Floating scroll bars (#3539)

* Move scroll bar spacing settings to a `struct ScrollSpacing`

* Add a demo for changing scroll bar appearance

* Add setting for ScrollBarVisibility in demo

* Add `#[inline]` to a `ScrollArea` builder methods

* Refactor how scroll bar show/hide is computed

* Add support for floating scroll bars

* Tweak color and opacity of the scroll handle

* Allow allocating a fixed size even for floating scroll bars

* Add three pre-sets of scroll bars: solid, thin, floating

* Use floating scroll bars as the default

* Fix id-clash with bidir scroll areas

* Improve demo

* Fix doclink

* Remove reset button from demo

* Fix doclinks

* Fix visual artifact with thin rounded rectangles

* Fix doclink

* typos

crates/emath/src/rect.rs

@@ -150,6 +150,34 @@ impl Rect {
         rect
     }
 
+    #[inline]
+    #[must_use]
+    pub fn with_min_x(mut self, min_x: f32) -> Self {
+        self.min.x = min_x;
+        self
+    }
+
+    #[inline]
+    #[must_use]
+    pub fn with_min_y(mut self, min_y: f32) -> Self {
+        self.min.y = min_y;
+        self
+    }
+
+    #[inline]
+    #[must_use]
+    pub fn with_max_x(mut self, max_x: f32) -> Self {
+        self.max.x = max_x;
+        self
+    }
+
+    #[inline]
+    #[must_use]
+    pub fn with_max_y(mut self, max_y: f32) -> Self {
+        self.max.y = max_y;
+        self
+    }
+
     /// Expand by this much in each direction, keeping the center
     #[must_use]
     pub fn expand(self, amnt: f32) -> Self {

crates/emath/src/vec2.rs

@@ -274,6 +274,16 @@ impl Vec2 {
         self.x.max(self.y)
     }
 
+    /// Swizzle the axes.
+    #[inline]
+    #[must_use]
+    pub fn yx(self) -> Vec2 {
+        Vec2 {
+            x: self.y,
+            y: self.x,
+        }
+    }
+
     #[must_use]
     #[inline]
     pub fn clamp(self, min: Self, max: Self) -> Self {