4 files changed, 77 insertions, 0 deletions
diff --git a/src/input.rs b/src/input.rs
index 49546faa..d9b902a8 100644
--- a/src/input.rs
+++ b/src/input.rs
@@ -368,6 +368,10 @@ impl State {
                 self.backend.toggle_debug_tint();
                 self.niri.queue_redraw_all();
             }
+            Action::DebugToggleOpaqueRegions => {
+                self.niri.debug_draw_opaque_regions = !self.niri.debug_draw_opaque_regions;
+                self.niri.queue_redraw_all();
+            }
             Action::Spawn(command) => {
                 spawn(command);
             }
diff --git a/src/niri.rs b/src/niri.rs
index 8e2807db..79808ac4 100644
--- a/src/niri.rs
+++ b/src/niri.rs
@@ -107,6 +107,7 @@ use crate::protocols::foreign_toplevel::{self, ForeignToplevelManagerState};
 use crate::protocols::gamma_control::GammaControlManagerState;
 use crate::protocols::screencopy::{Screencopy, ScreencopyManagerState};
 use crate::pw_utils::{Cast, PipeWire};
+use crate::render_helpers::debug::draw_opaque_regions;
 use crate::render_helpers::renderer::NiriRenderer;
 use crate::render_helpers::{
     render_to_shm, render_to_texture, render_to_vec, shaders, RenderTarget,
@@ -236,6 +237,8 @@ pub struct Niri {
     pub hotkey_overlay: HotkeyOverlay,
     pub exit_confirm_dialog: Option<ExitConfirmDialog>,
 
+    pub debug_draw_opaque_regions: bool,
+
     #[cfg(feature = "dbus")]
     pub dbus: Option<crate::dbus::DBusServers>,
     #[cfg(feature = "dbus")]
@@ -1422,6 +1425,8 @@ impl Niri {
             hotkey_overlay,
             exit_confirm_dialog,
 
+            debug_draw_opaque_regions: false,
+
             #[cfg(feature = "dbus")]
             dbus: None,
             #[cfg(feature = "dbus")]
@@ -2382,6 +2387,9 @@ impl Niri {
                 .into(),
             );
 
+            if self.debug_draw_opaque_regions {
+                draw_opaque_regions(&mut elements, output_scale);
+            }
             return elements;
         }
 
@@ -2408,6 +2416,9 @@ impl Niri {
             // Add the background for outputs that were connected while the screenshot UI was open.
             elements.push(background);
 
+            if self.debug_draw_opaque_regions {
+                draw_opaque_regions(&mut elements, output_scale);
+            }
             return elements;
         }
 
@@ -2463,6 +2474,9 @@ impl Niri {
         // Then the background.
         elements.push(background);
 
+        if self.debug_draw_opaque_regions {
+            draw_opaque_regions(&mut elements, output_scale);
+        }
         elements
     }
 
diff --git a/src/render_helpers/debug.rs b/src/render_helpers/debug.rs
new file mode 100644
index 00000000..f67abdb3
--- /dev/null
+++ b/src/render_helpers/debug.rs
@@ -0,0 +1,58 @@
+use smithay::backend::renderer::element::solid::SolidColorRenderElement;
+use smithay::backend::renderer::element::{Element, Id, Kind};
+use smithay::backend::renderer::utils::CommitCounter;
+use smithay::utils::Scale;
+
+use super::renderer::NiriRenderer;
+use crate::niri::OutputRenderElements;
+
+pub fn draw_opaque_regions<R: NiriRenderer>(
+    elements: &mut Vec<OutputRenderElements<R>>,
+    scale: Scale<f64>,
+) {
+    let _span = tracy_client::span!("draw_opaque_regions");
+
+    let mut i = 0;
+    while i < elements.len() {
+        let elem = &elements[i];
+        i += 1;
+
+        // HACK
+        if format!("{elem:?}").contains("ExtraDamage") {
+            continue;
+        }
+
+        let geo = elem.geometry(scale);
+        let mut opaque = elem.opaque_regions(scale);
+
+        for rect in &mut opaque {
+            rect.loc += geo.loc;
+        }
+
+        let semitransparent = geo.subtract_rects(opaque.iter().copied());
+
+        for rect in opaque {
+            let color = SolidColorRenderElement::new(
+                Id::new(),
+                rect,
+                CommitCounter::default(),
+                [0., 0., 0.2, 0.2],
+                Kind::Unspecified,
+            );
+            elements.insert(i - 1, OutputRenderElements::SolidColor(color));
+            i += 1;
+        }
+
+        for rect in semitransparent {
+            let color = SolidColorRenderElement::new(
+                Id::new(),
+                rect,
+                CommitCounter::default(),
+                [0.3, 0., 0., 0.3],
+                Kind::Unspecified,
+            );
+            elements.insert(i - 1, OutputRenderElements::SolidColor(color));
+            i += 1;
+        }
+    }
+}
diff --git a/src/render_helpers/mod.rs b/src/render_helpers/mod.rs
index b1f8fd03..c7a4025a 100644
--- a/src/render_helpers/mod.rs
+++ b/src/render_helpers/mod.rs
@@ -19,6 +19,7 @@ use self::primary_gpu_texture::PrimaryGpuTextureRenderElement;
 pub mod border;
 pub mod clipped_surface;
 pub mod damage;
+pub mod debug;
 pub mod offscreen;
 pub mod primary_gpu_texture;
 pub mod render_elements;