LibGUI: Implement calculated sizes for Slider

Userland/Libraries/LibGUI/Slider.cpp

@@ -24,6 +24,8 @@ Slider::Slider(Orientation orientation)
         { KnobSizeMode::Fixed, "Fixed" },
         { KnobSizeMode::Proportional, "Proportional" });
     REGISTER_BOOL_PROPERTY("jump_to_cursor", jump_to_cursor, set_jump_to_cursor);
+
+    set_preferred_size(SpecialDimension::Fit);
 }
 
 void Slider::paint_event(PaintEvent& event)
@@ -199,4 +201,18 @@ void Slider::set_knob_hovered(bool hovered)
     update(knob_rect());
 }
 
+Optional<UISize> Slider::calculated_min_size() const
+{
+    if (orientation() == Gfx::Orientation::Vertical)
+        return { { knob_secondary_size(), knob_fixed_primary_size() * 2 + track_margin() * 2 } };
+    return { { knob_fixed_primary_size() * 2 + track_margin() * 2, knob_secondary_size() } };
+}
+
+Optional<UISize> Slider::calculated_preferred_size() const
+{
+    if (orientation() == Gfx::Orientation::Vertical)
+        return { { SpecialDimension::Shrink, SpecialDimension::OpportunisticGrow } };
+    return { { SpecialDimension::OpportunisticGrow, SpecialDimension::Shrink } };
+}
+
 }

Userland/Libraries/LibGUI/Slider.h

@@ -46,6 +46,9 @@ public:
 protected:
     explicit Slider(Orientation = Orientation::Vertical);
 
+    virtual Optional<UISize> calculated_min_size() const override;
+    virtual Optional<UISize> calculated_preferred_size() const override;
+
     virtual void paint_event(PaintEvent&) override;
     void start_drag(Gfx::IntPoint);
     virtual void mousedown_event(MouseEvent&) override;