chore: add the rounded rectangle strip helper

src/surface/corner_radius.rs

@@ -0,0 +1,86 @@
+use iced::Rectangle;
+use iced_runtime::platform_specific::wayland::CornerRadius;
+
+#[must_use]
+pub fn rounded_rect_strips(rect: Rectangle<f32>, radius: CornerRadius) -> Vec<Rectangle<f32>> {
+    let mut out = Vec::new();
+
+    let w = rect.width.max(0.0);
+    let h = rect.height.max(0.0);
+
+    if w <= 0.0 || h <= 0.0 {
+        return out;
+    }
+
+    let tl = radius.top_left as i32;
+    let tr = radius.top_right as i32;
+    let bl = radius.bottom_left as i32;
+    let br = radius.bottom_right as i32;
+
+    let max_top = tl.max(tr);
+    let max_bottom = bl.max(br);
+
+    let center_y = rect.y + max_top as f32;
+    let center_h = (h as i32 - max_top - max_bottom).max(0) as f32;
+
+    if center_h > 0.0 {
+        out.push(Rectangle {
+            x: rect.x,
+            y: center_y,
+            width: w,
+            height: center_h,
+        });
+    }
+
+    for y in 0..max_top {
+        let left = if y < tl { circle_inset(tl, y) } else { 0 };
+
+        let right = if y < tr { circle_inset(tr, y) } else { 0 };
+
+        let strip_x = rect.x + left as f32;
+        let strip_w = (w as i32 - left - right).max(0) as f32;
+
+        if strip_w > 0.0 {
+            out.push(Rectangle {
+                x: strip_x,
+                y: rect.y + y as f32,
+                width: strip_w,
+                height: 1.0,
+            });
+        }
+    }
+
+    for y in 0..max_bottom {
+        let cy = max_bottom - 1 - y;
+        let left = if cy < bl { circle_inset(bl, cy) } else { 0 };
+
+        let right = if cy < br { circle_inset(br, cy) } else { 0 };
+
+        let strip_x = rect.x + left as f32;
+        let strip_w = (w as i32 - left - right).max(0) as f32;
+
+        if strip_w > 0.0 {
+            out.push(Rectangle {
+                x: strip_x,
+                y: rect.y + h - max_bottom as f32 + y as f32,
+                width: strip_w,
+                height: 1.0,
+            });
+        }
+    }
+
+    out
+}
+
+fn circle_inset(radius: i32, y: i32) -> i32 {
+    if radius <= 0 {
+        return 0;
+    }
+
+    let fy = y as f32 + 0.5;
+    let r = radius as f32;
+
+    let x = r - (r * r - (r - fy) * (r - fy)).sqrt();
+
+    x.floor() as i32
+}

src/surface/mod.rs

@@ -2,6 +2,8 @@
 // SPDX-License-Identifier: MPL-2.0
 
 pub mod action;
+#[cfg(all(feature = "wayland", target_os = "linux"))]
+pub mod corner_radius;
 
 use iced::{Limits, Size, Task};
 use std::any::Any;

src/widget/button/widget.rs

@@ -488,7 +488,7 @@ impl<'a, Message: 'a + Clone> Widget<Message, crate::Theme, crate::Renderer>
                 None => {
                     styling.border_radius = theme.cosmic().radius_0().into();
                 }
-            };
+            }
         }
 
         let mut icon_color = styling.icon_color.unwrap_or(renderer_style.icon_color);