LibWeb: Implement user-select

This implements all values of user-select.

Libraries/LibWeb/CSS/ComputedProperties.cpp

@@ -1395,6 +1395,12 @@ Optional<CSS::WritingMode> ComputedProperties::writing_mode() const
     return keyword_to_writing_mode(value.to_keyword());
 }
 
+Optional<CSS::UserSelect> ComputedProperties::user_select() const
+{
+    auto const& value = property(CSS::PropertyID::UserSelect);
+    return keyword_to_user_select(value.to_keyword());
+}
+
 Optional<CSS::MaskType> ComputedProperties::mask_type() const
 {
     auto const& value = property(CSS::PropertyID::MaskType);

Libraries/LibWeb/CSS/ComputedProperties.h

@@ -158,6 +158,7 @@ class ComputedProperties final : public JS::Cell {
     Optional<CSS::Direction> direction() const;
     Optional<CSS::UnicodeBidi> unicode_bidi() const;
     Optional<CSS::WritingMode> writing_mode() const;
+    Optional<CSS::UserSelect> user_select() const;
 
     static Vector<CSS::Transformation> transformations_for_style_value(CSSStyleValue const& value);
     Vector<CSS::Transformation> transformations() const;

Libraries/LibWeb/CSS/ComputedValues.h

@@ -168,6 +168,7 @@ class InitialValues {
     static CSS::Direction direction() { return CSS::Direction::Ltr; }
     static CSS::UnicodeBidi unicode_bidi() { return CSS::UnicodeBidi::Normal; }
     static CSS::WritingMode writing_mode() { return CSS::WritingMode::HorizontalTb; }
+    static CSS::UserSelect user_select() { return CSS::UserSelect::Auto; }
 
     // https://www.w3.org/TR/SVG/geometry.html
     static LengthPercentage cx() { return CSS::Length::make_px(0); }
@@ -421,6 +422,7 @@ class ComputedValues {
     CSS::Direction direction() const { return m_inherited.direction; }
     CSS::UnicodeBidi unicode_bidi() const { return m_noninherited.unicode_bidi; }
     CSS::WritingMode writing_mode() const { return m_inherited.writing_mode; }
+    CSS::UserSelect user_select() const { return m_noninherited.user_select; }
 
     CSS::LengthBox const& inset() const { return m_noninherited.inset; }
     const CSS::LengthBox& margin() const { return m_noninherited.margin; }
@@ -671,6 +673,8 @@ class ComputedValues {
         CSS::ObjectFit object_fit { InitialValues::object_fit() };
         CSS::ObjectPosition object_position { InitialValues::object_position() };
         CSS::UnicodeBidi unicode_bidi { InitialValues::unicode_bidi() };
+        CSS::UserSelect user_select { InitialValues::user_select() };
+
         Optional<CSS::Transformation> rotate;
         Optional<CSS::Transformation> translate;
         Optional<CSS::Transformation> scale;
@@ -841,6 +845,7 @@ class MutableComputedValues final : public ComputedValues {
     void set_direction(CSS::Direction value) { m_inherited.direction = value; }
     void set_unicode_bidi(CSS::UnicodeBidi value) { m_noninherited.unicode_bidi = value; }
     void set_writing_mode(CSS::WritingMode value) { m_inherited.writing_mode = value; }
+    void set_user_select(CSS::UserSelect value) { m_noninherited.user_select = value; }
 
     void set_fill(SVGPaint value) { m_inherited.fill = move(value); }
     void set_stroke(SVGPaint value) { m_inherited.stroke = move(value); }

Libraries/LibWeb/CSS/Enums.json

@@ -538,6 +538,13 @@
     "normal",
     "plaintext"
   ],
+  "user-select": [
+    "all",
+    "auto",
+    "contain",
+    "none",
+    "text"
+  ],
   "vertical-align": [
     "baseline",
     "bottom",

Libraries/LibWeb/CSS/Properties.json

@@ -2819,12 +2819,8 @@
     "animation-type": "discrete",
     "inherited": false,
     "initial": "auto",
-    "valid-identifiers": [
-      "all",
-      "auto",
-      "contain",
-      "none",
-      "text"
+    "valid-types": [
+      "user-select"
     ]
   },
   "vertical-align": {

Libraries/LibWeb/Layout/Node.cpp

@@ -22,6 +22,7 @@
 #include <LibWeb/CSS/StyleValues/URLStyleValue.h>
 #include <LibWeb/DOM/Document.h>
 #include <LibWeb/Dump.h>
+#include <LibWeb/HTML/FormAssociatedElement.h>
 #include <LibWeb/HTML/HTMLHtmlElement.h>
 #include <LibWeb/Layout/BlockContainer.h>
 #include <LibWeb/Layout/FormattingContext.h>
@@ -996,6 +997,9 @@ void NodeWithStyle::apply_style(const CSS::ComputedProperties& computed_style)
     if (auto writing_mode = computed_style.writing_mode(); writing_mode.has_value())
         computed_values.set_writing_mode(writing_mode.value());
 
+    if (auto user_select = computed_style.user_select(); user_select.has_value())
+        computed_values.set_user_select(user_select.value());
+
     propagate_style_to_anonymous_wrappers();
 }
 
@@ -1206,4 +1210,53 @@ DOM::Document const& Node::document() const
     return m_dom_node->document();
 }
 
