how to accelerate the replot?

[rambo83]

Hello,

I have implemented the dragging function of some QwtPlotMarkers by using the QwtPlotPicker ( see code below), but I'm not satisfied about the speed of replot, because when I move the items they don't move fluently but with jumps and I can also see the for loop in it, because first one item is moved then the second and so on. How can I move the selected items simultaneously? Help me please.

Thank you

best regards,

Vitali

// this function provides the ability to move items on the plot
void Plot::cursorMoved( const QwtDoublePoint& Point){
 
if(_mf->getMode() == mainFrame::Recombination){		// allow to move the plot items only in Recombination phase
 
	if(!selected_Points.empty()){		//if the list with selected items is not empty, then...
		for(int i=0; i< selected_Points.size(); ++i) {
			picker->setRubberBand(QwtPicker::NoRubberBand);		// switch off the rubber band during drag process
			 double delta_x = Point.x() - clickpos->x();	// calculate the x difference
			 double delta_y = Point.y() - clickpos->y();	// calculate the y difference
 
			 unsigned idx=_mf->objFunction;
			double rangex1[2] = {optProbList[idx]->range_x1[0], optProbList[idx]->range_x1[1]};
			double rangex2[2] = {optProbList[idx]->range_x2[0], optProbList[idx]->range_x2[1]};
 
		 // set the new coordinates to the moved item, but check first whether the movement is within the valid area
			 if((selected_Points[i]->xValue() + delta_x) < rangex1[1] && (selected_Points[i]->xValue() + delta_x) > rangex1[0]){
				 selected_Points[i]->setXValue(selected_Points[i]->xValue() + delta_x);
			 }
			 if((selected_Points[i]->yValue() + delta_y) < rangex2[1] && (selected_Points[i]->yValue() + delta_y) > rangex2[0]){
				selected_Points[i]->setYValue(selected_Points[i]->yValue() + delta_y);
				 }
			// check which index does this selected item have
			int index = (selected_Points[i]->title().text().toInt());	// transform from string to integer
			_mf->updateChromosome( selected_Points[i]->value(),index);	// update the individuals with new values
		}
		this->replot();	// replot the plot widget after the selected point was moved
	}
	else{
		picker->setRubberBand(QwtPicker::RectRubberBand);		// switch on the rectangle rubber band
	}
	clickpos = new QwtDoublePoint(Point);		// update the reference point
}
else return;
}

// this function provides the ability to move items on the plot
void Plot::cursorMoved( const QwtDoublePoint& Point){

if(_mf->getMode() == mainFrame::Recombination){		// allow to move the plot items only in Recombination phase

	if(!selected_Points.empty()){		//if the list with selected items is not empty, then...
		for(int i=0; i< selected_Points.size(); ++i) {
			picker->setRubberBand(QwtPicker::NoRubberBand);		// switch off the rubber band during drag process
			 double delta_x = Point.x() - clickpos->x();	// calculate the x difference
			 double delta_y = Point.y() - clickpos->y();	// calculate the y difference

			 unsigned idx=_mf->objFunction;
			double rangex1[2] = {optProbList[idx]->range_x1[0], optProbList[idx]->range_x1[1]};
			double rangex2[2] = {optProbList[idx]->range_x2[0], optProbList[idx]->range_x2[1]};

		 // set the new coordinates to the moved item, but check first whether the movement is within the valid area
			 if((selected_Points[i]->xValue() + delta_x) < rangex1[1] && (selected_Points[i]->xValue() + delta_x) > rangex1[0]){
				 selected_Points[i]->setXValue(selected_Points[i]->xValue() + delta_x);
			 }
			 if((selected_Points[i]->yValue() + delta_y) < rangex2[1] && (selected_Points[i]->yValue() + delta_y) > rangex2[0]){
				selected_Points[i]->setYValue(selected_Points[i]->yValue() + delta_y);
				 }
			// check which index does this selected item have
			int index = (selected_Points[i]->title().text().toInt());	// transform from string to integer
			_mf->updateChromosome( selected_Points[i]->value(),index);	// update the individuals with new values
		}
		this->replot();	// replot the plot widget after the selected point was moved
	}
	else{
		picker->setRubberBand(QwtPicker::RectRubberBand);		// switch on the rectangle rubber band
	}
	clickpos = new QwtDoublePoint(Point);		// update the reference point
}
else return;
}

To copy to clipboard, switch view to plain text mode 

[Uwe]

Dragging something on a plot widget needs to be implemented as overlay widget ( like text and rubberband of a picker ). Another ( less optimal ) solution is to introduce a pixmap cache for all plot items below your marker and reimplement YourPlot::drawItems().

The way you want to implement dragging only works fast enough for simple scenes without much data.

Uwe

[rambo83]

Uwe, thank you for your reply.

You told me already, that I have to implemente it as overlay widget, but I don't know what do you mean with "overlay widget".
By dragging a rectangle around multiple items I get the selected items in my list/vector of QwtPlotMarkers, now how should I implement the overlay widget, which will acomplish the movement of them? It would be very helpful, if you provide more details on "overlay widget". Thank you.

best regards,

Vitali

[KosyakOFF]

Overlay widget means widget which is placed and drawn above qwtplot, it is its
children but it's not a qwtplot item. QwtPlotMarker is an plot item. So you must
replot whole plot just to drag one item. As it was said before performance speed
in this case should be suitable only if scene is very simple.

1) You can create widget with transparent background, draw markers on it (or some simple models of them like crosses or dots)
in some kind of drawing zone (like rect of your selection) or resize this widget to size of selection rect and raise() it.
2) With mouse dragging you simply move your widget around your plot canvas (it will look like you moving copy of markers around)
3) After mouse realease calculate coordinates, place markers there and replot the plot


http://wiki.qtcentre.org/index.php?title=Widget_Overlay - this is example of overlay widget. Instead of simple line you can draw some kind of "markers" of your markers on this widget

[Uwe]

Probably the easiest implementation is using one of the internal overlay widgets of a QwtPlotPicker ( f.e. reimplementing YourPicker::drawRubberband() ).

Uwe

[rmk]

Hello,

Can anyone tell me if there is another place where I can get access to the code for this overlay widget example? The Wiki is still down. Does anyone have the example code that they could email me?

Thanks, rmk

[KosyakOFF]

Type in google "qt overlay widget", second or third link should lead to this Wiki. Click on "Cached" near link to Wiki and in opened window "Text only version" (top right corner of the page).