Add step to Slider, + tests + docs

docs-src/docs/slider.md

@@ -13,7 +13,8 @@ __init__(
     visible=True, 
     enabled=None, 
     width=None, 
-    height=None)
+    height=None,
+    step=1)
 ```
 
 ### What is it?
@@ -33,7 +34,7 @@ slider = Slider(app)
 app.display()
 ```
 
-### Starting paramters
+### Starting parameters
 
 When you create a `Slider` object, you **must** specify a `master` and you can specify any of the the optional parameters. Specify parameters in the brackets, like this: `slider = Slider(app, horizontal=False)`
 
@@ -50,6 +51,7 @@ When you create a `Slider` object, you **must** specify a `master` and you can s
 | enabled    | boolean            | None    | No         | If the widget should be enabled. If `None` (the default) the enabled property will be inherited from the master |
 | width      | [size](size.md)    | None    | No         | Set the width of the widget in pixels or to `"fill"`                                                            |
 | height     | [size](size.md)    | None    | No         | Set the height of the widget in pixels or to `"fill"`                                                           |
+| step       | int                | 1       | No         | The increment of the slider's value                                                                             |
 
 
 ### Methods
@@ -93,6 +95,7 @@ You can set and get the following properties:
 | value      | string             | The current value of the slider                                                                       |
 | visible    | boolean            | If this widget is visible                                                                             |
 | width      | [size](size.md)    | Set the width of the widget in pixels or to `"fill"`                                                  |
+| step       | int                | The increment of the slider's value                                                                   |
 
 ### Examples
 

guizero/Slider.py

@@ -16,14 +16,15 @@ def __init__(
         visible=True, 
         enabled=None, 
         width=None, 
-        height=None):
+        height=None,
+        step=1):
 
         # Set the direction
         self._horizontal = horizontal
         orient = HORIZONTAL if horizontal else VERTICAL
 
         # Create a tk Scale object within this object
-        tk = Scale(master.tk, from_=start, to=end, orient=orient, command=self._command_callback)
+        tk = Scale(master.tk, from_=start, to=end, resolution=step, orient=orient, command=self._command_callback)
 
         super().__init__(master, tk, grid, align, visible, enabled, width, height)
 
@@ -57,6 +58,14 @@ def end(self):
     def end(self, value):
         self._set_tk_config("to", value)
 
+    @property
+    def step(self):
+        return self._get_tk_config("resolution")
+
+    @step.setter
+    def step(self, value):
+        self._set_tk_config("resolution", value)
+
     # Resize
     def resize(self, width, height):
         self._set_width(width)

tests/test_slider.py

@@ -17,25 +17,30 @@
     auto_layout_test
     )
 
-def test_start_end_change():
+def test_start_end_step_change():
     a = App()
     s = Slider(a)
     assert s.tk.cget("from") == 0
     assert s.tk.cget("to") == 100
-    s.start = 1
-    assert s.tk.cget("from") == 1
-    s.end = 99
-    assert s.tk.cget("to") == 99
+    assert s.tk.cget("resolution") == 1
+    s.start = 20
+    assert s.tk.cget("from") == 20
+    s.end = 90
+    assert s.tk.cget("to") == 90
+    s.step = 10
+    assert s.tk.cget("resolution") == 10
     # Also check that getters have worked
-    assert s.start == 1
-    assert s.end == 99
+    assert s.start == 20
+    assert s.end == 90
+    assert s.step == 10
     a.destroy()
 
 def test_default_values():
     a = App()
     s = Slider(a)
     assert s.tk.cget("from") == 0
     assert s.tk.cget("to") == 100
+    assert s.tk.cget("resolution") == 1
     assert s.tk.cget("orient") == "horizontal"
     assert s.master == a
     assert s.grid == None
@@ -53,7 +58,8 @@ def test_alt_values():
         grid = [0,1],
         align = "top",
         width=10,
-        height=11)
+        height=11,
+        step=5)
 
     assert s.tk.cget("from") == 10
     assert s.tk.cget("to") == 20
@@ -63,6 +69,7 @@ def test_alt_values():
     assert s.align == "top"
     assert s.width == 10
     assert s.height == 11
+    assert s.tk.cget("resolution") == 5
     a.destroy()
 
 def test_getters_setters():