Problems with setCursor in QGraphicsScene/View

[lightning2911]

In the code sample below I have found a problem with changing cursors.

Basically I have a MyScene with two MyRect items shown with a MyView.

In the view I change "modes" by pressing F1 - F3. To visually represent the modes I want to change the cursor of the view (background) and the items.

If I do not move the mouse cursor over items the cursor of the view changes fine. As soon as I move the cursors over the items, the item cursors change ok but the view cursor does not change or changes wrong.

Is this a bug or am I doing something wrong here?

from PyQt4.QtCore import *
from PyQt4.QtGui import *
 
class MyRect(QGraphicsRectItem):
 
    def __init__(self, parent=None, scene=None):
        # init parent
        super().__init__(parent, scene)
 
        # set flags
        self.setFlag(QGraphicsItem.ItemIsSelectable, True)
        self.setFlag(QGraphicsItem.ItemIsMovable, True)
        self.setFlag(self.ItemSendsGeometryChanges, True)
        self.setAcceptHoverEvents(True)
 
    def paint(self, painter, option, widget):
        if self.isSelected():
            painter.setPen(QPen(Qt.black, 1, Qt.DotLine))
        else:            
            painter.setPen(QPen(Qt.black, 1, Qt.SolidLine))
 
        painter.setBrush(QBrush(Qt.white, Qt.SolidPattern))
        painter.drawRect(self.rect())
 
class MyView(QGraphicsView):
 
    def __init__(self, parent=None):
        super().__init__(parent)
        self.setMouseTracking(True)
        self.scale(1,1)
        self.startPos = None
 
    def setSelectMode(self):
        print("view setting select mode")
        self.scene().setViewMode(MyScene.SELECTMODE)
 
    def setEditMode(self):
        print("view setting edit mode")
        self.scene().setViewMode(MyScene.EDITMODE)
        if len(self.scene().selectedItems()) > 1:
            self.scene().clearSelection()
 
    def setDrawMode(self):
        print("view setting draw mode")
        self.scene().setViewMode(MyScene.DRAWMODE)
        self.scene().clearSelection()
 
    def updateItems(self):
        print("view updateItems")
        m = self.scene().viewMode()
 
        if m == MyScene.SELECTMODE:
            print("is select mode")
            self.setCursor(Qt.ArrowCursor)
            print(self.cursor().shape())
            #self.update()
            itemCursor = Qt.OpenHandCursor
 
        elif m == MyScene.EDITMODE:
            print("is edit mode")
            self.setCursor(Qt.ForbiddenCursor)
            print(self.cursor().shape())
            #self.update()
            itemCursor = Qt.PointingHandCursor
 
        elif m == MyScene.DRAWMODE:
            print("is draw mode")
            self.setCursor(Qt.CrossCursor)
            print(self.cursor().shape())
            #self.update()
            itemCursor = Qt.WaitCursor
 
        items = self.scene().items()
 
        for item in items:
            item.setCursor(itemCursor)
            #item.update()
 
    def drawBackground(self, painter, rect):
        # draw a rect in size of sceneRect
 
        painter.setPen(QPen(Qt.red, 0, Qt.NoPen))
        painter.setBrush(QBrush(Qt.lightGray, Qt.SolidPattern))                
        painter.drawRect(self.scene().sceneRect())        
 
    def mousePressEvent(self, mouseEvent):
        print("view mousePress")
        curPos = mouseEvent.pos()
        self.startPos = self.mapToScene(curPos)
 
        if self.scene().viewMode() == MyScene.DRAWMODE:
            self.scene().newItem = MyRect(scene=self.scene())
            self.scene().newItem.setRect(QRectF(self.startPos, QSizeF(0, 0)))
            self.scene().newItem.setSelected(True)
 
        else:
            super().mousePressEvent(mouseEvent)
 
    def mouseMoveEvent(self, mouseEvent):
        #print("view mouseMove")
        curPos = self.mapToScene(mouseEvent.pos())
 
        if self.scene().viewMode() == MyScene.DRAWMODE:
            if self.scene().newItem:
                newRectF = QRectF(self.startPos, curPos)
                if newRectF != self.scene().newItem.rect():
                    self.scene().newItem.setRect(newRectF.normalized())
 
        else:
            super().mouseMoveEvent(mouseEvent)
 
    def mouseReleaseEvent(self, mouseEvent):
        print("view mouseRelease")
 
        if self.scene().newItem:
            # delete item if zero height or width
            if (self.scene().newItem.rect().width() == 0 
                or self.scene().newItem.rect().height() == 0):
                self.scene().removeItem(self.scene().newItem)
                del self.scene().newItem
 
        self.startPos = None
        self.scene().newItem = None
        super().mouseReleaseEvent(mouseEvent)
 
    def keyPressEvent(self, keyEvent):
        if keyEvent.key() == Qt.Key_F1:
            self.setSelectMode()
            self.updateItems()
 
        elif keyEvent.key() == Qt.Key_F2:
            self.setEditMode()
            self.updateItems()
 
        elif keyEvent.key() == Qt.Key_F3:
            self.setDrawMode()
            self.updateItems()
 
        elif keyEvent.key() == Qt.Key_Delete:
            if self.scene().viewMode() == MyScene.SELECTMODE:
                items = self.scene().selectedItems()
                if len(items):
                    for item in items:
                        self.scene().removeItem(item)
                        del item                   
 
class MyScene(QGraphicsScene):
 
