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Merge pull request #3617 from lightpanda-io/iterative-semantic-tree

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mem: SemanticTree and AXNode recursive walk -> iterative
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Karl Seguin authored and GitHub committed 2026-09-25 06:12:53 +08:00
2 parents 7f4387b9c7 1151eaebf3
commit 1950a81753
2 files changed
+115 -56
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src/SemanticTree.zig
+92 -36
View File
@@ -79,7 +79,7 @@ pub fn jsonStringify(self: @This(), jw: *std.json.Stringify) error{WriteFailed}!
.listener_targets = listener_targets,
.label_index = &label_index,
};
self.walk(&ctx, self.dom_node, null, &visitor, 1, 0) catch |err| {
self.walk(&ctx, &visitor) catch |err| {
log.err(.app, "semantic tree json dump failed", .{ .err = err });
return error.WriteFailed;
};
@@ -98,7 +98,7 @@ pub fn textStringify(self: @This(), writer: *std.Io.Writer) error{WriteFailed}!v
.listener_targets = listener_targets,
.label_index = &label_index,
};
self.walk(&ctx, self.dom_node, null, &visitor, 1, 0) catch |err| {
self.walk(&ctx, &visitor) catch |err| {
log.err(.app, "semantic tree text dump failed", .{ .err = err });
return error.WriteFailed;
};
@@ -130,15 +130,60 @@ const WalkContext = struct {
label_index: *Label.LabelByForIndex,
};
fn walk(
// A node whose children are still being walked
const Open = struct {
next_child: ?*Node,
// for the children's xpath index
tag_counts: std.StringArrayHashMapUnmanaged(usize) = .empty,
name: ?[]const u8, // The children's parent_name
xpath_len: usize,
visited: bool,
};
fn walk(self: @This(), ctx: *WalkContext, visitor: anytype) !void {
var stack: std.ArrayList(Open) = .empty;
defer stack.deinit(self.arena);
try self.visitNode(ctx, &stack, self.dom_node, null, visitor, 1);
while (stack.items.len > 0) {
// Everything read from `top` is read before visitNode, which can grow (move) the stack.
const top = &stack.items[stack.items.len - 1];
if (top.next_child) |child| {
top.next_child = child._next;
var tag: []const u8 = "text()";
if (child.is(Element)) |el| {
tag = el.getTagNameLower();
}
const gop = try top.tag_counts.getOrPut(self.arena, tag);
if (!gop.found_existing) {
gop.value_ptr.* = 0;
}
gop.value_ptr.* += 1;
try self.visitNode(ctx, &stack, child, top.name, visitor, gop.value_ptr.*);
continue;
}
const done = stack.pop().?;
if (done.visited) {
try visitor.leave();
}
ctx.xpath_buffer.shrinkRetainingCapacity(done.xpath_len);
}
}
// Every ancestor of `node` below the root is open, so the stack's length is its depth.
fn visitNode(
self: @This(),
ctx: *WalkContext,
stack: *std.ArrayList(Open),
node: *Node,
parent_name: ?[]const u8,
visitor: anytype,
index: usize,
current_depth: u32,
) !void {
const current_depth = stack.items.len;
if (current_depth > self.max_depth) return;
// 1. Skip non-content nodes
@@ -216,8 +261,6 @@ fn walk(
try appendXPathSegment(node, ctx.xpath_buffer, self.arena, index);
const xpath = ctx.xpath_buffer.items;
var name = try axn.getName(self.frame, self.arena, ctx.label_index);
const has_explicit_label = if (node.is(Element)) |el|
el.getAttributeInterned("aria-label") != null or el.getAttributeInterned("title") != null
else
@@ -225,12 +268,14 @@ fn walk(
const structural = isStructuralRole(role);
// Filter out computed concatenated names for generic containers without explicit labels.
// No computed concatenated names for generic containers without explicit labels.
// This prevents token bloat and ensures their StaticText children aren't incorrectly pruned.
// We ignore interactivity because a generic wrapper with an event listener still shouldn't hoist all text.
if (name != null and structural and !has_explicit_label) {
name = null;
}
// Not computing it also keeps a deep chain of containers from being O(depth²).
const name = if (structural and !has_explicit_label)
null
else
try axn.getName(self.frame, self.arena, ctx.label_index);
var should_visit = true;
if (self.interactive_only) {
@@ -285,32 +330,12 @@ fn walk(
did_visit = false;
}
if (should_walk_children) {
// If we are printing this node normally OR skipping it and unrolling its children,
// we walk the children iterator.
