gui: add visualisation to the slider step feature

CHANGELOG.md

@@ -8,6 +8,8 @@ Arcade [PyPi Release History](https://pypi.org/project/arcade/#history) page.
 - GUI
   - Fix `UIScrollArea.add` always returning None
   - Support `layer` in `UIView.add_widget()`
+  - Fix a bug which caused `UIScrollArea` to refresh on every frame
+  - Add stepping to `UISlider` (thanks [csd4ni3l](https://github.com/csd4ni3l))
 - Text objects are now lazy and can be created before the window
 - Introduce `arcade.SpriteSequence[T]` as a covariant supertype of `arcade.SpriteList[T]`
   (this is similar to Python's `Sequence[T]`, which is a supertype of `list[T]`)

arcade/examples/gui/2_widgets.py

@@ -410,12 +410,35 @@ def _show_interactive_widgets(self):
                 size_hint=(0.3, 0),
             )
         )
-        slider_row.add(
+        s1 = slider_row.add(UISlider(size_hint=(0.3, 1), step=1, style=UISlider.NO_STEP_STYLE))
+        s2 = slider_row.add(
+            UISlider(
+                size_hint=(0.3, 1),
+                step=5,
+            )
+        )
+        s3 = slider_row.add(
             UISlider(
-                size_hint=(0.2, None),
+                size_hint=(0.3, 1),
+                step=10,
             )
         )
 
+        @s1.event("on_change")
+        def _(event: UIOnChangeEvent):
+            s2.value = event.new_value
+            s3.value = event.new_value
+
+        @s2.event("on_change")
+        def _(event: UIOnChangeEvent):
+            s1.value = event.new_value
+            s3.value = event.new_value
+
+        @s3.event("on_change")
+        def _(event: UIOnChangeEvent):
+            s1.value = event.new_value
+            s2.value = event.new_value
+
         tex_slider_row = UIBoxLayout(vertical=False, size_hint=(1, 0.1), space_between=10)
         box.add(tex_slider_row)
 
@@ -428,7 +451,7 @@ def _show_interactive_widgets(self):
             )
         )
 
-        s1 = tex_slider_row.add(
+        ts1 = tex_slider_row.add(
             UITextureSlider(
                 thumb_texture=TEX_SLIDER_THUMB_BLUE,
                 track_texture=NinePatchTexture(10, 10, 10, 10, TEX_SLIDER_TRACK_BLUE),
@@ -440,7 +463,7 @@ def _show_interactive_widgets(self):
         green_style["normal"].filled_track = arcade.uicolor.GREEN_GREEN_SEA
         green_style["hover"].filled_track = arcade.uicolor.GREEN_EMERALD
         green_style["press"].filled_track = arcade.uicolor.GREEN_GREEN_SEA
-        s2 = tex_slider_row.add(
+        ts2 = tex_slider_row.add(
             UITextureSlider(
                 thumb_texture=TEX_SLIDER_THUMB_GREEN,
                 track_texture=NinePatchTexture(10, 10, 10, 10, TEX_SLIDER_TRACK_GREEN),
@@ -453,7 +476,7 @@ def _show_interactive_widgets(self):
         red_style["normal"].filled_track = arcade.uicolor.RED_POMEGRANATE
         red_style["hover"].filled_track = arcade.uicolor.RED_ALIZARIN
         red_style["press"].filled_track = arcade.uicolor.RED_POMEGRANATE
-        s3 = tex_slider_row.add(
+        ts3 = tex_slider_row.add(
             UITextureSlider(
                 thumb_texture=TEX_SLIDER_THUMB_RED,
                 track_texture=NinePatchTexture(10, 10, 10, 10, TEX_SLIDER_TRACK_RED),
@@ -462,20 +485,20 @@ def _show_interactive_widgets(self):
             )
         )
 
-        @s1.event("on_change")
+        @ts1.event("on_change")
         def _(event: UIOnChangeEvent):
-            s2.value = event.new_value
-            s3.value = event.new_value
+            ts2.value = event.new_value
+            ts3.value = event.new_value
 
-        @s2.event("on_change")
+        @ts2.event("on_change")
         def _(event: UIOnChangeEvent):
-            s1.value = event.new_value
-            s3.value = event.new_value
+            ts1.value = event.new_value
+            ts3.value = event.new_value
 
