feat: generate human readable table cell IDs

in almost all real-world cases these IDs require less memory than the binary IDs
used before, and they are also require less storage in PDF files, since binary
data is encoded in hex escape sequences, taking up 4 bytes per byte of data.

2 files changed, 6 insertions, 5 deletions

diff --git a/crates/typst-pdf/Cargo.toml b/crates/typst-pdf/Cargo.toml
index 5745d053..b96a2802 100644
--- a/crates/typst-pdf/Cargo.toml
+++ b/crates/typst-pdf/Cargo.toml
@@ -27,6 +27,7 @@ infer = { workspace = true }
 krilla = { workspace = true }
 krilla-svg = { workspace = true }
 serde = { workspace = true }
+smallvec = { workspace = true }
 
 [lints]
 workspace = true
diff --git a/crates/typst-pdf/src/tags/table.rs b/crates/typst-pdf/src/tags/table.rs
index eb13a139..c27f95a1 100644
--- a/crates/typst-pdf/src/tags/table.rs
+++ b/crates/typst-pdf/src/tags/table.rs
@@ -1,8 +1,10 @@
+use std::io::Write as _;
 use std::num::{NonZeroU32, NonZeroUsize};
 
 use krilla::tagging::{
     TableCellSpan, TableDataCell, TableHeaderCell, TagBuilder, TagId, TagIdRefs, TagKind,
 };
+use smallvec::SmallVec;
 use typst_library::foundations::{Packed, Smart, StyleChain};
 use typst_library::model::{TableCell, TableCellKind, TableElem, TableHeaderScope};
 
@@ -313,11 +315,9 @@ fn should_group_rows(a: TableCellKind, b: TableCellKind) -> bool {
 }
 
 fn table_cell_id(table_id: TableId, x: u32, y: u32) -> TagId {
-    let mut bytes = [0; 12];
-    bytes[0..4].copy_from_slice(&table_id.0.to_ne_bytes());
-    bytes[4..8].copy_from_slice(&x.to_ne_bytes());
-    bytes[8..12].copy_from_slice(&y.to_ne_bytes());
-    TagId::from_slice(&bytes)
+    let mut buf = SmallVec::new();
+    _ = write!(&mut buf, "{}x{x}y{y}", table_id.0);
+    TagId::from_smallvec(buf)
 }
 
 fn table_header_scope(scope: TableHeaderScope) -> krilla::tagging::TableHeaderScope {