fix(edit): editor font enumeration reads a face name without building font metrics (#6086)

crates/edit/src/text/editor.rs

@@ -2,7 +2,7 @@ use super::blocks::{BlockStyle, TextBlock};
 use super::fallback::MAX_TYPE3_GLYPHS;
 use super::lines::{page_dict, text_lines};
 use super::rewrite::rewrite_block_from;
-use super::{DecodeBudget, Dict, Document, EditError, Metrics, Object, TextLine, TextSession};
+use super::{DecodeBudget, Dict, Document, EditError, Object, TextLine, TextSession};
 
 /// An embedded source font or an approved bundled document-font choice.
 /// Source bytes stay in memory and are never installed or copied into another document.
@@ -45,7 +45,7 @@ pub fn text_editor_fonts(doc: &Document, page: usize) -> Result<Vec<TextEditorFo
         budget -= bytes.len();
         result.push(TextEditorFont {
             resource: String::from_utf8_lossy(name).into_owned(),
-            face: Metrics::from_dict(doc, &font).base_font.rsplit('+').next().unwrap_or_default().to_owned(),
+            face: pdfcraft_fonts::pdf::base_font_name(doc, &font).rsplit('+').next().unwrap_or_default().to_owned(),
             bytes,
             choice_only: false,
         });

crates/fonts/src/pdf.rs

@@ -821,6 +821,20 @@ fn number(t: &Tok) -> Option<u32> {
     }
 }
 
+/// The font's `/BaseFont` (a Type 3 font's descriptor `/FontName` when it has none), read without
+/// building its metrics, so it decodes no CMap.
+pub fn base_font_name(doc: &Document, font: &Dict) -> String {
+    font.name(b"BaseFont")
+        .map(|name| String::from_utf8_lossy(name).into_owned())
+        .or_else(|| {
+            (font.name(b"Subtype") == Some(b"Type3"))
+                .then(|| dict(doc, font.get(b"FontDescriptor")))
+                .flatten()
+                .and_then(|d| d.name(b"FontName").map(|name| String::from_utf8_lossy(name).into_owned()))
+        })
+        .unwrap_or_default()
+}
+
 /// Codespace ranges and CID mappings from an embedded CMap stream, at most
 /// [`MAX_CMAP_RANGES`] of each (every glyph searches them).
 #[allow(clippy::type_complexity)]
@@ -909,16 +923,7 @@ impl Metrics {
     pub fn from_dict_within(doc: &Document, font: &Dict, budget: &mut DecodeBudget) -> Self {
         let mut reads = Reads::new(doc, budget);
         let mut m = Self::read_metrics(doc, font, &mut reads);
-        let base = font
-            .name(b"BaseFont")
-            .map(|name| String::from_utf8_lossy(name).into_owned())
-            .or_else(|| {
-                (font.name(b"Subtype") == Some(b"Type3"))
-                    .then(|| dict(doc, font.get(b"FontDescriptor")))
-                    .flatten()
-                    .and_then(|d| d.name(b"FontName").map(|name| String::from_utf8_lossy(name).into_owned()))
-            })
-            .unwrap_or_default();
+        let base = base_font_name(doc, font);
         m.subset = base.len() > 7 && base.as_bytes()[6] == b'+' && base[..6].bytes().all(|b| b.is_ascii_uppercase());
         let (bold, italic) = style_from_name(&base);
         m.bold |= bold;

crates/fonts/src/pdf/tests.rs

@@ -1823,6 +1823,16 @@ fn low_codes_resolve_to_the_covering_range() {
     assert_eq!((u.covering(0xFFFF).is_some(), u.covering(0x1_0001).is_some(), u.covering(0x1_0002).is_none()), (true, true, true));
 }
 
+#[test]
+fn base_font_name_matches_the_metrics_name() {
+    let doc = Document::new_empty();
+    let mut f = Dict::new();
+    f.set(b"BaseFont".to_vec(), Object::name("ABCDEF+Body"));
+    assert_eq!(base_font_name(&doc, &f), "ABCDEF+Body");
+    assert_eq!(base_font_name(&doc, &f), Metrics::from_dict(&doc, &f).base_font);
+    assert_eq!(base_font_name(&doc, &Dict::new()), "");
+}
+
 #[test]
 fn refused_subset_reads_do_not_encode_unverified_glyphs() {
     let mut doc = Document::new_empty();