Printing: expose native commands through control discovery

crates/ui-egui/src/control.rs

@@ -184,6 +184,16 @@ pub fn handle(app: &mut SheetApp, ctx: &egui::Context, method: &str, p: &Json) -
                 ("view.interfaceScale", "Interface Size", "{percent: 75–200 | \"auto\"} (100 = auto; clamped)"),
                 ("ui.dialog", "Open Dialog", ""),
                 ("ui.backstage", "File (Backstage view)", "{page?: home|new|open|info|saveAs|print|export|options|close}"),
+                (
+                    "ui.printSettings",
+                    "Print Settings",
+                    "{printer?: discovered name, copies?: 1..999, duplex?: printerDefault|off|longEdge|shortEdge|null, grayscale?: bool, refresh?: bool} → {printer,copies,duplex,grayscale,printers,ready,busy,discovering,status,detail}; {} inspects without submitting",
+                ),
+                (
+                    "ui.printSubmit",
+                    "Submit Print Job",
+                    "existing file.print sheet/pagination params → {printing,bytes,pending}; submits without opening a dialog",
+                ),
                 ("app.language.set", "Interface Language", "{language: \"en\"|\"zh\"|\"ja\"|\"ko\"|\"ru\"|\"pt\"|\"de\"|\"cs\"} (alias: code)"),
                 ("app.language.english", "Interface Language: English", ""),
                 ("app.language.japanese", "Interface Language: Japanese", ""),
@@ -494,4 +504,29 @@ mod tests {
         assert!(filter_commands(sample(), Some("catalog_no_match_7391")).is_empty());
         assert_eq!(filter_commands(sample(), None).len(), 3);
     }
+
+    #[test]
+    fn print_command_discovery_documents_settings_and_submission() {
+        let mut session = gridcraft_engine::Session::new();
+        session.new_workbook();
+        let mut app = SheetApp::new(session, crate::Services::default());
+        let Outcome::Done(reply) = handle(&mut app, &egui::Context::default(), "engine.commands", &json!({"search":"print"})) else {
+            panic!("command discovery must return immediately");
+        };
+        assert_eq!(reply["ok"], true);
+        let commands = reply["result"].as_array().unwrap();
+        for (id, expected_docs) in [
+            ("ui.printSettings", &["copies", "duplex", "refresh", "discovering", "status", "detail"][..]),
+            ("ui.printSubmit", &["file.print", "pagination", "pending", "without opening a dialog"][..]),
+        ] {
+            let command = commands.iter().find(|command| command["id"] == id).unwrap();
+            assert_eq!(command["ui"], true);
+            let docs = command["params"].as_str().unwrap();
+            for expected in expected_docs {
+                assert!(docs.contains(expected), "{id}: missing {expected}");
+            }
+        }
+        assert!(!app.printing.busy(), "discovery must not submit a job");
+        assert!(app.backstage.is_none(), "discovery must not open settings");
+    }
 }

docs/control-protocol.md

@@ -68,6 +68,9 @@ see [`mcp.md`](mcp.md) and [`cli.md`](cli.md).
 
 ### Native printing
 
+Desktop `engine.commands {"search":"print"}` (and connected MCP `list_commands`)
+lists `ui.printSettings` and `ui.printSubmit` with their parameter and result fields.
+
 `engine.execute` can call `ui.printSettings` with `{}` to inspect the printer list, selected
 printer, copies, duplex, grayscale, discovery/submission status and backend receipt/error.
 `{"refresh":true}` starts background discovery; poll the same command until `discovering` is