QT: Drawing Primitves to Follow Cursor

Question

I am a bit new to QT. I have a separate Crosshair class that simply renders a crosshair using the QPainter and QPen. I used the paint() function and it does display the crosshairs at some position in the window. How can make the crosshairs follow the current mouse position?

This is my approach but I can't get it to work. I was following the VoidRealms tutorial.

void Crosshair::mouseMoveEvent(QGraphicsSceneMouseEvent *event){

   // i want to update the x and y position when the mouse moves
   //x = mouse.x
   //y = mouse.y
   QGraphicsItem::mouseMoveEvent(event);
   update();
 }

you can use scenePos () or screenPos() api from QGraphicsSceneMouseEvent, to get mouse's x and y cordinate — Kunal, Jul 10 '13 at 05:38
Wouldn't it be easier to just use the QCursor class and QWindow::setCursor(const QCursor&) function, or is there a specific reason why you're re-inventing this wheel? — TheDarkKnight, Jul 10 '13 at 08:06
The class name is a bit misleading. I'm drawing primitives at the cursor position. — lambda, Jul 12 '13 at 01:11

score 2 · Accepted Answer · edited May 23 '17 at 10:25

2

This should do it for you:

this->setPos(event->x(), event->y());

There are also other helper functions available if you are doing a mapping to your scene when you are outside of QGraphicsSceneMouseEvent.

I described it here:

How to draw a point (on mouseclick) on a QGraphicsScene?

Hope that helps.

edited May 23 '17 at 10:25

Community

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answered Jul 10 '13 at 04:35

phyatt

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is it possible to do this without mouse click? I want the crosshair to follow the cursor at all times – lambda Jul 12 '13 at 01:22

QT: Drawing Primitves to Follow Cursor

1 Answers1