[Qt-interest] QGraphicsView performance issue

[Santhosh Y]

Santhosh Y wrote:
> 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.
>
>   
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
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.

I have no QGraphicsView::update() calls in my code, but I have the  
QGraphicsScene::update() calls.
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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