85 lines
3.7 KiB
Rust
85 lines
3.7 KiB
Rust
// Mermaid diagrams in chat (```mermaid fences), like the original's own Mermaid-compatible
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// engine: pure Rust (mermaid-rs-renderer → SVG), drawn with resvg using AnyBot's fonts so
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// Chinese labels show. Flowcharts, sequence, class, state, ER, gantt, pie, mindmap, timeline…
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use std::sync::OnceLock;
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/// The original refuses diagrams over 50 000 characters.
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pub const MAX_SOURCE: usize = 50_000;
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fn fontdb() -> std::sync::Arc<resvg::usvg::fontdb::Database> {
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static DB: OnceLock<std::sync::Arc<resvg::usvg::fontdb::Database>> = OnceLock::new();
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DB.get_or_init(|| {
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let mut db = resvg::usvg::fontdb::Database::new();
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db.load_font_data(crate::HUNINN.to_vec());
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db.load_system_fonts();
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// Every family the diagram asks for falls back to 粉圓體 (it has Latin and CJK).
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let found: Option<String> = db.faces().find(|f| f.families.iter().any(|(n, _)| n.to_lowercase().contains("huninn") || n.contains("粉圓"))).and_then(|f| f.families.first().map(|(n, _)| n.clone()));
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if let Some(name) = found {
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db.set_sans_serif_family(name.clone());
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db.set_serif_family(name);
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}
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std::sync::Arc::new(db)
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})
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.clone()
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}
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/// Mermaid source → SVG text.
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pub fn svg(source: &str, dark: bool) -> Result<String, String> {
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if source.len() > MAX_SOURCE {
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return Err("圖表太大".into());
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}
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let mut opts = mermaid_rs_renderer::RenderOptions::default();
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if dark {
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opts.theme = mermaid_rs_renderer::Theme::dark();
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}
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opts.theme.font_family = "sans-serif".into();
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// A panic inside the layout must not take the window down.
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let src = source.to_string();
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std::panic::catch_unwind(move || mermaid_rs_renderer::render_strict(&src, opts).map_err(|e| e.to_string()))
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.map_err(|_| "圖表排版失敗".to_string())?
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}
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/// Mermaid source → RGBA pixels at `scale` (2.0 for sharp text on Retina).
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pub fn render(source: &str, dark: bool, scale: f32) -> Result<image::RgbaImage, String> {
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let svg = svg(source, dark)?;
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let opt = resvg::usvg::Options { fontdb: fontdb(), font_family: "sans-serif".into(), ..Default::default() };
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let tree = resvg::usvg::Tree::from_str(&svg, &opt).map_err(|e| e.to_string())?;
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let size = tree.size();
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let (w, h) = ((size.width() * scale).ceil().max(1.0) as u32, (size.height() * scale).ceil().max(1.0) as u32);
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if w as u64 * h as u64 > 40_000_000 {
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return Err("圖表太大".into());
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}
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let mut pm = resvg::tiny_skia::Pixmap::new(w, h).ok_or("圖表太大")?;
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resvg::render(&tree, resvg::tiny_skia::Transform::from_scale(scale, scale), &mut pm.as_mut());
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// tiny-skia is premultiplied; egui wants straight alpha.
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let mut px = pm.take();
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for c in px.as_chunks_mut::<4>().0 {
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let a = c[3] as u32;
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if a > 0 && a < 255 {
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for v in &mut c[..3] {
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*v = ((*v as u32 * 255 + a / 2) / a).min(255) as u8;
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}
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}
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}
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image::RgbaImage::from_raw(w, h, px).ok_or_else(|| "圖表轉換失敗".into())
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn flowchart_and_errors() {
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let img = render("flowchart TD\n A[開始] --> B{要不要出門？}\n B -->|要| C[帶傘]\n B -->|不要| D[在家看書]\n C --> E[結束]\n D --> E", false, 1.0).unwrap();
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assert!(img.width() > 100 && img.height() > 100);
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// Some ink in the picture (not all transparent).
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assert!(img.pixels().filter(|p| p.0[3] > 0).count() > 1000);
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if let Ok(out) = std::env::var("ANYBOT_DIAGRAM_OUT") {
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img.save(out).unwrap();
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}
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assert!(render("this is not mermaid at all {{{", false, 1.0).is_err());
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assert!(render(&"x".repeat(MAX_SOURCE + 1), false, 1.0).is_err());
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}
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}
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