examples: add multiple_fonts POC — single CJK OTC, per-language glyph variants, subsetting

Cargo.toml

@@ -247,6 +247,11 @@ name = "otf-font-subset"
 path = "examples/otf-font-subset.rs"
 required-features = []
 
+[[example]]
+name = "multiple_fonts"
+path = "examples/multiple_fonts.rs"
+required-features = []
+
 [[example]]
 name = "baseline_alignment"
 path = "examples/baseline_alignment.rs"

examples/multiple_fonts.rs

@@ -0,0 +1,110 @@
+//! Same document as `otf-font.rs`, saved with `subset_fonts: true`.
+//!
+//! Writes `font_subset.pdf`. CI validates both PDFs with
+//! `scripts/verify_pdf_font.py` (fontTools) — the subset path exercises the
+//! allsorts CFF subsetter, whose subset charset keeps the ORIGINAL font's CIDs,
+//! so the Identity-H codes must be those CIDs, not the renumbered gids (#280).
+
+use printpdf::*;
+
+fn main() {
+    let mut doc = PdfDocument::new("Demo of multiple fonts, subsetted");
+
+    let font_slice = include_bytes!("./assets/fonts/SourceHanSerif.ttc");
+
+    // One group per language: each face in the collection cycles
+    // JA/KR/SC/TC (verified against the collection's `name` table — this is
+    // NOT alphabetical), so offset `i` (0..4) selects the language and
+    // stepping by 4 walks its weights.
+    let texts = [
+        "新しい時代のこころを映すタイプフェイスデザイン",
+        "동해 물과 백두산이 마르고 닳도록 하느님이 보우하사 우리나라 만세.",
+        "这句话后来演变成“饮水思源”这个成语，意为喝水的时候想一想流水的源头，比喻不忘本。",
+        "這句話後來演變成「飲水思源」這個成語，意為喝水的時候想一想流水的源頭，比喻不忘本。",
+    ];
+
+    let font_groups: Vec<Vec<(FontId, String)>> = (0..4)
+        .map(|offset| {
+            (offset..28)
+                .step_by(4)
+                .map(|i| {
+                    let parsed_font = ParsedFont::from_bytes(font_slice, i, &mut vec![]).unwrap();
+                    let name = parsed_font
+                        .font_name
+                        .clone()
+                        .unwrap_or_else(|| "Undefined".to_string());
+                    (doc.add_font(&parsed_font), name)
+                })
+                .collect()
+        })
+        .collect();
+
+    let mut ops = vec![
+        Op::StartTextSection,
+        Op::SetTextCursor {
+            pos: Point {
+                x: Mm(10.0).into(),
+                y: Mm(285.0).into(),
+            },
+        },
+        Op::SetLineHeight { lh: Pt(14.0) },
+        Op::SetCharacterSpacing { multiplier: 0.0 },
+    ];
+
+    for (i, (group, text)) in font_groups.iter().zip(texts).enumerate() {
+        for (font_id, font_name) in group {
+            ops.push(Op::SetFont {
+                font: PdfFontHandle::External(font_id.clone()),
+                size: Pt(12.0),
+            });
+            ops.push(Op::ShowText {
+                items: vec![TextItem::Text(font_name.clone())],
+            });
+            ops.push(Op::AddLineBreak);
+            ops.push(Op::ShowText {
+                items: vec![TextItem::Text(text.to_string())],
+            });
+            ops.push(Op::AddLineBreak);
+        }
+        if i + 1 < font_groups.len() {
+            ops.push(Op::SetLineHeight { lh: Pt(8.0) });
+            ops.push(Op::AddLineBreak);
+            ops.push(Op::SetLineHeight { lh: Pt(14.0) });
+        }
+    }
+
+    ops.push(Op::SetTextCursor {
+        pos: Point {
+            x: Mm(120.0).into(),
+            y: Mm(255.0).into(),
+        },
+    });
+    for group in &font_groups {
+        ops.push(Op::SetFont {
+            font: PdfFontHandle::External(group[2].0.clone()),
+            size: Pt(24.0),
+        });
+        ops.push(Op::ShowText {
+            items: vec![TextItem::Text("\u{66DC}".to_string())],
+        });
+    }
+    ops.push(Op::EndTextSection);
+
+    let page = PdfPage::new(Mm(210.0), Mm(297.0), ops.to_vec());
+    let pages = vec![page];
+
+    let mut options = PdfSaveOptions::default();
+    options.subset_fonts = true;
+    options.optimize = false;
+
+    let mut warnings = vec![];
+    let bytes = doc.with_pages(pages).save(&options, &mut warnings);
+
+    std::fs::write("./multiple_fonts.pdf", bytes).unwrap();
+
+    for warning in warnings {
+        if warning.severity != PdfParseErrorSeverity::Info {
+            println!("{:#?}", warning);
+        }
+    }
+}