AxisItem bugfix: corrected x-linked view update behavior

Added MultiplePlotAxes example

examples/MultiplePlotAxes.py

@@ -0,0 +1,67 @@
+# -*- coding: utf-8 -*-
+"""
+Demonstrates a way to put multiple axes around a single plot. 
+
+(This will eventually become a built-in feature of PlotItem)
+
+"""
+import initExample ## Add path to library (just for examples; you do not need this)
+
+import pyqtgraph as pg
+from pyqtgraph.Qt import QtCore, QtGui
+import numpy as np
+
+pg.mkQApp()
+
+pw = pg.PlotWidget()
+pw.show()
+pw.setWindowTitle('pyqtgraph example: MultiplePlotAxes')
+p1 = pw.plotItem
+p1.setLabels(left='axis 1')
+
+## create a new ViewBox, link the right axis to its coordinate system
+p2 = pg.ViewBox()
+p1.showAxis('right')
+p1.scene().addItem(p2)
+p1.getAxis('right').linkToView(p2)
+p2.setXLink(p1)
+p1.getAxis('right').setLabel('axis2', color='#0000ff')
+
+## create third ViewBox. 
+## this time we need to create a new axis as well.
+p3 = pg.ViewBox()
+ax3 = pg.AxisItem('right')
+p1.layout.addItem(ax3, 2, 3)
+p1.scene().addItem(p3)
+ax3.linkToView(p3)
+p3.setXLink(p1)
+ax3.setZValue(-10000)
+ax3.setLabel('axis 3', color='#ff0000')
+
+
+## Handle view resizing 
+def updateViews():
+    ## view has resized; update auxiliary views to match
+    global p1, p2, p3
+    p2.setGeometry(p1.vb.sceneBoundingRect())
+    p3.setGeometry(p1.vb.sceneBoundingRect())
+    
+    ## need to re-update linked axes since this was called
+    ## incorrectly while views had different shapes.
+    ## (probably this should be handled in ViewBox.resizeEvent)
+    p2.linkedViewChanged(p1.vb, p2.XAxis)
+    p3.linkedViewChanged(p1.vb, p3.XAxis)
+
+updateViews()
+p1.vb.sigResized.connect(updateViews)
+
+
+p1.plot([1,2,4,8,16,32])
+p2.addItem(pg.PlotCurveItem([10,20,40,80,40,20], pen='b'))
+p3.addItem(pg.PlotCurveItem([3200,1600,800,400,200,100], pen='r'))
+
+## Start Qt event loop unless running in interactive mode or using pyside.
+if __name__ == '__main__':
+    import sys
+    if (sys.flags.interactive != 1) or not hasattr(QtCore, 'PYQT_VERSION'):
+        QtGui.QApplication.instance().exec_()

pyqtgraph/graphicsItems/AxisItem.py

@@ -314,10 +314,13 @@ class AxisItem(GraphicsWidget):
         view.sigResized.connect(self.linkedViewChanged)
         
     def linkedViewChanged(self, view, newRange=None):
-        if self.orientation in ['right', 'left'] and view.yInverted():
+        if self.orientation in ['right', 'left']:
             if newRange is None:
                 newRange = view.viewRange()[1]
-            self.setRange(*newRange[::-1])
+            if view.yInverted():
+                self.setRange(*newRange[::-1])
+            else:
+                self.setRange(*newRange)
         else:
             if newRange is None:
                 newRange = view.viewRange()[0]
@@ -330,18 +333,12 @@ class AxisItem(GraphicsWidget):
             ## extend rect if ticks go in negative direction
             ## also extend to account for text that flows past the edges
             if self.orientation == 'left':
-                #rect.setRight(rect.right() - min(0,self.tickLength))
-                #rect.setTop(rect.top() - 15)
-                #rect.setBottom(rect.bottom() + 15)
                 rect = rect.adjusted(0, -15, -min(0,self.tickLength), 15)
             elif self.orientation == 'right':
-                #rect.setLeft(rect.left() + min(0,self.tickLength))
                 rect = rect.adjusted(min(0,self.tickLength), -15, 0, 15)
             elif self.orientation == 'top':
-                #rect.setBottom(rect.bottom() - min(0,self.tickLength))
                 rect = rect.adjusted(-15, 0, 15, -min(0,self.tickLength))
             elif self.orientation == 'bottom':
-                #rect.setTop(rect.top() + min(0,self.tickLength))
                 rect = rect.adjusted(-15, min(0,self.tickLength), 15, 0)
             return rect
         else: