Fix RangeEdit step min (#701)

* fix: fix step of zero on RangeEdit

* fix rangetstep tests

Author: tlambert03

src/magicgui/widgets/_concrete.py

@@ -6,6 +6,7 @@
 
 from __future__ import annotations
 
+import builtins
 import datetime
 import inspect
 import math
@@ -515,6 +516,12 @@ def __init__(
         maxstart, maxstop, maxstep = self._validate_min_max(max, "max", 9999999)
         self.start = SpinBox(value=start, min=minstart, max=maxstart, name="start")
         self.stop = SpinBox(value=stop, min=minstop, max=maxstop, name="stop")
+
+        if self._value_type is range:
+            if stop >= start:
+                minstep, maxstep = builtins.max(1, minstep), maxstep
+            else:
+                minstep, maxstep = -maxstep, -builtins.min(1, abs(minstep))
         self.step = SpinBox(value=step, min=minstep, max=maxstep, name="step")
         self.start.changed.connect(self._emit_current_value)
         self.stop.changed.connect(self._emit_current_value)

tests/test_widgets.py

@@ -463,6 +463,7 @@ def add(num1: int, num2: int) -> int:
 def test_range_widget():
     args = (-100, 1000, 2)
     rw = widgets.RangeEdit(*args)
+    assert rw.step.min == 1
     v = rw.value
     assert isinstance(v, range)
     assert (v.start, v.stop, v.step) == args