mirror of
https://github.com/aphrody-labs/cef.git
synced 2026-10-13 21:07:07 +00:00
Marshall Greenblatt
b6e302c3aa
Adds role-aware collapsing of off-screen nodes to CDP accessibility tree serialization (Accessibility.getFullAXTree). When enabled, off-screen landmarks and headings are serialized as summaries (role + name only) and other off-screen nodes are pruned. Position:fixed/sticky descendants of off-screen parents are still discovered and fully serialized. Reduces snapshot size for AI agents using Playwright ariaSnapshot(). Platform screen readers are unaffected — they use a separate code path. CDP nodesUpdated events are suppressed when active. The setting is a per-browser CefBrowserSettings field threaded through WebPreferences, with a runtime override via SetAxViewportCollapse(). Both APIs are guarded with CEF_API_ADDED(CEF_EXPERIMENTAL).
ax_viewport_collapse Debug Tools
Manual verification tools for the ax_viewport_collapse CefBrowserSettings feature.
These connect to a running cefclient via CDP to inspect the accessibility tree.
Prerequisites
python3 -m pip install websocket-client
Usage
1. Launch cefclient with remote debugging
cefclient.exe --remote-debugging-port=9222 --remote-allow-origins=* --ax-viewport-collapse
The --ax-viewport-collapse flag maps to CefBrowserSettings.ax_viewport_collapse = STATE_ENABLED in cefclient.
To load the test page directly:
cefclient.exe --remote-debugging-port=9222 --remote-allow-origins=* --ax-viewport-collapse --url=file:///<path>/test_viewport_collapse.html
2. Run the verification script
python3 verify_viewport_collapse.py
Or navigate to a URL first:
python3 verify_viewport_collapse.py --url https://example.com
Options
| Flag | Description |
|---|---|
--host |
CDP host (default: 127.0.0.1) |
--port |
CDP port (default: 9222) |
--url |
Navigate to URL before fetching tree |
--raw |
Print full JSON response instead of summary |
Comparing with/without collapse
Run two cefclient instances on different ports:
cefclient.exe --cache-path=<path1> --remote-debugging-port=9222 --remote-allow-origins=* --ax-viewport-collapse
cefclient.exe --cache-path=<path2> --remote-debugging-port=9223 --remote-allow-origins=*
python3 verify_viewport_collapse.py --port 9222 --raw > with.json
python3 verify_viewport_collapse.py --port 9223 --raw > without.json
diff with.json without.json
Expected output (with collapse enabled)
AX Tree Summary
============================================================
Total nodes returned: 77
Ignored: 3
Full (with children):70
Summary (collapsed): 4
Collapsed summary nodes (off-screen landmarks/headings):
------------------------------------------------------------
region: "Content preferences"
region: "Audio quality"
region: "Display"
region: "Storage"
Off-screen landmark sections appear as leaf nodes with role + name only. In-viewport nodes are fully serialized with children.
Files
verify_viewport_collapse.py— CDP script that callsAccessibility.getFullAXTree()and prints a summary or raw JSONtest_viewport_collapse.html— Test page with 6 landmark sections, 2 in viewport and 4 pushed off-screen by a spacer