undulators: write move attribute only when target is outside tolerance

id26/controllers/id26undulators.py

+import pytest
 from bliss.common.axis import NoSettingsAxis
+from bliss.common.logtools import log_debug, log_warning
 from bliss.controllers.motors.esrf_undulator import ESRF_Undulator
 from bliss.controllers.motors import esrf_undulator 
 
@@ -41,4 +43,23 @@ class ID26_Undulator(ESRF_Undulator):
     def __init__(self, *args, **kwargs):
         ESRF_Undulator.__init__(self, *args, **kwargs)
 
- 
+
+    def start_one(self, motion, t0=None):
+        if motion.target_pos != pytest.approx(motion.axis.position, abs=motion.axis.tolerance):
+            self._set_attribute(
+                motion.axis,
+                "attr_pos_name",
+                float(motion.target_pos / motion.axis.steps_per_unit),
+            )
+        else:
+            log_warning(self, 
+                        "{0} within tolerance {1}: {2} (requested new pos id: {3})".format(
+                            motion.axis.name,
+                            motion.axis.tolerance,
+                            motion.axis.position,
+                            motion.target_pos,
+                            )
+            )
+            
+        log_debug(self, f"end of start {motion.axis.name}")
+