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hermes-agent/tools/computer_use/cua_backend_parse.py
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Python

"""Pure parsing helpers for the cua-driver backend: MCP result flattening, ``list_windows`` /
``get_window_state`` payload normalisation, key combos. No I/O, no module state — every function
depends only on its inputs, so the MCP and CLI transports share them safely."""
from __future__ import annotations
import contextlib
import json
import re
from typing import Any, Dict, List, Optional, Tuple
from tools.computer_use.backend import ActionResult, UIElement, image_dimensions_from_bytes
# Linux/X11 surfaces GNOME Shell / desktop backdrop windows ahead of real app windows with no useful z-order; they
# are targetable but capture as empty, so default capture skips them.
_NON_APP_WINDOW_TITLE_PREFIXES = ("@!", "Desktop", "gnome-shell", "GNOME Shell") # "@!" = GNOME helpers
_ELEMENT_LINE_RE = re.compile(
r'^\s*(?:-\s+)?\[(\d+)\]\s+(\w+)'
r'(?:'
r'\s*=\s*"([^"]*)"' # = "value"
r'|\s+"([^"]*)"' # "value"
r'|\s+\((?!\d+\))([^)]*)\)' # (value) but not a pure-digit (order) number
r')?'
r'(?:\s+(?:\(\d+\)\s+)?id=([^\s\[\]]+))?', # optional id=value (after an optional (order))
re.MULTILINE,
)
"""get_window_state AX-tree markdown line: ``[N] AXRole`` + label in one of four forms (``= "value"``, ``"quoted"``,
``(paren)``, ``id=Label`` optionally after an ``(order)`` number). A parenthesised pure-digit group is an ORDER
index, not a label, and is excluded so the id= label wins. Group 1 index, group 2 role, groups 3-6 the label."""
def _mcp_field(obj, snake: str, camel: str, default=None):
"""Read an MCP model field across the 1.x -> 2.x rename: mcp 2.0 exposes snake_case attributes and keeps
camelCase only as a serialization alias, so ``getattr(result, "isError", False)`` is False for every 2.x result
and a denied call looks like success. Deliberately duplicated from ``tools.mcp_tool.mcp_field`` so computer_use
never loads the much larger config-driven MCP client module."""
return getattr(obj, snake, getattr(obj, camel, default))
def _action_result_from(name: str, ok: bool, message: str, meta: Dict[str, Any],
structured: Dict[str, Any], *, requested_delivery: Optional[str] = None) -> ActionResult:
"""Build an ActionResult, lifting cua-driver's structured verdict. structuredContent is canonical, the flattened
``meta`` copy the fallback. Every structured field is additive: a driver that omits one leaves the attribute
``None`` so old drivers see unchanged behavior.
See the action response shape in cua-driver's mcp-tool-notes and NousResearch/hermes-agent#67052.
"""
sc = structured if isinstance(structured, dict) else {}
def _raw(key: str) -> Any:
return sc.get(key) if key in sc else meta.get(key)
def _typed(value: Any, typ) -> Any:
return value if isinstance(value, typ) else None
return ActionResult(
ok=ok, action=name, message=message, meta=meta,
verified=_typed(_raw("verified"), bool), effect=_typed(_raw("effect"), str),
escalation=_typed(_raw("escalation"), dict), path=_typed(_raw("path"), str),
degraded=_typed(_raw("degraded"), bool),
# What we asked for; the driver's `path` records the rung that ran.
delivery_mode=_typed(requested_delivery, str),
# Refusal/limitation code — drivers spell it "code" or "reason_code".
code=_typed(_raw("code") or _raw("reason_code"), str),
)
def _z_index_uninformative(windows: List[Dict[str, Any]]) -> bool:
"""True when every window shares the same z_index (common on Linux/X11)."""
return len({w.get("z_index", 0) for w in windows}) <= 1
def _parse_xprop_net_active_window(stdout: str) -> Optional[int]:
"""Parse ``xprop -root _NET_ACTIVE_WINDOW`` stdout into a window id: the ``window id # 0x...`` form, falling
back to the first hex token."""
text = stdout or ""
match = re.search(r"window id # (0x[0-9a-fA-F]+)", text) or re.search(r"(0x[0-9a-fA-F]+)", text)
return int(match.group(1), 16) if match else None
def _is_real_app_window(w: Dict[str, Any]) -> bool:
"""Return False for desktop/shell helper windows that capture as empty."""
title = w.get("title", "")
return not any(title.startswith(p) or title.lower().startswith(p.lower()) for p in _NON_APP_WINDOW_TITLE_PREFIXES)
def _parse_elements_from_tree(markdown: str) -> List[UIElement]:
"""Parse UIElements from get_window_state AX-tree markdown — last-resort fallback for drivers without
``structuredContent.elements``. Bounds are always ``(0, 0, 0, 0)`` (the markdown carries none), fine for
element-index clicks since the driver resolves the frame.
