Add an exmaple for tracking limits

examples/limits.rs

@@ -0,0 +1,53 @@
+//! This example shows how you can track PDF limits of your chunks.
+
+use pdf_writer::{Chunk, Content, Limits, Name, Ref};
+
+fn main() {
+    let mut limits = Limits::new();
+
+    let mut content = Content::new();
+    content.transform([-3.4, 0.0, 0.0, 3.1, 100.0, 100.0]);
+    content.line_to(15.0, -26.1);
+    let buf = content.finish();
+    // This will have the limits:
+    // - Max real number: 26.1 (for negative values we use their absolute value)
+    // - Max int number 100 (even though above 100.0 is a float number, it will be coerced into an
+    //   integer, and thus counts towards the int limit)
+    limits.merge(buf.limits());
+
+    let mut chunk = Chunk::new();
+    chunk.stream(Ref::new(1), &buf.into_bytes());
+    chunk.type3_font(Ref::new(2)).name(Name(b"A_long_font_name"));
+    // This will update the limit for the maximum name and dictionary length.
+    limits.merge(chunk.limits());
+
+    // This is what the final PDF will look like.
+    assert_eq!(
+        chunk.as_bytes(),
+        b"1 0 obj
+<<
+  /Length 34
+>>
+stream
+-3.4 0 0 3.1 100 100 cm
+15 -26.1 l
+endstream
+endobj
+
+2 0 obj
+<<
+  /Type /Font
+  /Subtype /Type3
+  /Name /A_long_font_name
+>>
+endobj
+
+"
+    );
+
+    // And the limits should match, as well!
+    assert_eq!(limits.int(), 100);
+    assert_eq!(limits.real(), 26.1);
+    assert_eq!(limits.name_len(), 16);
+    assert_eq!(limits.dict_entries(), 3);
+}