From 446779ab83c5082067473ea7518076457812e873 Mon Sep 17 00:00:00 2001
From: Julian Orth <ju.orth@gmail.com>
Date: Mon, 24 Feb 2025 10:31:00 +0100
Subject: [PATCH] wl_surface: check if partially-opaque surface is opaque
 within render bounds

---
 src/ifs/wl_surface.rs |  4 ++++
 src/rect/region.rs    |  5 +++++
 src/renderer.rs       | 25 ++++++++++++++++++++++++-
 3 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/src/ifs/wl_surface.rs b/src/ifs/wl_surface.rs
index 41118523..8f7b4cf2 100644
--- a/src/ifs/wl_surface.rs
+++ b/src/ifs/wl_surface.rs
@@ -1654,6 +1654,10 @@ impl WlSurface {
     pub fn opaque(&self) -> bool {
         self.is_opaque.get()
     }
+
+    pub fn opaque_region(&self) -> Option<Rc<Region>> {
+        self.opaque_region.get()
+    }
 }
 
 object_base! {
diff --git a/src/rect/region.rs b/src/rect/region.rs
index 21abd7df..0814cb17 100644
--- a/src/rect/region.rs
+++ b/src/rect/region.rs
@@ -177,11 +177,16 @@ where
     }
 
     pub fn contains_rect(&self, rect: &Rect) -> bool {
+        self.contains_rect2(rect, |r| *r)
+    }
+
+    pub fn contains_rect2(&self, rect: &Rect, map: impl Fn(&Rect<T>) -> Rect<T>) -> bool {
         if rect.is_empty() {
             return true;
         }
         let mut y1 = rect.y1();
         for r in self.rects() {
+            let r = map(r);
             if r.y2() <= y1 || r.x2() <= rect.x1() {
                 continue;
             }
diff --git a/src/renderer.rs b/src/renderer.rs
index 53ad5254..fa8a0458 100644
--- a/src/renderer.rs
+++ b/src/renderer.rs
@@ -423,6 +423,10 @@ impl Renderer<'_> {
     ) {
         let alpha = surface.alpha();
         if let Some(tex) = buffer.buffer.get_texture(surface) {
+            let mut opaque = surface.opaque();
+            if !opaque && tex.format().has_alpha {
+                opaque = self.bounds_are_opaque(x, y, bounds, surface);
+            }
             self.base.render_texture(
                 &tex,
                 alpha,
@@ -435,7 +439,7 @@ impl Renderer<'_> {
                 Some(buffer.clone()),
                 AcquireSync::Unnecessary,
                 buffer.release_sync,
-                surface.opaque(),
+                opaque,
             );
         } else if let Some(color) = &buffer.buffer.color {
             if let Some(rect) = Rect::new_sized(x, y, tsize.0, tsize.1) {
@@ -519,4 +523,23 @@ impl Renderer<'_> {
         let (dx, dy) = surface.surface.extents.get().position();
         self.render_surface(&surface.surface, x - dx, y - dy, None);
     }
+
+    fn bounds_are_opaque(
+        &self,
+        x: i32,
+        y: i32,
+        bounds: Option<&Rect>,
+        surface: &WlSurface,
+    ) -> bool {
+        let Some(bounds) = bounds else {
+            return false;
+        };
+        let Some(region) = surface.opaque_region() else {
+            return false;
+        };
+        let surface_size = surface.buffer_abs_pos.get().at_point(0, 0);
+        let surface_size = self.base.scale_rect(surface_size);
+        let bounds = bounds.move_(-x, -y).intersect(surface_size);
+        region.contains_rect2(&bounds, |r| self.base.scale_rect(*r))
+    }
 }