GraphicsView performance problems

[camel]

just a note:
If you like to profile further into the drawing part,
you need to call:

valgrind --tool=callgrind --seperate-callers=5 --seperate-recs=10 ./YOUR_APP

Otherwise you will get "cycles", which is not very helpfull in this task..

BUT: this takes up much more memory to analyze later...

[camel]

Hi,

well I just love to play with this... ;-)


Here is another (and much faster) way to write the drawBackground function...with the added niceness that it helps avoiding the color errors ;-)

You might want to check if this survives zooming etc.

void drawBackground(QPainter *painter, const QRectF &rect)
      {
         const int gridSize = 25;
 
        if (backgroundCache.isNull()) {
            backgroundCache = QPixmap(gridSize, gridSize);
            const int middle = gridSize / 2;
            QPainter backgroundPainter(&backgroundCache);
            backgroundPainter.setRenderHints(painter->renderHints());
            backgroundPainter.fillRect(QRect(0, 0, gridSize, gridSize), QBrush(Qt::white));
            backgroundPainter.setPen(backgroundPen);
            backgroundPainter.setBrush(backgroundBrush);
            backgroundPainter.drawLine(0, middle, gridSize, middle);
            backgroundPainter.drawLine(middle, 0, middle, gridSize);
        }
 
         const int realLeft = static_cast<int>(std::floor(rect.left()));
         const int realRight = static_cast<int>(std::ceil(rect.right()));
         const int realTop = static_cast<int>(std::floor(rect.top()));
         const int realBottom = static_cast<int>(std::ceil(rect.bottom()));
 
 
         const int firstLeftGridLine = realLeft - (realLeft % gridSize);
         const int firstTopGridLine = realTop - (realTop % gridSize);
 
 
         QPainterPath background;
         for (int x = firstLeftGridLine; x < realRight; x += gridSize) {
            for (int y = firstTopGridLine; y < realBottom; y += gridSize) {
                painter->drawPixmap(x, y, backgroundCache);
            }
        }
      }

void drawBackground(QPainter *painter, const QRectF &rect)
      {
         const int gridSize = 25;

        if (backgroundCache.isNull()) {
            backgroundCache = QPixmap(gridSize, gridSize);
            const int middle = gridSize / 2;
            QPainter backgroundPainter(&backgroundCache);
            backgroundPainter.setRenderHints(painter->renderHints());
            backgroundPainter.fillRect(QRect(0, 0, gridSize, gridSize), QBrush(Qt::white));
            backgroundPainter.setPen(backgroundPen);
            backgroundPainter.setBrush(backgroundBrush);
            backgroundPainter.drawLine(0, middle, gridSize, middle);
            backgroundPainter.drawLine(middle, 0, middle, gridSize);
        }

         const int realLeft = static_cast<int>(std::floor(rect.left()));
         const int realRight = static_cast<int>(std::ceil(rect.right()));
         const int realTop = static_cast<int>(std::floor(rect.top()));
         const int realBottom = static_cast<int>(std::ceil(rect.bottom()));


         const int firstLeftGridLine = realLeft - (realLeft % gridSize);
         const int firstTopGridLine = realTop - (realTop % gridSize);


         QPainterPath background;
         for (int x = firstLeftGridLine; x < realRight; x += gridSize) {
            for (int y = firstTopGridLine; y < realBottom; y += gridSize) {
                painter->drawPixmap(x, y, backgroundCache);
            }
        }
      }

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Have a nice day :-)

[Gopala Krishna]

Hi,

well I just love to play with this... ;-)


Here is another way to write the drawBackground function...with the added niceness that it helps avoiding the color errors ;-)

You might want to check if this survives zooming etc.

void drawBackground(QPainter *painter, const QRectF &rect)
      ...

void drawBackground(QPainter *painter, const QRectF &rect)
      ...

To copy to clipboard, switch view to plain text mode 

Have a nice day :-)

Not bad idea! That problem solved !!! Thanks a lot.
Now the next problem is performance !
A good day to you too

[Gopala Krishna]

just a note:
If you like to profile further into the drawing part,
you need to call:


Otherwise you will get "cycles", which is not very helpfull in this task..

BUT: this takes up much more memory to analyze later...

I get the following error

valgrind: Bad option '--seperate-callers=5'; aborting.

I am trying to analyse the code as it is now. I am getting lost here and there but kcachegrind is a cool tool. Needs some time to get used to it. Thanks for helping me till now. I'll continue with this tomorrow.

[camel]

I get the following error
valgrind: Bad option '--seperate-callers=5'; aborting.

I think they changed the option names during 3.1 and 3.2 (which I use)

try:
valgrind --tool=callgrind --fn-caller=5 --fn-recursion=10 ./YOUR_APP