Implement layer rules: opacity and block-out-from

niri-config/src/layer_rule.rs

@@ -0,0 +1,22 @@
+use crate::{BlockOutFrom, RegexEq};
+
+#[derive(knuffel::Decode, Debug, Default, Clone, PartialEq)]
+pub struct LayerRule {
+    #[knuffel(children(name = "match"))]
+    pub matches: Vec<Match>,
+    #[knuffel(children(name = "exclude"))]
+    pub excludes: Vec<Match>,
+
+    #[knuffel(child, unwrap(argument))]
+    pub opacity: Option<f32>,
+    #[knuffel(child, unwrap(argument))]
+    pub block_out_from: Option<BlockOutFrom>,
+}
+
+#[derive(knuffel::Decode, Debug, Default, Clone, PartialEq)]
+pub struct Match {
+    #[knuffel(property, str)]
+    pub namespace: Option<RegexEq>,
+    #[knuffel(property)]
+    pub at_startup: Option<bool>,
+}

niri-config/src/lib.rs

@@ -10,6 +10,7 @@ use std::time::Duration;
 use bitflags::bitflags;
 use knuffel::errors::DecodeError;
 use knuffel::Decode as _;
+use layer_rule::LayerRule;
 use miette::{miette, Context, IntoDiagnostic, NarratableReportHandler};
 use niri_ipc::{ConfiguredMode, LayoutSwitchTarget, SizeChange, Transform, WorkspaceReferenceArg};
 use smithay::backend::renderer::Color32F;
@@ -20,6 +21,8 @@ use smithay::reexports::input;
 
 pub const DEFAULT_BACKGROUND_COLOR: Color = Color::from_array_unpremul([0.2, 0.2, 0.2, 1.]);
 
+pub mod layer_rule;
+
 mod utils;
 pub use utils::RegexEq;
 
@@ -53,6 +56,8 @@ pub struct Config {
     pub environment: Environment,
     #[knuffel(children(name = "window-rule"))]
     pub window_rules: Vec<WindowRule>,
+    #[knuffel(children(name = "layer-rule"))]
+    pub layer_rules: Vec<LayerRule>,
     #[knuffel(child, default)]
     pub binds: Binds,
     #[knuffel(child, default)]
@@ -3119,6 +3124,11 @@ mod tests {
                 }
             }
 
+            layer-rule {
+                match namespace="^notifications$"
+                block-out-from "screencast"
+            }
+
             binds {
                 Mod+T allow-when-locked=true { spawn "alacritty"; }
                 Mod+Q { close-window; }
@@ -3391,6 +3401,17 @@ mod tests {
                     },
                     ..Default::default()
                 }],
+                layer_rules: vec![
+                    LayerRule {
+                        matches: vec![layer_rule::Match {
+                            namespace: Some(RegexEq::from_str("^notifications$").unwrap()),
+                            at_startup: None,
+                        }],
+                        excludes: vec![],
+                        opacity: None,
+                        block_out_from: Some(BlockOutFrom::Screencast),
+                    }
+                ],
                 workspaces: vec![
                     Workspace {
                         name: WorkspaceName("workspace-1".to_string()),

src/handlers/layer_shell.rs

@@ -11,6 +11,7 @@ use smithay::wayland::shell::wlr_layer::{
 };
 use smithay::wayland::shell::xdg::PopupSurface;
 
+use crate::layer::{MappedLayer, ResolvedLayerRules};
 use crate::niri::State;
 use crate::utils::send_scale_transform;
 
@@ -60,6 +61,7 @@ impl WlrLayerShellHandler for State {
                 layer.map(|layer| (o.clone(), map, layer))
             }) {
             map.unmap_layer(&layer);
+            self.niri.mapped_layer_surfaces.remove(&layer);
             Some(output)
         } else {
             None
@@ -128,6 +130,21 @@ impl State {
                 if is_mapped {
                     let was_unmapped = self.niri.unmapped_layer_surfaces.remove(surface);
 
+                    // Resolve rules for newly mapped layer surfaces.
+                    if was_unmapped {
+                        let rules = &self.niri.config.borrow().layer_rules;
+                        let rules =
+                            ResolvedLayerRules::compute(rules, layer, self.niri.is_at_startup);
+                        let mapped = MappedLayer::new(layer.clone(), rules);
+                        let prev = self
+                            .niri
+                            .mapped_layer_surfaces
+                            .insert(layer.clone(), mapped);
+                        if prev.is_some() {
+                            error!("MappedLayer was present for an unmapped surface");
+                        }
+                    }
+
                     // Give focus to newly mapped on-demand surfaces. Some launchers like
                     // lxqt-runner rely on this behavior. While this behavior doesn't make much
                     // sense for other clients like panels, the consensus seems to be that it's not
@@ -151,6 +168,7 @@ impl State {
                         self.niri.layer_shell_on_demand_focus = Some(layer.clone());
                     }
                 } else {
+                    self.niri.mapped_layer_surfaces.remove(layer);
                     self.niri.unmapped_layer_surfaces.insert(surface.clone());
                 }
             } else {

