Add cleanup to Range

In https://github.com/lightpanda-io/browser/pull/1774 we started to track Ranges
in the page in order to correctly make them "live". But, without correct
lifetime, they would continue to be "live" even if out of scope in JS.

This commit adds finalizers to Range via reference counting similar to Events.
It _is_ possible for a Range to outlive its page, so we can't just remove the
range from the Page's _live_range list - the page might not be valid. This
commit gives every page an unique id and the ability to try and get the page
by id from the session. By capturing the page_id at creation-time, a Range
can defensively remove itself from the page's list. If the page is already
gone, then there's no need to do anything.

src/browser/Factory.zig

@@ -265,13 +265,15 @@ pub fn blob(_: *const Factory, arena: Allocator, child: anytype) !*@TypeOf(child
     return chain.get(1);
 }
 
-pub fn abstractRange(self: *Factory, child: anytype, page: *Page) !*@TypeOf(child) {
-    const allocator = self._slab.allocator();
-    const chain = try PrototypeChain(&.{ AbstractRange, @TypeOf(child) }).allocate(allocator);
+pub fn abstractRange(_: *const Factory, arena: Allocator, child: anytype, page: *Page) !*@TypeOf(child) {
+    const chain = try PrototypeChain(&.{ AbstractRange, @TypeOf(child) }).allocate(arena);
 
     const doc = page.document.asNode();
     const abstract_range = chain.get(0);
     abstract_range.* = AbstractRange{
+        ._rc = 0,
+        ._arena = arena,
+        ._page_id = page.id,
         ._type = unionInit(AbstractRange.Type, chain.get(1)),
         ._end_offset = 0,
         ._start_offset = 0,

src/browser/Page.zig

@@ -80,6 +80,8 @@ pub const BUF_SIZE = 1024;
 
 const Page = @This();
 
+id: u32,
+
 // This is the "id" of the frame. It can be re-used from page-to-page, e.g.
 // when navigating.
 _frame_id: u32,
@@ -254,6 +256,7 @@ pub fn init(self: *Page, frame_id: u32, session: *Session, parent: ?*Page) !void
     })).asDocument();
 
     self.* = .{
+        .id = session.nextPageId(),
         .js = undefined,
         .parent = parent,
         .arena = session.page_arena,

src/browser/Session.zig

@@ -84,6 +84,7 @@ queued_navigation: std.ArrayList(*Page),
 // about:blank navigations (which may add to queued_navigation).
 queued_queued_navigation: std.ArrayList(*Page),
 
+page_id_gen: u32,
 frame_id_gen: u32,
 
 pub fn init(self: *Session, browser: *Browser, notification: *Notification) !void {
@@ -103,6 +104,7 @@ pub fn init(self: *Session, browser: *Browser, notification: *Notification) !voi
         .page_arena = page_arena,
         .factory = Factory.init(page_arena),
         .history = .{},
+        .page_id_gen = 0,
         .frame_id_gen = 0,
         // The prototype (EventTarget) for Navigation is created when a Page is created.
         .navigation = .{ ._proto = undefined },
@@ -297,9 +299,24 @@ pub const WaitResult = enum {
     cdp_socket,
 };
 
-pub fn findPage(self: *Session, frame_id: u32) ?*Page {
+pub fn findPageByFrameId(self: *Session, frame_id: u32) ?*Page {
     const page = self.currentPage() orelse return null;
-    return if (page._frame_id == frame_id) page else null;
+    return findPageBy(page, "_frame_id", frame_id);
+}
+
+pub fn findPageById(self: *Session, id: u32) ?*Page {
+    const page = self.currentPage() orelse return null;
+    return findPageBy(page, "id", id);
+}
+
+fn findPageBy(page: *Page, comptime field: []const u8, id: u32) ?*Page {
+    if (@field(page, field) == id) return page;
+    for (page.frames.items) |f| {
+        if (findPageBy(f, field, id)) |found| {
+            return found;
+        }
+    }
+    return null;
 }
 
 pub fn wait(self: *Session, wait_ms: u32) WaitResult {
@@ -636,3 +653,9 @@ pub fn nextFrameId(self: *Session) u32 {
     self.frame_id_gen = id;
     return id;
 }
+
+pub fn nextPageId(self: *Session) u32 {
+    const id = self.page_id_gen +% 1;
+    self.page_id_gen = id;
+    return id;
+}

src/browser/webapi/AbstractRange.zig

@@ -19,15 +19,22 @@
 const std = @import("std");
 const js = @import("../js/js.zig");
 
