I am stuck with two versions of code that only differ in the way the rect is assigned. How are they different? and how does this effect the different behaviour?

(What I want is rectangles that are painted correctly with another style for selected ones and that can be moved around if in selection mode. I distinguish the mode in self.newItem. If True I am in adding-rectangles mode and if False I am in selection mode.)

This code below produces rectangles that are
- painted "correct" (snapped to grid)

- are selectable (but not drawn in red and yellow as in the paint method but with a black dashed line; although in debugging i see that the if-code for selected is visited)

- can be moved (snapped to grid)

Qt Code: 
  1. class DesignerBlock(QGraphicsRectItem):
  2.     def __init__(self, rect=QRectF(0, 0, 0, 0), parent=None, scene=None):
  3.         super(DesignerBlock, self).__init__(parent, scene)
  4.         self.setFlag(self.ItemIsMovable, True)
  5.         self.setFlag(self.ItemIsSelectable, True)
  6.         self.setFlag(self.ItemSendsGeometryChanges, True)
  7.         self.setPen(QPen(Qt.black, 1, Qt.SolidLine))
  8.         self.setBrush(QBrush(Qt.white, Qt.SolidPattern))
  9.         self.moving = False
  10.         self.setRect(rect) # <-----
  11.         self.setSelected(True)
  12.         self.setFocus()
  13.         self.update()
  14.  
  15.     def paint(self, painter, option, widget):
  16.         pen = self.pen()
  17.         brush = self.brush()
  18.         if self.isSelected():
  19.             pen = QPen(Qt.red, 1, Qt.SolidLine)
  20.             brush = QBrush(Qt.yellow, Qt.SolidPattern)
  21.         painter.setPen(pen)
  22.         painter.setBrush(brush)
  23.         painter.drawRect(self.rect()) # <-----
  24.         super(DesignerBlock, self).paint(painter, option, widget)
  25.  
  26.     def deferPosition(self, value):
  27.         big = abs(value) / SCREEN_GRID
  28.         little = abs(value) % SCREEN_GRID
  29.  
  30.         if little > (SCREEN_GRID / 2):
  31.             little = 1
  32.         else:
  33.             little = 0
  34.  
  35.         if value > 0:
  36.             direction = 1
  37.         else:
  38.             direction = -1
  39.  
  40.         return (big + little) * SCREEN_GRID * direction
  41.  
  42.  
  43.     def itemChange(self, change, value):
  44.         if change == QGraphicsItem.ItemPositionChange:
  45.             x = value.toPoint().x()
  46.             y = value.toPoint().y()
  47.             newPosition = value.toPoint()
  48.  
  49.             newPosition.setX(self.deferPosition(x))
  50.  
  51.             newPosition.setY(self.deferPosition(y))
  52.  
  53.             return newPosition
  54.         else:
  55.             return value
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Now this code below (the same except the two indicated changes) makes rectangles that
- are painted only in the rect of the mouse selection (but not adjusted to snap to grid)
with that i mean that if i rubberband a rect smaller than the grid point, only this area is painted although after i force a repaint (as in window minimize/maximize) the rectitem is drawn correct from gridPoint to gridPoint.

- selected rect is painted in red and yellow

- when selecting with rubberband the view is "erased" and click select does not work and they dont move

Qt Code: 
  1. class DesignerBlock(QGraphicsRectItem):
  2.     def __init__(self, rect=QRectF(0, 0, 0, 0), parent=None, scene=None):
  3.         super(DesignerBlock, self).__init__(parent, scene)
  4.         self.setFlag(self.ItemIsMovable, True)
  5.         self.setFlag(self.ItemIsSelectable, True)
  6.         self.setFlag(self.ItemSendsGeometryChanges, True)
  7.         self.setPen(QPen(Qt.black, 1, Qt.SolidLine))
  8.         self.setBrush(QBrush(Qt.white, Qt.SolidPattern))
  9.         self.moving = False
  10.         self.rect = rect # <----------
  11.         #self.setRect(rect)
  12.         self.setSelected(True)
  13.         self.setFocus()
  14.         self.update()
  15.  
  16.     def paint(self, painter, option, widget):
  17.         pen = self.pen()
  18.         brush = self.brush()
  19.         if self.isSelected():
  20.             pen = QPen(Qt.red, 1, Qt.SolidLine)
  21.             brush = QBrush(Qt.yellow, Qt.SolidPattern)
  22.         painter.setPen(pen)
  23.         painter.setBrush(brush)
  24.         painter.drawRect(self.rect) # <-----------
  25.         #painter.drawRect(self.rect())
  26.         super(DesignerBlock, self).paint(painter, option, widget)
  27.  
  28.     def deferPosition(self, value):
  29.         big = abs(value) / SCREEN_GRID
  30.         little = abs(value) % SCREEN_GRID
  31.  
  32.         if little > (SCREEN_GRID / 2):
  33.             little = 1
  34.         else:
  35.             little = 0
  36.  
  37.         if value > 0:
  38.             direction = 1
  39.         else:
  40.             direction = -1
  41.  
  42.         return (big + little) * SCREEN_GRID * direction
  43.  
  44.  
  45.     def itemChange(self, change, value):
  46.         if change == QGraphicsItem.ItemPositionChange:
  47.             x = value.toPoint().x()
  48.             y = value.toPoint().y()
  49.             newPosition = value.toPoint()
  50.  
  51.             newPosition.setX(self.deferPosition(x))
  52.  
  53.             newPosition.setY(self.deferPosition(y))
  54.  
  55.             return newPosition
  56.         else:
  57.             return value
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this is scene code for handling the mouse events:
Qt Code: 
  1. def mousePressEvent(self, mouseEvent):
  2.         self.startPos = mouseEvent.scenePos()
  3.         self.emit(SIGNAL("startSet"), self.gridPos(self.startPos))
  4.         if self.newItem == False:
  5.             super(DesignerScene, self).mousePressEvent(mouseEvent) 
  6.  
  7.     def mouseMoveEvent(self, mouseEvent):
  8.         self.emit(SIGNAL("updateCoords"), self.gridPos(mouseEvent.scenePos()))
  9.         super(DesignerScene, self).mouseMoveEvent(mouseEvent) 
  10.  
  11.     def mouseReleaseEvent(self, mouseEvent):
  12.         self.endPos = mouseEvent.scenePos()
  13.         self.emit(SIGNAL("endSet"), self.gridPos(self.endPos))
  14.         if self.newItem:
  15.             self.emit(SIGNAL("createBox"), self.gridPos(self.startPos), self.gridPos(self.endPos))
  16.         else:
  17.             super(DesignerScene, self).mousePressEvent(mouseEvent) 
  18.  
  19.     def createBox(self, start, end):
  20.         xs = start.x()
  21.         ys =  start.y()
  22.         xe =  end.x()
  23.         ye =  end.y()
  24.         if ys <> ye and xs <> xe:
  25.             # insert only if not a line
  26.             self.addItem(DesignerBlock(QRectF(xs, ys, xe-xs, ye-ys).normalized()))
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