-        @s3.event("on_change")
+        @ts3.event("on_change")
         def _(event: UIOnChangeEvent):
-            s1.value = event.new_value
-            s2.value = event.new_value
+            ts1.value = event.new_value
+            ts2.value = event.new_value
 
         box.add(UISpace(size_hint=(0.2, 0.1)))
         text_area = box.add(

arcade/examples/gui/6_size_hints.py

@@ -98,7 +98,9 @@ def __init__(self):
         width_slider_box = center_box.add(UIBoxLayout(vertical=False, size_hint=(1, 0)))
         width_slider_box.add(UILabel("Modify size_hint:", bold=True))
         width_slider = width_slider_box.add(
-            arcade.gui.UISlider(min_value=0, max_value=10, value=0, size_hint=None, height=30)
+            arcade.gui.UISlider(
+                min_value=0, max_value=1, value=0, size_hint=None, height=30, step=0.1
+            )
         )
         width_value = width_slider_box.add(UILabel(bold=True))
 
@@ -116,17 +118,17 @@ def __init__(self):
 
         def update_size_hint_value(value: float):
             width_value.text = f"({value:.2f})"
-            dummy1.size_hint = (value / 10, 1)
-            dummy1.text = f"size_hint = ({value / 10:.2f}, 1)"
+            dummy1.size_hint = (value, 1)
+            dummy1.text = f"size_hint = ({value:.2f}, 1)"
 
-            dummy2.size_hint = (1 - value / 10, 1)
-            dummy2.text = f"size_hint = ({1 - value / 10:.2f}, 1)"
+            dummy2.size_hint = (1 - value, 1)
+            dummy2.text = f"size_hint = ({1 - value:.2f}, 1)"
 
         @width_slider.event("on_change")
         def on_change(event: UIOnChangeEvent):
             update_size_hint_value(event.new_value)
 
-        initial_value = 10
+        initial_value = 1
         width_slider.value = initial_value
         update_size_hint_value(initial_value)
 

arcade/gui/widgets/slider.py

@@ -84,20 +84,29 @@ def __init__(
         )
 
         self.step = step
-        self.value = self._apply_step(value)
+        self.value = value
         self.min_value = min_value
         self.max_value = max_value
 
         self._cursor_width = self.height // 3
 
         # trigger render on value changes
         bind(self, "value", self.trigger_full_render)
+        bind(self, "value", self._ensure_step)
         bind(self, "hovered", self.trigger_render)
         bind(self, "pressed", self.trigger_render)
         bind(self, "disabled", self.trigger_render)
 
         self.register_event_type("on_change")
 
+    def _ensure_step(self):
+        """Ensure that the step is applied."""
+        if self.step is not None:
+            # this will trigger the change once again
+            # only option to prevent this would be to make `value` a property,
+            # which might break code of users
+            self.value = self._apply_step(self.value)
+
     def _apply_step(self, value: float):
         if self.step:
             inverse = 1 / self.step
@@ -120,9 +129,7 @@ def norm_value(self):
     @norm_value.setter
     def norm_value(self, value):
         """Normalized value between 0.0 and 1.0"""
-        self.value = self._apply_step(
-            min(value * (self.max_value - self.min_value) + self.min_value, self.max_value)
-        )
+        self.value = min(value * (self.max_value - self.min_value) + self.min_value, self.max_value)
 
     @property
     def _thumb_x(self):
@@ -147,6 +154,7 @@ def do_render(self, surface: Surface):
         """Render the slider, including track and thumb."""
         self.prepare_render(surface)
         self._render_track(surface)
+        self._render_steps(surface)
         self._render_thumb(surface)
 
     @abstractmethod
@@ -162,6 +170,19 @@ def _render_track(self, surface: Surface):
         """
         pass
 