Last-resort fallback for cua-driver builds that don't carry the canonical ``structuredContent.elements``
array (see ``_parse_elements_from_structured`` — Surface 2 of #47072 prefers that path).
"""
return [
# groups 3-6: value / quoted / paren / id= label (first non-None wins)
UIElement(index=int(m.group(1)), role=m.group(2),
label=m.group(3) or m.group(4) or m.group(5) or m.group(6) or "", bounds=(0, 0, 0, 0))
for m in _ELEMENT_LINE_RE.finditer(markdown)
]
def _parse_elements_from_structured(raw_elements: List[Dict[str, Any]]) -> List[UIElement]:
"""Read the canonical ``structuredContent.elements`` array: ``element_index``, ``role``, ``label`` and, when
AT-SPI / AXFrame returned usable bounds, ``frame`` ``{x, y, w, h}`` — so real pixel bounds survive (the
markdown path loses them). Malformed entries are skipped.
Surface 2 of NousResearch/hermes-agent#47072: read the canonical ``structuredContent.elements`` array
cua-driver-rs emits on every ``get_window_state`` response (trycua/cua#1961).
"""
elements: List[UIElement] = []
for raw in raw_elements:
idx = raw.get("element_index") if isinstance(raw, dict) else None
if not isinstance(idx, int):
continue
role, label, frame, token = (raw.get(k) for k in ("role", "label", "frame", "element_token"))
bounds: Tuple[int, int, int, int] = (0, 0, 0, 0)
with contextlib.suppress(TypeError, ValueError):
if isinstance(frame, dict) and frame:
bounds = tuple(int(frame.get(k, 0)) for k in ("x", "y", "w", "h")) # type: ignore[assignment]
elements.append(UIElement(
index=idx, role=role if isinstance(role, str) else "", label=label if isinstance(label, str) else "",
bounds=bounds,
# Opaque `s{snapshot_hex}:{index}` token — the driver owns parse + LRU semantics.
element_token=token if isinstance(token, str) and token else None,
))
return elements
def _image_dimensions_from_bytes(raw: bytes) -> Tuple[int, int]:
"""Best-effort PNG/JPEG dimension sniff; ``(0, 0)`` when unreadable or non-positive."""
dims = image_dimensions_from_bytes(raw)
return dims if dims and dims[0] > 0 and dims[1] > 0 else (0, 0)
def _split_tree_text(full_text: str) -> Tuple[str, str]:
"""Split get_window_state text into (summary_line, tree_markdown)."""
summary, _, tree = full_text.partition("\n")
return summary, tree
_MODIFIER_NAMES = frozenset({"cmd", "command", "shift", "option", "alt", "ctrl", "control", "fn"})
_KEY_ALIASES = {"command": "cmd", "alt": "option", "control": "ctrl"}
def _parse_key_combo(keys: str) -> Tuple[Optional[str], List[str]]:
"""Parse 'cmd+s' / 'ctrl-alt-t' into (key, modifiers); last non-modifier wins."""
modifiers: List[str] = []
key = None
for part in (p.strip().lower() for p in re.split(r'[+\-]', keys) if p.strip()):
normalized = _KEY_ALIASES.get(part, part)
if normalized in _MODIFIER_NAMES:
modifiers.append(normalized)
else:
key = part
return key, modifiers
def _tool_envelope(data: Any, images: List[str], structured: Any, is_error: bool,
image_mime_types: Optional[List[str]] = None) -> Dict[str, Any]:
"""The normalised tool-result dict every transport emits: ``{data, images, [image_mime_types,] structuredContent,
isError}``. ``image_mime_types`` is only present when the transport can report it (MCP image parts)."""
out: Dict[str, Any] = {"data": data, "images": images}
if image_mime_types is not None:
out["image_mime_types"] = image_mime_types
out["structuredContent"], out["isError"] = structured, is_error
return out
def _extract_tool_result(mcp_result: Any) -> Dict[str, Any]:
"""Flatten an mcp CallToolResult into ``{data, images, image_mime_types, structuredContent, isError}``. ``data``
is the joined text parts (parsed as JSON when it looks like JSON); ``image_mime_types`` is parallel to
``images`` with ``""`` where the part carried no mimeType (older drivers — callers then sniff the base64 prefix).
`image_mime_types` is the explicit `mimeType` cua-driver emits on every image part as of trycua/cua#1961
(Surface 7 of NousResearch/hermes-agent#47072). Each entry corresponds index-for-index with `images`; an
empty string entry signals the part carried no mimeType (older cua-driver build), and the caller should
fall back to base64-prefix sniffing.
