Added custom graphicsitem example

examples/customGraphicsItem.py

+import pyqtgraph as pg
+from pyqtgraph import QtCore, QtGui
+
+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):
+        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):
+        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)
+
+QtGui.QApplication.exec_()
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