Added code for inverting X axis

CHANGELOG

@@ -48,6 +48,7 @@ pyqtgraph-0.9.9  [unreleased]
     - Added AxisItem.setStyle()
     - Added configurable formatting for TableWidget
     - Added 'stepMode' argument to PlotDataItem()
+    - Added ViewBox.invertX()
 
   Bugfixes:
     - PlotCurveItem now has correct clicking behavior--clicks within a few px

pyqtgraph/graphicsItems/AxisItem.py

@@ -454,7 +454,10 @@ class AxisItem(GraphicsWidget):
         else:
             if newRange is None:
                 newRange = view.viewRange()[0]
-            self.setRange(*newRange)
+            if view.xInverted():
+                self.setRange(*newRange[::-1])
+            else:
+                self.setRange(*newRange)
         
     def boundingRect(self):
         linkedView = self.linkedView()

pyqtgraph/graphicsItems/PlotItem/PlotItem.py

@@ -78,6 +78,7 @@ class PlotItem(GraphicsWidget):
     :func:`disableAutoRange <pyqtgraph.ViewBox.disableAutoRange>`,
     :func:`setAspectLocked <pyqtgraph.ViewBox.setAspectLocked>`,
     :func:`invertY <pyqtgraph.ViewBox.invertY>`,
+    :func:`invertX <pyqtgraph.ViewBox.invertX>`,
     :func:`register <pyqtgraph.ViewBox.register>`,
     :func:`unregister <pyqtgraph.ViewBox.unregister>`
     
@@ -299,7 +300,7 @@ class PlotItem(GraphicsWidget):
     for m in ['setXRange', 'setYRange', 'setXLink', 'setYLink', 'setAutoPan',         # NOTE: 
               'setAutoVisible', 'setRange', 'autoRange', 'viewRect', 'viewRange',     # If you update this list, please 
               'setMouseEnabled', 'setLimits', 'enableAutoRange', 'disableAutoRange',  # update the class docstring 
-              'setAspectLocked', 'invertY', 'register', 'unregister']:                # as well.
+              'setAspectLocked', 'invertY', 'invertX', 'register', 'unregister']:                # as well.
                 
         def _create_method(name):
             def method(self, *args, **kwargs):

pyqtgraph/graphicsItems/ViewBox/ViewBox.py

@@ -104,7 +104,7 @@ class ViewBox(GraphicsWidget):
     NamedViews = weakref.WeakValueDictionary()   # name: ViewBox
     AllViews = weakref.WeakKeyDictionary()       # ViewBox: None
     
-    def __init__(self, parent=None, border=None, lockAspect=False, enableMouse=True, invertY=False, enableMenu=True, name=None):
+    def __init__(self, parent=None, border=None, lockAspect=False, enableMouse=True, invertY=False, enableMenu=True, name=None, invertX=False):
         """
         ==============  =============================================================
         **Arguments:**
@@ -115,6 +115,7 @@ class ViewBox(GraphicsWidget):
                         coorinates to. (or False to allow the ratio to change)
         *enableMouse*   (bool) Whether mouse can be used to scale/pan the view
         *invertY*       (bool) See :func:`invertY <pyqtgraph.ViewBox.invertY>`
+        *invertX*       (bool) See :func:`invertX <pyqtgraph.ViewBox.invertX>`
         ==============  =============================================================
         """
         
@@ -139,6 +140,7 @@ class ViewBox(GraphicsWidget):
             'viewRange': [[0,1], [0,1]],     ## actual range viewed
         
