Bugfix to slice canvas - hidden canvases were not re-creating GLObjects,

because they were unable to set the GL context. But it seems that GL
stuff can be created without setting the context. May need to test on
other platform(s) to confirm this.

fsl/fslview/gl/slicecanvas.py

@@ -525,12 +525,9 @@ class SliceCanvas(props.HasProperties):
         render texture associated with the overlay is destroyed.
         """
         
-        if not self._setGLContext():
-            return
-
         # Tell the previous GLObject (if
         # any) to clean up after itself
-        globj = self._glObjects.get(overlay, None)
+        globj = self._glObjects.pop(overlay, None)
         if globj is not None:
             globj.destroy()
 

fsl/fslview/views/orthopanel.py

@@ -189,6 +189,7 @@ class OrthoPanel(canvaspanel.CanvasPanel):
         self._displayCtx .removeListener('location',        self._name)
         self._displayCtx .removeListener('bounds',          self._name)
         self._displayCtx .removeListener('selectedOverlay', self._name)
+        self._displayCtx .removeListener('overlayOrder',    self._name)
         self._overlayList.removeListener('overlays',        self._name)
 
         # The _overlayListChanged method adds
@@ -612,11 +613,7 @@ class OrthoPanel(canvaspanel.CanvasPanel):
         flag = wx.ALIGN_CENTRE_HORIZONTAL | wx.ALIGN_CENTRE_VERTICAL
         
         for w in widgets:
-
-            if w in [self._xcanvas, self._ycanvas, self._zcanvas]:
-                self._canvasSizer.Add(w, flag=flag)
-            else:
-                self._canvasSizer.Add(w, flag=flag)
+            self._canvasSizer.Add(w, flag=flag)
                                           
         self.getCanvasPanel().SetSizer(self._canvasSizer)