LibWeb: Implement a large chunk of the Selection API

This patch implements enough of the Selection API specification
that we stop hitting unimplemented functions when loading Twitter.

1 files changed, 235 insertions, 38 deletions

diff --git a/Userland/Libraries/LibWeb/Selection/Selection.cpp b/Userland/Libraries/LibWeb/Selection/Selection.cpp
index 250bcb48b8..20f7dbef30 100644
--- a/Userland/Libraries/LibWeb/Selection/Selection.cpp
+++ b/Userland/Libraries/LibWeb/Selection/Selection.cpp
@@ -1,117 +1,243 @@
 /*
- * Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2021-2022, Andreas Kling <kling@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
 #include <LibWeb/Bindings/Intrinsics.h>
+#include <LibWeb/DOM/Document.h>
+#include <LibWeb/DOM/Range.h>
 #include <LibWeb/Selection/Selection.h>
 
 namespace Web::Selection {
 
-JS::NonnullGCPtr<Selection> Selection::create(JS::Realm& realm)
+JS::NonnullGCPtr<Selection> Selection::create(JS::NonnullGCPtr<JS::Realm> realm, JS::NonnullGCPtr<DOM::Document> document)
 {
-    return *realm.heap().allocate<Selection>(realm, realm);
+    return *realm->heap().allocate<Selection>(realm, realm, document);
 }
 
-Selection::Selection(JS::Realm& realm)
+Selection::Selection(JS::NonnullGCPtr<JS::Realm> realm, JS::NonnullGCPtr<DOM::Document> document)
     : PlatformObject(realm)
+    , m_document(document)
 {
     set_prototype(&Bindings::cached_web_prototype(realm, "Selection"));
 }
 
 Selection::~Selection() = default;
 
-DOM::Node* Selection::anchor_node()
+// https://w3c.github.io/selection-api/#dfn-empty
+bool Selection::is_empty() const
 {
-    TODO();
+    // Each selection can be associated with a single range.
+    // When there is no range associated with the selection, the selection is empty.
+    // The selection must be initially empty.
+
+    // NOTE: This function should not be confused with Selection.empty() which empties the selection.
+    return !m_range;
 }
 
+void Selection::visit_edges(Cell::Visitor& visitor)
+{
+    Base::visit_edges(visitor);
+    visitor.visit(m_range);
+    visitor.visit(m_document);
+}
+
+// https://w3c.github.io/selection-api/#dfn-anchor
+JS::GCPtr<DOM::Node> Selection::anchor_node()
+{
+    if (!m_range)
+        return nullptr;
+    if (m_direction == Direction::Forwards)
+        return m_range->start_container();
+    return m_range->end_container();
+}
+
+// https://w3c.github.io/selection-api/#dfn-anchor
 unsigned Selection::anchor_offset()
 {
-    TODO();
+    if (!m_range)
+        return 0;
+    if (m_direction == Direction::Forwards)
+        return m_range->start_offset();
+    return m_range->end_offset();
 }
 
-DOM::Node* Selection::focus_node()
+// https://w3c.github.io/selection-api/#dfn-focus
+JS::GCPtr<DOM::Node> Selection::focus_node()
 {
-    TODO();
+    if (!m_range)
+        return nullptr;
+    if (m_direction == Direction::Forwards)
+        return m_range->end_container();
+    return m_range->start_container();
 }
 
+// https://w3c.github.io/selection-api/#dfn-focus
 unsigned Selection::focus_offset() const
 {
-    TODO();
+    if (!m_range)
+        return 0;
+    if (m_direction == Direction::Forwards)
+        return m_range->end_offset();
+    return m_range->start_offset();
 }
 
+// https://w3c.github.io/selection-api/#dom-selection-iscollapsed
 bool Selection::is_collapsed() const
 {
-    TODO();
+    // The attribute must return true if and only if the anchor and focus are the same
+    // (including if both are null). Otherwise it must return false.
+    return const_cast<Selection*>(this)->anchor_node() == const_cast<Selection*>(this)->focus_node();
 }
 
+// https://w3c.github.io/selection-api/#dom-selection-rangecount
 unsigned Selection::range_count() const
 {
-    TODO();
+    if (m_range)
+        return 1;
+    return 0;
 }
 
 String Selection::type() const
 {
-    TODO();
+    if (!m_range)
+        return "None";
+    if (m_range->collapsed())
+        return "Caret";
+    return "Range";
 }
 
-DOM::Range* Selection::get_range_at(unsigned index)
+// https://w3c.github.io/selection-api/#dom-selection-getrangeat
+WebIDL::ExceptionOr<JS::GCPtr<DOM::Range>> Selection::get_range_at(unsigned index)
 {
-    (void)index;
-    TODO();
+    // The method must throw an IndexSizeError exception if index is not 0, or if this is empty.
+    if (index != 0 || is_empty())
+        return WebIDL::IndexSizeError::create(realm(), "Selection.getRangeAt() on empty Selection or with invalid argument"sv);
+
+    // Otherwise, it must return a reference to (not a copy of) this's range.
+    return m_range;
 }
 
