config: add rounded corner exponent option

docs/wiki/Configuration:-Layer-Rules.md

@@ -193,6 +193,25 @@ layer-rule {
 }
 ```
 
+#### `geometry-corner-radius-exponent`
+
+<sup>Since: next release</sup>
+
+Sets the exponent used for corner rounding, using the superellipse equation `x^n + y^n = 1`.
+
+- 2 is the default circular rounding.
+- Values greater than 2 produce "squircle" corners.
+- Values closer to 1 produce chamfer-like corners.
+
+```kdl
+layer-rule {
+    match namespace="^launcher$"
+
+    geometry-corner-radius 12
+    geometry-corner-radius-exponent 4
+}
+```
+
 #### `place-within-backdrop`
 
 <sup>Since: 25.05</sup>

docs/wiki/Configuration:-Layout.md

@@ -73,6 +73,7 @@ layout {
         position "right"
         gaps-between-tabs 2
         corner-radius 8
+        corner-radius-exponent 4
         active-color "red"
         inactive-color "gray"
         urgent-color "blue"
@@ -459,6 +460,15 @@ It can be `left`, `right`, `top`, or `bottom`.
 `corner-radius` sets the rounded corner radius for tabs in the indicator in logical pixels.
 When `gaps-between-tabs` is zero, only the first and the last tabs have rounded corners, otherwise all tabs do.
 
+`corner-radius-exponent` <sup>Since: next release</sup> sets the shape of the rounded corners.
+The default is `2` for normal circular rounding, values greater than `2` make "squircle" corners, and `1` make the corners "chamfered".
+
+Tab corner exponents are picked in this order:
+
+1. `corner-radius-exponent` from the `tab-indicator` window rule, if set.
+1. `geometry-corner-radius-exponent` from the window rule, if set.
+1. `corner-radius-exponent` from the `tab-indicator` layout options.
+
 `active-color`, `inactive-color`, `urgent-color`, `active-gradient`, `inactive-gradient`, `urgent-gradient` let you override the colors for the tabs.
 They have the same semantics as the border and focus ring colors and gradients.
 

docs/wiki/Configuration:-Window-Rules.md

@@ -811,6 +811,7 @@ window-rule {
 
     tab-indicator {
         inactive-color "darkred"
+        corner-radius-exponent 4
     }
 }
 ```
@@ -847,6 +848,23 @@ This way, you can match GTK 3 applications which have square bottom corners:
 
 ![A screenshot showing a window with only the top corners rounded](./img/different-corner-radius.png)
 
+#### `geometry-corner-radius-exponent`
+
+<sup>Since: next release</sup>
+
+Sets the exponent used for corner rounding, using the superellipse equation `x^n + y^n = 1`.
+
+- 2 is the default circular rounding.
+- Values greater than 2 produce "squircle" corners.
+- Values closer to 1 produce chamfer-like corners.
+
+```kdl
+window-rule {
+    geometry-corner-radius 12
+    geometry-corner-radius-exponent 4
+}
+```
+
 #### `clip-to-geometry`
 
 <sup>Since: 0.1.6</sup>
@@ -994,6 +1012,7 @@ window-rule {
     popups {
         // Matches the default libadwaita pop-up corner radius.
         geometry-corner-radius 15
+        geometry-corner-radius-exponent 2
 
         // Note: it'll look better to set background opacity
         // through your GTK theme CSS and not here.

niri-config/src/appearance.rs

@@ -148,6 +148,8 @@ pub struct CornerRadius {
     pub bottom_left: f32,
 }
 
+pub const DEFAULT_CORNER_RADIUS_EXPONENT: f32 = 2.;
+
 impl From<CornerRadius> for [f32; 4] {
     fn from(value: CornerRadius) -> Self {
         [
@@ -466,6 +468,7 @@ pub struct TabIndicator {
     pub position: TabIndicatorPosition,
     pub gaps_between_tabs: f64,
     pub corner_radius: f64,
+    pub corner_radius_exponent: f64,
     pub active_color: Option<Color>,
     pub inactive_color: Option<Color>,
     pub urgent_color: Option<Color>,
@@ -488,6 +491,7 @@ impl Default for TabIndicator {
             position: TabIndicatorPosition::Left,
             gaps_between_tabs: 0.,
             corner_radius: 0.,
+            corner_radius_exponent: DEFAULT_CORNER_RADIUS_EXPONENT as f64,
             active_color: None,
             inactive_color: None,
             urgent_color: None,
@@ -513,6 +517,7 @@ impl MergeWith<TabIndicatorPart> for TabIndicator {
             width,
             gaps_between_tabs,
             corner_radius,
+            corner_radius_exponent,
         );
 
