Implement window shadows

niri-config/src/lib.rs

@@ -3,6 +3,7 @@ extern crate tracing;
 
 use std::collections::HashSet;
 use std::ffi::OsStr;
+use std::ops::Mul;
 use std::path::{Path, PathBuf};
 use std::str::FromStr;
 use std::time::Duration;
@@ -436,6 +437,8 @@ pub struct Layout {
     #[knuffel(child, default)]
     pub border: Border,
     #[knuffel(child, default)]
+    pub shadow: Shadow,
+    #[knuffel(child, default)]
     pub insert_hint: InsertHint,
     #[knuffel(child, unwrap(children), default)]
     pub preset_column_widths: Vec<PresetSize>,
@@ -460,6 +463,7 @@ impl Default for Layout {
         Self {
             focus_ring: Default::default(),
             border: Default::default(),
+            shadow: Default::default(),
             insert_hint: Default::default(),
             preset_column_widths: Default::default(),
             default_column_width: Default::default(),
@@ -608,6 +612,49 @@ impl From<FocusRing> for Border {
     }
 }
 
+#[derive(knuffel::Decode, Debug, Clone, Copy, PartialEq)]
+pub struct Shadow {
+    #[knuffel(child)]
+    pub on: bool,
+    #[knuffel(child, default = Self::default().offset)]
+    pub offset: ShadowOffset,
+    #[knuffel(child, unwrap(argument), default = Self::default().softness)]
+    pub softness: FloatOrInt<0, 1024>,
+    #[knuffel(child, unwrap(argument), default = Self::default().spread)]
+    pub spread: FloatOrInt<0, 1024>,
+    #[knuffel(child, unwrap(argument), default = Self::default().draw_behind_window)]
+    pub draw_behind_window: bool,
+    #[knuffel(child, default = Self::default().color)]
+    pub color: Color,
+    #[knuffel(child)]
+    pub inactive_color: Option<Color>,
+}
+
+impl Default for Shadow {
+    fn default() -> Self {
+        Self {
+            on: false,
+            offset: ShadowOffset {
+                x: FloatOrInt(0.),
+                y: FloatOrInt(5.),
+            },
+            softness: FloatOrInt(30.),
+            spread: FloatOrInt(5.),
+            draw_behind_window: false,
+            color: Color::from_rgba8_unpremul(0, 0, 0, 0x70),
+            inactive_color: None,
+        }
+    }
+}
+
+#[derive(knuffel::Decode, Debug, Clone, Copy, PartialEq)]
+pub struct ShadowOffset {
+    #[knuffel(property, default)]
+    pub x: FloatOrInt<-65535, 65535>,
+    #[knuffel(property, default)]
+    pub y: FloatOrInt<-65535, 65535>,
+}
+
 #[derive(knuffel::Decode, Debug, Clone, Copy, PartialEq)]
 pub struct InsertHint {
     #[knuffel(child)]
@@ -679,6 +726,15 @@ impl Color {
     }
 }
 
+impl Mul<f32> for Color {
+    type Output = Self;
+
+    fn mul(mut self, rhs: f32) -> Self::Output {
+        self.a *= rhs;
+        self
+    }
+}
+
 #[derive(knuffel::Decode, Debug, PartialEq)]
 pub struct Cursor {
     #[knuffel(child, unwrap(argument), default = String::from("default"))]
@@ -1007,6 +1063,8 @@ pub struct WindowRule {
     pub focus_ring: BorderRule,
     #[knuffel(child, default)]
     pub border: BorderRule,
+    #[knuffel(child, default)]
+    pub shadow: ShadowRule,
     #[knuffel(child, unwrap(argument))]
     pub draw_border_with_background: Option<bool>,
     #[knuffel(child, unwrap(argument))]
@@ -1084,6 +1142,26 @@ pub struct BorderRule {
     pub inactive_gradient: Option<Gradient>,
 }
 
+#[derive(knuffel::Decode, Debug, Default, Clone, Copy, PartialEq)]
+pub struct ShadowRule {
+    #[knuffel(child)]
+    pub off: bool,
+    #[knuffel(child)]
+    pub on: bool,
+    #[knuffel(child)]
+    pub offset: Option<ShadowOffset>,
+    #[knuffel(child, unwrap(argument))]
+    pub softness: Option<FloatOrInt<0, 1024>>,
+    #[knuffel(child, unwrap(argument))]
+    pub spread: Option<FloatOrInt<0, 1024>>,
+    #[knuffel(child, unwrap(argument))]
+    pub draw_behind_window: Option<bool>,
+    #[knuffel(child)]
+    pub color: Option<Color>,
+    #[knuffel(child)]
+    pub inactive_color: Option<Color>,
+}
+
 #[derive(knuffel::Decode, Debug, Clone, Copy, PartialEq)]
 pub struct FloatingPosition {
     #[knuffel(property)]
@@ -1803,6 +1881,67 @@ impl BorderRule {
     }
 }
 
