Clipboard: a .ai or .ait file copied in a file manager pastes as its art

Paste takes a file copied in a file manager by its flavor, which
file_flavour tells from the file's first 4,096 bytes through
fileio::detect. detect names PDF or PostScript bytes in a file called
.ai or .ait by that extension, and file_flavour gave no flavor for
the format ids ai and ait. So a copied .ai or .ait file did not paste
as its art, while the same bytes in a .pdf or .eps file did.

A copied .ai or .ait file whose bytes are a PDF now pastes through the
PDF flavor (clipboard.importPdf), and one whose bytes are PostScript
pastes through the EPS flavor (clipboard.importEps). Other files
with those extensions paste as before. A .ai saved without its PDF
part also gets the PDF flavor, and Paste answers it with
clipboard.importPdf's error, as it does for the same file named .pdf.

Docs: docs/control-protocol.md, docs/development.md,
docs/target-app-parity.md.

crates/engine/src/cmd/clipboard/flavours.rs

@@ -71,13 +71,16 @@ pub const FILE_HEAD: usize = 4096;
 
 /// What a file copied in a file manager pastes as, if one of `mimes` (`image/*`: any bitmap):
 /// SVG, PDF, EPS, a Windows metafile or a bitmap (its own `image/…` type), told from its first
-/// [`FILE_HEAD`] bytes and its name. The file's bytes are that flavour's data.
+/// [`FILE_HEAD`] bytes and its name. A `.ai` or `.ait` file pastes as PDF when its bytes are a
+/// PDF and as EPS when they are PostScript. The file's bytes are that flavour's data.
 pub fn file_flavour(name: &str, head: &[u8], mimes: &[&str]) -> Option<&'static str> {
     let f = fileio::detect(name, head)?;
     let (asked, mime) = match f.id {
         "svg" => (SVG, SVG),
         "pdf" => (PDF, PDF),
         "eps" => (EPS, EPS),
+        "ai" | "ait" if head.starts_with(b"%PDF") => (PDF, PDF),
+        "ai" | "ait" if vectorcraft_pdf::is_postscript(head) => (EPS, EPS),
         "emf" | "wmf" => (EMF, EMF),
         _ if f.raster => (BITMAP, f.mime),
         _ => return None,

crates/engine/src/tests_clipflavours.rs

@@ -7,7 +7,7 @@ use vectorcraft_geom::Point;
 use vectorcraft_tools::{Mods, PointerEvent, PointerKind, ToolKey};
 
 use super::*;
-use crate::cmd::clipboard::{BITMAP, FILE_HEAD, PASTE_ORDER, PDF, PNG, SVG, TEXT, file_flavour};
+use crate::cmd::clipboard::{BITMAP, EPS, FILE_HEAD, PASTE_ORDER, PDF, PNG, SVG, TEXT, file_flavour};
 
 fn session() -> Session {
     let mut s = Session::new();
@@ -141,6 +141,27 @@ fn copied_files_paste_by_their_content() {
     assert_eq!(file_flavour("art.svg", svg, &[BITMAP]), None);
 }
 
+#[test]
+fn copied_ai_files_paste_as_the_pdf_or_postscript_inside() {
+    let mut s = session();
+    copy_red_square(&mut s);
+    let pdf = decode(&run(&mut s, "clipboard.exportPdf", json!({})));
+    let ps = b"%!PS-Adobe-3.0\n%%BoundingBox: 0 0 40 40\n%%EndComments\n1 0 0 setrgbcolor\nnewpath 0 0 moveto 40 0 lineto 40 40 lineto closepath fill\nshowpage\n";
+    let of = |name: &str, bytes: &[u8]| file_flavour(name, &bytes[..bytes.len().min(FILE_HEAD)], &PASTE_ORDER);
+    for name in ["art.ai", "art.ait", "ART.AI"] {
+        assert_eq!(of(name, &pdf), Some(PDF), "{name}");
+        assert_eq!(of(name, ps), Some(EPS), "{name}");
+    }
+    // Neither PDF nor PostScript: nothing to paste, whatever the name says.
+    assert_eq!(of("art.ai", b"hello"), None);
+    // Only what was asked for.
+    assert_eq!(file_flavour("art.ai", &pdf, &[EPS]), None);
+    assert_eq!(file_flavour("art.ait", ps, &[PDF]), None);
+    // clipboard.importEps, the EPS flavor's command, reads the PostScript.
+    let r = run(&mut s, "clipboard.importEps", json!({"dataBase64": vectorcraft_format::base64_encode(ps)}));
+    assert_eq!(r["count"], 1, "{r}");
+}
+
 #[test]
 fn import_text_then_paste_gives_point_text() {
     let mut s = session();