fix(frontend): wire clipboard copy/paste in XtermTerminal

frontend/src/renderer/components/XtermTerminal.tsx

@@ -71,6 +71,72 @@ const terminalThemes = buildTerminalThemes();
 // events stop reaching zellij. The clear only wipes pixels; modes stay up.
 const CLEAR_SEQUENCE = "\x1b[3J\x1b[2J\x1b[H";
 
+type ClipboardPlatform = "mac" | "windows" | "linux";
+
+function detectClipboardPlatform(): ClipboardPlatform {
+	const platform = navigator.platform || navigator.userAgent;
+	if (/mac/i.test(platform)) return "mac";
+	if (/win/i.test(platform)) return "windows";
+	return "linux";
+}
+
+type ClipboardChords = {
+	isCopy: (event: KeyboardEvent) => boolean;
+	isPaste: (event: KeyboardEvent) => boolean;
+};
+
+// Per-platform chords, not one shared chord: on macOS, Ctrl is free for
+// copy/paste because Ctrl+C/Ctrl+V have no PTY meaning there — Cmd owns
+// shortcuts. On Windows/Linux, Ctrl+C *is* SIGINT and Ctrl+V can be a
+// literal-paste control code in some shells, so plain Ctrl+C/Ctrl+V must keep
+// reaching the PTY untouched; those platforms use Ctrl+Shift+C/V instead, the
+// same convention GNOME Terminal and Windows Terminal use. Add a platform
+// here to extend.
+const CLIPBOARD_CHORDS: Record<ClipboardPlatform, ClipboardChords> = {
+	mac: {
+		isCopy: (event) => event.metaKey && !event.shiftKey && event.key.toLowerCase() === "c",
+		isPaste: (event) => event.metaKey && !event.shiftKey && event.key.toLowerCase() === "v",
+	},
+	windows: {
+		isCopy: (event) => event.ctrlKey && event.shiftKey && event.key.toLowerCase() === "c",
+		isPaste: (event) => event.ctrlKey && event.shiftKey && event.key.toLowerCase() === "v",
+	},
+	linux: {
+		isCopy: (event) => event.ctrlKey && event.shiftKey && event.key.toLowerCase() === "c",
+		isPaste: (event) => event.ctrlKey && event.shiftKey && event.key.toLowerCase() === "v",
+	},
+};
+
+// xterm's selection is an internal model rendered to canvas/WebGL, not a DOM
+// selection, so the OS/Electron "Copy" command can never see it — we must
+// intercept the copy chord ourselves. When nothing is selected we let the
+// event fall through unchanged (so plain Ctrl+C still reaches the PTY as
+// SIGINT on every platform). The paste chord is wired explicitly too: relying
+// on xterm's native DOM 'paste' event is not reliable across platforms under
+// Electron.
+function attachClipboardHandling(term: Terminal): void {
+	const chords = CLIPBOARD_CHORDS[detectClipboardPlatform()];
+
+	term.attachCustomKeyEventHandler((event) => {
+		if (event.type !== "keydown") return true;
+
+		if (chords.isCopy(event)) {
+			if (!term.hasSelection()) return true;
+			void navigator.clipboard.writeText(term.getSelection());
+			return false;
+		}
+
+		if (chords.isPaste(event)) {
+			void navigator.clipboard.readText().then((text) => {
+				if (text) term.paste(text);
+			});
+			return false;
+		}
+
+		return true;
+	});
+}
+
 export function XtermTerminal(props: XtermTerminalProps) {
 	const hostRef = useRef<HTMLDivElement | null>(null);
 	const termRef = useRef<Terminal | null>(null);
@@ -99,6 +165,13 @@ export function XtermTerminal(props: XtermTerminalProps) {
 				// Required for the Unicode 11 width addon below.
 				allowProposedApi: true,
 				cursorBlink: true,
+				// zellij's SGR mouse tracking otherwise eats every drag as a mouse
+				// report. xterm.js only overrides this for local selection on Shift+drag
+				// on Windows/Linux — on macOS the override key is Option/Alt, and it's
+				// gated behind this option (default false). Without it, Mac users have
+				// no way to select text at all, so hasSelection() is always false and
+				// copy silently no-ops.
+				macOptionClickForcesSelection: true,
 				// Resolve the Nerd Font stack from --font-mono (styles.css) at
 				// construction so terminal glyphs follow the app's font tokens. The
 				// box-drawing grid is rasterized by the WebGL/canvas renderer itself,
@@ -142,6 +215,7 @@ export function XtermTerminal(props: XtermTerminalProps) {
 
 		term.open(host);
 		loadRenderer(term);
+		attachClipboardHandling(term);
 
 		const fitTerminal = () => {
 			try {