+const Session = @import("../Session.zig");
+
 const Node = @import("Node.zig");
 const Range = @import("Range.zig");
 
+const Allocator = std.mem.Allocator;
+const IS_DEBUG = @import("builtin").mode == .Debug;
+
 const AbstractRange = @This();
 
 pub const _prototype_root = true;
 
+_rc: u8,
 _type: Type,
-
+_page_id: u32,
+_arena: Allocator,
 _end_offset: u32,
 _start_offset: u32,
 _end_container: *Node,
@@ -36,6 +43,27 @@ _start_container: *Node,
 // Intrusive linked list node for tracking live ranges on the Page.
 _range_link: std.DoublyLinkedList.Node = .{},
 
+pub fn acquireRef(self: *AbstractRange) void {
+    self._rc += 1;
+}
+
+pub fn deinit(self: *AbstractRange, shutdown: bool, session: *Session) void {
+    _ = shutdown;
+    const rc = self._rc;
+    if (comptime IS_DEBUG) {
+        std.debug.assert(rc != 0);
+    }
+
+    if (rc == 1) {
+        if (session.findPageById(self._page_id)) |page| {
+            page._live_ranges.remove(&self._range_link);
+        }
+        session.releaseArena(self._arena);
+        return;
+    }
+    self._rc = rc - 1;
+}
+
 pub const Type = union(enum) {
     range: *Range,
     // TODO: static_range: *StaticRange,
@@ -310,6 +338,8 @@ pub const JsApi = struct {
         pub const name = "AbstractRange";
         pub const prototype_chain = bridge.prototypeChain();
         pub var class_id: bridge.ClassId = undefined;
+        pub const weak = true;
+        pub const finalizer = bridge.finalizer(AbstractRange.deinit);
     };
 
     pub const startContainer = bridge.accessor(AbstractRange.getStartContainer, null, .{});

src/browser/webapi/Range.zig

@@ -21,22 +21,31 @@ const String = @import("../../string.zig").String;
 
 const js = @import("../js/js.zig");
 const Page = @import("../Page.zig");
+const Session = @import("../Session.zig");
 
 const Node = @import("Node.zig");
 const DocumentFragment = @import("DocumentFragment.zig");
 const AbstractRange = @import("AbstractRange.zig");
 const DOMRect = @import("DOMRect.zig");
 
+const Allocator = std.mem.Allocator;
+
 const Range = @This();
 
 _proto: *AbstractRange,
 
-pub fn asAbstractRange(self: *Range) *AbstractRange {
-    return self._proto;
+pub fn init(page: *Page) !*Range {
+    const arena = try page.getArena(.{ .debug = "Range" });
+    errdefer page.releaseArena(arena);
+    return page._factory.abstractRange(arena, Range{ ._proto = undefined }, page);
 }
 
-pub fn init(page: *Page) !*Range {
-    return page._factory.abstractRange(Range{ ._proto = undefined }, page);
+pub fn deinit(self: *Range, shutdown: bool, session: *Session) void {
+    self._proto.deinit(shutdown, session);
+}
+
+pub fn asAbstractRange(self: *Range) *AbstractRange {
+    return self._proto;
 }
 
 pub fn setStart(self: *Range, node: *Node, offset: u32) !void {
@@ -309,7 +318,10 @@ pub fn intersectsNode(self: *const Range, node: *Node) bool {
 }
 
 pub fn cloneRange(self: *const Range, page: *Page) !*Range {
-    const clone = try page._factory.abstractRange(Range{ ._proto = undefined }, page);
+    const arena = try page.getArena(.{ .debug = "Range.clone" });
+    errdefer page.releaseArena(arena);
+
+    const clone = try page._factory.abstractRange(arena, Range{ ._proto = undefined }, page);
     clone._proto._end_offset = self._proto._end_offset;
     clone._proto._start_offset = self._proto._start_offset;
     clone._proto._end_container = self._proto._end_container;
@@ -687,6 +699,8 @@ pub const JsApi = struct {
         pub const name = "Range";
         pub const prototype_chain = bridge.prototypeChain();
         pub var class_id: bridge.ClassId = undefined;
+        pub const weak = true;
+        pub const finalizer = bridge.finalizer(Range.deinit);
     };
 
