From 977d17134df25d691fc3ee84b7366a48a60de677 Mon Sep 17 00:00:00 2001
From: Tony S Yu <tsyu80@gmail.com>
Date: Mon, 23 Jul 2012 00:45:11 -0400
Subject: [PATCH] Change image_viewer to Plugin property.

Raise an error when using Plugin.image_viewer before it is set. This error prevents other, more obscure, errors from getting raised.
---
 skimage/viewer/plugins/base.py | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/skimage/viewer/plugins/base.py b/skimage/viewer/plugins/base.py
index 7532472b..560eec8c 100644
--- a/skimage/viewer/plugins/base.py
+++ b/skimage/viewer/plugins/base.py
@@ -48,6 +48,16 @@ class Plugin(QtGui.QDialog):
         self.cids = []
         self.artists = []
 
+    @property
+    def image_viewer(self):
+        if self._image_viewer is None:
+            raise RuntimeError("Plugin is not attached to ImageViewer")
+        return self._image_viewer
+
+    @image_viewer.setter
+    def image_viewer(self, image_viewer):
+        self._image_viewer = image_viewer
+
     def attach(self, image_viewer):
         self.setParent(image_viewer)
         self.setWindowFlags(Qt.Dialog)