craft-libs/vendor/krilla/patches/04-knockout.patch

diff --git a/src/content.rs b/src/content.rs
index 751cb2f..f723f20 100644
--- a/src/content.rs
+++ b/src/content.rs
@@ -16,7 +16,7 @@ use crate::configure::ValidationError;
 #[cfg(feature = "raster-images")]
 use crate::geom::Size;
 use crate::geom::{Point, Rect, Transform};
-use crate::graphics::blend::Overprint;
+use crate::graphics::blend::{GroupOptions, Overprint};
 use crate::graphics::color::{Color, ColorSpace};
 use crate::graphics::graphics_state::{ExtGState, GraphicsStates};
 #[cfg(feature = "raster-images")]
@@ -933,14 +933,15 @@ impl ContentBuilder {
         self.draw_xobject(sc, chunk_container, x_object, &state);
     }
 
-    pub(crate) fn draw_isolated(
+    pub(crate) fn draw_group(
         &mut self,
         sc: &mut SerializeContext,
         chunk_container: &mut ChunkContainer,
+        options: GroupOptions,
         stream: Stream,
     ) {
         let state = ExtGState::new();
-        let x_object = XObject::new(stream, true, false, None);
+        let x_object = XObject::group(stream, options);
         self.draw_xobject(sc, chunk_container, x_object, &state);
     }
 
diff --git a/src/graphics/blend.rs b/src/graphics/blend.rs
index 8d7c5c7..7f01733 100644
--- a/src/graphics/blend.rs
+++ b/src/graphics/blend.rs
@@ -79,3 +79,21 @@ impl Overprint {
         }
     }
 }
+
+/// Attributes of a transparency group pushed with [`Surface::push_group`].
+///
+/// A group with neither attribute set is drawn as a plain form XObject: composited with
+/// the Normal blend mode at full opacity, it looks the same as its contents drawn directly.
+///
+/// [`Surface::push_group`]: crate::surface::Surface::push_group
+#[derive(Debug, Copy, Clone, Default, Eq, PartialEq, Hash)]
+pub struct GroupOptions {
+    /// Isolated group (`/I true`): its contents composite onto a fully transparent
+    /// backdrop instead of the group's backdrop, so blend modes inside it don't reach
+    /// what lies beneath.
+    pub isolated: bool,
+    /// Knockout group (`/K true`): each object inside composites with the group's
+    /// initial backdrop instead of the objects before it, so where objects overlap only
+    /// the topmost shows.
+    pub knockout: bool,
+}
diff --git a/src/graphics/xobject.rs b/src/graphics/xobject.rs
index 6c56b0e..a8c9568 100644
--- a/src/graphics/xobject.rs
+++ b/src/graphics/xobject.rs
@@ -7,6 +7,7 @@ use pdf_writer::{Finish, Name, Ref};
 use crate::chunk_container::ChunkContainer;
 use crate::configure::ValidationError;
 use crate::geom::Rect;
+use crate::graphics::blend::GroupOptions;
 use crate::graphics::color::{rgb, DEVICE_CMYK, DEVICE_RGB};
 use crate::resource;
 use crate::resource::{Resource, Resourceable};
@@ -28,6 +29,7 @@ pub(crate) enum GroupRole {
 struct Repr {
     stream: Stream,
     isolated: bool,
+    knockout: bool,
     transparency_group_color_space: bool,
     custom_bbox: Option<Rect>,
     role: GroupRole,
@@ -52,9 +54,39 @@ impl XObject {
         )
     }
 
+    /// A content group with the given group attributes.
+    pub(crate) fn group(stream: Stream, options: GroupOptions) -> Self {
+        Self::build(
+            stream,
+            options.isolated,
+            options.knockout,
+            false,
+            None,
+            GroupRole::Content,
+        )
+    }
+
     pub(crate) fn with_role(
         stream: Stream,
         isolated: bool,
+        transparency_group_color_space: bool,
+        custom_bbox: Option<Rect>,
+        role: GroupRole,
+    ) -> Self {
+        Self::build(
+            stream,
+            isolated,
+            false,
+            transparency_group_color_space,
+            custom_bbox,
+            role,
+        )
+    }
+
+    fn build(
+        stream: Stream,
+        isolated: bool,
+        knockout: bool,
         mut transparency_group_color_space: bool,
         custom_bbox: Option<Rect>,
         role: GroupRole,
@@ -74,6 +106,7 @@ impl XObject {
         Self(Arc::new(Prehashed::new(Repr {
             stream,
             isolated,
+            knockout,
             transparency_group_color_space,
             custom_bbox,
             role,
@@ -102,7 +135,8 @@ impl Cacheable for XObject {
             sc.register_validation_error(validation_error.clone());
         }
 
-        let use_transparency_group = self.0.isolated || self.0.transparency_group_color_space;
+        let use_transparency_group =
+            self.0.isolated || self.0.knockout || self.0.transparency_group_color_space;
 
         if use_transparency_group {
             sc.register_validation_error(ValidationError::Transparency(sc.location));
@@ -166,6 +200,10 @@ impl Cacheable for XObject {
                 transparency.isolated(self.0.isolated);
             }
 
+            if self.0.knockout {
+                transparency.knockout(true);
+            }
+
             if let Some(transparency_group_cs) = transparency_group_cs {
                 write_group_color_space(transparency, transparency_group_cs);
             }
diff --git a/src/surface.rs b/src/surface.rs
index 09b1b40..0cbbc4b 100644
--- a/src/surface.rs
+++ b/src/surface.rs
@@ -16,7 +16,7 @@ use crate::geom::Path;
 use crate::geom::Size;
 use crate::geom::{Point, Transform};
 use crate::graphic::Graphic;
-use crate::graphics::blend::{BlendMode, Overprint};
+use crate::graphics::blend::{BlendMode, GroupOptions, Overprint};
 use crate::graphics::graphics_state::ExtGState;
 #[cfg(feature = "raster-images")]
 use crate::graphics::image::Image;
@@ -494,9 +494,19 @@ impl<'a> Surface<'a> {
         }
     }
 
-    /// Push a new isolated layer.
+    /// Push a new isolated layer. Shorthand for [`Surface::push_group`] with only
+    /// `isolated` set.
     pub fn push_isolated(&mut self) {
-        self.push_instructions.push(PushInstruction::Isolated);
+        self.push_group(GroupOptions {
+            isolated: true,
+            knockout: false,
+        });
+    }
+
+    /// Push a new transparency group with the given attributes. Everything drawn until
+    /// the matching [`Surface::pop`] goes into the group.
+    pub fn push_group(&mut self, options: GroupOptions) {
+        self.push_instructions.push(PushInstruction::Group(options));
         self.bd
             .sub_builders
             .push(ContentBuilder::new(Transform::identity(), true, self.sc));
@@ -526,11 +536,11 @@ impl<'a> Surface<'a> {
                     .get_mut()
                     .draw_masked(self.sc, self.chunk_container, *mask, stream)
             }
-            PushInstruction::Isolated => {
+            PushInstruction::Group(options) => {
                 let stream = self.bd.sub_builders.pop().unwrap().finish(self.sc);
                 self.bd
                     .get_mut()
-                    .draw_isolated(self.sc, self.chunk_container, stream);
+                    .draw_group(self.sc, self.chunk_container, options, stream);
             }
         }
     }
@@ -683,5 +693,5 @@ pub(crate) enum PushInstruction {
     BlendMode,
     Overprint,
     Mask(Box<Mask>),
-    Isolated,
+    Group(GroupOptions),
 }