Browser: Add Accessibility Tab to Inspector Widget

This tab allows you to view the accessibility tree like you do
the DOM tree. The implementation limited to the role currently,
once we add the name and description calculation algorithm, those
will be displayed here as well. Selections are also not currently
supported.

Userland/Libraries/LibWebView/AccessibilityTreeModel.cpp

@@ -0,0 +1,117 @@
+/*
+ * Copyright (c) 2022, Jonah Shafran <jonahshafran@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWebView/AccessibilityTreeModel.h>
+
+namespace WebView {
+
+AccessibilityTreeModel::AccessibilityTreeModel(JsonObject accessibility_tree, GUI::TreeView* tree_view)
+    : m_tree_view(tree_view)
+    , m_accessibility_tree(move(accessibility_tree))
+{
+    map_accessibility_nodes_to_parent(nullptr, &m_accessibility_tree);
+}
+
+AccessibilityTreeModel::~AccessibilityTreeModel() = default;
+
+GUI::ModelIndex AccessibilityTreeModel::index(int row, int column, GUI::ModelIndex const& parent) const
+{
+    if (!parent.is_valid()) {
+        return create_index(row, column, &m_accessibility_tree);
+    }
+
+    auto const& parent_node = *static_cast<JsonObject const*>(parent.internal_data());
+    auto const* children = get_children(parent_node);
+    if (!children)
+        return create_index(row, column, &m_accessibility_tree);
+
+    auto const& child_node = children->at(row).as_object();
+    return create_index(row, column, &child_node);
+}
+
+GUI::ModelIndex AccessibilityTreeModel::parent_index(GUI::ModelIndex const& index) const
+{
+    if (!index.is_valid())
+        return {};
+
+    auto const& node = *static_cast<JsonObject const*>(index.internal_data());
+
+    auto const* parent_node = get_parent(node);
+    if (!parent_node)
+        return {};
+
+    // If the parent is the root document, we know it has index 0, 0
+    if (parent_node == &m_accessibility_tree) {
+        return create_index(0, 0, parent_node);
+    }
+
+    // Otherwise, we need to find the grandparent, to find the index of parent within that
+    auto const* grandparent_node = get_parent(*parent_node);
+    VERIFY(grandparent_node);
+
+    auto const* grandparent_children = get_children(*grandparent_node);
+    if (!grandparent_children)
+        return {};
+
+    for (size_t grandparent_child_index = 0; grandparent_child_index < grandparent_children->size(); ++grandparent_child_index) {
+        auto const& child = grandparent_children->at(grandparent_child_index).as_object();
+        if (&child == parent_node)
+            return create_index(grandparent_child_index, 0, parent_node);
+    }
+
+    return {};
+}
+
+int AccessibilityTreeModel::row_count(GUI::ModelIndex const& index) const
+{
+    if (!index.is_valid())
+        return 1;
+
+    auto const& node = *static_cast<JsonObject const*>(index.internal_data());
+    auto const* children = get_children(node);
+    return children ? children->size() : 0;
+}
+
+int AccessibilityTreeModel::column_count(const GUI::ModelIndex&) const
+{
+    return 1;
+}
+
+GUI::Variant AccessibilityTreeModel::data(GUI::ModelIndex const& index, GUI::ModelRole role) const
+{
+    auto const& node = *static_cast<JsonObject const*>(index.internal_data());
+    auto type = node.get("type"sv).as_string_or("unknown"sv);
+
+    if (role == GUI::ModelRole::Display) {
+        if (type == "text")
+            return node.get("text"sv).as_string();
+
+        auto node_role = node.get("role"sv).as_string();
+        if (type != "element")
+            return node_role;
+
+        StringBuilder builder;
+        builder.append(node_role.to_lowercase());
+        return builder.to_deprecated_string();
+    }
+    return {};
+}
+
+void AccessibilityTreeModel::map_accessibility_nodes_to_parent(JsonObject const* parent, JsonObject const* node)
+{
+    m_accessibility_node_to_parent_map.set(node, parent);
+
+    auto const* children = get_children(*node);
+    if (!children)
+        return;
+
+    children->for_each([&](auto const& child) {
+        auto const& child_node = child.as_object();
+        map_accessibility_nodes_to_parent(node, &child_node);
+    });
+}
+
+}