             'yInverted': invertY,
+            'xInverted': invertX,
             'aspectLocked': False,    ## False if aspect is unlocked, otherwise float specifies the locked ratio.
             'autoRange': [True, True],  ## False if auto range is disabled, 
                                           ## otherwise float gives the fraction of data that is visible
@@ -996,7 +998,10 @@ class ViewBox(GraphicsWidget):
                     x2 = vr.right()
                 else:  ## views overlap; line them up
                     upp = float(vr.width()) / vg.width()
-                    x1 = vr.left() + (sg.x()-vg.x()) * upp
+                    if self.xInverted():
+                        x1 = vr.left()   + (sg.right()-vg.right()) * upp
+                    else:
+                        x1 = vr.left()   + (sg.x()-vg.x()) * upp
                     x2 = x1 + sg.width() * upp
                 self.enableAutoRange(ViewBox.XAxis, False)
                 self.setXRange(x1, x2, padding=0)
@@ -1054,10 +1059,27 @@ class ViewBox(GraphicsWidget):
         #self.updateMatrix(changed=(False, True))
         self.updateViewRange()
         self.sigStateChanged.emit(self)
+        self.sigYRangeChanged.emit(self, tuple(self.state['viewRange'][1]))
 
     def yInverted(self):
         return self.state['yInverted']
         
+    def invertX(self, b=True):
+        """
+        By default, the positive x-axis points rightward on the screen. Use invertX(True) to reverse the x-axis.
+        """
+        if self.state['xInverted'] == b:
+            return
+        
+        self.state['xInverted'] = b
+        #self.updateMatrix(changed=(False, True))
+        self.updateViewRange()
+        self.sigStateChanged.emit(self)
+        self.sigXRangeChanged.emit(self, tuple(self.state['viewRange'][0]))
+
+    def xInverted(self):
+        return self.state['xInverted']
+        
     def setAspectLocked(self, lock=True, ratio=1):
         """
         If the aspect ratio is locked, view scaling must always preserve the aspect ratio.
@@ -1555,6 +1577,7 @@ class ViewBox(GraphicsWidget):
             if link is not None:
                 link.linkedViewChanged(self, ax)
         
+        self.update()
         self._matrixNeedsUpdate = True
 
     def updateMatrix(self, changed=None):
@@ -1567,6 +1590,8 @@ class ViewBox(GraphicsWidget):
         scale = Point(bounds.width()/vr.width(), bounds.height()/vr.height())
         if not self.state['yInverted']:
             scale = scale * Point(1, -1)
+        if self.state['xInverted']:
+            scale = scale * Point(-1, 1)
         m = QtGui.QTransform()
         
         ## First center the viewport at 0

pyqtgraph/graphicsItems/ViewBox/ViewBoxMenu.py

@@ -56,7 +56,7 @@ class ViewBoxMenu(QtGui.QMenu):
             for sig, fn in connects:
                 sig.connect(getattr(self, axis.lower()+fn))
 
-        self.ctrl[0].invertCheck.hide()  ## no invert for x-axis
+        self.ctrl[0].invertCheck.toggled.connect(self.xInvertToggled)
         self.ctrl[1].invertCheck.toggled.connect(self.yInvertToggled)
         ## exporting is handled by GraphicsScene now
         #self.export = QtGui.QMenu("Export")
@@ -139,8 +139,9 @@ class ViewBoxMenu(QtGui.QMenu):
             
             self.ctrl[i].autoPanCheck.setChecked(state['autoPan'][i])
             self.ctrl[i].visibleOnlyCheck.setChecked(state['autoVisibleOnly'][i])
-
-        self.ctrl[1].invertCheck.setChecked(state['yInverted'])
+            xy = ['x', 'y'][i]
+            self.ctrl[i].invertCheck.setChecked(state.get(xy+'Inverted', False))
+        
         self.valid = True
         
     def popup(self, *args):
@@ -217,19 +218,19 @@ class ViewBoxMenu(QtGui.QMenu):
     def yInvertToggled(self, b):
         self.view().invertY(b)
 
+    def xInvertToggled(self, b):
+        self.view().invertX(b)
 
     def exportMethod(self):
         act = self.sender()
         self.exportMethods[str(act.text())]()
 
-
     def set3ButtonMode(self):
         self.view().setLeftButtonAction('pan')
         
     def set1ButtonMode(self):
         self.view().setLeftButtonAction('rect')
         
-        
     def setViewList(self, views):
         names = ['']
         self.viewMap.clear()