         merge_clone!((self, part), length, position);
@@ -548,6 +553,8 @@ pub struct TabIndicatorPart {
     pub gaps_between_tabs: Option<FloatOrInt<0, 65535>>,
     #[knuffel(child, unwrap(argument))]
     pub corner_radius: Option<FloatOrInt<0, 65535>>,
+    #[knuffel(child, unwrap(argument))]
+    pub corner_radius_exponent: Option<FloatOrInt<1, { i32::MAX }>>,
     #[knuffel(child)]
     pub active_color: Option<Color>,
     #[knuffel(child)]
@@ -666,6 +673,8 @@ pub struct ShadowRule {
 
 #[derive(knuffel::Decode, Debug, Default, Clone, Copy, PartialEq)]
 pub struct TabIndicatorRule {
+    #[knuffel(child, unwrap(argument))]
+    pub corner_radius_exponent: Option<FloatOrInt<1, { i32::MAX }>>,
     #[knuffel(child)]
     pub active_color: Option<Color>,
     #[knuffel(child)]
@@ -713,6 +722,8 @@ impl MergeWith<Self> for ShadowRule {
 
 impl MergeWith<Self> for TabIndicatorRule {
     fn merge_with(&mut self, part: &Self) {
+        merge_clone_opt!((self, part), corner_radius_exponent);
+
         merge_color_gradient_opt!(
             (self, part),
             (active_color, active_gradient),

niri-config/src/layer_rule.rs

@@ -1,6 +1,7 @@
 use crate::appearance::{BackgroundEffectRule, BlockOutFrom, CornerRadius, ShadowRule};
 use crate::utils::RegexEq;
 use crate::window_rule::PopupsRule;
+use crate::FloatOrInt;
 
 #[derive(knuffel::Decode, Debug, Default, Clone, PartialEq)]
 pub struct LayerRule {
@@ -18,6 +19,8 @@ pub struct LayerRule {
     #[knuffel(child)]
     pub geometry_corner_radius: Option<CornerRadius>,
     #[knuffel(child, unwrap(argument))]
+    pub geometry_corner_radius_exponent: Option<FloatOrInt<1, { i32::MAX }>>,
+    #[knuffel(child, unwrap(argument))]
     pub place_within_backdrop: Option<bool>,
     #[knuffel(child, unwrap(argument))]
     pub baba_is_float: Option<bool>,

niri-config/src/lib.rs

@@ -1377,6 +1377,7 @@ mod tests {
                     position: Top,
                     gaps_between_tabs: 0.0,
                     corner_radius: 0.0,
+                    corner_radius_exponent: 2.0,
                     active_color: None,
                     inactive_color: None,
                     urgent_color: None,
@@ -1837,6 +1838,7 @@ mod tests {
                         inactive_color: None,
                     },
                     tab_indicator: TabIndicatorRule {
+                        corner_radius_exponent: None,
                         active_color: Some(
                             Color {
                                 r: 1.0,
@@ -1854,6 +1856,7 @@ mod tests {
                     draw_border_with_background: None,
                     opacity: None,
                     geometry_corner_radius: None,
+                    geometry_corner_radius_exponent: None,
                     clip_to_geometry: None,
                     baba_is_float: None,
                     block_out_from: None,
@@ -1883,6 +1886,7 @@ mod tests {
                     popups: PopupsRule {
                         opacity: None,
                         geometry_corner_radius: None,
+                        geometry_corner_radius_exponent: None,
                         background_effect: BackgroundEffectRule {
                             xray: None,
                             blur: None,
@@ -1923,6 +1927,7 @@ mod tests {
                         inactive_color: None,
                     },
                     geometry_corner_radius: None,
+                    geometry_corner_radius_exponent: None,
                     place_within_backdrop: None,
                     baba_is_float: None,
                     background_effect: BackgroundEffectRule {
@@ -1934,6 +1939,7 @@ mod tests {
                     popups: PopupsRule {
                         opacity: None,
                         geometry_corner_radius: None,
+                        geometry_corner_radius_exponent: None,
                         background_effect: BackgroundEffectRule {
                             xray: None,
                             blur: None,

