qgraphicsview

I'm developing a custom widget with QGraphicsScene/View and I have no prior experience with it. The custom widget is an image viewer that needs to track mouse movement and send signal(s) to it's parent dialog / window. The signal(s) will be the position of the pixel under the mouse cursor and it's color (in RGB). A status bar will use that information. I use a QGraphicsPixmapItem to display the image I load from a file in the scene. Thanks. First of all you have to implement the mouseMoveEvent in your custom item. In this function you can easily get the mouse position calling the pos function.

The easy way to create the long cross line cursor (as long as viewport) is create a cross line graphicsItem , when mouse moved, set the item's pos property. But this way will be very slow when the scene is complex, because it should update the whole viewport to update the cursor's pos . The another easy way is setCursor(QCursor(..)) ,use a QPixmap to define the long cross line, this way will very fast , but the cursor will exceed the viewport rect. Is there another way to show a long cross line cursor fastly? Thanks very much! If I understand correctly, you want to draw an horizontal line and

Is there a way to restrict the area where a QGraphicsItem like QRect can be moved when setFlag(ItemIsMovable) is set? I'm new to pyqt and trying to find a way to move an item with the mouse, and the restrict it to only vertically/horizontally. If you want to keep a limited area you can reimplement the ItemChanged() Declare: #ifndef GRAPHIC_H #define GRAPHIC_H #include <QGraphicsRectItem> class Graphic : public QGraphicsRectItem { public: Graphic(const QRectF & rect, QGraphicsItem * parent = 0); protected: virtual QVariant itemChange ( GraphicsItemChange change, const QVariant & value ); };

I subclassed QGraphicsScene and added method mouseMoveEvent to handle mouse move event. I created a ruler on top of GraphicsView and have the ruler tracking mouse movement. In the QGraphicsScene::mousemoveEvent I calls mouseMoveEvent of the ruler widget explcitely. The purpose is to have the ruler knows that the current mouse position. Now it seems that QGraphicsScene::mousemoveEvent is not called when I move the mouse. However, I can get it to work if I press the left mouse button and move it while holding the button. This is not what I'd like to see; I'd like this method is called whenever I

I'm going to start programming a 2D tile-based game in Qt and read about the QGraphicsScene and QGraphicsView classes which are intended for displaying and handling lots of 2D objects. My question is that will it be feasible to create a world with lots of tiles using QGraphicsScene? Can I add the whole world at once tile-by-tile or should I try to implement something to restrict the area a bit? I've read that QGraphicsScene can handle "thousands of items" but a 2D tile map can easily get really, really big (200x200 tiles? not that many, but that's already 40,000 objects which is a lot). The