-void Selection::add_range(DOM::Range&)
+// https://w3c.github.io/selection-api/#dom-selection-addrange
+void Selection::add_range(JS::NonnullGCPtr<DOM::Range> range)
 {
-    TODO();
+    // 1. If the root of the range's boundary points are not the document associated with this, abort these steps.
+    if (&range->start_container()->root() != m_document.ptr())
+        return;
+
+    // 2. If rangeCount is not 0, abort these steps.
+    if (range_count() != 0)
+        return;
+
+    // 3. Set this's range to range by a strong reference (not by making a copy).
+    m_range = range;
 }
 
-void Selection::remove_range(DOM::Range&)
+// https://w3c.github.io/selection-api/#dom-selection-removerange
+WebIDL::ExceptionOr<void> Selection::remove_range(JS::NonnullGCPtr<DOM::Range> range)
 {
-    TODO();
+    // The method must make this empty by disassociating its range if this's range is range.
+    if (m_range == range) {
+        m_range = nullptr;
+        return {};
+    }
+
+    // Otherwise, it must throw a NotFoundError.
+    return WebIDL::NotFoundError::create(realm(), "Selection.removeRange() with invalid argument"sv);
 }
 
+// https://w3c.github.io/selection-api/#dom-selection-removeallranges
 void Selection::remove_all_ranges()
 {
-    TODO();
+    // The method must make this empty by disassociating its range if this has an associated range.
+    m_range = nullptr;
 }
 
+// https://w3c.github.io/selection-api/#dom-selection-empty
 void Selection::empty()
 {
-    TODO();
+    // The method must be an alias, and behave identically, to removeAllRanges().
+    remove_all_ranges();
 }
 
-void Selection::collapse(DOM::Node*, unsigned offset)
+// https://w3c.github.io/selection-api/#dom-selection-collapse
+void Selection::collapse(JS::GCPtr<DOM::Node>, unsigned offset)
 {
     (void)offset;
     TODO();
 }
 
-void Selection::set_position(DOM::Node*, unsigned offset)
+// https://w3c.github.io/selection-api/#dom-selection-setposition
+void Selection::set_position(JS::GCPtr<DOM::Node> node, unsigned offset)
 {
-    (void)offset;
-    TODO();
+    // The method must be an alias, and behave identically, to collapse().
+    collapse(node, offset);
 }
 
+// https://w3c.github.io/selection-api/#dom-selection-collapsetostart
 void Selection::collapse_to_start()
 {
     TODO();
 }
 
+// https://w3c.github.io/selection-api/#dom-selection-collapsetoend
 void Selection::collapse_to_end()
 {
     TODO();
 }
 
-void Selection::extend(DOM::Node&, unsigned offset)
+// https://w3c.github.io/selection-api/#dom-selection-extend
+WebIDL::ExceptionOr<void> Selection::extend(JS::NonnullGCPtr<DOM::Node> node, unsigned offset)
 {
-    (void)offset;
-    TODO();
+    // 1. If node's root is not the document associated with this, abort these steps.
+    if (&node->root() != m_document.ptr())
+        return {};
+
+    // 2. If this is empty, throw an InvalidStateError exception and abort these steps.
+    if (!m_range) {
+        return WebIDL::InvalidStateError::create(realm(), "Selection.extend() on empty range"sv);
+    }
+
+    // 3. Let oldAnchor and oldFocus be the this's anchor and focus, and let newFocus be the boundary point (node, offset).
+    auto& old_anchor_node = *anchor_node();
+    auto old_anchor_offset = anchor_offset();
+
+    auto& new_focus_node = node;
+    auto new_focus_offset = offset;
+
+    // 4. Let newRange be a new range.
+    auto new_range = DOM::Range::create(*m_document);
+
+    // 5. If node's root is not the same as the this's range's root, set the start newRange's start and end to newFocus.
+    if (&node->root() != &m_range->start_container()->root()) {
+        new_range->set_start(new_focus_node, new_focus_offset);
+    }
+    // 6. Otherwise, if oldAnchor is before or equal to newFocus, set the start newRange's start to oldAnchor, then set its end to newFocus.
+    else if (old_anchor_node.is_before(new_focus_node) || &old_anchor_node == new_focus_node.ptr()) {
+        new_range->set_end(new_focus_node, new_focus_offset);
+    }
+    // 7. Otherwise, set the start newRange's start to newFocus, then set its end to oldAnchor.
+    else {
+        new_range->set_start(new_focus_node, new_focus_offset);
+        new_range->set_end(old_anchor_node, old_anchor_offset);
+    }
+
+    // 8. Set this's range to newRange.
+    m_range = new_range;
+
+    // 9. If newFocus is before oldAnchor, set this's direction to backwards. Otherwise, set it to forwards.
+    if (new_focus_node->is_before(old_anchor_node)) {
+        m_direction = Direction::Backwards;
+    } else {
+        m_direction = Direction::Forwards;
+    }
+
+    return {};
 }
 
