Relay browser touches through the harness into the real touchscreen

harness/stream.go

@@ -22,7 +22,7 @@ const page = `<!doctype html>
 <meta name="viewport" content="width=device-width">
 <title>cabletest</title>
 <body style="margin:0;background:#000;min-height:100vh;display:grid;place-items:center">
-<canvas style="max-width:100vw;max-height:100vh"></canvas>
+<canvas style="max-width:100vw;max-height:100vh;touch-action:none"></canvas>
 <script>
 (async () => {
   const cv = document.querySelector('canvas'), g = cv.getContext('2d');
@@ -59,6 +59,34 @@ addEventListener('keydown', e => {
     fetch('keys', {method: 'POST', body: e.key});
   }
 });
+(() => {
+  const cv = document.querySelector('canvas');
+  let q = Promise.resolve(), held = -1, lastMove = 0;
+  const send = b => q = q.then(() => fetch('touch', {method: 'POST', body: b}).catch(() => {}));
+  const at = e => {
+    const r = cv.getBoundingClientRect();
+    return Math.round((e.clientX - r.left) * cv.width / r.width) + ' ' +
+           Math.round((e.clientY - r.top) * cv.height / r.height);
+  };
+  cv.addEventListener('pointerdown', e => {
+    e.preventDefault();
+    held = e.pointerId;
+    cv.setPointerCapture(held);
+    send('down ' + at(e));
+  });
+  cv.addEventListener('pointermove', e => {
+    if (e.pointerId !== held || e.timeStamp - lastMove < 50) return;
+    lastMove = e.timeStamp;
+    send('move ' + at(e));
+  });
+  const lift = e => {
+    if (e.pointerId !== held) return;
+    held = -1;
+    send('up');
+  };
+  cv.addEventListener('pointerup', lift);
+  cv.addEventListener('pointercancel', lift);
+})();
 </script>
 `
 
@@ -87,6 +115,9 @@ func serveStream() error {
 	if err != nil {
 		return err
 	}
+	if touchscreen, err = openTouchscreen(); err != nil {
+		return err
+	}
 	ln, err := net.Listen("tcp", streamAddr)
 	if err != nil {
 		return err
@@ -104,6 +135,7 @@ func serveStream() error {
 	})
 	mux.HandleFunc("/frames", frames)
 	mux.HandleFunc("/keys", keys)
+	mux.HandleFunc("/touch", touch)
 	go http.Serve(ln, mux)
 	return nil
 }