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AXNode: simplify iterative walks and scope the ignore cache to one call

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The list marker is written by writeNode, so writeTree and walkQuery share
one loop shape. IgnoreCache lives on its own pooled arena for the call
instead of frame.call_arena, which only resets on JS calls. The scan no
longer caches its root, which is never asked about again.
This commit is contained in:
Adrià Arrufat committed 2026-09-24 16:16:25 +02:00
1 parent 555415da88
commit 0d3dfa50f8
1 file changed
+77 -89
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src/server/cdp/AXNode.zig
+77 -89
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@@ -80,7 +80,10 @@ pub const Writer = struct {
}
fn toJSON(self: *const Writer, w: anytype) !void {
var ignore_cache: IgnoreCache = .empty;
const cache_arena = try self.frame.getArena(.medium, "AXNode.IgnoreCache");
defer cache_arena.release();
var ignore_cache: IgnoreCache = .{ .allocator = cache_arena.allocator() };
try w.beginArray();
if (self.filter != null) {
try self.walkQuery(self.root.dom, &ignore_cache, w);
@@ -119,18 +122,8 @@ pub const Writer = struct {
fn writeTree(self: *const Writer, root: AXNode, root_hidden: bool, ignore_cache: *IgnoreCache, w: anytype) !void {
var walker: Walker = .init(root.dom);
var axn = root;
var descend = try self.writeNode(self.root.id, root, false, root_hidden, ignore_cache, w);
while (true) {
if (descend) {
if (axn.dom.is(DOMNode.Element)) |el| {
if (el.getTag() == .li) {
try self.writeListMarker(axn.dom, w);
}
}
}
const dom_node = walker.next(descend) orelse return;
while (walker.next(descend)) |dom_node| {
descend = false;
switch (dom_node._type) {
.cdata => {
@@ -154,8 +147,7 @@ pub const Writer = struct {
}
const node = try self.registry.register(dom_node);
axn = AXNode.fromNode(node.dom);
descend = try self.writeNode(node.id, axn, walker.inAriaHidden(), false, ignore_cache, w);
descend = try self.writeNode(node.id, .fromNode(dom_node), walker.inAriaHidden(), false, ignore_cache, w);
}
}
@@ -492,7 +484,6 @@ pub const Writer = struct {
// write a node. returns true if children must be written.
fn writeNode(self: *const Writer, id: u32, axn: AXNode, in_aria_hidden: bool, hidden: bool, ignore_cache: *IgnoreCache, w: anytype) !bool {
// ignore empty texts
try w.beginObject();
try w.objectField("nodeId");
@@ -602,6 +593,14 @@ pub const Writer = struct {
try w.endObject();
if (write_children) {
if (n.is(DOMNode.Element)) |el| {
if (el.getTag() == .li) {
try self.writeListMarker(n, w);
}
}
}
return write_children;
}
@@ -646,19 +645,19 @@ pub const Writer = struct {
// ones, per the queryAXTree spec) and defers emission to emitMatch.
fn walkQuery(self: *const Writer, root: *DOMNode, ignore_cache: *IgnoreCache, w: anytype) !void {
var walker: Walker = .init(root);
var node = root;
while (true) {
const axn = AXNode.fromNode(node);
const root_axn: AXNode = .fromNode(root);
try self.emitMatch(root_axn, false, ignore_cache, w);
// <head>, <script>, <style> never expose AX content — skip their children.
var descend = !root_axn.ignoreChildren();
while (walker.next(descend)) |node| {
descend = false;
switch (node._type) {
.element, .cdata => {},
else => continue,
}
const axn: AXNode = .fromNode(node);
try self.emitMatch(axn, walker.inAriaHidden(), ignore_cache, w);
// <head>, <script>, <style> never expose AX content — skip their children.
var descend = !axn.ignoreChildren();
node = while (walker.next(descend)) |next| {
switch (next._type) {
.element, .cdata => break next,
else => descend = false,
}
} else return;
descend = !axn.ignoreChildren();
}
}
@@ -1123,9 +1122,8 @@ fn writeAccessibleNameFallback(node: *DOMNode, writer: *std.Io.Writer) !void {
}
}
/// Pre-order walk of a subtree's descendants that tracks whether one of the
/// current node's ancestors (the root included) is aria-hidden. Iterative, so
/// a deep DOM can't overflow the native stack.
/// Pre-order walk counting aria-hidden ancestors (root included), which
/// TreeWalker can't: it leaves subtrees without saying so.
const Walker = struct {
root: *DOMNode,
current: *DOMNode,
@@ -1135,7 +1133,7 @@ const Walker = struct {
return .{ .root = root, .current = root };
}
/// The node after the current one, entering its children only if `descend`.
/// `descend` false skips the current node's children.
fn next(self: *Walker, descend: bool) ?*DOMNode {
if (descend) {
if (self.current.firstChild()) |child| {
@@ -1154,7 +1152,6 @@ const Walker = struct {
node = node._parent.?;
if (isAriaHidden(node)) self.aria_hidden_ancestors -= 1;
}
self.current = self.root;
return null;
}
@@ -1359,64 +1356,59 @@ fn ignoreChildren(self: AXNode) bool {
};
}
// Generic containers are ignored unless a non-ignored node sits under them
// through other generic containers. Asking that of every node in a deep chain
// is quadratic, so the answers are memoized for the duration of one walk.
const IgnoreCache = std.AutoHashMapUnmanaged(*DOMNode, bool);
// A generic container's answer depends on the ones below it; without a memo,
// a walk asking about every node of a deep chain is O(depth²).
const IgnoreCache = struct {
allocator: std.mem.Allocator,
map: std.AutoHashMapUnmanaged(*DOMNode, bool) = .empty,
// `hidden` comes from the caller: the tree walk prunes, so its children never
// are; the root and the query walk probe the whole chain.