-void Selection::set_base_and_extent(DOM::Node& anchor_node, unsigned anchor_offset, DOM::Node& focus_node, unsigned focus_offset)
+// https://w3c.github.io/selection-api/#dom-selection-setbaseandextent
+void Selection::set_base_and_extent(JS::NonnullGCPtr<DOM::Node> anchor_node, unsigned anchor_offset, JS::NonnullGCPtr<DOM::Node> focus_node, unsigned focus_offset)
 {
     (void)anchor_node;
     (void)anchor_offset;
@@ -120,25 +246,96 @@ void Selection::set_base_and_extent(DOM::Node& anchor_node, unsigned anchor_offs
     TODO();
 }
 
-void Selection::select_all_children(DOM::Node&)
+// https://w3c.github.io/selection-api/#dom-selection-selectallchildren
+WebIDL::ExceptionOr<void> Selection::select_all_children(JS::NonnullGCPtr<DOM::Node> node)
 {
-    TODO();
+    // 1. If node's root is not the document associated with this, abort these steps.
+    if (&node->root() != m_document.ptr())
+        return {};
+
+    // 2. Let newRange be a new range and childCount be the number of children of node.
+    auto new_range = DOM::Range::create(*m_document);
+    auto child_count = node->child_count();
+
+    // 3. Set newRange's start to (node, 0).
+    TRY(new_range->set_start(node, 0));
+
+    // 4. Set newRange's end to (node, childCount).
+    TRY(new_range->set_end(node, child_count));
+
+    // 5. Set this's range to newRange.
+    m_range = new_range;
+
+    // 6. Set this's direction to forwards.
+    m_direction = Direction::Forwards;
+
+    return {};
 }
 
-void Selection::delete_from_document()
+// https://w3c.github.io/selection-api/#dom-selection-deletefromdocument
+WebIDL::ExceptionOr<void> Selection::delete_from_document()
 {
-    TODO();
+    // The method must invoke deleteContents() on this's range if this is not empty.
+    // Otherwise the method must do nothing.
+    if (!is_empty())
+        return m_range->delete_contents();
+    return {};
 }
 
-bool Selection::contains_node(DOM::Node&, bool allow_partial_containment) const
+// https://w3c.github.io/selection-api/#dom-selection-containsnode
+bool Selection::contains_node(JS::NonnullGCPtr<DOM::Node> node, bool allow_partial_containment) const
 {
-    (void)allow_partial_containment;
-    TODO();
+    // The method must return false if this is empty or if node's root is not the document associated with this.
+    if (!m_range)
+        return false;
+    if (&node->root() != m_document.ptr())
+        return false;
+
+    // Otherwise, if allowPartialContainment is false, the method must return true if and only if
+    // start of its range is before or visually equivalent to the first boundary point in the node
+    // and end of its range is after or visually equivalent to the last boundary point in the node.
+    if (!allow_partial_containment) {
+        auto start_relative_position = DOM::position_of_boundary_point_relative_to_other_boundary_point(
+            *m_range->start_container(),
+            m_range->start_offset(),
+            node,
+            0);
+        auto end_relative_position = DOM::position_of_boundary_point_relative_to_other_boundary_point(
+            *m_range->end_container(),
+            m_range->end_offset(),
+            node,
+            node->length());
+
+        return (start_relative_position == DOM::RelativeBoundaryPointPosition::Before || start_relative_position == DOM::RelativeBoundaryPointPosition::Equal)
+            && (end_relative_position == DOM::RelativeBoundaryPointPosition::Equal || end_relative_position == DOM::RelativeBoundaryPointPosition::After);
+    }
+
+    // If allowPartialContainment is true, the method must return true if and only if
+    // start of its range is before or visually equivalent to the last boundary point in the node
+    // and end of its range is after or visually equivalent to the first boundary point in the node.
+
+    auto start_relative_position = DOM::position_of_boundary_point_relative_to_other_boundary_point(
+        *m_range->start_container(),
+        m_range->start_offset(),
+        node,
+        node->length());
+    auto end_relative_position = DOM::position_of_boundary_point_relative_to_other_boundary_point(
+        *m_range->end_container(),
+        m_range->end_offset(),
+        node,
+        0);
+
+    return (start_relative_position == DOM::RelativeBoundaryPointPosition::Before || start_relative_position == DOM::RelativeBoundaryPointPosition::Equal)
+        && (end_relative_position == DOM::RelativeBoundaryPointPosition::Equal || end_relative_position == DOM::RelativeBoundaryPointPosition::After);
 }
 
 String Selection::to_string() const
 {
-    TODO();
+    // FIXME: This needs more work to be compatible with other engines.
+    //        See https://www.w3.org/Bugs/Public/show_bug.cgi?id=10583
+    if (!m_range)
+        return String::empty();
+    return m_range->to_string();
 }
 
 }