added shutter opened/closed contexts

slic/devices/general/shutter.py

@@ -1,6 +1,8 @@
 from slic.core.adjustable import PVAdjustable
 from slic.utils import typename
 
+from .shutterctx import ShutterContextMixin
+
 
 #REQUEST
 # 0: close
@@ -15,7 +17,7 @@ from slic.utils import typename
 # 1: TRUE
 
 
-class Shutter:
+class Shutter(ShutterContextMixin):
 
     def __init__(self, ID):
         self.ID = ID

slic/devices/general/shutterctx.py

@@ -0,0 +1,42 @@
+class ShutterContextMixin:
+
+    def opened(self):
+        """
+        Returns a context manager that opens the shutter on enter and closes on exit
+        """
+        return ShutterCloser(self.open, self.close)
+
+    def closed(self):
+        """
+        Returns a context manager that closes the shutter on enter and opens on exit
+        """
+        return ShutterOpener(self.close, self.open)
+
+
+
+class Context:
+
+    def __init__(self, on_enter, on_exit):
+        self.on_enter = on_enter
+        self.on_exit = on_exit
+
+    def __enter__(self):
+        self.on_enter()
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        self.on_exit()
+
+
+
+# subclasses such that returned objects have meaningful names
+# if opened/closed are called directly, i.e., outside with
+
+class ShutterCloser(Context):
+    pass
+
+class ShutterOpener(Context):
+    pass
+
+
+