

never executed: default:

408

break;

never executed: break;

409 } -

410 } -

411 -

412 /*! -

413 \fn virtual int QGraphicsLayout::count() const = 0 -

414 -

415 This pure virtual function must be reimplemented in a subclass of -

416 QGraphicsLayout to return the number of items in the layout. -

417 -

418 The subclass is free to decide how to store the items. -

419 -

420 \sa itemAt(), removeAt() -

421 */ -

422 -

423 /*! -

424 \fn virtual QGraphicsLayoutItem *QGraphicsLayout::itemAt(int i) const = 0 -

425 -

426 This pure virtual function must be reimplemented in a subclass of -

427 QGraphicsLayout to return a pointer to the item at index \a i. The -

428 reimplementation can assume that \a i is valid (i.e., it respects the -

429 value of count()). -

430 Together with count(), it is provided as a means of iterating over all items in a layout. -

431 -

432 The subclass is free to decide how to store the items, and the visual arrangement -

433 does not have to be reflected through this function. -

434 -

435 \sa count(), removeAt() -

436 */ -

437 -

438 /*! -

439 \fn virtual void QGraphicsLayout::removeAt(int index) = 0 -

440 -

441 This pure virtual function must be reimplemented in a subclass of -

442 QGraphicsLayout to remove the item at \a index. The -

443 reimplementation can assume that \a index is valid (i.e., it -

444 respects the value of count()). -

445 -

446 The implementation must ensure that the parentLayoutItem() of -

447 the removed item does not point to this layout, since the item is -

448 considered to be removed from the layout hierarchy. -

449 -

450 If the layout is to be reused between applications, we recommend -

451 that the layout deletes the item, but the graphics view framework -

452 does not depend on this. -

453 -

454 The subclass is free to decide how to store the items. -

455 -

456 \sa itemAt(), count() -

457 */ -

458 -

459 /*! -

460 \since 4.6 -

461 -

462 This function is a convenience function provided for custom layouts, and will go through -

463 all items in the layout and reparent their graphics items to the closest QGraphicsWidget -

464 ancestor of the layout. -

465 -

466 If \a layoutItem is already in a different layout, it will be removed from that layout. -

467 -

468 If custom layouts want special behaviour they can ignore to use this function, and implement -

469 their own behaviour. -

470 -

471 \sa graphicsItem() -

472 */ -

473 void QGraphicsLayout::addChildLayoutItem(QGraphicsLayoutItem *layoutItem) -

474 { -

475 Q_D(QGraphicsLayout); -

476 d->addChildLayoutItem(layoutItem); -

477

}

never executed: end of block

478 -

479 static bool g_instantInvalidatePropagation = false; -

480 -

481 /*! -

482 \internal -

483 \since 4.8 -

484 \sa instantInvalidatePropagation() -

485 -

486 Calling this function with \a enable set to true will enable a feature that -

487 makes propagation of invalidation up to ancestor layout items to be done in -

488 one go. It will propagate up the parentLayoutItem() hierarchy until it has -

489 reached the root. If the root item is a QGraphicsWidget, it will *post* a -

490 layout request to it. When the layout request is consumed it will traverse -

491 down the hierarchy of layouts and widgets and activate all layouts that is -

492 invalid (not activated). This is the recommended behaviour. -

493 -

494 If not set it will also propagate up the parentLayoutItem() hierarchy, but -

495 it will stop at the \e{first widget} it encounters, and post a layout -

496 request to the widget. When the layout request is consumed, this might -

497 cause it to continue propagation up to the parentLayoutItem() of the -

498 widget. It will continue in this fashion until it has reached a widget with -

499 no parentLayoutItem(). This strategy might cause drawing artifacts, since -

500 it is not done in one go, and the consumption of layout requests might be -

501 interleaved by consumption of paint events, which might cause significant -

502 flicker. -

503 Note, this is not the recommended behavior, but for compatibility reasons -

504 this is the default behaviour. -

505 */ -

506 void QGraphicsLayout::setInstantInvalidatePropagation(bool enable) -

507 { -

508 g_instantInvalidatePropagation = enable; -

509

}

never executed: end of block

510 -

511 /*! -

512 \internal -

513 \since 4.8 -

514 \sa setInstantInvalidatePropagation() -

515 -

516 returns \c true if the complete widget/layout hierarchy is rearranged in one go. -

517 */ -

518 bool QGraphicsLayout::instantInvalidatePropagation() -

519 { -

520

return g_instantInvalidatePropagation;

never executed: return g_instantInvalidatePropagation;

521 } -

522 -

523 QT_END_NAMESPACE -

524 -

525 #endif //QT_NO_GRAPHICSVIEW -

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