diff --git a/src/functions.rs b/src/functions.rs
index 2a15bb4..9cbe3fd 100644
--- a/src/functions.rs
+++ b/src/functions.rs
@@ -237,7 +237,7 @@ impl<'a> PostScriptFunction<'a> {
 deref!('a, PostScriptFunction<'a> => Stream<'a>, stream);
 
 /// PostScript operators for use in Type 4 functions.
-#[derive(Debug, Clone, Copy, PartialEq)]
+#[derive(Debug, Copy, Clone, PartialEq)]
 pub enum PostScriptOp<'a> {
     /// Push a real number.
     Real(f32),
@@ -333,7 +333,7 @@ pub enum PostScriptOp<'a> {
     Roll,
 }
 
-impl PostScriptOp<'_> {
+impl<'a> PostScriptOp<'a> {
     /// Encode a slice of operations into a byte stream.
     pub fn encode(ops: &[Self]) -> Buf {
         let mut buf = Buf::new();
@@ -446,8 +446,8 @@ mod tests {
         ];
 
         assert_eq!(
-            PostScriptOp::encode(&ops).to_bytes(),
-            b"{\n3.0\n2.0\nmul\nexch\ndup\n0.0\nge\n{\n1.0\nadd\n}\n{neg}\nifelse\nadd\n}"
+            PostScriptOp::encode(&ops),
+            b"{ 3.0 2.0 mul exch dup 0.0 ge { 1.0 add } {neg} ifelse add }"
         );
     }
 }
diff --git a/src/structure.rs b/src/structure.rs
index bcf939a..4f9ab5c 100644
--- a/src/structure.rs
+++ b/src/structure.rs
@@ -290,6 +290,14 @@ impl<'a> ViewerPreferences<'a> {
         self
     }
 
+    /// Write the `/DisplayDocTitle` attribute to set whether the viewer should
+    /// display the document's title from the `Title` entry as the window's title.
+    /// PDF 1.4+
+    pub fn display_doc_title(&mut self, display: bool) -> &mut Self {
+        self.pair(Name(b"DisplayDocTitle"), display);
+        self
+    }
+
     /// Write the `/NonFullScreenPageMode` attribute to set which chrome
     /// elements the viewer should show for a document which requests full
     /// screen rendering in its catalog when it is not shown in full screen
@@ -413,6 +421,13 @@ impl<'a> StructElement<'a> {
         self
     }
 
+    /// Write the `/ID` attribute to specify the element identifier of this
+    /// structure element.
+    pub fn id(&mut self, id: Str) -> &mut Self {
+        self.dict.pair(Name(b"ID"), id);
+        self
+    }
+
     /// Write the `/Pg` attribute to specify the page some or all of this
     /// structure element is located on.
     pub fn page(&mut self, page: Ref) -> &mut Self {