1 files changed, 169 insertions, 0 deletions
diff --git a/packages/meshbay-hub/tests/harness/scroll_probe.py b/packages/meshbay-hub/tests/harness/scroll_probe.py
new file mode 100644
index 0000000..73ff0f1
--- /dev/null
+++ b/packages/meshbay-hub/tests/harness/scroll_probe.py
@@ -0,0 +1,169 @@
+#!/usr/bin/env python3
+"""
+Does the page scroll vertically when it should not?
+
+`layout_probe.py` answers "where is this box". This one answers "is the document
+taller than the window", which is a different question and the one behind two
+separate reports of a scrollbar that would not go away.
+
+The sizing code under test is **read out of `app.js` and run here**, not
+reimplemented: a copy of the formula living in the test would go on passing
+after the real one changed, which is the failure mode worth avoiding in a file
+whose whole purpose is to catch an arithmetic slip.
+
+    scroll_probe.py <html-fragment-file> [<height>,<height>,...]
+
+Reports per viewport height: the window, the document, the difference, every
+element hanging below the fold, and the chat panel's box if there is one.
+"""
+import http.server
+import json
+import re
+import socketserver
+import subprocess
+import sys
+import tempfile
+import threading
+import time
+from pathlib import Path
+
+STATIC = Path(__file__).resolve().parents[2] / "src" / "meshbay_hub" / "static"
+APP = STATIC / "app.js"
+PORT = 8736
+FRAG = Path(sys.argv[1]).read_text()
+HEIGHTS = ([int(h) for h in sys.argv[2].split(",")]
+           if len(sys.argv) > 2 else [700, 900, 1200])
+
+
+def chat_fit_body() -> str:
+    """
+    The body of the chat panel's `fit()`, lifted from `app.js`.
+
+    It closes over `el` and two constants, so those are supplied around it;
+    everything between the braces — the second pass included — is the shipped
+    code. A rename breaks this loudly, which is intended: a skipped test here
+    would be worse than a failing one.
+    """
+    source = APP.read_text(encoding="utf-8")
+    start = source.index("    const fit = () => {")
+    end = source.index("\n    };", start)
+    body = source[source.index("{", start) + 1:end]
+    consts = {}
+    for name in ("CHAT_MIN_HEIGHT", "CHAT_BOTTOM_GAP"):
+        line = re.search(rf"^const {name} = (\d+);", source, re.M)
+        assert line, f"{name} is gone or was renamed"
+        consts[name] = line.group(1)
+    return ("(el, window, document) => {"
+            f"const CHAT_MIN_HEIGHT = {consts['CHAT_MIN_HEIGHT']};"
+            f"const CHAT_BOTTOM_GAP = {consts['CHAT_BOTTOM_GAP']};"
+            + body + "}")
+
+
+PAGE = """<!doctype html><html><head><meta charset=utf-8></head><body style="margin:0">
+<!-- One iframe per height: a headless window has a floor of its own, and an
+     iframe establishes the viewport we actually mean. -->
+<div id="frames"></div><script>
+const HEIGHTS = %(heights)s, FRAG = %(frag)s;
+const host = document.getElementById('frames');
+for (const h of HEIGHTS) {
+  const f = document.createElement('iframe');
+  f.id = 'f' + h;
+  f.style.cssText = `width:1100px;height:${h}px;border:0;display:block`;
+  host.appendChild(f);
+  const d = f.contentDocument;
+  d.open();
+  d.write(`<!doctype html><html><head><meta charset=utf-8>
+<link rel="stylesheet" href="/style.css"></head><body>${FRAG}</body></html>`);
+  d.close();
+}
+// The real fit() from app.js. A <script> written into the fragment does not
+// fire, so it is applied from out here once the stylesheet has settled.
+const FIT = %(fit)s;
+setTimeout(() => {
+  for (const h of HEIGHTS) {
+    const win = document.getElementById('f' + h).contentWindow;
+    const el = win.document.querySelector('.chat-panel');
+    if (el) FIT(el, win, win.document);
+  }
+}, 200);
+setTimeout(() => {
+  const out = {};
+  for (const h of HEIGHTS) {
+    const win = document.getElementById('f' + h).contentWindow;
+    const doc = win.document.documentElement;
+    const past = [];
+    for (const el of win.document.querySelectorAll('*')) {
+      const b = el.getBoundingClientRect();
+      if (b.bottom > win.innerHeight + 0.5)
+        past.push((el.className || el.tagName) + ' +' +
+                  Math.round(b.bottom - win.innerHeight));
+    }
+    const panel = win.document.querySelector('.chat-panel');
+    const pb = panel && panel.getBoundingClientRect();
+    out[h] = {viewport: win.innerHeight, scrollHeight: doc.scrollHeight,
+              overflow: doc.scrollHeight - win.innerHeight,
+              past: past.slice(0, 12),
+              panel: pb ? {top: Math.round(pb.top), bottom: Math.round(pb.bottom),
+                           height: Math.round(pb.height)} : null};
+  }
+  fetch('/log', {method: 'POST', body: JSON.stringify(out)});
+}, 700);
+</script></body></html>"""
+
+RECORDS = []
+socketserver.TCPServer.allow_reuse_address = True
+
+
+class H(http.server.BaseHTTPRequestHandler):
+    def log_message(self, *a):
+        pass
+
+    def do_POST(self):
+        RECORDS.append(json.loads(
+            self.rfile.read(int(self.headers["Content-Length"])).decode()))
+        self.send_response(204)
+        self.end_headers()
+
+    def do_GET(self):
+        if self.path == "/":
+            # A "</script>" inside the fragment would close the inline script
+            # it is embedded in, and the page would measure nothing.
+            body = (PAGE % {"frag": json.dumps(FRAG).replace("</", "<\\/"),
+                            "heights": json.dumps(HEIGHTS),
+                            "fit": chat_fit_body()}).encode()
+            ctype = "text/html; charset=utf-8"
+        elif self.path == "/style.css":
+            body = (STATIC / "style.css").read_bytes()
+            ctype = "text/css"
+        else:
+            self.send_response(404)
+            self.end_headers()
+            return
+        self.send_response(200)
+        self.send_header("Content-Type", ctype)
+        self.send_header("Content-Length", str(len(body)))
+        self.end_headers()
+        self.wfile.write(body)
+
+
+def main() -> int:
+    with socketserver.TCPServer(("127.0.0.1", PORT), H) as srv:
+        threading.Thread(target=srv.serve_forever, daemon=True).start()
+        with tempfile.TemporaryDirectory() as profile:
+            subprocess.run(
+                ["google-chrome", "--headless", "--disable-gpu", "--no-sandbox",
+                 f"--user-data-dir={profile}", "--window-size=1100,1300",
+                 "--virtual-time-budget=6000", "--dump-dom",
+                 f"http://127.0.0.1:{PORT}/"],
+                capture_output=True, timeout=120)
+        for _ in range(50):
+            if RECORDS:
+                break
+            time.sleep(0.1)
+    print(json.dumps(RECORDS[0] if RECORDS else {"error": "no measurement"},
+                     indent=1))
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())