I have a function in my code that takes a list of points () from a QMap with key 'linekey'. Linekey is a QString describing which 'Line' I want to get from the map. My code is as follows:

Qt Code: 
  1. foreach (const QString linekey, linekeys) {
  2.  
  3.             if (groupValues.contains(linekey))
  4.                 continue;
  5.             QList<ReceiverGraphicsItem *> receiverlist =  lineGroup.values(linekey);
  6.             if (lod <= .03) {
  7.                 points2[0] = mapToPix(receiverlist.at(0)->pos());
  8.                 points2[1] = mapToPix(receiverlist.at(receiverlist.size()/4)->pos());
  9.                 points2[2] =  mapToPix(receiverlist.at((receiverlist.size()*2)/4)->pos());
  10.                 points2[3] =  mapToPix(receiverlist.at((receiverlist.size()*3)/4)->pos());
  11.                 points2[4] =  mapToPix(receiverlist.at((receiverlist.size()-1))->pos());
  12.                 ptrr.drawPolyline(points2,small);
  13.             } else {
  14.                 points[0] = mapToPix(receiverlist.at(0)->pos());
  15.                 points[1] = mapToPix(receiverlist.at(receiverlist.size()/14)->pos());
  16.                 points[2] =  mapToPix(receiverlist.at((receiverlist.size()*2)/14)->pos());
  17.                 points[3] =  mapToPix(receiverlist.at((receiverlist.size()*3)/14)->pos());
  18.                 points[4] =  mapToPix(receiverlist.at((receiverlist.size()*4)/14)->pos());
  19.                 points[5] =  mapToPix(receiverlist.at((receiverlist.size()*5)/14)->pos());
  20.                 points[6] =  mapToPix(receiverlist.at((receiverlist.size()*6)/14)->pos());
  21.                 points[7] =  mapToPix(receiverlist.at((receiverlist.size()*7)/14)->pos());
  22.                 points[8] =  mapToPix(receiverlist.at((receiverlist.size()*8)/14)->pos());
  23.                 points[9] =  mapToPix(receiverlist.at((receiverlist.size()*9)/14)->pos());
  24.                 points[10] =  mapToPix(receiverlist.at((receiverlist.size()*10)/14)->pos());
  25.                 points[11] =  mapToPix(receiverlist.at((receiverlist.size()*11)/14)->pos());
  26.                 points[12] =  mapToPix(receiverlist.at((receiverlist.size()*12)/14)->pos());
  27.                 points[13] =  mapToPix(receiverlist.at((receiverlist.size()*13)/14)->pos());
  28.                 points[14] =  mapToPix(receiverlist.at((receiverlist.size()-1))->pos());
  29.                 ptrr.drawPolyline(points,big);
  30.             }
  31.         }
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The ptrr is a QPainter that is connected to a QPixmap (QImage in threaded version!).

This works fine but is slow with hundreds of lines to draw; thus the idea is to use Threads. if I use the loop method directly as it was but in a thread class then I get hundreds of threads; My question is, how do I make it so that only x number of threads run at one time? I have heard of a queue but have not seen one example of it. Maybe there is a better way to split up this job to use threading?


thank you,

JW
sw developer

"Some days you just can't get rid of a bomb." Batman movie - 1966