niri-config/src/window_rule.rs

@@ -60,6 +60,8 @@ pub struct WindowRule {
     #[knuffel(child)]
     pub geometry_corner_radius: Option<CornerRadius>,
     #[knuffel(child, unwrap(argument))]
+    pub geometry_corner_radius_exponent: Option<FloatOrInt<1, { i32::MAX }>>,
+    #[knuffel(child, unwrap(argument))]
     pub clip_to_geometry: Option<bool>,
     #[knuffel(child, unwrap(argument))]
     pub baba_is_float: Option<bool>,
@@ -88,6 +90,8 @@ pub struct PopupsRule {
     pub opacity: Option<f32>,
     #[knuffel(child)]
     pub geometry_corner_radius: Option<CornerRadius>,
+    #[knuffel(child, unwrap(argument))]
+    pub geometry_corner_radius_exponent: Option<FloatOrInt<1, { i32::MAX }>>,
     #[knuffel(child, default)]
     pub background_effect: BackgroundEffectRule,
 }
@@ -100,6 +104,8 @@ pub struct ResolvedPopupsRules {
 
     /// Corner radius to assume the popups have.
     pub geometry_corner_radius: Option<CornerRadius>,
+    /// Exponent to use for popup corner rounding.
+    pub geometry_corner_radius_exponent: Option<f32>,
 
     /// Background effect configuration for popups.
     pub background_effect: BackgroundEffect,
@@ -113,6 +119,9 @@ impl MergeWith<PopupsRule> for ResolvedPopupsRules {
         if let Some(x) = part.geometry_corner_radius {
             self.geometry_corner_radius = Some(x);
         }
+        if let Some(x) = part.geometry_corner_radius_exponent {
+            self.geometry_corner_radius_exponent = Some(x.0 as f32);
+        }
         self.background_effect.merge_with(&part.background_effect);
     }
 }

niri-visual-tests/src/cases/gradient_angle.rs

@@ -2,7 +2,7 @@ use std::f32::consts::{FRAC_PI_2, PI};
 use std::time::Duration;
 
 use niri::render_helpers::border::BorderRenderElement;
-use niri_config::{Color, CornerRadius, GradientInterpolation};
+use niri_config::{Color, CornerRadius, GradientInterpolation, DEFAULT_CORNER_RADIUS_EXPONENT};
 use smithay::backend::renderer::element::RenderElement;
 use smithay::backend::renderer::gles::GlesRenderer;
 use smithay::utils::{Physical, Point, Rectangle, Size};
@@ -62,6 +62,7 @@ impl TestCase for GradientAngle {
             Rectangle::from_size(area.size),
             0.,
             CornerRadius::default(),
+            DEFAULT_CORNER_RADIUS_EXPONENT,
             1.,
             1.,
         )

niri-visual-tests/src/cases/gradient_area.rs

@@ -3,7 +3,7 @@ use std::time::Duration;
 
 use niri::layout::focus_ring::FocusRing;
 use niri::render_helpers::border::BorderRenderElement;
-use niri_config::{Color, CornerRadius, GradientInterpolation};
+use niri_config::{Color, CornerRadius, GradientInterpolation, DEFAULT_CORNER_RADIUS_EXPONENT};
 use smithay::backend::renderer::element::RenderElement;
 use smithay::backend::renderer::gles::GlesRenderer;
 use smithay::utils::{Physical, Point, Rectangle, Size};
@@ -86,6 +86,7 @@ impl TestCase for GradientArea {
             false,
             Rectangle::default(),
             CornerRadius::default(),
+            DEFAULT_CORNER_RADIUS_EXPONENT,
             1.,
             1.,
         );
@@ -103,6 +104,7 @@ impl TestCase for GradientArea {
                 Rectangle::from_size(rect_size).to_f64(),
                 0.,
                 CornerRadius::default(),
+                DEFAULT_CORNER_RADIUS_EXPONENT,
                 1.,
                 1.,
             )

