Add release event for lasso_demo

Author: devRD

examples/event_handling/lasso_demo.py

@@ -57,7 +57,10 @@ def __init__(self, ax, data):
 
         ax.add_collection(self.collection)
 
-        self.cid = self.canvas.mpl_connect('button_press_event', self.on_press)
+        self.cid_press = self.canvas.mpl_connect('button_press_event',
+                                                 self.on_press)
+        self.cid_release = self.canvas.mpl_connect('button_release_event',
+                                                   self.on_release)
 
     def callback(self, verts):
         facecolors = self.collection.get_facecolors()
@@ -70,7 +73,6 @@ def callback(self, verts):
                 facecolors[i] = Datum.colorout
 
         self.canvas.draw_idle()
-        self.canvas.widgetlock.release(self.lasso)
         del self.lasso
 
     def on_press(self, event):
@@ -84,6 +86,11 @@ def on_press(self, event):
         # acquire a lock on the widget drawing
         self.canvas.widgetlock(self.lasso)
 
+    def on_release(self, event):
+        if self.canvas.widgetlock.locked():
+            self.canvas.widgetlock.release(self.lasso)
+            return
+
 
 if __name__ == '__main__':