Improve realization and page layout (#4840)

1 files changed, 35 insertions, 0 deletions

diff --git a/crates/typst-utils/src/lib.rs b/crates/typst-utils/src/lib.rs
index 831b2374..79d4bb09 100644
--- a/crates/typst-utils/src/lib.rs
+++ b/crates/typst-utils/src/lib.rs
@@ -106,6 +106,18 @@ impl<T> OptionExt<T> for Option<T> {
 
 /// Extra methods for [`[T]`](slice).
 pub trait SliceExt<T> {
+    /// Returns a slice with all matching elements from the start of the slice
+    /// removed.
+    fn trim_start_matches<F>(&self, f: F) -> &[T]
+    where
+        F: FnMut(&T) -> bool;
+
+    /// Returns a slice with all matching elements from the end of the slice
+    /// removed.
+    fn trim_end_matches<F>(&self, f: F) -> &[T]
+    where
+        F: FnMut(&T) -> bool;
+
     /// Split a slice into consecutive runs with the same key and yield for
     /// each such run the key and the slice of elements with that key.
     fn group_by_key<K, F>(&self, f: F) -> GroupByKey<'_, T, F>
@@ -115,6 +127,29 @@ pub trait SliceExt<T> {
 }
 
 impl<T> SliceExt<T> for [T] {
+    fn trim_start_matches<F>(&self, mut f: F) -> &[T]
+    where
+        F: FnMut(&T) -> bool,
+    {
+        let len = self.len();
+        let mut i = 0;
+        while i < len && f(&self[i]) {
+            i += 1;
+        }
+        &self[i..]
+    }
+
+    fn trim_end_matches<F>(&self, mut f: F) -> &[T]
+    where
+        F: FnMut(&T) -> bool,
+    {
+        let mut i = self.len();
+        while i > 0 && f(&self[i - 1]) {
+            i -= 1;
+        }
+        &self[..i]
+    }
+
     fn group_by_key<K, F>(&self, f: F) -> GroupByKey<'_, T, F> {
         GroupByKey { slice: self, f }
     }