"""
data: Any = None
images: List[str] = []
image_mime_types: List[str] = []
text_chunks: List[str] = []
for part in getattr(mcp_result, "content", []) or []:
ptype = getattr(part, "type", None)
if ptype == "text":
text_chunks.append(getattr(part, "text", "") or "")
elif ptype == "image" and getattr(part, "data", None):
images.append(part.data)
image_mime_types.append(_mcp_field(part, "mime_type", "mimeType") or "")
if text_chunks:
joined = "\n".join(t for t in text_chunks if t)
try:
data = json.loads(joined) if joined.strip().startswith(("{", "[")) else joined
except json.JSONDecodeError:
data = joined
return _tool_envelope(
data, images, _mcp_field(mcp_result, "structured_content", "structuredContent") or None,
# Identity, not truthiness: mocks/proxies synthesize truthy attributes.
_mcp_field(mcp_result, "is_error", "isError", False) is True, image_mime_types)
def _image_from_tool_result(out: Dict[str, Any]) -> tuple[Optional[str], Optional[str]]:
"""Pull ``(b64, mime_type)`` out of a flattened tool result. cua-driver delivers screenshots as an MCP ``image``
part (``out["images"]``) or as ``screenshot_png_b64`` in structuredContent (newer builds, CLI transport);
checking both keeps capture() robust to the driver moving it."""
images = out.get("images") or []
if images and images[0]:
mimes = out.get("image_mime_types") or []
return images[0], (mimes[0] if mimes and mimes[0] else None)
structured = out.get("structuredContent") or {}
b64 = structured.get("screenshot_png_b64") or structured.get("png_b64")
if b64:
return b64, (structured.get("screenshot_mime_type") or structured.get("mime_type") or None)
return None, None
def _int_or_none(value: Any) -> Optional[int]:
"""``int(value)`` for int/numeric-str inputs; None for bools, other types and malformed strings."""
if isinstance(value, bool) or not isinstance(value, (int, str)):
return None
try:
return int(value)
except ValueError:
return None
def _positive_int(value: Any) -> Optional[int]:
"""Return a positive integer, rejecting booleans and malformed values."""
parsed = _int_or_none(value)
return parsed if parsed is not None and parsed > 0 else None
def _is_placeholder_id(value: Any) -> bool:
"""True when *value* is a schema-filler id (``0`` / negative) rather than a target: some providers zero-fill
every optional integer, and treating that as targeting would drop the caller's ``app=``. Non-numeric values
are NOT placeholders — they still reach validation."""
parsed = _int_or_none(value)
return parsed is not None and parsed <= 0
def _ingest_windows(raw_windows: List[Dict[str, Any]]) -> List[Dict[str, Any]]:
"""Normalise cua-driver ``list_windows`` entries, dropping unusable ones. Every downstream call needs integer
``pid`` and ``window_id``; on X11 the PID comes from the optional ``_NET_WM_PID`` property, so root/panel/popup
windows report ``pid: null`` — skip those instead of aborting the enumeration. ``z_index``: higher = closer to
front; Wayland's null (undefined stacking) sorts lowest so real windows stay above the desktop."""
windows: List[Dict[str, Any]] = []
for w in raw_windows:
if not isinstance(w, dict): # untrusted compatibility envelopes
continue
pid_int, window_id_int = _positive_int(w.get("pid")), _positive_int(w.get("window_id"))
if pid_int is None or window_id_int is None:
continue
z_raw, app_name, title = w.get("z_index"), w.get("app_name", ""), w.get("title", "")
windows.append({
"app_name": app_name if isinstance(app_name, str) else "",
"pid": pid_int,
"window_id": window_id_int,
# Only explicit False means off-screen; null (Linux 0.6.x) means unknown.
"off_screen": w.get("is_on_screen") is False,
"title": title if isinstance(title, str) else "",
"z_index": z_raw if isinstance(z_raw, (int, float)) and not isinstance(z_raw, bool) else 0,
})
return windows
def _windows_from_tool_result(out: Dict[str, Any]) -> List[Dict[str, Any]]:
"""Return list_windows payloads across cua-driver result shapes: structuredContent.windows, then ``windows`` /
``_legacy_windows`` in the text payload, then on the envelope itself."""
candidates = ((out.get("structuredContent"), ("windows",)),
(out.get("data"), ("windows", "_legacy_windows")),
(out, ("windows", "_legacy_windows")))
for container, keys in candidates:
if isinstance(container, dict):
for key in keys:
value = container.get(key)
if isinstance(value, list) and value:
return value
return []
def _apps_from_windows(windows: List[Dict[str, Any]]) -> List[Dict[str, Any]]:
apps: List[Dict[str, Any]] = []
seen: set[tuple[str, int]] = set()
for summary in _ingest_windows(windows):
name, key = summary["app_name"], (summary["app_name"], summary["pid"])
if name and key not in seen:
seen.add(key)
apps.append({"name": name, "pid": summary["pid"]})
return apps