Swatches: swatch.library.save counts only the swatches the file holds

swatch.library.save replied with the number of solid colors and
gradients it was asked to save, including the gradients the format
leaves out. For a new document saved as .ase, count was 50 and the file
held 46 colors. The .gpl and .ase writers keep solid colors only, and
the CSS writer leaves freeform gradients out.

count is now the number of swatches written. The new
PaletteFormat::holds returns whether a file of a format keeps a swatch
with a given paint, and swatch.library.save counts the swatches for
which it returns true. The reply has the same fields as before.

Tests: after a freeform gradient is added to a new document's swatches,
the test checks that count has these values: 51 for .vcswatches, 46 for
.gpl and .ase, and 50 for CSS. Each file holds that many swatches.

Docs: docs/mcp.md.

crates/color/src/palette_io.rs

@@ -57,6 +57,19 @@ impl PaletteFormat {
     pub fn binary(self) -> bool {
         self == PaletteFormat::Ase
     }
+    /// Does [`write`] keep a swatch with `paint` in a file of this format? None and patterns are
+    /// never written; `.gpl` and `.ase` hold solid colors only, and CSS holds no freeform gradients.
+    pub fn holds(self, paint: &Paint) -> bool {
+        match paint {
+            Paint::Solid { .. } => true,
+            Paint::Gradient(g) => match self {
+                PaletteFormat::Native => true,
+                PaletteFormat::Css => g.gradient.kind != GradientKind::Freeform,
+                PaletteFormat::Gpl | PaletteFormat::Ase => false,
+            },
+            Paint::None | Paint::Pattern { .. } => false,
+        }
+    }
 }
 
 /// The native file: a header around the library.
@@ -792,6 +805,23 @@ mod tests {
         assert!(read(&text, "x").is_err(), "CSS is written only");
     }
 
+    #[test]
+    fn holds_counts_the_swatches_each_format_writes() {
+        // `sample()` holds the spot color Ink, the linear gradient Fade, the pattern Tiles and two solid colors in a group.
+        let mut lib = sample();
+        let Paint::Gradient(mut mesh) = lib.swatches[1].paint.clone() else { panic!("Fade is a gradient") };
+        mesh.gradient.kind = GradientKind::Freeform;
+        lib.swatches.push(Swatch { name: "Mesh".into(), paint: Paint::Gradient(mesh), global: false, spot: false });
+        lib.swatches.push(Swatch { name: "[None]".into(), paint: Paint::None, global: false, spot: false });
+        let held = |f: PaletteFormat| lib.iter().filter(|w| f.holds(&w.paint)).count();
+        assert_eq!(PaletteFormat::ALL.map(held), [5, 3, 3, 4], "vcswatches, gpl, ase, css");
+        for f in [PaletteFormat::Native, PaletteFormat::Gpl, PaletteFormat::Ase] {
+            assert_eq!(read_bytes(&write(&lib, f).unwrap(), "x").unwrap().len(), held(f), "{f:?}");
+        }
+        let css = written(&lib, PaletteFormat::Css);
+        assert_eq!(css.lines().filter(|l| l.starts_with("  --")).count(), held(PaletteFormat::Css), "one property each: {css}");
+    }
+
     /// A swatch exchange file of `blocks` (type, body).
     fn ase(blocks: &[(u16, Vec<u8>)]) -> Vec<u8> {
         let mut out = b"ASEF\0\x01\0\0".to_vec();
@@ -1088,5 +1118,15 @@ mod tests {
                 prop_assert!(same_swatches(&g.swatches, &ase_expected(&want.swatches)), "{}: {:?}", g.name, g.swatches);
             }
         }
+
+        /// A written `.vcswatches`, `.gpl` or `.ase` file reads back with as many swatches as
+        /// [`PaletteFormat::holds`] counts.
+        #[test]
+        fn written_files_read_back_with_the_swatches_holds_counts(lib in arb_library()) {
+            for f in [PaletteFormat::Native, PaletteFormat::Gpl, PaletteFormat::Ase] {
+                let back = read_bytes(&write(&lib, f).unwrap(), &lib.name).unwrap();
+                prop_assert_eq!(back.len(), lib.iter().filter(|w| f.holds(&w.paint)).count(), "{:?}", f);
+            }
+        }
     }
 }