     // Constants for compareBoundaryPoints

src/browser/webapi/Selection.zig

@@ -21,6 +21,8 @@ const log = @import("../../log.zig");
 
 const js = @import("../js/js.zig");
 const Page = @import("../Page.zig");
+const Session = @import("../Session.zig");
+
 const Range = @import("Range.zig");
 const AbstractRange = @import("AbstractRange.zig");
 const Node = @import("Node.zig");
@@ -37,13 +39,22 @@ _direction: SelectionDirection = .none,
 
 pub const init: Selection = .{};
 
+pub fn deinit(self: *Selection, shutdown: bool, session: *Session) void {
+    if (self._range) |r| {
+        r.deinit(shutdown, session);
+        self._range = null;
+    }
+}
+
 fn dispatchSelectionChangeEvent(page: *Page) !void {
     const event = try Event.init("selectionchange", .{}, page);
     try page._event_manager.dispatch(page.document.asEventTarget(), event);
 }
 
 fn isInTree(self: *const Selection) bool {
-    if (self._range == null) return false;
+    if (self._range == null) {
+        return false;
+    }
     const anchor_node = self.getAnchorNode() orelse return false;
     const focus_node = self.getFocusNode() orelse return false;
     return anchor_node.isConnected() and focus_node.isConnected();
@@ -104,21 +115,33 @@ pub fn getIsCollapsed(self: *const Selection) bool {
 }
 
 pub fn getRangeCount(self: *const Selection) u32 {
-    if (self._range == null) return 0;
-    if (!self.isInTree()) return 0;
+    if (self._range == null) {
+        return 0;
+    }
+    if (!self.isInTree()) {
+        return 0;
+    }
 
     return 1;
 }
 
 pub fn getType(self: *const Selection) []const u8 {
-    if (self._range == null) return "None";
-    if (!self.isInTree()) return "None";
-    if (self.getIsCollapsed()) return "Caret";
+    if (self._range == null) {
+        return "None";
+    }
+    if (!self.isInTree()) {
+        return "None";
+    }
+    if (self.getIsCollapsed()) {
+        return "Caret";
+    }
     return "Range";
 }
 
 pub fn addRange(self: *Selection, range: *Range, page: *Page) !void {
-    if (self._range != null) return;
+    if (self._range != null) {
+        return;
+    }
 
     // Only add the range if its root node is in the document associated with this selection
     const start_node = range.asAbstractRange().getStartContainer();
@@ -126,22 +149,25 @@ pub fn addRange(self: *Selection, range: *Range, page: *Page) !void {
         return;
     }
 
-    self._range = range;
+    self.setRange(range, page);
     try dispatchSelectionChangeEvent(page);
 }
 
 pub fn removeRange(self: *Selection, range: *Range, page: *Page) !void {
-    if (self._range == range) {
-        self._range = null;
-        try dispatchSelectionChangeEvent(page);
-        return;
-    } else {
+    const existing_range = self._range orelse return error.NotFound;
+    if (existing_range != range) {
         return error.NotFound;
     }
+    self.setRange(null, page);
+    try dispatchSelectionChangeEvent(page);
 }
 
 pub fn removeAllRanges(self: *Selection, page: *Page) !void {
-    self._range = null;
+    if (self._range == null) {
+        return;
+    }
+
+    self.setRange(null, page);
     self._direction = .none;
     try dispatchSelectionChangeEvent(page);
 }
@@ -157,7 +183,7 @@ pub fn collapseToEnd(self: *Selection, page: *Page) !void {
     try new_range.setStart(last_node, last_offset);
     try new_range.setEnd(last_node, last_offset);
 
-    self._range = new_range;
+    self.setRange(new_range, page);
     self._direction = .none;
     try dispatchSelectionChangeEvent(page);
 }
@@ -173,7 +199,7 @@ pub fn collapseToStart(self: *Selection, page: *Page) !void {
     try new_range.setStart(first_node, first_offset);
     try new_range.setEnd(first_node, first_offset);
 
-    self._range = new_range;
+    self.setRange(new_range, page);
     self._direction = .none;
     try dispatchSelectionChangeEvent(page);
 }
@@ -255,7 +281,7 @@ pub fn extend(self: *Selection, node: *Node, _offset: ?u32, page: *Page) !void {
         },
     }
 