/// Keyed on the node alone: never reached under aria-hidden (ignoreSelf
/// says .ignored). `root` isn't cached, walks ask about each node once.
fn isGenericIgnored(self: *IgnoreCache, root: *DOMNode, frame: *Frame) !bool {
if (self.map.get(root)) |ignored| return ignored;
var tw = TreeWalker.FullExcludeSelf.init(root, .{});
const exposed = while (tw.next()) |node| {
const node_hidden = if (node.is(DOMNode.Element)) |el| isHidden(el, frame, .{ .ancestors = false }) else false;
switch (AXNode.fromNode(node).ignoreSelf(false, node_hidden)) {
.ignored => tw.skipChildren(),
.exposed => break node,
.generic => {
// Until an exposed node turns up under it.
const gop = try self.map.getOrPut(self.allocator, node);
if (!gop.found_existing) {
gop.value_ptr.* = true;
} else if (gop.value_ptr.*) {
tw.skipChildren();
} else {
break node;
}
},
}
} else return true;
var node = exposed._parent.?;
while (node != root) : (node = node._parent.?) {
self.map.getPtr(node).?.* = false;
}
return false;
}
};
/// `hidden` comes from the caller: the tree walk prunes, so its children never
/// are; the root and the query walk probe the whole chain.
fn isIgnore(self: AXNode, frame: *Frame, in_aria_hidden: bool, hidden: bool, cache: *IgnoreCache) !bool {
return switch (self.ignoreSelf(in_aria_hidden, hidden)) {
.ignored => true,
.exposed => false,
.generic => isGenericIgnored(self.dom, frame, cache),
.generic => cache.isGenericIgnored(self.dom, frame),
};
}
/// Only reached outside aria-hidden (ignoreSelf would have said .ignored), so
/// the answer depends on the node alone.
fn isGenericIgnored(root: *DOMNode, frame: *Frame, cache: *IgnoreCache) !bool {
const allocator = frame.call_arena;
if (cache.get(root)) |ignored| return ignored;
// Every generic container the scan enters is provisionally ignored: it is
// unless it's an ancestor of the exposed node that ends the scan.
try cache.put(allocator, root, true);
var tw = TreeWalker.FullExcludeSelf.init(root, .{});
const exposed = while (tw.next()) |node| {
const node_hidden = if (node.is(DOMNode.Element)) |el| isHidden(el, frame, .{ .ancestors = false }) else false;
switch (AXNode.fromNode(node).ignoreSelf(false, node_hidden)) {
.ignored => tw.skipChildren(),
.exposed => break node,
.generic => {
const gop = try cache.getOrPut(allocator, node);
if (!gop.found_existing) {
gop.value_ptr.* = true;
} else if (gop.value_ptr.*) {
tw.skipChildren();
} else {
break node;
}
},
}
} else return true;
var node = exposed;
while (node != root) {
node = node._parent.?;
try cache.put(allocator, node, false);
}
return false;
}
/// isIgnore for `self` alone, leaving generic containers to the caller.
fn ignoreSelf(self: AXNode, in_aria_hidden: bool, hidden: bool) enum { ignored, exposed, generic } {
const node = self.dom;
const role_attr = self.role_attr;
// Don't ignore non-Element node: CData, Document...
const elt = node.is(DOMNode.Element) orelse return if (in_aria_hidden) .ignored else .exposed;
const elt = self.dom.is(DOMNode.Element) orelse return if (in_aria_hidden) .ignored else .exposed;
// Ignore non-HTML elements: svg...
if (elt._type != .html) {
return .ignored;
@@ -1447,7 +1439,7 @@ fn ignoreSelf(self: AXNode, in_aria_hidden: bool, hidden: bool) enum { ignored,
else => {},
}
if (role_attr) |role| {
if (self.role_attr) |role| {
if (std.ascii.eqlIgnoreCase(role, "none") or std.ascii.eqlIgnoreCase(role, "presentation")) {
return .ignored;
}
@@ -2116,29 +2108,25 @@ test "AXNode: writer prunes children when root is hidden" {
}
test "AXNode: generic containers share memoized ignore answers" {
var registry = NodeRegistry.init(testing.allocator);
defer registry.deinit();
const frame = try testing.base.createFrame();
defer testing.base.test_session.closeAllPages();
const root = try frame.window._document.createElement("div", null, frame);
// Scanning #a provisionally ignores #b, #c and #d; the text under #d then
// flips #c and #d, while #b (only a decorative image) stays ignored.
// #b holds only a decorative image; the text under #d exposes #c and #d.
try root.setInnerHTML(
\\<div id="a"><div id="b"><img></div><div id="c"><span id="d">text</span></div></div>
, frame);
var cache: IgnoreCache = .empty;
var cache: IgnoreCache = .{ .allocator = testing.arena_allocator };
const expected = [_]struct { []const u8, bool }{ .{ "#a", false }, .{ "#b", true }, .{ "#c", false }, .{ "#d", false } };
for (expected) |e| {
const el = (try root.querySelector(e[0], frame)).?;
try testing.expectEqual(e[1], try AXNode.fromNode(el.asNode()).isIgnore(frame, false, false, &cache));
}
// Every answer after #a's came from the one scan.
try testing.expectEqual(4, cache.count());
// Filled by #a's scan.
try testing.expectEqual(3, cache.map.count());
var fresh: IgnoreCache = .empty;
var fresh: IgnoreCache = .{ .allocator = testing.arena_allocator };
for (expected[1..]) |e| {
const el = (try root.querySelector(e[0], frame)).?;
try testing.expectEqual(e[1], try AXNode.fromNode(el.asNode()).isIgnore(frame, false, false, &fresh));