Update docs

docs/developer_guides/viewer/viewer_control.md

@@ -63,7 +63,7 @@ class MyModel(nn.Module):  # Must inherit from nn.Module
 ```
 
 ## Double-click Callbacks
-We forward *double* clicks inside the viewer to the ViewerControl object, which you can use to interact with the scene. To do this, register a callback using `register_click_cb()`. The click is defined to be a ray that starts at the camera origin and passes through the click point on the screen, in world coordinates. 
+We forward *single* clicks inside the viewer to the ViewerControl object, which you can use to interact with the scene. To do this, register a callback using `register_click_cb()`. The click is defined to be a ray that starts at the camera origin and passes through the click point on the screen, in world coordinates. 
 
 ```python
 from nerfstudio.viewer.server.viewer_elements import ViewerControl,ViewerClick
@@ -77,6 +77,16 @@ class MyModel(nn.Module):  # must inherit from nn.Module
         self.viewer_control.register_click_cb(click_cb)
 ```
 
+You can also use `unregister_click_cb()` to remove callbacks that are no longer needed. A good example is a "Click on Scene" button, that when pressed, would register a callback that would wait for the next click, and then unregister itself.
+```python
+    ...
+    def button_cb(button: ViewerButton):
+        def click_cb(click: ViewerClick):
+            print(f"Click at {click.origin} in direction {click.direction}")
+            self.viewer_control.unregister_click_cb(click_cb)
+        self.viewer_control.register_click_cb(click_cb)
+```
+
 ### Thread safety
 Just like `ViewerElement` callbacks, click callbacks are asynchronous to training and can potentially interrupt a call to `get_outputs()`.