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MCP: headless Xvfb on WSLg, and arrow/punctuation key names #6

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MCP: headless Xvfb on WSLg, and arrow/punctuation key names #6

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24 changes: 19 additions & 5 deletions mcp-server/index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -1532,11 +1532,15 @@ function selectXvfbDisplay(preferred) {
throw makeError('CAPABILITY_UNAVAILABLE', 'No free Xvfb display number found');
}

async function waitForXvfb(display, timeoutMs = 3000) {
async function waitForXvfb(display, timeoutMs = 3000, ready = () => false) {
// Xvfb writes the display number to -displayfd once it is accepting
// connections. Watching for /tmp/.X11-unix/X<n> alone fails where that
// directory is read-only (WSLg), and Xvfb then listens only on the
// abstract socket, which Xlib still reaches.
const socketPath = `/tmp/.X11-unix/X${display}`;
const deadline = Date.now() + timeoutMs;
while (Date.now() < deadline) {
if (fs.existsSync(socketPath)) return true;
if (ready() || fs.existsSync(socketPath)) return true;
await new Promise((resolve) => setTimeout(resolve, 50));
}
return false;
Expand All @@ -1550,8 +1554,10 @@ async function startXvfbForSession(display, screen) {
});
}
const displayName = `:${display}`;
const argv = [displayName, '-screen', '0', screen, '-nolisten', 'tcp'];
const proc = spawn(xvfbPath, argv, { stdio: ['ignore', 'pipe', 'pipe'] });
const argv = [displayName, '-screen', '0', screen, '-nolisten', 'tcp', '-displayfd', '3'];
const proc = spawn(xvfbPath, argv, { stdio: ['ignore', 'pipe', 'pipe', 'pipe'] });
let displayfdReady = false;
proc.stdio[3].on('data', () => { displayfdReady = true; });
session.xvfb = {
pid: proc.pid,
path: xvfbPath,
Expand All @@ -1570,7 +1576,7 @@ async function startXvfbForSession(display, screen) {
session.xvfb.exit_code = code;
session.xvfb.signal = signal;
});
if (!(await waitForXvfb(display))) {
if (!(await waitForXvfb(display, 3000, () => displayfdReady))) {
proc.kill('SIGTERM');
throw makeError('CAPABILITY_UNAVAILABLE', 'Xvfb did not become ready before timeout', {
display: displayName,
Expand Down Expand Up @@ -2850,6 +2856,14 @@ const KEY_CODES = {
0: 50, 1: 31, 2: 30, 3: 26, 4: 24, 5: 29, 6: 27, 7: 51, 8: 53, 9: 48,
space: 33, ' ': 33, return: 12, enter: 12, escape: 28, esc: 28,
tab: 44, backspace: 52,
// Atari800 AKEY codes (src/akey.h): the arrows are CTRL with - = + *,
// and the shifted symbols carry AKEY_SHFT (0x40) in the code itself.
up: 0x8e, down: 0x8f, left: 0x86, right: 0x87,
help: 0x11, atari: 0x27, caps: 0x3c, delete: 52,
'-': 0x0e, '=': 0x0f, '+': 0x06, '*': 0x07, '/': 0x26, '<': 0x36,
'>': 0x37, ',': 0x20, '.': 0x22, ';': 0x02, ':': 0x42, '?': 0x66,
'!': 0x5f, '"': 0x73, '#': 0x5a, '$': 0x58, '%': 0x5d, '&': 0x5b,
'@': 0x75, '(': 0x70, ')': 0x72,
};

function resolveKey(key, shift = undefined) {
Expand Down