build: reach lopdf and encoding_rs through printpdf and the codec

#1418 added both as direct dependencies although each was already in the
tree: printpdf's to_lopdf_doc returns the lopdf document whose compress
and save_to are plain methods, and the codec's encoding_from_code_page
hands back the Big5 / GBK / Shift_JIS / EUC-KR encodings by their DXF
code-page names. Cargo.toml keeps its dependency list.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

Cargo.lock

@@ -18,7 +18,6 @@ dependencies = [
  "console_error_panic_hook",
  "cosmic-text 0.15.0",
  "dwg-thumbnailer",
- "encoding_rs",
  "env_logger",
  "flate2",
  "fluent-syntax",
@@ -38,7 +37,6 @@ dependencies = [
  "js-sys",
  "libloading",
  "log",
- "lopdf",
  "lyon_tessellation",
  "meshopt",
  "naga 27.0.3",

Cargo.toml

@@ -55,9 +55,6 @@ ttf-parser = "0.25"
 cosmic-text = "0.15"
 unicode-bidi = "0.3"
 lyon_tessellation = "1.0.20"
-# Big-font (.shx) lookups: encode a char to the font's Big5 / GBK / Shift_JIS
-# / EUC-KR double-byte code. Already in the tree through other deps.
-encoding_rs = "0.8"
 pollster = "0.4"
 
 [dev-dependencies]
@@ -93,8 +90,6 @@ i18n-embed = { version = "0.16", features = ["desktop-requester"] }
 rayon = "1"
 open = "5"
 printpdf = { version = "0.9.1", default-features = false, features = ["images"] }
-# The lopdf printpdf builds on: used to Flate-compress the exported PDF streams.
-lopdf = { version = "0.39.0", default-features = false, features = ["time"] }
 ureq = { version = "3", default-features = false, features = ["rustls", "platform-verifier", "win-system-proxy"] }
 
 [target.'cfg(target_arch = "wasm32")'.dependencies]

src/scene/text/shx.rs

@@ -203,25 +203,24 @@ pub fn is_bigfont(path: &str) -> bool {
     load_file(path).is_some_and(|f| f.kind == ShxKind::Bigfont)
 }
 
-/// The double-byte legacy encodings a big font may be keyed by, most likely
-/// first for this file name. The font itself does not say; try them in turn
-/// and take the first code the font actually has.
-fn bigfont_encodings(path: &str) -> [&'static encoding_rs::Encoding; 4] {
-    use encoding_rs::{BIG5, EUC_KR, GBK, SHIFT_JIS};
+/// The code pages a big font's double-byte codes may be in, most likely
+/// first, guessed from the file name. The codec maps a name to its encoding
+/// (`ansi_950` Big5, `ansi_936` GBK, `ansi_932` Shift_JIS, `ansi_949` EUC-KR).
+fn bigfont_code_pages(path: &str) -> [&'static str; 4] {
     let name = path
         .rsplit(['/', '\\'])
         .next()
         .unwrap_or(path)
         .to_ascii_lowercase();
     if name.contains("gb") || name.contains("hz") || name.contains("china") {
-        [GBK, BIG5, SHIFT_JIS, EUC_KR]
+        ["ansi_936", "ansi_950", "ansi_932", "ansi_949"]
     } else if name.contains("bigfont") || name.contains("extfont") || name.contains("jp") {
-        [SHIFT_JIS, BIG5, GBK, EUC_KR]
+        ["ansi_932", "ansi_950", "ansi_936", "ansi_949"]
     } else if name.contains("whg") || name.contains("kor") || name.contains("han") {
-        [EUC_KR, BIG5, GBK, SHIFT_JIS]
+        ["ansi_949", "ansi_950", "ansi_936", "ansi_932"]
     } else {
         // `chineset.shx` and most Taiwanese fonts.
-        [BIG5, GBK, SHIFT_JIS, EUC_KR]
+        ["ansi_950", "ansi_936", "ansi_932", "ansi_949"]
     }
 }
 
@@ -235,7 +234,10 @@ pub fn bigfont_glyph(path: &str, ch: char) -> Option<Arc<crate::scene::text::lff
     }
     let mut buf = [0u8; 4];
     let s = ch.encode_utf8(&mut buf);
-    for enc in bigfont_encodings(path) {
+    for page in bigfont_code_pages(path) {
+        let Some(enc) = acadrust::io::dxf::code_page::encoding_from_code_page(page) else {
+            continue;
+        };
         let (bytes, _, unmappable) = enc.encode(s);
         if unmappable || bytes.len() != 2 {
             continue;