+impl ShadowRule {
+    pub fn merge_with(&mut self, other: &Self) {
+        if other.off {
+            self.off = true;
+            self.on = false;
+        }
+
+        if other.on {
+            self.off = false;
+            self.on = true;
+        }
+
+        if let Some(x) = other.offset {
+            self.offset = Some(x);
+        }
+        if let Some(x) = other.softness {
+            self.softness = Some(x);
+        }
+        if let Some(x) = other.spread {
+            self.spread = Some(x);
+        }
+        if let Some(x) = other.draw_behind_window {
+            self.draw_behind_window = Some(x);
+        }
+        if let Some(x) = other.color {
+            self.color = Some(x);
+        }
+        if let Some(x) = other.inactive_color {
+            self.inactive_color = Some(x);
+        }
+    }
+
+    pub fn resolve_against(&self, mut config: Shadow) -> Shadow {
+        config.on |= self.on;
+        if self.off {
+            config.on = false;
+        }
+
+        if let Some(x) = self.offset {
+            config.offset = x;
+        }
+        if let Some(x) = self.softness {
+            config.softness = x;
+        }
+        if let Some(x) = self.spread {
+            config.spread = x;
+        }
+        if let Some(x) = self.draw_behind_window {
+            config.draw_behind_window = x;
+        }
+        if let Some(x) = self.color {
+            config.color = x;
+        }
+        if let Some(x) = self.inactive_color {
+            config.inactive_color = Some(x);
+        }
+
+        config
+    }
+}
+
 impl CornerRadius {
     pub fn fit_to(self, width: f32, height: f32) -> Self {
         // Like in CSS: https://drafts.csswg.org/css-backgrounds/#corner-overlap
@@ -3221,6 +3360,10 @@ mod tests {
                     inactive-color "rgba(255, 200, 100, 0.0)"
                 }
 
+                shadow {
+                    offset x=10 y=-20
+                }
+
                 preset-column-widths {
                     proportion 0.25
                     proportion 0.5
@@ -3460,6 +3603,13 @@ mod tests {
                         active_gradient: None,
                         inactive_gradient: None,
                     },
+                    shadow: Shadow {
+                        offset: ShadowOffset {
+                            x: FloatOrInt(10.),
+                            y: FloatOrInt(-20.),
+                        },
+                        ..Default::default()
+                    },
                     insert_hint: InsertHint {
                         off: false,
                         color: Color::from_rgba8_unpremul(255, 200, 127, 255),

resources/default-config.kdl

@@ -191,6 +191,43 @@ layout {
         // inactive-gradient from="#505050" to="#808080" angle=45 relative-to="workspace-view"
     }
 
+    // You can enable drop shadows for windows.
+    shadow {
+        // Uncomment the next line to enable shadows.
+        // on
+
+        // By default, the shadow draws only around its window, and not behind it.
+        // Uncomment this setting to make the shadow draw behind its window.
+        //
+        // Note that niri has no way of knowing about the CSD window corner
+        // radius. It has to assume that windows have square corners, leading to
+        // shadow artifacts inside the CSD rounded corners. This setting fixes
+        // those artifacts.
+        // 
+        // However, instead you may want to set prefer-no-csd and/or
+        // geometry-corner-radius. Then, niri will know the corner radius and
+        // draw the shadow correctly, without having to draw it behind the
+        // window. These will also remove client-side shadows if the window
+        // draws any.
+        // 
+        // draw-behind-window true
+
+        // You can change how shadows look. The values below are in logical
+        // pixels and match the CSS box-shadow properties.
+
+        // Softness controls the shadow blur radius.
+        softness 30
+
+        // Spread expands the shadow.
+        spread 5
+
+        // Offset moves the shadow relative to the window.
+        offset x=0 y=5
+
+        // You can also change the shadow color and opacity.
+        color "#0007"
+    }
+
     // Struts shrink the area occupied by windows, similarly to layer-shell panels.
     // You can think of them as a kind of outer gaps. They are set in logical pixels.
     // Left and right struts will cause the next window to the side to always be visible.

src/layout/mod.rs

@@ -77,6 +77,7 @@ pub mod insert_hint_element;
 pub mod monitor;
 pub mod opening_window;
 pub mod scrolling;
+pub mod shadow;
 pub mod tile;
 pub mod workspace;
 
@@ -304,6 +305,7 @@ pub struct Options {
     pub struts: Struts,
     pub focus_ring: niri_config::FocusRing,
     pub border: niri_config::Border,
+    pub shadow: niri_config::Shadow,
     pub insert_hint: niri_config::InsertHint,
     pub center_focused_column: CenterFocusedColumn,
     pub always_center_single_column: bool,
@@ -327,6 +329,7 @@ impl Default for Options {
             struts: Default::default(),
             focus_ring: Default::default(),
             border: Default::default(),
+            shadow: Default::default(),
             insert_hint: Default::default(),
             center_focused_column: Default::default(),
             always_center_single_column: false,
@@ -509,6 +512,7 @@ impl Options {
             struts: layout.struts,
             focus_ring: layout.focus_ring,
             border: layout.border,
+            shadow: layout.shadow,
             insert_hint: layout.insert_hint,
             center_focused_column: layout.center_focused_column,
             always_center_single_column: layout.always_center_single_column,
@@ -7072,12 +7076,26 @@ mod tests {
         }
     }
 
+    prop_compose! {
+        fn arbitrary_shadow()(
+            on in any::<bool>(),
+            width in arbitrary_spacing(),
+        ) -> niri_config::Shadow {
+            niri_config::Shadow {
+                on,
+                softness: FloatOrInt(width),
+                ..Default::default()
+            }
+        }
+    }
+
     prop_compose! {
         fn arbitrary_options()(
             gaps in arbitrary_spacing(),
             struts in arbitrary_struts(),
             focus_ring in arbitrary_focus_ring(),
             border in arbitrary_border(),
+            shadow in arbitrary_shadow(),
             center_focused_column in arbitrary_center_focused_column(),
             always_center_single_column in any::<bool>(),
             empty_workspace_above_first in any::<bool>(),
@@ -7090,6 +7108,7 @@ mod tests {
                 empty_workspace_above_first,
                 focus_ring,
                 border,
+                shadow,
                 ..Default::default()
             }
         }