-    self._range = new_range;
+    self.setRange(new_range, page);
     try dispatchSelectionChangeEvent(page);
 }
 
@@ -560,7 +586,8 @@ fn applyModify(self: *Selection, alter: ModifyAlter, new_node: *Node, new_offset
             const new_range = try Range.init(page);
             try new_range.setStart(new_node, new_offset);
             try new_range.setEnd(new_node, new_offset);
-            self._range = new_range;
+
+            self.setRange(new_range, page);
             self._direction = .none;
             try dispatchSelectionChangeEvent(page);
         },
@@ -582,7 +609,7 @@ pub fn selectAllChildren(self: *Selection, parent: *Node, page: *Page) !void {
     const child_count = parent.getChildrenCount();
     try range.setEnd(parent, @intCast(child_count));
 
-    self._range = range;
+    self.setRange(range, page);
     self._direction = .forward;
     try dispatchSelectionChangeEvent(page);
 }
@@ -630,7 +657,7 @@ pub fn setBaseAndExtent(
         },
     }
 
-    self._range = range;
+    self.setRange(range, page);
     try dispatchSelectionChangeEvent(page);
 }
 
@@ -656,7 +683,7 @@ pub fn collapse(self: *Selection, _node: ?*Node, _offset: ?u32, page: *Page) !vo
     try range.setStart(node, offset);
     try range.setEnd(node, offset);
 
-    self._range = range;
+    self.setRange(range, page);
     self._direction = .none;
     try dispatchSelectionChangeEvent(page);
 }
@@ -666,6 +693,16 @@ pub fn toString(self: *const Selection, page: *Page) ![]const u8 {
     return try range.toString(page);
 }
 
+fn setRange(self: *Selection, new_range: ?*Range, page: *Page) void {
+    if (self._range) |existing| {
+        existing.deinit(false, page._session);
+    }
+    if (new_range) |nr| {
+        nr.asAbstractRange().acquireRef();
+    }
+    self._range = new_range;
+}
+
 pub const JsApi = struct {
     pub const bridge = js.Bridge(Selection);
 
@@ -673,6 +710,7 @@ pub const JsApi = struct {
         pub const name = "Selection";
         pub const prototype_chain = bridge.prototypeChain();
         pub var class_id: bridge.ClassId = undefined;
+        pub const finalizer = bridge.finalizer(Selection.deinit);
     };
 
     pub const anchorNode = bridge.accessor(Selection.getAnchorNode, null, .{});

src/cdp/domains/accessibility.zig

@@ -53,8 +53,8 @@ fn getFullAXTree(cmd: anytype) !void {
         const frame_id = params.frameId orelse {
             break :blk session.currentPage() orelse return error.PageNotLoaded;
         };
-        const page_id = try id.toPageId(.frame_id, frame_id);
-        break :blk session.findPage(page_id) orelse {
+        const page_frame_id = try id.toPageId(.frame_id, frame_id);
+        break :blk session.findPageByFrameId(page_frame_id) orelse {
             return cmd.sendError(-32000, "Frame with the given id does not belong to the target.", .{});
         };
     };

src/cdp/domains/dom.zig

@@ -502,9 +502,9 @@ fn getFrameOwner(cmd: anytype) !void {
     })) orelse return error.InvalidParams;
 
     const bc = cmd.browser_context orelse return error.BrowserContextNotLoaded;
-    const page_id = try id.toPageId(.frame_id, params.frameId);
+    const page_frame_id = try id.toPageId(.frame_id, params.frameId);
 
-    const page = bc.session.findPage(page_id) orelse {
+    const page = bc.session.findPageByFrameId(page_frame_id) orelse {
         return cmd.sendError(-32000, "Frame with the given id does not belong to the target.", .{});
     };
 

src/cdp/domains/network.zig

@@ -238,7 +238,7 @@ pub fn httpRequestStart(bc: anytype, msg: *const Notification.RequestStart) !voi
     const transfer = msg.transfer;
     const req = &transfer.req;
     const frame_id = req.frame_id;
-    const page = bc.session.findPage(frame_id) orelse return;
+    const page = bc.session.findPageByFrameId(frame_id) orelse return;
 
     // Modify request with extra CDP headers
     for (bc.extra_headers.items) |extra| {