    SELECTMODE, EDITMODE, DRAWMODE = (0, 1, 2)
    validViewModes = [SELECTMODE, EDITMODE, DRAWMODE]
 
    def __init__(self, parent=None):
        super().__init__(parent)
 
        self._viewMode = MyScene.SELECTMODE
        self.newItem = None
 
        self.setSceneRect(-300, -200, 600, 400)
 
        # add some item
        someRect = MyRect(scene=self)
        someRect.setRect(QRectF(0, 0, 160, 80))
 
        # add another item
        anotherRect = MyRect(scene=self)
        anotherRect.setRect(QRectF(-80, -40, 80, 160))
 
        # add own item
        #myItem = MyItem(scene=self)
 
    def setViewMode(self, value):
        if value != self._viewMode:
            if value in MyScene.validViewModes:
                self._viewMode = value
            else:
                raise ValueError("invalid view mode")
 
    def viewMode(self):
        return self._viewMode
 
class MainWindow(QMainWindow):
 
    def __init__(self, parent=None):
        # call parent init
        super().__init__(parent)
 
        # setup scene object
        self.scene = MyScene()
 
        # setup view object
        self.view = MyView()
 
        # connect scene to view
        self.view.setScene(self.scene)
 
        # create layout
        layout = QVBoxLayout()
 
        # add view to layout
        layout.addWidget(self.view)
 
        # set the margin of the object in the layout
        layout.setContentsMargins(0, 0, 0, 0)
 
        # create the central widget
        self.widget = QWidget()
 
        # lay it out
        self.widget.setLayout(layout)
 
        # set it to central
        self.setCentralWidget(self.widget)        
 
if __name__ == "__main__":
 
    import sys
 
    # setup application object
    app = QApplication(sys.argv)
 
    # create (parent) main window
    mainWindow = MainWindow()
    mainWindow.setWindowTitle("testScene")
    mainWindow.show()
 
    # run application object
    sys.exit(app.exec_())

from PyQt4.QtCore import *
from PyQt4.QtGui import *

class MyRect(QGraphicsRectItem):
    
    def __init__(self, parent=None, scene=None):
        # init parent
        super().__init__(parent, scene)
        
        # set flags
        self.setFlag(QGraphicsItem.ItemIsSelectable, True)
        self.setFlag(QGraphicsItem.ItemIsMovable, True)
        self.setFlag(self.ItemSendsGeometryChanges, True)
        self.setAcceptHoverEvents(True)
        
    def paint(self, painter, option, widget):
        if self.isSelected():
            painter.setPen(QPen(Qt.black, 1, Qt.DotLine))
        else:            
            painter.setPen(QPen(Qt.black, 1, Qt.SolidLine))

        painter.setBrush(QBrush(Qt.white, Qt.SolidPattern))
        painter.drawRect(self.rect())
        
class MyView(QGraphicsView):
    
    def __init__(self, parent=None):
        super().__init__(parent)
        self.setMouseTracking(True)
        self.scale(1,1)
        self.startPos = None
            
    def setSelectMode(self):
        print("view setting select mode")
        self.scene().setViewMode(MyScene.SELECTMODE)
        
    def setEditMode(self):
        print("view setting edit mode")
        self.scene().setViewMode(MyScene.EDITMODE)
        if len(self.scene().selectedItems()) > 1:
            self.scene().clearSelection()

    def setDrawMode(self):
        print("view setting draw mode")
        self.scene().setViewMode(MyScene.DRAWMODE)
        self.scene().clearSelection()
        
    def updateItems(self):
        print("view updateItems")
        m = self.scene().viewMode()
        
        if m == MyScene.SELECTMODE:
            print("is select mode")
            self.setCursor(Qt.ArrowCursor)
            print(self.cursor().shape())
            #self.update()
            itemCursor = Qt.OpenHandCursor
            
        elif m == MyScene.EDITMODE:
            print("is edit mode")
            self.setCursor(Qt.ForbiddenCursor)
            print(self.cursor().shape())
            #self.update()
            itemCursor = Qt.PointingHandCursor
            
        elif m == MyScene.DRAWMODE:
            print("is draw mode")
            self.setCursor(Qt.CrossCursor)
            print(self.cursor().shape())
            #self.update()
            itemCursor = Qt.WaitCursor
            
        items = self.scene().items()
        
        for item in items:
            item.setCursor(itemCursor)
            #item.update()
            
    def drawBackground(self, painter, rect):
        # draw a rect in size of sceneRect
        
