[PyQt] Newbie - QGraphicsItem & QGraphicsScene problems

[Aysun Bascetincelik]

Hi,
I am trying to implement a simple paint like program. I am having mainly two
problems:

1. I have an item class inherited from QGraphicsItem and I use
QGraphicsScene.addItem() to add it to the scene. However, I can only see the
last added item. Although all previous items (when I use
QGraphicsScene.items()) are present and their visible properties are true,
they are not shown on my scene. This thing only happens when I use addItem()
with the class I implemented. If I use addLine() more than once, I can see
all items created by that addLine() function.

2.The other problem is when I try to select an item with a left mouse click.
I did not implement the mousePressEvent() inside the item class but I
implemented the one in scene class. I can get the mouse scenePos() easily
and use it to add items. After adding an item, if I use itemAt() function
with a new click on the item and scenePos(), it always returns None. I set
the flags of the item all true.

I am afraid these two problems are related but I could not find a solution.

Thanks

Aysun Bascetincelik


Here is the code:
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#!/usr/bin/env python

import sys
from PyQt4 import QtCore, QtGui
from graphicsForm import Ui_MainWindow

class DiagramScene(QtGui.QGraphicsScene):

    def __init__(self, graphicsView, parent=None):
        QtGui.QGraphicsScene.__init__(self,
QtCore.QRectF(QtCore.QPointF(0,0), QtCore.QPointF(450,350)), parent)
    self.itemToAdd = 0
    self.mode = 0 # 0: add mode, 1:select mode
    self.view = graphicsView

    def mousePressEvent(self, mouseEvent):
        if (mouseEvent.button() != QtCore.Qt.LeftButton):
            return
    x = mouseEvent.scenePos().x()
    y = mouseEvent.scenePos().y()

    if(self.mode == 0):
        self.createItem(x, y)
    elif(self.mode == 1):
        self.selectItem(x, y)
        QtGui.QGraphicsScene.mousePressEvent(self, mouseEvent)

    def createItem(self, x, y):
    if (self.itemToAdd == 0):
        self.addItem(MyPoint(x, y))
    elif (self.itemToAdd == 1):
        self.addLine(QtCore.QLineF(x,y,x+50,y+50))
    self.update()
#    self.view.update()
#    self.view.show()

    def selectItem(self, x, y):
    selected = self.itemAt(x,y)
    print selected
    if selected:
        selected.setSelected(True)

class StartProgram(QtGui.QMainWindow):

    def __init__(self, parent=None):
        QtGui.QWidget.__init__(self, parent)
        self.ui = Ui_MainWindow()
        self.ui.setupUi(self)
    self.scene = DiagramScene(self.ui.graphicsView)
    self.ui.graphicsView.setScene(self.scene)
    self.ui.pointButton.setChecked(True)
    self.ui.pathButton.setChecked(False)

    QtCore.QObject.connect(self.ui.pointButton,QtCore.SIGNAL("clicked()"),
self.pointButtonClicked)
    QtCore.QObject.connect(self.ui.pathButton,QtCore.SIGNAL("clicked()"),
self.pathButtonClicked)
    QtCore.QObject.connect(self.ui.selectButton,QtCore.SIGNAL("clicked()"),
self.selectButtonClicked)

    def pointButtonClicked(self):
    self.ui.pointButton.setChecked(True)
    self.ui.pathButton.setChecked(False)
    self.scene.itemToAdd = 0 #0 is point

    def pathButtonClicked(self):
    self.ui.pathButton.setChecked(True)
    self.ui.pointButton.setChecked(False)
    self.scene.itemToAdd = 1 #1 is path

    def selectButtonClicked(self):
    if self.ui.selectButton.isChecked():
        self.scene.mode = 1
    else :
        self.scene.mode = 0

class MyPoint(QtGui.QGraphicsPathItem):
    pointToDraw = QtCore.QRectF()

    def __init__(self, x, y, parent=None, scene=None):
      super(MyPoint, self).__init__()
    self.x = x
    self.y = y
    MyPoint.pointToDraw.setCoords(x,y, x+15,y+15)
    self.setFlag(QtGui.QGraphicsItem.ItemIsSelectable, True)
    self.setFlag(QtGui.QGraphicsItem.ItemIsMovable, True)

    def paint(self, painter, option, widget=None):
    if self.isSelected():
        painter.setBrush(QtGui.QBrush(QtGui.QColor(0,255,255)))
    else:
         painter.setBrush(QtGui.QBrush(QtGui.QColor(0,0,255)))
    painter.drawRect(MyPoint.pointToDraw)

    def path(self):
    path = QtGui.QPainterPath()
    path.addEllipse(MyPoint.pointToDraw) #to add ellipse?!?!?!?!?
    return path

if __name__ == "__main__":
    app = QtGui.QApplication(sys.argv)
    myapp = StartProgram()
    myapp.show()
    sys.exit(app.exec_())

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