src/layer/mapped.rs

@@ -0,0 +1,122 @@
+use std::cell::RefCell;
+
+use niri_config::layer_rule::LayerRule;
+use smithay::backend::renderer::element::surface::{
+    render_elements_from_surface_tree, WaylandSurfaceRenderElement,
+};
+use smithay::backend::renderer::element::Kind;
+use smithay::desktop::{LayerSurface, PopupManager};
+use smithay::utils::{Logical, Rectangle, Scale};
+
+use super::ResolvedLayerRules;
+use crate::niri_render_elements;
+use crate::render_helpers::renderer::NiriRenderer;
+use crate::render_helpers::solid_color::{SolidColorBuffer, SolidColorRenderElement};
+use crate::render_helpers::{RenderTarget, SplitElements};
+
+#[derive(Debug)]
+pub struct MappedLayer {
+    /// The surface itself.
+    surface: LayerSurface,
+
+    /// Up-to-date rules.
+    rules: ResolvedLayerRules,
+
+    /// Buffer to draw instead of the surface when it should be blocked out.
+    block_out_buffer: RefCell<SolidColorBuffer>,
+}
+
+niri_render_elements! {
+    LayerSurfaceRenderElement<R> => {
+        Wayland = WaylandSurfaceRenderElement<R>,
+        SolidColor = SolidColorRenderElement,
+    }
+}
+
+impl MappedLayer {
+    pub fn new(surface: LayerSurface, rules: ResolvedLayerRules) -> Self {
+        Self {
+            surface,
+            rules,
+            block_out_buffer: RefCell::new(SolidColorBuffer::new((0., 0.), [0., 0., 0., 1.])),
+        }
+    }
+
+    pub fn surface(&self) -> &LayerSurface {
+        &self.surface
+    }
+
+    pub fn rules(&self) -> &ResolvedLayerRules {
+        &self.rules
+    }
+
+    /// Recomputes the resolved layer rules and returns whether they changed.
+    pub fn recompute_layer_rules(&mut self, rules: &[LayerRule], is_at_startup: bool) -> bool {
+        let new_rules = ResolvedLayerRules::compute(rules, &self.surface, is_at_startup);
+        if new_rules == self.rules {
+            return false;
+        }
+
+        self.rules = new_rules;
+        true
+    }
+
+    pub fn render<R: NiriRenderer>(
+        &self,
+        renderer: &mut R,
+        geometry: Rectangle<i32, Logical>,
+        scale: Scale<f64>,
+        target: RenderTarget,
+    ) -> SplitElements<LayerSurfaceRenderElement<R>> {
+        let mut rv = SplitElements::default();
+
+        let alpha = self.rules.opacity.unwrap_or(1.).clamp(0., 1.);
+
+        if target.should_block_out(self.rules.block_out_from) {
+            // Round to physical pixels.
+            let geometry = geometry
+                .to_f64()
+                .to_physical_precise_round(scale)
+                .to_logical(scale);
+
+            let mut buffer = self.block_out_buffer.borrow_mut();
+            buffer.resize(geometry.size.to_f64());
+            let elem = SolidColorRenderElement::from_buffer(
+                &buffer,
+                geometry.loc,
+                alpha,
+                Kind::Unspecified,
+            );
+            rv.normal.push(elem.into());
+        } else {
+            // Layer surfaces don't have extra geometry like windows.
+            let buf_pos = geometry.loc;
+
+            let surface = self.surface.wl_surface();
+            for (popup, popup_offset) in PopupManager::popups_for_surface(surface) {
+                // Layer surfaces don't have extra geometry like windows.
+                let offset = popup_offset - popup.geometry().loc;
+
+                rv.popups.extend(render_elements_from_surface_tree(
+                    renderer,
+                    popup.wl_surface(),
+                    (buf_pos + offset).to_physical_precise_round(scale),
+                    scale,
+                    alpha,
+                    Kind::Unspecified,
+                ));
+            }
+
+            rv.normal = render_elements_from_surface_tree(
+                renderer,
+                surface,
+                buf_pos.to_physical_precise_round(scale),
+                scale,
+                alpha,
+                Kind::Unspecified,
+            );
+        }
+
+        rv
+    }
+}

src/layer/mod.rs

@@ -0,0 +1,69 @@
+use niri_config::layer_rule::{LayerRule, Match};
+use niri_config::BlockOutFrom;
+use smithay::desktop::LayerSurface;
+
+pub mod mapped;
+pub use mapped::MappedLayer;
+
+/// Rules fully resolved for a layer-shell surface.
+#[derive(Debug, PartialEq)]
+pub struct ResolvedLayerRules {
+    /// Extra opacity to draw this window with.
+    pub opacity: Option<f32>,
+    /// Whether to block out this window from certain render targets.
+    pub block_out_from: Option<BlockOutFrom>,
+}
+
+impl ResolvedLayerRules {
+    pub const fn empty() -> Self {
+        Self {
+            opacity: None,
+            block_out_from: None,
+        }
+    }
+
+    pub fn compute(rules: &[LayerRule], surface: &LayerSurface, is_at_startup: bool) -> Self {
+        let _span = tracy_client::span!("ResolvedLayerRules::compute");
+
+        let mut resolved = ResolvedLayerRules::empty();
+
+        for rule in rules {
+            let matches = |m: &Match| {
+                if let Some(at_startup) = m.at_startup {
+                    if at_startup != is_at_startup {
+                        return false;
+                    }
+                }
+
+                surface_matches(surface, m)
+            };
+
+            if !(rule.matches.is_empty() || rule.matches.iter().any(matches)) {
+                continue;
+            }
+
+            if rule.excludes.iter().any(matches) {
+                continue;
+            }
+
+            if let Some(x) = rule.opacity {
+                resolved.opacity = Some(x);
+            }
+            if let Some(x) = rule.block_out_from {
+                resolved.block_out_from = Some(x);
+            }
+        }
+
+        resolved
+    }
+}
+
+fn surface_matches(surface: &LayerSurface, m: &Match) -> bool {
+    if let Some(namespace_re) = &m.namespace {
+        if !namespace_re.0.is_match(surface.namespace()) {
+            return false;
+        }
+    }
+
+    true
+}

src/lib.rs

@@ -11,6 +11,7 @@ pub mod frame_clock;
 pub mod handlers;
 pub mod input;
 pub mod ipc;
+pub mod layer;
 pub mod layout;
 pub mod niri;
 pub mod protocols;