        painter.setPen(QPen(Qt.red, 0, Qt.NoPen))
        painter.setBrush(QBrush(Qt.lightGray, Qt.SolidPattern))                
        painter.drawRect(self.scene().sceneRect())        
                    
    def mousePressEvent(self, mouseEvent):
        print("view mousePress")
        curPos = mouseEvent.pos()
        self.startPos = self.mapToScene(curPos)
        
        if self.scene().viewMode() == MyScene.DRAWMODE:
            self.scene().newItem = MyRect(scene=self.scene())
            self.scene().newItem.setRect(QRectF(self.startPos, QSizeF(0, 0)))
            self.scene().newItem.setSelected(True)
            
        else:
            super().mousePressEvent(mouseEvent)
        
    def mouseMoveEvent(self, mouseEvent):
        #print("view mouseMove")
        curPos = self.mapToScene(mouseEvent.pos())
                              
        if self.scene().viewMode() == MyScene.DRAWMODE:
            if self.scene().newItem:
                newRectF = QRectF(self.startPos, curPos)
                if newRectF != self.scene().newItem.rect():
                    self.scene().newItem.setRect(newRectF.normalized())
                    
        else:
            super().mouseMoveEvent(mouseEvent)
        
    def mouseReleaseEvent(self, mouseEvent):
        print("view mouseRelease")
        
        if self.scene().newItem:
            # delete item if zero height or width
            if (self.scene().newItem.rect().width() == 0 
                or self.scene().newItem.rect().height() == 0):
                self.scene().removeItem(self.scene().newItem)
                del self.scene().newItem
                    
        self.startPos = None
        self.scene().newItem = None
        super().mouseReleaseEvent(mouseEvent)
        
    def keyPressEvent(self, keyEvent):
        if keyEvent.key() == Qt.Key_F1:
            self.setSelectMode()
            self.updateItems()
            
        elif keyEvent.key() == Qt.Key_F2:
            self.setEditMode()
            self.updateItems()

        elif keyEvent.key() == Qt.Key_F3:
            self.setDrawMode()
            self.updateItems()
            
        elif keyEvent.key() == Qt.Key_Delete:
            if self.scene().viewMode() == MyScene.SELECTMODE:
                items = self.scene().selectedItems()
                if len(items):
                    for item in items:
                        self.scene().removeItem(item)
                        del item                   
                        
class MyScene(QGraphicsScene):
   
    SELECTMODE, EDITMODE, DRAWMODE = (0, 1, 2)
    validViewModes = [SELECTMODE, EDITMODE, DRAWMODE]
    
    def __init__(self, parent=None):
        super().__init__(parent)
        
        self._viewMode = MyScene.SELECTMODE
        self.newItem = None
        
        self.setSceneRect(-300, -200, 600, 400)
        
        # add some item
        someRect = MyRect(scene=self)
        someRect.setRect(QRectF(0, 0, 160, 80))
    
        # add another item
        anotherRect = MyRect(scene=self)
        anotherRect.setRect(QRectF(-80, -40, 80, 160))
        
        # add own item
        #myItem = MyItem(scene=self)

    def setViewMode(self, value):
        if value != self._viewMode:
            if value in MyScene.validViewModes:
                self._viewMode = value
            else:
                raise ValueError("invalid view mode")
            
    def viewMode(self):
        return self._viewMode
            
class MainWindow(QMainWindow):

    def __init__(self, parent=None):
        # call parent init
        super().__init__(parent)
        
        # setup scene object
        self.scene = MyScene()

        # setup view object
        self.view = MyView()
        
        # connect scene to view
        self.view.setScene(self.scene)
        
        # create layout
        layout = QVBoxLayout()
        
        # add view to layout
        layout.addWidget(self.view)
        
        # set the margin of the object in the layout
        layout.setContentsMargins(0, 0, 0, 0)
        
        # create the central widget
        self.widget = QWidget()
        
        # lay it out
        self.widget.setLayout(layout)
        
        # set it to central
        self.setCentralWidget(self.widget)        

if __name__ == "__main__":
        
    import sys
    
    # setup application object
    app = QApplication(sys.argv)
    
    # create (parent) main window
    mainWindow = MainWindow()
    mainWindow.setWindowTitle("testScene")
    mainWindow.show()
        
    # run application object
    sys.exit(app.exec_())

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[lightning2911]

btw this is on win7 using Python 3.1, PyQt 4.7.3, Qt 4.6.2

[norobro]

Found this on Qt Bug Tracker. Do a search for setCursor. There seem to be a lot of bugs related to it.

I ginned up a C++ version of your app and tried setting the cursor on the viewport as suggested in the first comment, but it didn't completely work either. And I'm using 4.7.0-beta1. It works okay if the cursor is not over one of the graphicsitems when F1||F2||F3 is pressed and then moved onto an item, but not the other way round. The view always retains its last setting if a button is pressed while the cursor is over an item.

[lightning2911]

SOLVED it. have to set the view cursors with self.viewport().setCursor instead of self.setCursor() in the updateItems() method of MyView() class.