Added very simple, enterable object for setting busy cursor during long operations

widgets/BusyCursor.py

+from pyqtgraph.Qt import QtGui, QtCore
+
+__all__ = ['BusyCursor']
+
+class BusyCursor:
+    """Class for displaying a busy mouse cursor during long operations.
+    Usage::
+
+        with pyqtgraph.BusyCursor():
+            doLongOperation()
+
+    May be nested.
+    """
+    active = []
+
+    def __enter__(self):
+        QtGui.QApplication.setOverrideCursor(QtGui.QCursor(QtCore.Qt.WaitCursor))
+        BusyCursor.active.append(self)
+
+    def __exit__(self, *args):
+        BusyCursor.active.pop(-1)
+        if len(BusyCursor.active) == 0:
+            QtGui.QApplication.restoreOverrideCursor()
+        
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