var it = node.childrenIterator();
var tag_counts: std.StringArrayHashMapUnmanaged(usize) = .empty;
while (it.next()) |child| {
var tag: []const u8 = "text()";
if (child.is(Element)) |el| {
tag = el.getTagNameLower();
}
const gop = try tag_counts.getOrPut(self.arena, tag);
if (!gop.found_existing) {
gop.value_ptr.* = 0;
}
gop.value_ptr.* += 1;
try self.walk(ctx, child, name, visitor, gop.value_ptr.*, current_depth + 1);
}
}
if (did_visit) {
try visitor.leave();
}
ctx.xpath_buffer.shrinkRetainingCapacity(initial_xpath_len);
try stack.append(self.arena, .{
.next_child = if (should_walk_children) node._first_child else null,
.name = name,
.xpath_len = initial_xpath_len,
.visited = did_visit,
});
}
fn extractSelectOptions(node: *Node, frame: *Frame, arena: std.mem.Allocator) ![]OptionData {
@@ -787,3 +812,34 @@ test "SemanticTree max_depth" {
try testing.expect(std.mem.indexOf(u8, text_str, "other") == null);
}
test "SemanticTree: deep nesting doesn't overflow the native stack" {
var registry: NodeRegistry = .init(testing.allocator);
defer registry.deinit();
const frame = try testing.createFrame();
defer testing.test_session.closeAllPages();
// The link's name comes from its content: the whole chain. The <g>s are
// pruned, so the JSON only nests link > text. SVG, as an HTML element's
// pointer-events lookup walks its ancestors: O(depth²).
const depth = 50_000;
const doc = frame.window._document;
var top = try doc.createTextNode("deep");
for (0..depth) |_| {
const parent = (try doc.createElementNS("http://www.w3.org/2000/svg", "g", frame)).asNode();
_ = try parent.appendChild(top, frame);
top = parent;
}
const link = try doc.createElement("a", null, frame);
try link.setAttribute(.wrap("href"), .wrap("#"), frame);
_ = try link.asNode().appendChild(top, frame);
const st: Self = try .init(testing.arena_allocator, link.asNode(), &registry, frame, .{});
const json_str = try std.json.Stringify.valueAlloc(testing.allocator, st, .{});
defer testing.allocator.free(json_str);
try testing.expect(std.mem.indexOf(u8, json_str, "\"role\":\"link\",\"name\":\"deep\"") != null);
try testing.expectEqual(depth, std.mem.count(u8, json_str, "/g[1]"));
try testing.expect(std.mem.endsWith(u8, json_str, "/text()[1]\",\"nodeType\":3,\"nodeValue\":\"deep\",\"children\":[]}]}"));
}
src/server/cdp/AXNode.zig
+23 -20
View File
@@ -22,6 +22,7 @@ const lp = @import("lightpanda");
const Frame = @import("../../browser/Frame.zig");
const DOMNode = @import("../../browser/webapi/Node.zig");
const Label = @import("../../browser/webapi/element/html/Label.zig");
const TreeWalker = @import("../../browser/webapi/TreeWalker.zig");
const interactive = @import("../../browser/interactive.zig");
const NodeRegistry = @import("../../NodeRegistry.zig");
@@ -1058,7 +1059,7 @@ fn writeName(
if (use_name_for_content) {
var buf: std.Io.Writer.Allocating = .init(scratchAllocator(temp_arena, frame));
try writeAccessibleNameFallback(node, &buf.writer, frame);
try writeAccessibleNameFallback(node, &buf.writer);
if (buf.written().len > 0) {
try writeString(buf.written(), w);
return .contents;
@@ -1085,9 +1086,22 @@ fn writeName(
};
}
fn writeAccessibleNameFallback(node: *DOMNode, writer: *std.Io.Writer, frame: *Frame) !void {
var it = node.childrenIterator();
while (it.next()) |child| {
fn writeAccessibleNameFallback(node: *DOMNode, writer: *std.Io.Writer) !void {
var tw = TreeWalker.FullExcludeSelf.init(node, .{});
while (tw.next()) |child| {
const parent = child._parent.?;
const in_svg = if (parent.is(DOMNode.Element)) |p| p.getTag() == .svg else false;
if (in_svg and parent != node) {
// Inside an SVG, only a <title> names it
const is_title = if (child.is(DOMNode.Element)) |el| std.mem.eql(u8, el.getTagNameLower(), "title") else false;
if (is_title) {
try writer.writeByte(' ');
} else {
tw.skipChildren();
}
continue;
}
switch (child._type) {
.cdata => {
const cd = child.subtype(DOMNode.CData);
@@ -1101,26 +1115,15 @@ fn writeAccessibleNameFallback(node: *DOMNode, writer: *std.Io.Writer, frame: *F
},
.element => {
const el = child.subtype(DOMNode.Element);
if (el.getTag() == .img) {
const tag = el.getTag();
if (tag == .img) {
if (el.getAttributeSafe(.wrap("alt"))) |alt| {
try writer.writeAll(alt);
try writer.writeByte(' ');
}
} else if (el.getTag() == .svg) {
// Try to find a <title> inside SVG
var sit = child.childrenIterator();
while (sit.next()) |s_child| {
if (s_child.is(DOMNode.Element)) |s_el| {
if (std.mem.eql(u8, s_el.getTagNameLower(), "title")) {
try writeAccessibleNameFallback(s_child, writer, frame);
try writer.writeByte(' ');
}
}
}
} else {
if (!el.getTag().isMetadata()) {
try writeAccessibleNameFallback(child, writer, frame);
}
tw.skipChildren();
} else if (tag != .svg and tag.isMetadata()) {
tw.skipChildren();
}
},
else => {},