M2: a page's own /MediaBox wins and a nearest box without area gives Letter, tested in the renderer and model (view.render-pages)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Pq7HyCHD1R3rywQBPCHXZA

crates/model/src/lib.rs

@@ -303,6 +303,35 @@ mod tests {
         assert_ne!(p.view_matrix(&d), view_matrix_for(0, [0.0, 0.0, 300.0, 400.0]), "the origin is kept");
     }
 
+    /// The nearest ancestor's `/MediaBox` wins over the root's, origin and all: the crop and the view matrix come from
+    /// the intermediate `/Pages` node's box.
+    #[test]
+    fn a_page_takes_its_nearest_ancestors_media_box_and_origin() {
+        let d = doc_from(&[
+            "<< /Type /Catalog /Pages 2 0 R >>".to_string(),
+            "<< /Type /Pages /Kids [3 0 R] /Count 1 /MediaBox [0 0 612 792] >>".to_string(),
+            "<< /Type /Pages /Parent 2 0 R /Kids [4 0 R] /Count 1 /MediaBox [100 200 400 600] >>".to_string(),
+            "<< /Type /Page /Parent 3 0 R >>".to_string(),
+        ]);
+        let p = &pages(&d)[0];
+        assert_eq!(p.crop(&d), [100.0, 200.0, 400.0, 600.0]);
+        assert_eq!(p.view_matrix(&d), view_matrix_for(0, [100.0, 200.0, 400.0, 600.0]));
+    }
+
+    /// An intermediate `/Pages` node's `/MediaBox` without area is the inherited one, so the page is US Letter, not
+    /// its grandparent's box.
+    #[test]
+    fn a_nearest_media_box_without_area_gives_letter_not_a_further_ancestors() {
+        let d = doc_from(&[
+            "<< /Type /Catalog /Pages 2 0 R >>".to_string(),
+            "<< /Type /Pages /Kids [3 0 R] /Count 1 /MediaBox [0 0 300 400] >>".to_string(),
+            "<< /Type /Pages /Parent 2 0 R /Kids [4 0 R] /Count 1 /MediaBox [0 0 0 0] >>".to_string(),
+            "<< /Type /Page /Parent 3 0 R >>".to_string(),
+        ]);
+        let p = &pages(&d)[0];
+        assert_eq!(p.crop(&d), [0.0, 0.0, 612.0, 792.0]);
+    }
+
     /// A `/MediaBox` without area (`[0 0 0 0]`) is US Letter too, as the renderer draws it.
     #[test]
     fn a_page_whose_media_box_has_no_area_is_letter() {

crates/render/src/raster/tests.rs

@@ -5602,6 +5602,49 @@ trailer << /Root 1 0 R >>
     assert_eq!((info.pages[0].width, info.pages[0].height), (300.0, 400.0), "inspected size");
 }
 
+/// A page's own `/MediaBox` wins over its parent's: rendered and inspected at the page's 200 × 100, the content placed by
+/// the page box's origin.
+#[test]
+fn a_pages_own_media_box_wins_over_its_parents() {
+    let pdf = b"%PDF-1.4
+1 0 obj << /Type /Catalog /Pages 2 0 R >> endobj
+2 0 obj << /Type /Pages /Kids [3 0 R] /Count 1 /MediaBox [0 0 300 400] >> endobj
+3 0 obj << /Type /Page /Parent 2 0 R /MediaBox [50 50 250 150] /Contents 4 0 R >> endobj
+4 0 obj << /Length 25 >> stream
+0 0 1 rg 60 60 50 50 re f
+endstream endobj
+trailer << /Root 1 0 R >>
+%%EOF"
+        .to_vec();
+    let page = render_first_page(pdf.clone());
+    assert_eq!((page.width, page.height), (200, 100), "the page's box, not its parent's");
+    // The square sits 10 pt in from the page box's lower-left corner, at (50, 50).
+    assert_eq!(rgb_at(&page.rgba, page.width as usize, 30, 100 - 30), [0, 0, 255], "placed by the page box's origin");
+    let info = crate::inspect(Arc::new(pdf), None).expect("inspect");
+    assert_eq!((info.pages[0].width, info.pages[0].height), (200.0, 100.0), "inspected size");
+}
+
+/// The nearest ancestor's `/MediaBox` is the inherited one even when it has no area: an intermediate `/Pages` node's
+/// `[0 0 0 0]` gives US Letter, not the grandparent's 300 × 400 (ISO 32000-2 §7.7.3.4).
+#[test]
+fn a_nearest_media_box_without_area_gives_letter_not_a_further_ancestors() {
+    let pdf = b"%PDF-1.4
+1 0 obj << /Type /Catalog /Pages 2 0 R >> endobj
+2 0 obj << /Type /Pages /Kids [5 0 R] /Count 1 /MediaBox [0 0 300 400] >> endobj
+5 0 obj << /Type /Pages /Parent 2 0 R /Kids [3 0 R] /Count 1 /MediaBox [0 0 0 0] >> endobj
+3 0 obj << /Type /Page /Parent 5 0 R /Contents 4 0 R >> endobj
+4 0 obj << /Length 25 >> stream
+0 0 1 rg 10 10 50 50 re f
+endstream endobj
+trailer << /Root 1 0 R >>
+%%EOF"
+        .to_vec();
+    let page = render_first_page(pdf.clone());
+    assert_eq!((page.width, page.height), (612, 792), "rendered size");
+    let info = crate::inspect(Arc::new(pdf), None).expect("inspect");
+    assert_eq!((info.pages[0].width, info.pages[0].height), (612.0, 792.0), "inspected size");
+}
+
 /// A page whose content expands far beyond its compressed stream stops at the expansion budget,
 /// which is 64 times the compressed size and at least `MAX_DECODED_STREAM`, and the page says so.
 #[test]