Darken background color when the window is inactive

src/deco.rs

@@ -26,6 +26,7 @@ use crate::{
 #[derive(Default, Debug, Clone, PartialEq)]
 struct DecoParams {
     has_geometry: bool,
+    is_active: bool,
     bounds: Bounds,
     restricted_edges: Edges<bool>,
 }
@@ -208,6 +209,11 @@ impl Deco {
         params.restricted_edges = edges;
     }
 
+    pub fn set_active(&self, is_active: bool) {
+        let mut params = self.next_params.borrow_mut();
+        params.is_active = is_active;
+    }
+
     pub fn handle_commit(&self) -> eyre::Result<()> {
         self.draw()
     }
@@ -248,12 +254,14 @@ impl Deco {
         let (buf, map) = pool.buffer(width, height)?;
         let (pre, pix, post) = unsafe { map.align_to_mut::<u32>() };
         assert!(pre.len() == 0 && post.len() == 0);
-        let bg = crate::ARGS
-            .get()
-            .unwrap()
-            .background
-            .premultiply()
-            .to_rgba8();
+        let set_bg = crate::ARGS.get().unwrap().background;
+        let bg = (if params.is_active {
+            set_bg
+        } else {
+            set_bg.scale_chroma(0.6)
+        })
+        .premultiply()
+        .to_rgba8();
         let bg_argb = u32::from_be_bytes([bg.a, bg.r, bg.g, bg.b]);
         for y in 0..height {
             for x in 0..width {

src/xdg.rs

@@ -293,6 +293,7 @@ impl XdgToplevelHandler for ClientXdgToplevel {
             ToplevelState::Fullscreen => outer_state.push(XdgToplevelState::FULLSCREEN),
         };
 
+        self.deco.set_active(activated);
         self.deco.set_restricted_edges(restricted_edges);
         let (width, height) = self.deco.transform_configure(width, height);
         let (_prefix, states, _suffix) = unsafe { outer_state.align_to::<u8>() };