[Qt-interest] QGraphicsView performance issue
Santhosh Y
santhosh at softjin.com
Mon May 11 16:10:04 CEST 2009
Please read my comments below
Alexis Ménard wrote:
> On Monday 11 May 2009 15:01:52 Santhosh Y wrote:
>
>> Santhosh Y wrote:
>>
>>> Hi,
>>>
> Hi,
>
>>> I added 30,000 items to the scene.
>>> While updating the scene, the response from the view is very slow.
>>>
>>> Among these 30,000 items only 3,000 items have the distinctive locations
>>> and the rest of 27,000 items have the same location of those 3,000 items.
>>>
>>> In such a scenario to improve the performance, what flags
>>> I should use on the scene to improve the performance.
>>>
> If the painting (paint method) is slow on items, you can use the cache mode,
> itemCoordinateCache if you have no transformations otherwise
> DeviceCoordinateCache.
>
I am not able to find the above flag for setting cache mode.
I am using 4.3.3 version of Qt.
I can use only cacheNone or cacheBackGround.
> If you trigger full updates on the scene, then you need to set the
> viewportUpdate to fullviewport update because sometimes it is slower to
> caculate the exact dirty area than repainting the all scene (aka OpenGL).
>
>> To add to the above issue, what I have observed is that, paintEvent() on
>> QGraphicsview is being called multiple times
>> which is taking around 3 sec for each call to pick the items from the
>> visible region for sending to
>>
> That why we are working on an API to allow you to create your custom indexing
> where you can skip some parts of the scene or skipping items that you don't
> need.
>
>> QGraphicsScene::drawItems(QPainter* p, int numItems, QGraphicsItem**
>> items, const QStyleOptionGraphicsItem* options )
>> function dispatch.
>>
>> Can anybody tell me how to track from where this paintEvent call is
>> dispatched so many times.
>>
>>
> recalculateContentSize can be the source of those calls because you query a
> full update (see below).
>
>> I have no QGraphicsView::update() calls in my code, but I have the
>> QGraphicsScene::update() calls.
>>
> Calling update on the scene is not a good idea unless you give a rectangle to
> update(). Without parameter it will redraw everything... Why do you need to
> update the whole scene? Updating the content should triggers updates on items
> for you...
>
>
I removed all the QGraphicsScene::update () calls. Still the performance
have not improved.
>> But none of the QGraphicsScene::update () call is immediately resulting
>> a QGraphicsView::paintEvent(QPaintEvent*)
>>
>> My observation is that all the mutliple calls on
>> QGraphicsView::paintEvent(QPaintEvent*) are resulting from the following
>> stack.
>> ---------------------------------------------------------------------------
>> --------------------------- QGraphicsView::paintEvent(QPaintEvent *
>> e=0x0012b550) Line 1282 C++ QtGuid4.dll!QWidget::event(QEvent *
>> event=0x0012b550) Line 6256 C++ QtGuid4.dll!QFrame::event(QEvent *
>> e=0x0012b550) Line 641 C++
>> QtGuid4.dll!QAbstractScrollArea::viewportEvent(QEvent *
>> e=0x0012b550) Line 909 + 0xc bytes C++
>> QtGuid4.dll!QGraphicsView::viewportEvent(QEvent *
>> event=0x0012b550) Line 2324 C++
>> QtGuid4.dll!QAbstractScrollAreaPrivate::viewportEvent(QEvent *
>> event=0x0012b550) Line 78 + 0x28 bytes C++
>> QtGuid4.dll!QAbstractScrollAreaFilter::eventFilter(QObject *
>> o=0x08705aa0, QEvent * e=0x0012b550) Line 89 + 0x29 bytes C++
>> QtGuid4.dll!QApplicationPrivate::notify_helper(QObject *
>> receiver=0x08705aa0, QEvent * e=0x0012b550) Line 3533 + 0x1b bytes C++
>> QtGuid4.dll!QApplication::notify(QObject * receiver=0x08705aa0,
>> QEvent * e=0x0012b550) Line 3482 + 0x10 bytes C++
>> QtCored4.dll!QCoreApplication::notifyInternal(QObject *
>> receiver=0x08705aa0, QEvent * event=0x0012b550) Line 516 C++
>> QtCored4.dll!QCoreApplication::sendSpontaneousEvent(QObject *
>> receiver=0x08705aa0, QEvent * event=0x0012b550) Line 188 + 0x38
>> bytes C++
>> QtGuid4.dll!qt_sendSpontaneousEvent(QObject * receiver=0x08705aa0,
>> QEvent * event=0x0012b550) Line 1182 + 0xe bytes C++
>> QtGuid4.dll!QWidgetPrivate::drawWidget(QPaintDevice *
>> pdev=0x02a0a878, const QRegion & rgn={...}, const QPoint & offset={...},