niri-visual-tests/src/cases/gradient_oklab.rs

@@ -1,6 +1,7 @@
 use niri::render_helpers::border::BorderRenderElement;
 use niri_config::{
     Color, CornerRadius, GradientColorSpace, GradientInterpolation, HueInterpolation,
+    DEFAULT_CORNER_RADIUS_EXPONENT,
 };
 use smithay::backend::renderer::element::RenderElement;
 use smithay::backend::renderer::gles::GlesRenderer;
@@ -43,6 +44,7 @@ impl TestCase for GradientOklab {
             Rectangle::from_size(area.size),
             0.,
             CornerRadius::default(),
+            DEFAULT_CORNER_RADIUS_EXPONENT,
             1.,
             1.,
         )

niri-visual-tests/src/cases/gradient_oklab_alpha.rs

@@ -1,5 +1,7 @@
 use niri::render_helpers::border::BorderRenderElement;
-use niri_config::{Color, CornerRadius, GradientColorSpace, GradientInterpolation};
+use niri_config::{
+    Color, CornerRadius, GradientColorSpace, GradientInterpolation, DEFAULT_CORNER_RADIUS_EXPONENT,
+};
 use smithay::backend::renderer::element::RenderElement;
 use smithay::backend::renderer::gles::GlesRenderer;
 use smithay::utils::{Physical, Point, Rectangle, Size};
@@ -41,6 +43,7 @@ impl TestCase for GradientOklabAlpha {
             Rectangle::from_size(area.size),
             0.,
             CornerRadius::default(),
+            DEFAULT_CORNER_RADIUS_EXPONENT,
             1.,
             1.,
         )

niri-visual-tests/src/cases/gradient_oklch_alpha.rs

@@ -1,6 +1,7 @@
 use niri::render_helpers::border::BorderRenderElement;
 use niri_config::{
     Color, CornerRadius, GradientColorSpace, GradientInterpolation, HueInterpolation,
+    DEFAULT_CORNER_RADIUS_EXPONENT,
 };
 use smithay::backend::renderer::element::RenderElement;
 use smithay::backend::renderer::gles::GlesRenderer;
@@ -43,6 +44,7 @@ impl TestCase for GradientOklchAlpha {
             Rectangle::from_size(area.size),
             0.,
             CornerRadius::default(),
+            DEFAULT_CORNER_RADIUS_EXPONENT,
             1.,
             1.,
         )

niri-visual-tests/src/cases/gradient_oklch_decreasing.rs

@@ -1,6 +1,7 @@
 use niri::render_helpers::border::BorderRenderElement;
 use niri_config::{
     Color, CornerRadius, GradientColorSpace, GradientInterpolation, HueInterpolation,
+    DEFAULT_CORNER_RADIUS_EXPONENT,
 };
 use smithay::backend::renderer::element::RenderElement;
 use smithay::backend::renderer::gles::GlesRenderer;
@@ -43,6 +44,7 @@ impl TestCase for GradientOklchDecreasing {
             Rectangle::from_size(area.size),
             0.,
             CornerRadius::default(),
+            DEFAULT_CORNER_RADIUS_EXPONENT,
             1.,
             1.,
         )

niri-visual-tests/src/cases/gradient_oklch_increasing.rs

@@ -1,6 +1,7 @@
 use niri::render_helpers::border::BorderRenderElement;
 use niri_config::{
     Color, CornerRadius, GradientColorSpace, GradientInterpolation, HueInterpolation,
+    DEFAULT_CORNER_RADIUS_EXPONENT,
 };
 use smithay::backend::renderer::element::RenderElement;
 use smithay::backend::renderer::gles::GlesRenderer;
@@ -43,6 +44,7 @@ impl TestCase for GradientOklchIncreasing {
             Rectangle::from_size(area.size),
             0.,
             CornerRadius::default(),
+            DEFAULT_CORNER_RADIUS_EXPONENT,
             1.,
             1.,
         )

niri-visual-tests/src/cases/gradient_oklch_longer.rs

@@ -1,6 +1,7 @@
 use niri::render_helpers::border::BorderRenderElement;
 use niri_config::{
     Color, CornerRadius, GradientColorSpace, GradientInterpolation, HueInterpolation,
+    DEFAULT_CORNER_RADIUS_EXPONENT,
 };
 use smithay::backend::renderer::element::RenderElement;
 use smithay::backend::renderer::gles::GlesRenderer;
@@ -43,6 +44,7 @@ impl TestCase for GradientOklchLonger {
             Rectangle::from_size(area.size),
             0.,
             CornerRadius::default(),
+            DEFAULT_CORNER_RADIUS_EXPONENT,
             1.,
             1.,
         )