pyqtgraph/examples/customGraphicsItem.py

"""
Demonstrate creation of a custom graphic (a candlestick plot)

"""
import initExample ## Add path to library (just for examples; you do not need this)

import pyqtgraph as pg
from pyqtgraph import QtCore, QtGui

## Create a subclass of GraphicsObject.
## The only required methods are paint() and boundingRect() 
## (see QGraphicsItem documentation)
class CandlestickItem(pg.GraphicsObject):
    def __init__(self, data):
        pg.GraphicsObject.__init__(self)
        self.data = data  ## data must have fields: time, open, close, min, max
        self.generatePicture()
    
    def generatePicture(self):
        ## pre-computing a QPicture object allows paint() to run much more quickly, 
        ## rather than re-drawing the shapes every time.
        self.picture = QtGui.QPicture()
        p = QtGui.QPainter(self.picture)
        p.setPen(pg.mkPen('w'))
        w = (self.data[1][0] - self.data[0][0]) / 3.
        for (t, open, close, min, max) in self.data:
            p.drawLine(QtCore.QPointF(t, min), QtCore.QPointF(t, max))
            if open > close:
                p.setBrush(pg.mkBrush('r'))
            else:
                p.setBrush(pg.mkBrush('g'))
            p.drawRect(QtCore.QRectF(t-w, open, w*2, close-open))
        p.end()
    
    def paint(self, p, *args):
        p.drawPicture(0, 0, self.picture)
    
    def boundingRect(self):
        ## boundingRect _must_ indicate the entire area that will be drawn on
        ## or else we will get artifacts and possibly crashing.
        ## (in this case, QPicture does all the work of computing the bouning rect for us)
        return QtCore.QRectF(self.picture.boundingRect())

data = [  ## fields are (time, open, close, min, max).
    (1., 10, 13, 5, 15),
    (2., 13, 17, 9, 20),
    (3., 17, 14, 11, 23),
    (4., 14, 15, 5, 19),
    (5., 15, 9, 8, 22),
    (6., 9, 15, 8, 16),
]
item = CandlestickItem(data)
plt = pg.plot()
plt.addItem(item)
plt.setWindowTitle('pyqtgraph example: customGraphicsItem')

if __name__ == '__main__':
    pg.mkQApp().exec_()