Here is two delegated QListView of 1000 items,
One is fast, the other is slow.



When the area is wider, the painting is *much* slower.

Here is my delegate paint function
Qt Code: 
  1. void ZeChatRoom_delegate::paint(QPainter *painter, 
  2. 								  const QStyleOptionViewItem &option, 
  3. 								  const QModelIndex &index) const 
  4. {
  5.    // QItemDelegate::paint(painter, option, index);
  6.  
  7. 	ZeChatRoom_data * chatData = index.data().value<ZeChatRoom_data *>();
  8.  
  9. 	// Display rects
  10. 	QRect pictureRect(option.rect.x() + 2, option.rect.y() + 2, 32, 32);
  11.  
  12. 	QRect displayRect = QRect(option.rect.x() + 36, option.rect.y() + 2,
  13. 							  option.rect.width() - 38, (option.rect.height() - 4) / 2);
  14.  
  15. 	QRect displayRect2 = QRect(option.rect.x() + 36, option.rect.y() + option.rect.height() / 2,
  16. 							  option.rect.width() - 38, (option.rect.height() - 4) / 2);
  17.  
  18. 	QColor textColor = Qt::black;
  19. 	QColor descriptionColor = ZeStyle::get()->getDarkBorderColor();
  20.  
  21. 	if (option.state & QStyle::State_MouseOver)
  22. 	{
  23. 		ZePainterController::get()->DrawHighlight(*painter, option.rect);
  24.  
  25. 		textColor = ZeStyle::get()->getHighlightTextColor();
  26. 		descriptionColor = ZeStyle::get()->getHighlightTextColor();
  27.  
  28. 		ZePainterController::get()->
  29. 		DrawBottomLine(*painter, option.rect, QColor(100, 100, 100, 150));
  30. 	}
  31. 	else
  32. 	{
  33. 		if (index.row() %2 == 0)
  34. 		{
  35. 			ZePainterController::get()->
  36. 				DrawBack(*painter, option.rect, QColor(ZeStyle::get()->getBorderColor().red(),
  37. 							ZeStyle::get()->getBorderColor().green(),
  38. 							ZeStyle::get()->getBorderColor().blue(), 50), false);
  39. 		}
  40.  
  41. 			ZePainterController::get()->
  42. 		DrawBottomLine(*painter, option.rect, 
  43. 					   /*QColor(100, 100, 100, 150)*/ QColor(ZeStyle::get()->getBorderColor().red(),
  44. 							ZeStyle::get()->getBorderColor().green(),
  45. 							ZeStyle::get()->getBorderColor().blue(), 200));
  46. 	}
  47.  
  48. 	ZePainterController::get()->
  49. 		DrawPictureRatio(*painter, *chatData->mChatPixmap, pictureRect, 1.0f);
  50.  
  51. 	QFont font;
  52. 	font.setBold(true);
  53. 	ZePainterController::get()->DrawText(*painter, 
  54. 										 displayRect, 
  55. 										 chatData->mRoomName + " - " + QString::number(chatData->mParticipants),
  56. 										 Qt::AlignLeft | Qt::AlignVCenter | Qt::TextSingleLine, 
  57. 										 textColor,
  58. 										 &font);
  59.  
  60. 	ZePainterController::get()->DrawText(*painter, 
  61. 										 displayRect2, 
  62. 										 chatData->mDescription,
  63. 										 Qt::AlignLeft | Qt::AlignVCenter | Qt::TextSingleLine, 
  64. 										 descriptionColor);
  65. }
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Is there a way to optimize the painting ? Especially when you're painting plain grey rectangles at each refresh.