>> int flags=4) Line 1195 + 0xd bytes C++
>>
>> QtGuid4.dll!QWidgetBackingStore::paintSiblingsRecursive(QPaintDevice *
>> pdev=0x02a0a878, const QList<QObject *> & siblings={...}, int index=0,
>> const QRegion & rgn={...}, const QPoint & offset={...}, int flags=4)
>> Line 1099 C++
>> QtGuid4.dll!QWidgetPrivate::drawWidget(QPaintDevice *
>> pdev=0x02a0a878, const QRegion & rgn={...}, const QPoint & offset={...},
>> int flags=4) Line 1231 + 0x2e bytes C++
>>
>> QtGuid4.dll!QWidgetBackingStore::paintSiblingsRecursive(QPaintDevice *
>> pdev=0x02a0a878, const QList<QObject *> & siblings={...}, int index=2,
>> const QRegion & rgn={...}, const QPoint & offset={...}, int flags=4)
>> Line 1099 C++
>>
>> QtGuid4.dll!QWidgetBackingStore::paintSiblingsRecursive(QPaintDevice *
>> pdev=0x02a0a878, const QList<QObject *> & siblings={...}, int index=3,
>> const QRegion & rgn={...}, const QPoint & offset={...}, int flags=4)
>> Line 1089 + 0x20 bytes C++
>>
>> QtGuid4.dll!QWidgetBackingStore::paintSiblingsRecursive(QPaintDevice *
>> pdev=0x02a0a878, const QList<QObject *> & siblings={...}, int index=4,
>> const QRegion & rgn={...}, const QPoint & offset={...}, int flags=4)
>> Line 1089 + 0x20 bytes C++
>> QtGuid4.dll!QWidgetPrivate::drawWidget(QPaintDevice *
>> pdev=0x02a0a878, const QRegion & rgn={...}, const QPoint & offset={...},
>> int flags=4) Line 1231 + 0x2e bytes C++
>>
>> QtGuid4.dll!QWidgetBackingStore::paintSiblingsRecursive(QPaintDevice *
>> pdev=0x02a0a878, const QList<QObject *> & siblings={...}, int index=13,
>> const QRegion & rgn={...}, const QPoint & offset={...}, int flags=4)
>> Line 1099 C++
>> QtGuid4.dll!QWidgetPrivate::drawWidget(QPaintDevice *
>> pdev=0x02a0a878, const QRegion & rgn={...}, const QPoint & offset={...},
>> int flags=4) Line 1231 + 0x2e bytes C++
>>
>> QtGuid4.dll!QWidgetBackingStore::paintSiblingsRecursive(QPaintDevice *
>> pdev=0x02a0a878, const QList<QObject *> & siblings={...}, int index=5,
>> const QRegion & rgn={...}, const QPoint & offset={...}, int flags=4)
>> Line 1099 C++
>> QtGuid4.dll!QWidgetPrivate::drawWidget(QPaintDevice *
>> pdev=0x02a0a878, const QRegion & rgn={...}, const QPoint & offset={...},
>> int flags=4) Line 1231 + 0x2e bytes C++
>>
>> QtGuid4.dll!QWidgetBackingStore::paintSiblingsRecursive(QPaintDevice *
>> pdev=0x02a0a878, const QList<QObject *> & siblings={...}, int index=40,
>> const QRegion & rgn={...}, const QPoint & offset={...}, int flags=4)
>> Line 1099 C++
>>
>> QtGuid4.dll!QWidgetBackingStore::paintSiblingsRecursive(QPaintDevice *
>> pdev=0x02a0a878, const QList<QObject *> & siblings={...}, int index=41,
>> const QRegion & rgn={...}, const QPoint & offset={...}, int flags=4)
>> Line 1089 + 0x20 bytes C++
>>
>> QtGuid4.dll!QWidgetBackingStore::paintSiblingsRecursive(QPaintDevice *
>> pdev=0x02a0a878, const QList<QObject *> & siblings={...}, int index=42,
>> const QRegion & rgn={...}, const QPoint & offset={...}, int flags=4)
>> Line 1089 + 0x20 bytes C++
>> QtGuid4.dll!QWidgetPrivate::drawWidget(QPaintDevice *
>> pdev=0x02a0a878, const QRegion & rgn={...}, const QPoint & offset={...},
>> int flags=5) Line 1231 + 0x2e bytes C++
>> QtGuid4.dll!QWidgetBackingStore::cleanRegion(const QRegion &
>> rgn={...}, QWidget * widget=0x0012fd58, bool
>> recursiveCopyToScreen=false) Line 1000 C++
>> QtGuid4.dll!qt_syncBackingStore(QRegion rgn={...}, QWidget *
>> widget=0x0012fd58, bool recursive=false) Line 230 C++
>> QtGuid4.dll!QETWidget::translatePaintEvent(const tagMSG &
>> msg={...}) Line 3094 + 0x2b bytes C++
>> QtGuid4.dll!QtWndProc(HWND__ * hwnd=0x000a1118, unsigned int
>> message=15, unsigned int wParam=0, long lParam=0) Line 1680 + 0xc
>> bytes C++
>> ---------------------------------------------------------------------------
>> ---------------------------
>>
>> Please tell me how to track the event call of paint over QGraphicsView.
>>
>
>
--
----------------------------------------------------
Y Santhosh Kumar
Senior Software Engineer
SoftJin Technologies Private Limited
Unit No. 102, Mobius Tower,
I Floor, SJR I - Park,
EPIP, White Field,
Bangalore - 560066, India
U : www.softjin.com
E : santhosh at softjin.com
T : +91-80-41779999
M : +91-9740535265
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