Show X and Y coordinates lines in QGraphicsView

Question

I want to display an image in a QGraphicsView, actually in QGraphicsScene, this is the easy part, bu, when I move the cursor over the image, I want to see the X and Y coordinates lines (the yellow lines), like in this image, can anyone explain me how to do this?

score 4 · Accepted Answer · answered Jun 25 '19 at 07:46

To implement what you want there are 2 tasks:

Obtain the position of the cursor, for this case the flag mouseTracking is enabled so that mouseMoveEvent() is called where the position is obtained.
Paint on the top layer, for this we use the drawForeground() function.

from PyQt5 import QtCore, QtGui, QtWidgets


class GraphicsScene(QtWidgets.QGraphicsScene):
    def drawForeground(self, painter, rect):
        super(GraphicsScene, self).drawForeground(painter, rect)
        if not hasattr(self, "cursor_position"):
            return
        painter.save()
        pen = QtGui.QPen(QtGui.QColor("yellow"))
        pen.setWidth(4)
        painter.setPen(pen)
        linex = QtCore.QLineF(
            rect.left(),
            self.cursor_position.y(),
            rect.right(),
            self.cursor_position.y(),
        )
        liney = QtCore.QLineF(
            self.cursor_position.x(),
            rect.top(),
            self.cursor_position.x(),
            rect.bottom(),
        )
        for line in (linex, liney):
            painter.drawLine(line)
        painter.restore()

    def mouseMoveEvent(self, event):
        self.cursor_position = event.scenePos()
        self.update()
        super(GraphicsScene, self).mouseMoveEvent(event)


class GraphicsView(QtWidgets.QGraphicsView):
    def __init__(self, parent=None):
        super(GraphicsView, self).__init__(parent)
        self.setMouseTracking(True)
        scene = GraphicsScene(QtCore.QRectF(-200, -200, 400, 400), self)
        self.setScene(scene)


if __name__ == "__main__":
    import sys
    import random

    app = QtWidgets.QApplication(sys.argv)

    w = GraphicsView()

    for _ in range(4):
        r = QtCore.QRectF(
            *random.sample(range(-200, 200), 2),
            *random.sample(range(50, 150), 2)
        )
        it = w.scene().addRect(r)
        it.setBrush(QtGui.QColor(*random.sample(range(255), 3)))

    w.resize(640, 480)
    w.show()

    sys.exit(app.exec_())

Show X and Y coordinates lines in QGraphicsView

1 Answers1