add Lazy struct to prevent parsing unneeded objects (that may error)

examples/src/bin/form.rs

@@ -43,7 +43,8 @@ fn run() -> Result<(), PdfError> {
  let resources = file.create(resources)?;
 
  let page0 = file.get_page(0).unwrap();
- for annot in &page0.annotations {
+ let annots = page0.annotations.load(&file.resolver()).expect("can't load annotations");
+ for annot in &annots {
  if let Some(ref a) = annot.appearance_streams {
  let normal = file.resolver().get(a.normal);
  if let Ok(normal) = normal {

pdf/src/build.rs

@@ -132,7 +132,7 @@ impl CatalogBuilder {
  lgi: page.lgi,
  vp: page.vp,
  other: page.other,
- annotations: vec![]
+ annotations: Default::default(),
  };
  update.fulfill(promise, PagesNode::Leaf(page))?;
  }

pdf/src/object/mod.rs

@@ -430,6 +430,32 @@ impl<T> PartialEq for MaybeRef<T> {
 }
 impl<T> Eq for MaybeRef<T> {}
 
+#[derive(Debug, Clone, DataSize)]
+pub struct Lazy<T> {
+ primitive: Primitive,
+ _marker: PhantomData<T>
+}
+impl<T: Object> Lazy<T> {
+ pub fn load(&self, resolve: &impl Resolve) -> Result<T> {
+ T::from_primitive(self.primitive.clone(), resolve)
+ }
+}
+impl<T: Object> Object for Lazy<T> {
+ fn from_primitive(p: Primitive, _: &impl Resolve) -> Result<Self> {
+ Ok(Self { primitive: p, _marker: PhantomData })
+ }
+}
+impl<T: ObjectWrite> ObjectWrite for Lazy<T> {
+ fn to_primitive(&self, update: &mut impl Updater) -> Result<Primitive> {
+ Ok(self.primitive.clone())
+ }
+}
+impl<T> Default for Lazy<T> {
+ fn default() -> Self {
+ Lazy { primitive: Primitive::Null, _marker: PhantomData }
+ }
+}
+
 //////////////////////////////////////
 // Object for Primitives & other types
 //////////////////////////////////////

pdf/src/object/types.rs

@@ -294,8 +294,8 @@ pub struct Page {
  #[pdf(key="VP")]
  pub vp: Option<Primitive>,
 
- #[pdf(key="Annots", default="vec![]")]
- pub annotations: Vec<MaybeRef<Annot>>,
+ #[pdf(key="Annots")]
+ pub annotations: Lazy<Vec<MaybeRef<Annot>>>,
 
  #[pdf(other)]
  pub other: Dictionary,
@@ -326,7 +326,7 @@ impl Page {
  lgi: None,
  vp: None,
  other: Dictionary::new(),
- annotations: vec![]
+ annotations: Default::default(),
  }
  }
  pub fn media_box(&self) -> Result<Rectangle> {