Improve flat theme, colours

README.md

@@ -56,14 +56,13 @@ Installation and dependencies
 
 #### Rust
 
-KAS requires [Rust] version 1.52 or greater (currently in **beta**: *usually*
-we maintain compatibility with the latest stable release).
-Using the **nightly** channel does have a couple of advantages:
+KAS requires a recent [Rust] compiler. Currently, version 1.52 or greater is
+required. Using the **nightly** channel does have a few advantages:
 
 -   Proceedural macros emit better diagnostics. In some cases, diagnostics are
     missed without nightly rustc, hence **nightly is recommended for development**.
--   Documentation generated via `cargo doc` requires nightly for links
--   A few minor option things: see [Feature flags](#feature-flags) below.
+-   The `nightly` (`min_spec`) feature allows some visual improvements (see below).
+-   The `doc_cfg` feature may be used for API docs.
 
 ### Quick-start
 
@@ -137,8 +136,9 @@ The `kas` crate has the following feature flags:
 Additionally, the following flags require a nightly compiler:
 
 -   `nightly`: enables "more stable" unstable features
--   `min_spec` (enabled by `nightly`): use `min_specialization` to draw
-    underlines in `AccelLabel`
+-   `min_spec` (enabled by `nightly`): use `min_specialization` for some visual
+    improvements: scrolled regions are drawn under scrollbars,
+    underlines on checkbox accelerator keys show with the <kbd>Alt</kbd> key.
 -   `spec`: use `specialization` to enable `TryFormat`
 -   `gat`: compatibility with `kas-text/gat`
 

crates/kas-core/src/draw/color.rs

@@ -57,9 +57,14 @@ impl Rgba {
         Self::rgba(s, s, s, a)
     }
 
+    /// Get the sum of the three colour components
+    pub fn sum(self) -> f32 {
+        self.r + self.g + self.b
+    }
+
     /// Average three colour components (desaturate)
     pub fn average(self) -> Self {
-        Self::ga((self.r + self.g + self.b) * (1.0 / 3.0), self.a)
+        Self::ga(self.sum() * (1.0 / 3.0), self.a)
     }
 
     /// Multiply and clamp three colour components
@@ -131,9 +136,14 @@ impl Rgb {
         Self::rgb(s, s, s)
     }
 
+    /// Get the sum of the three colour components
+    pub fn sum(self) -> f32 {
+        self.r + self.g + self.b
+    }
+
     /// Average three colour components (desaturate)
     pub fn average(self) -> Self {
-        Self::grey((self.r + self.g + self.b) * (1.0 / 3.0))
+        Self::grey(self.sum() * (1.0 / 3.0))
     }
 
     /// Multiply and clamp three colour components

crates/kas-core/src/draw/handle.rs

@@ -138,6 +138,8 @@ pub trait SizeHandle {
     fn pixels_from_em(&self, em: f32) -> f32;
 
     /// Size of a frame around child widget(s)
+    ///
+    /// This already includes the margins specified by [`Self::frame_margins`].
     fn frame(&self, vert: bool) -> FrameRules;
 
     /// Frame/margin around a menu entry
@@ -160,6 +162,9 @@ pub trait SizeHandle {
     /// Widgets must not draw in outer margins.
     fn outer_margins(&self) -> Margins;
 
+    /// The margin around frames and separators
+    fn frame_margins(&self) -> Margins;
+
     /// The margin around text elements
     ///
     /// Similar to [`Self::outer_margins`], but intended for things like text
@@ -467,6 +472,9 @@ impl<S: SizeHandle + ?Sized, R: Deref<Target = S>> SizeHandle for R {
     fn outer_margins(&self) -> Margins {
         self.deref().outer_margins()
     }
+    fn frame_margins(&self) -> Margins {
+        self.deref().frame_margins()
+    }
     fn text_margins(&self) -> Margins {
         self.deref().text_margins()
     }

crates/kas-core/src/geom/vector.rs

@@ -146,6 +146,9 @@ macro_rules! impl_vec2 {
             /// Zero
             pub const ZERO: $T = $T::splat(0.0);
 
+            /// One
+            pub const ONE: $T = $T::splat(1.0);
+
             /// Positive infinity
             pub const INFINITY: $T = $T::splat(<$f>::INFINITY);
 
@@ -335,6 +338,14 @@ macro_rules! impl_vec2 {
             }
         }
 
+        impl Div<$T> for $f {
+            type Output = $T;
+            #[inline]
+            fn div(self, rhs: $T) -> Self::Output {
+                $T(self / rhs.0, self / rhs.1)
+            }
+        }
+
         impl From<($f, $f)> for $T {
             #[inline]
             fn from(arg: ($f, $f)) -> Self {