+    @abstractmethod
+    def _render_steps(self, surface: Surface):
+        """Render the steps of the slider track.
+
+        This method should be implemented in a slider implementation.
+
+        Steps should stay within self.content_rect.
+
+        Args:
+                surface: Surface to render on.
+        """
+        pass
+
     @abstractmethod
     def _render_thumb(self, surface: Surface):
         """Render the thumb of the slider.
@@ -236,15 +257,18 @@ class UISliderStyle(UIStyleBase):
         border: Border color.
         border_width: Width of the border.
         filled_track: Color of the filled track.
+        filled_step: Color of the step in filled area.
         unfilled_track: Color of the unfilled track.
-
+        unfilled_step: Color of the step in unfilled area.
     """
 
     bg: RGBA255 = uicolor.WHITE_SILVER
     border: RGBA255 = uicolor.DARK_BLUE_MIDNIGHT_BLUE
     border_width: int = 2
     filled_track: RGBA255 = uicolor.DARK_BLUE_MIDNIGHT_BLUE
+    filled_step: RGBA255 | None = uicolor.BLUE_PETER_RIVER
     unfilled_track: RGBA255 = uicolor.WHITE_SILVER
+    unfilled_step: RGBA255 | None = uicolor.BLUE_PETER_RIVER
 
 
 class UISlider(UIStyledWidget[UISliderStyle], UIBaseSlider):
@@ -277,20 +301,54 @@ class UISlider(UIStyledWidget[UISliderStyle], UIBaseSlider):
             border=uicolor.BLUE_PETER_RIVER,
             border_width=2,
             filled_track=uicolor.BLUE_PETER_RIVER,
+            filled_step=uicolor.DARK_BLUE_MIDNIGHT_BLUE,
+        ),
+        "press": UIStyle(
+            bg=uicolor.BLUE_PETER_RIVER,
+            border=uicolor.DARK_BLUE_WET_ASPHALT,
+            border_width=3,
+            filled_track=uicolor.BLUE_PETER_RIVER,
+            filled_step=uicolor.DARK_BLUE_MIDNIGHT_BLUE,
+        ),
+        "disabled": UIStyle(
+            bg=uicolor.WHITE_SILVER,
+            border_width=1,
+            filled_track=uicolor.GRAY_ASBESTOS,
+            unfilled_track=uicolor.WHITE_SILVER,
+        ),
+    }
+
+    NO_STEP_STYLE = {
+        "normal": UIStyle(
+            filled_step=None,
+            unfilled_step=None,
+        ),
+        "hover": UIStyle(
+            border=uicolor.BLUE_PETER_RIVER,
+            border_width=2,
+            filled_track=uicolor.BLUE_PETER_RIVER,
+            filled_step=None,
+            unfilled_step=None,
         ),
         "press": UIStyle(
             bg=uicolor.BLUE_PETER_RIVER,
             border=uicolor.DARK_BLUE_WET_ASPHALT,
             border_width=3,
             filled_track=uicolor.BLUE_PETER_RIVER,
+            filled_step=None,
+            unfilled_step=None,
         ),
         "disabled": UIStyle(
             bg=uicolor.WHITE_SILVER,
             border_width=1,
             filled_track=uicolor.GRAY_ASBESTOS,
             unfilled_track=uicolor.WHITE_SILVER,
+            filled_step=None,
+            unfilled_step=None,
         ),
     }
+    """Removing the step colors from the style.
+    So sliders with a step value do not show the steps visually."""
 
     def __init__(
         self,
@@ -374,6 +432,45 @@ def _render_track(self, surface: Surface):
             fg_slider_color,
         )
 
+    @override
+    def _render_steps(self, surface: Surface):
+        if not self.step:
+            return
+
+        style = self.get_current_style()
+        if style is None:
+            warnings.warn(f"No style found for state {self.get_current_state()}", UserWarning)
+            return
+
+        unfilled_steps = style.get("unfilled_step", UISlider.UIStyle.unfilled_step)
+        filled_steps = style.get("filled_step", UISlider.UIStyle.filled_step)
+
+        def float_range(start, stop, step):
+            while start < stop:
+                yield start
+                start += step
+            yield stop
+
+        steps = list(float_range(self.min_value, self.max_value, self.step))
+
+        for v in steps:
+            step_x = self._x_for_value(v) - self.content_rect.left
+            step_color = filled_steps if v <= self.value else unfilled_steps
+
+            if step_color:
+                # bigger circle for first and last step
+                circle_size = self._cursor_width // 4
+                if v in (steps[0], steps[-1]):
+                    circle_size = self._cursor_width // 2
+
+                arcade.draw_circle_filled(
+                    step_x,
+                    self.content_height // 2,
+                    circle_size,
+                    step_color,
+                    num_segments=8,
+                )
+
     @override
     def _render_thumb(self, surface: Surface):
         style = self.get_current_style()