Don't write empty resource dictionaries

Author: LaurenzV

Cargo.lock

@@ -7,7 +7,7 @@ edition = "2021"
 image = { version = "0.25.1", default-features = false, features = ["jpeg", "png", "gif", "webp"] }
 miniz_oxide = "0.7.4"
 once_cell = "1.19.0"
-pdf-writer = {git = "https://github.com/LaurenzV/pdf-writer", rev = "5aa89f5"}
+pdf-writer = {path = "../pdf-writer"}
 resvg = {git = "https://github.com/LaurenzV/resvg", rev = "1c2b6bd0"}
 siphasher = "1.0.1"
 skrifa = {git="https://github.com/LaurenzV/fontations", rev="0ed7955"}

Cargo.toml

@@ -32,7 +32,7 @@ impl Object for Page {
         let mut page = chunk.page(root_ref);
         self.stream
             .resource_dictionary
-            .to_pdf_resources(sc, &mut page.resources());
+            .to_pdf_resources(sc, &mut page);
 
         page.media_box(self.media_box.to_pdf_rect());
         page.parent(sc.page_tree_ref());

src/object/page.rs

@@ -65,7 +65,7 @@ impl Object for TilingPattern {
 
         self.stream
             .resource_dictionary
-            .to_pdf_resources(sc, &mut tiling_pattern.resources());
+            .to_pdf_resources(sc, &mut tiling_pattern);
 
         let final_bbox = pdf_writer::Rect::new(0.0, 0.0, self.width.get(), self.height.get());
 

src/object/tiling_pattern.rs

@@ -184,7 +184,7 @@ impl Object for Type3Font {
         font_descriptor.finish();
 
         let mut type3_font = chunk.type3_font(root_ref);
-        resource_dictionary.to_pdf_resources(sc, &mut type3_font.resources());
+        resource_dictionary.to_pdf_resources(sc, &mut type3_font);
 
         type3_font.bbox(bbox.to_pdf_rect());
         type3_font.to_unicode(cmap_ref);

src/object/type3_font.rs

@@ -47,7 +47,7 @@ impl Object for XObject {
 
         self.stream
             .resource_dictionary
-            .to_pdf_resources(sc, &mut x_object.resources());
+            .to_pdf_resources(sc, &mut x_object);
         x_object.bbox(self.custom_bbox.unwrap_or(self.stream.bbox).to_pdf_rect());
 
         if self.isolated || self.transparency_group_color_space {

src/object/xobject.rs

@@ -11,6 +11,7 @@ use crate::object::tiling_pattern::TilingPattern;
 use crate::object::xobject::XObject;
 use crate::serialize::{hash_item, Object, RegisterableObject, SerializerContext};
 use crate::util::NameExt;
+use pdf_writer::traits::ResourcesExt;
 use pdf_writer::writers::Resources;
 use pdf_writer::{Chunk, Dict, Finish, Ref};
 use std::collections::HashMap;
@@ -217,13 +218,28 @@ pub(crate) struct ResourceDictionary {
 }
 
 impl ResourceDictionary {
-    pub fn to_pdf_resources(self, sc: &mut SerializerContext, resources: &mut Resources) {
-        write_resource_type(sc, resources, self.color_spaces, false);
-        write_resource_type(sc, resources, self.ext_g_states, false);
-        write_resource_type(sc, resources, self.patterns, false);
-        write_resource_type(sc, resources, self.x_objects, false);
-        write_resource_type(sc, resources, self.shadings, false);
-        write_resource_type(sc, resources, self.fonts, true);
+    pub fn to_pdf_resources<T>(self, sc: &mut SerializerContext, parent: &mut T)
+    where
+        T: ResourcesExt,
+    {
+        if !self.is_empty() {
+            let resources = &mut parent.resources();
+            write_resource_type(sc, resources, self.color_spaces, false);
+            write_resource_type(sc, resources, self.ext_g_states, false);
+            write_resource_type(sc, resources, self.patterns, false);
+            write_resource_type(sc, resources, self.x_objects, false);
+            write_resource_type(sc, resources, self.shadings, false);
+            write_resource_type(sc, resources, self.fonts, true);
+        }
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.color_spaces.is_empty()
+            && self.ext_g_states.is_empty()
+            && self.patterns.is_empty()
+            && self.x_objects.is_empty()
+            && self.shadings.is_empty()
+            && self.fonts.is_empty()
     }
 }
 
@@ -266,6 +282,10 @@ where
         self.entries.len() as u32
     }
 
+    pub fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
+
     fn name_from_number(num: ResourceNumber) -> String {
         format!("{}{}", T::get_prefix(), num)
     }

src/resource.rs

@@ -6,7 +6,6 @@
   /Length 0
   /Type /XObject
   /Subtype /Form
-  /Resources <<>>
   /BBox [0 0 0 0]
   /Group <<
     /Type /Group

tests/snapshots/ext_g_state/all_set.txt

@@ -19,7 +19,6 @@ endobj
 3 0 obj
 <<
   /Type /Page
-  /Resources <<>>
   /MediaBox [0 0 200 200]
   /Parent 2 0 R
   /Contents 4 0 R