Add Scantool.step_sizes

docs/changelog.md

@@ -18,6 +18,7 @@
 
 Added:
 
+- The [Scantool.step_sizes][extra.components.Scantool.step_sizes] property (!58).
 - The [Scan][extra.components.Scan] component to automatically detect steps
   within a motor scan (!4).
 - [DldPulses][extra.components.DldPulses] to access pulse information saved during delay line detector event reconstruction (!42).

src/extra/components/scantool.py

@@ -88,6 +88,10 @@ def get_first_value(keys):
         self._stop_positions = dict(zip(self.motors,
                                         values["scanEnv.stopPoints.value"][:n_motors]))
 
+        # Calculate the step size
+        self._step_sizes = { motor: abs(self.start_positions[motor] - self.stop_positions[motor]) / self.steps[motor]
+                             for motor in self.motors }
+
     @property
     def source_name(self) -> str:
         """The name of the scantool device."""
@@ -140,6 +144,15 @@ def steps(self) -> dict:
         scanned over."""
         return self._steps
 
+    @property
+    def step_sizes(self) -> dict:
+        """A dictionary mapping motor aliases to their step size.
+
+        Unlike most other properties, this is calculated from the step
+        information rather than being read from a property.
+        """
+        return self._step_sizes
+
     @property
     def start_positions(self) -> dict:
         """A dictionary mapping motor aliases to their start positions."""