Enable web UI to run when no stage is connected

openflexure_microscope/api/templates/index_v1.html

@@ -26,7 +26,7 @@
         </p>
         <p>
           <button type="button" onclick="setStagePositionsFromInput();">GO</button>
-          <button type="button" onclick="getStagePositions();">Update</button>
+          <button type="button" onclick="api.getState(updateStateValues);">Update</button>
         </p>
 
         <p>

openflexure_microscope/api/v1/blueprints/stage.py

@@ -67,7 +67,7 @@ class PositionAPI(MicroscopeView):
         position = [0, 0, 0]
 
         # Handle absolute positioning (calculate a relative move from current position and target)
-        if payload.param('absolute') is True:
+        if (payload.param('absolute') is True) and (self.microscope.stage):  # Only if stage exists
             target_position = axes_to_array(payload.json, ['x', 'y', 'z'])
             logging.debug("TARGET: {}".format(target_position))
             position = [target_position[i] - self.microscope.stage.position[i] for i in range(3)]
@@ -79,7 +79,9 @@ class PositionAPI(MicroscopeView):
 
         logging.debug(position)
 
-        self.microscope.stage.move_rel(position)
+        # Move if stage exists
+        if self.microscope.stage:
+            self.microscope.stage.move_rel(position)
 
         out = filter_dict(self.microscope.state, ('stage', 'position'))
 

openflexure_microscope/microscope.py

@@ -138,7 +138,11 @@ class Microscope(object):
         }
 
         # Add stage position
-        position = self.stage.position
+        if self.stage:  # If stage exists, populate with real values
+            position = self.stage.position
+        else:  # Else, zero
+            position = [0, 0, 0]
+
         state['stage']['position'] = {
             'x': position[0],
             'y': position[1],
@@ -158,7 +162,11 @@ class Microscope(object):
             self._config.update(self.camera.config)
         
         # If attached to a stage
-        backlash = self.stage.backlash.tolist()
+        if self.stage:
+            backlash = self.stage.backlash.tolist()
+        else:
+            backlash = [0, 0, 0]
+
         self._config['backlash'] = {
             'x': backlash[0],
             'y': backlash[1],