crates/engine/src/cmd/swatchlib.rs

@@ -63,7 +63,7 @@ pub fn specs() -> Vec<CommandSpec> {
             "Save Swatch Library…",
             ["Window", "Swatches"],
             None,
-            "{path?, format?: \"vcswatches\" (lossless JSON: colour models, global, spot, gradients, groups) | \"gpl\" (8-bit RGB palette; groups as `# Group:` comments) | \"ase\" (swatch exchange, binary: solid colors in their own model (RGB, CMYK, Lab, Gray) as global, spot or process colors, and color groups; gradients are left out, and a tint swatch is saved as the color it shows) | \"css\" (custom properties on :root) (default: the path's extension, else vcswatches), names?: [swatch or colour group names] (default: all; None and patterns are never saved), name?: library name (default: the document's), user?: false (save into the user library folder, listed under User Defined)} save the document's swatches as a library → {path, format, count, library?: id when saved to the user folder}; without path or user → {data: the file's text, format, count}, or {dataBase64, format, count} for ase",
+            "{path?, format?: \"vcswatches\" (lossless JSON: colour models, global, spot, gradients, groups) | \"gpl\" (8-bit RGB palette; groups as `# Group:` comments) | \"ase\" (swatch exchange, binary: solid colors in their own model (RGB, CMYK, Lab, Gray) as global, spot or process colors, and color groups; gradients are left out, and a tint swatch is saved as the color it shows) | \"css\" (custom properties on :root) (default: the path's extension, else vcswatches), names?: [swatch or colour group names] (default: all; None and patterns are never saved), name?: library name (default: the document's), user?: false (save into the user library folder, listed under User Defined)} save the document's swatches as a library → {path, format, count: the swatches written (gpl and ase hold solid colors only, and css leaves freeform gradients out), library?: id when saved to the user folder}; without path or user → {data: the file's text, format, count}, or {dataBase64, format, count} for ase",
             has_doc,
             save
         ),
@@ -454,7 +454,7 @@ fn save(s: &mut Session, p: &Value) -> Result<Value> {
     let lib = document_library(&st.doc, &str_list(p, "names"), name, C)?;
     let bytes = palette_io::write(&lib, format).map_err(|e| bad(C, e))?;
     let data = if format.binary() { FileData::Binary(bytes) } else { FileData::Text(String::from_utf8_lossy(&bytes).into_owned()) };
-    let mut out = json!({"format": format.id(), "count": lib.len()});
+    let mut out = json!({"format": format.id(), "count": lib.iter().filter(|w| format.holds(&w.paint)).count()});
     s.swatch_libraries.write(p, &lib.name, format.id(), data, &mut out, C)?;
     Ok(out)
 }

crates/engine/src/tests_swatchlib.rs

@@ -283,6 +283,26 @@ fn swatch_exchange_files_save_with_models_kinds_and_groups() {
     let _ = std::fs::remove_dir_all(dir);
 }
 
+#[test]
+fn save_counts_the_swatches_the_file_holds() {
+    let mut s = session();
+    // A new document has 46 solid colors and 4 linear or radial gradients besides None. Mesh is a freeform gradient.
+    run(&mut s, "swatch.new", json!({"name": "Mesh", "gradient": {"kind": "freeform"}}));
+    let mut counts = vec![];
+    for format in ["vcswatches", "gpl", "ase", "css"] {
+        let r = run(&mut s, "swatch.library.save", json!({ "format": format }));
+        // The libraries load back with that many swatches, and the CSS file has one property for each.
+        let held = if format == "css" {
+            r["data"].as_str().unwrap().lines().filter(|l| l.starts_with("  --")).count() as u64
+        } else {
+            let load = json!({"data": r["data"], "dataBase64": r["dataBase64"], "name": format!("Saved.{format}")});
+            run(&mut s, "swatch.library.load", load)["count"].as_u64().unwrap()
+        };
+        counts.push((format, r["count"].as_u64().unwrap(), held));
+    }
+    assert_eq!(counts, [("vcswatches", 51, 51), ("gpl", 46, 46), ("ase", 46, 46), ("css", 50, 50)]);
+}
+
 #[test]
 fn loaded_libraries_copy_into_the_user_folder_without_replacing_files() {
     use vectorcraft_testkit::ase::{Block, ase, sample};

docs/mcp.md

@@ -931,7 +931,8 @@ groups; `.gpl` is 8-bit RGB; a swatch exchange `.ase` file keeps solid colors in
 (RGB, CMYK, Lab or Gray) as global, spot or process colors, and color groups, writes a tint swatch
 as the color it shows and leaves gradients out; CSS writes custom properties); without `path`
 it returns `{data}`, or `{dataBase64}` for `.ase`, and `user: true` saves into the user library
-folder of the desktop app (listed as category `user`, User Defined). `swatch.library.load {path? | data? |
+folder of the desktop app (listed as category `user`, User Defined). The reply's `count` is the number of swatches
+written: `.gpl` and `.ase` hold solid colors only, and CSS leaves freeform gradients out. `swatch.library.load {path? | data? |
 dataBase64?, name?}` loads a `.vcswatches`, `.gpl`, swatch exchange (`.ase`) or color book (`.acb`) file, or another
 document's swatches, as a library to add from. From an `.ase` file it reads RGB, CMYK, Lab and Gray colors as global,
 spot or process swatches and keeps their color groups. A color book (such as a Pantone book you own) gives its RGB,