From b3551e3ce62f8f4e080c694632349e80decca93c Mon Sep 17 00:00:00 2001
From: aiongg <aiongtaigi@gmail.com>
Date: Tue, 13 Oct 2026 19:37:52 +0000
Subject: [PATCH] Integration: #588 CMYK ink passes cull items to the area they
 cover

---
 crates/render/src/blendspace.rs | 24 +++++++++++++++++++++++-
 crates/render/src/lib.rs        |  5 +++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/crates/render/src/blendspace.rs b/crates/render/src/blendspace.rs
index e2f6600c5..5393d9cc2 100644
--- a/crates/render/src/blendspace.rs
+++ b/crates/render/src/blendspace.rs
@@ -370,13 +370,21 @@ impl Renderer {
         // Inside it: the two ink passes, with the render threads, over just the area.
         let (aw, ah) = (area.width() as u16, area.height() as u16);
         let shifted = Affine::translate((-area.x0, -area.y0)) * f.view;
+        // The passes draw only what reaches the area: items elsewhere are culled.
+        let visible = f.view.inverse().transform_rect_bbox(area);
         let stats = self.stats;
         let threads = self.threads;
         let mut pass = |plate| {
             let opts = RenderOptions { plate: Some(plate), ..rgb.clone() };
             crate::PLATE.with(|p| p.set(opts.plate));
             let mut off = RenderContext::new_with(aw, ah, vello_cpu::RenderSettings { num_threads: threads, ..Default::default() });
-            self.draw_spread(&mut off, &Frame { opts: &opts, view: shifted, mt: threads > 0, ..*f }, sr);
+            #[cfg(test)]
+            let items = self.stats.items;
+            self.draw_spread(&mut off, &Frame { opts: &opts, view: shifted, visible, mt: threads > 0, ..*f }, sr);
+            #[cfg(test)]
+            {
+                self.cmyk_pass_items = self.stats.items - items;
+            }
             off.flush();
             let mut pm = vello_cpu::Pixmap::new(aw, ah);
             off.render(&mut pm, &mut self.resources);
@@ -593,6 +601,20 @@ mod tests {
         assert!(renderer.cmyk_pass_pixels >= 75 * 45, "{} px", renderer.cmyk_pass_pixels);
     }
 
+    #[test]
+    fn ink_passes_draw_only_the_items_that_reach_their_area() {
+        // A small Multiply object in a corner and a solid one far from it: the ink passes cover the
+        // corner and draw just the Multiply object.
+        let mut doc = document();
+        rectangle(&mut doc, SpreadRef::Doc(0), Rect::new(100.0, 70.0, 150.0, 110.0), "C=100 M=0 Y=0 K=0", DcBlend::Normal);
+        rectangle(&mut doc, SpreadRef::Doc(0), Rect::new(5.0, 5.0, 25.0, 25.0), "C=0 M=100 Y=0 K=0", DcBlend::Multiply);
+        let mut renderer = Renderer::new();
+        renderer.threads = 0;
+        draw(&doc, &mut renderer);
+        assert_eq!(renderer.cmyk_passes, 2);
+        assert_eq!(renderer.cmyk_pass_items, 1);
+    }
+
     #[test]
     fn the_view_is_kept_only_when_the_ink_passes_ran() {
         let mut doc = document();
diff --git a/crates/render/src/lib.rs b/crates/render/src/lib.rs
index 8406795ab..c73353ad1 100644
--- a/crates/render/src/lib.rs
+++ b/crates/render/src/lib.rs
@@ -235,6 +235,9 @@ pub struct Renderer {
     /// Pixels the last ink pass covered (tests).
     #[cfg(test)]
     cmyk_pass_pixels: usize,
+    /// Items the last ink pass drew (tests).
+    #[cfg(test)]
+    cmyk_pass_items: usize,
     pub threads: u16,
     pub stats: FrameStats,
 }
@@ -287,6 +290,8 @@ impl Renderer {
             cmyk_passes: 0,
             #[cfg(test)]
             cmyk_pass_pixels: 0,
+            #[cfg(test)]
+            cmyk_pass_items: 0,
             threads: default_threads(),
             stats: FrameStats::default(),
         }