+// https://drafts.csswg.org/css-ui/#propdef-user-select
+CSS::UserSelect Node::user_select_used_value() const
+{
+    // The used value is the same as the computed value, except:
+    auto computed_value = computed_values().user_select();
+
+    // 1. on editable elements where the used value is always 'contain' regardless of the computed value
+
+    // 2. when the computed value is 'auto', in which case the used value is one of the other values as defined below
+
+    // For the purpose of this specification, an editable element is either an editing host or a mutable form control with
+    // textual content, such as textarea.
+    auto* form_control = dynamic_cast<HTML::FormAssociatedTextControlElement const*>(dom_node());
+    // FIXME: Check if this needs to exclude input elements with types such as color or range, and if so, which ones exactly.
+    if ((dom_node() && dom_node()->is_editing_host()) || (form_control && form_control->is_mutable())) {
+        return CSS::UserSelect::Contain;
+    } else if (computed_value == CSS::UserSelect::Auto) {
+        // The used value of 'auto' is determined as follows:
+        // - On the '::before' and '::after' pseudo-elements, the used value is 'none'
+        if (is_generated_for_before_pseudo_element() || is_generated_for_after_pseudo_element()) {
+            return CSS::UserSelect::None;
+        }
+
+        // - If the element is an editable element, the used value is 'contain'
+        // NOTE: We already handled this above.
+
+        auto parent_element = parent();
+        if (parent_element) {
+            auto parent_used_value = parent_element->user_select_used_value();
+
+            // - Otherwise, if the used value of user-select on the parent of this element is 'all', the used value is 'all'
+            if (parent_used_value == CSS::UserSelect::All) {
+                return CSS::UserSelect::All;
+            }
+
+            // - Otherwise, if the used value of user-select on the parent of this element is 'none', the used value is
+            //   'none'
+            if (parent_used_value == CSS::UserSelect::None) {
+                return CSS::UserSelect::None;
+            }
+        }
+
+        // - Otherwise, the used value is 'text'
+        return CSS::UserSelect::Text;
+    }
+
+    return computed_value;
+}
+
 }

Libraries/LibWeb/Layout/Node.h

@@ -188,6 +188,9 @@ class Node
         return false;
     }
 
+    // https://drafts.csswg.org/css-ui/#propdef-user-select
+    CSS::UserSelect user_select_used_value() const;
+
 protected:
     Node(DOM::Document&, DOM::Node*);
 

Libraries/LibWeb/Page/EventHandler.cpp

@@ -187,6 +187,137 @@ static CSSPixelPoint compute_mouse_event_offset(CSSPixelPoint position, Painting
     return offset;
 }
 
+// https://drafts.csswg.org/css-ui/#propdef-user-select
+static void set_user_selection(GC::Ptr<DOM::Node> anchor_node, unsigned anchor_offset, GC::Ptr<DOM::Node> focus_node, unsigned focus_offset, Selection::Selection* selection, CSS::UserSelect user_select)
+{
+    // https://drafts.csswg.org/css-ui/#valdef-user-select-contain
+    // NOTE: This is clamping the focus node to any node with user-select: contain that stands between it and the anchor node.
+    if (focus_node != anchor_node) {
+        // UAs must not allow a selection which is started in this element to be extended outside of this element.
+        auto potential_contain_node = anchor_node;
+
+        // NOTE: The way we do this is searching up the tree from the anchor, to find 'this element', i.e. its nearest contain ancestor.
+        //       We stop the search early when we reach an element that contains both the anchor and the focus node, as this means they
+        //       are inside the same contain element, or not in a contain element at all.
+        //       This takes care of the "selection trying to escape from a contain" case.
+        while (
+            (!potential_contain_node->is_element() || potential_contain_node->layout_node()->user_select_used_value() != CSS::UserSelect::Contain) && potential_contain_node->parent() && !potential_contain_node->is_inclusive_ancestor_of(*focus_node)) {
+            potential_contain_node = potential_contain_node->parent();
+        }
+
+        if (
+            potential_contain_node->layout_node()->user_select_used_value() == CSS::UserSelect::Contain && !potential_contain_node->is_inclusive_ancestor_of(*focus_node)) {
+            if (focus_node->is_before(*potential_contain_node)) {
+                focus_offset = 0;
+            } else {
+                focus_offset = potential_contain_node->length();
+            }
+            focus_node = potential_contain_node;
+            // NOTE: Prevents this from being handled again further down
+            user_select = CSS::UserSelect::Contain;
+        } else {
+            // A selection started outside of this element must not end in this element. If the user attempts to create such a
+            // selection, the UA must instead end the selection range at the element boundary.
+
+            // NOTE: This branch takes care of the "selection trying to intrude into a contain" case.
+            //       This is done by searching up the tree from the focus node, to see if there is a
+            //       contain element between it and the common ancestor that also includes the anchor.
+            //       We stop once reaching target_node, which is the common ancestor identified in step 1.
+            //       If target_node wasn't a common ancestor, we would not be here.
+            auto target_node = potential_contain_node;
+            potential_contain_node = focus_node;
+            while (
+                (!potential_contain_node->is_element() || potential_contain_node->layout_node()->user_select_used_value() != CSS::UserSelect::Contain) && potential_contain_node->parent() && potential_contain_node != target_node) {
+                potential_contain_node = potential_contain_node->parent();
+            }
+            if (
+                potential_contain_node->layout_node()->user_select_used_value() == CSS::UserSelect::Contain && !potential_contain_node->is_inclusive_ancestor_of(*anchor_node)) {
+                if (potential_contain_node->is_before(*anchor_node)) {
+                    focus_node = potential_contain_node->next_in_pre_order();
+                    while (potential_contain_node->is_inclusive_ancestor_of(*focus_node)) {
+                        focus_node = focus_node->next_in_pre_order();
+                    }
+                    focus_offset = 0;
+                } else {
+                    focus_node = potential_contain_node->previous_in_pre_order();
+                    while (potential_contain_node->is_inclusive_ancestor_of(*focus_node)) {
+                        focus_node = focus_node->previous_in_pre_order();
+                    }
+                    focus_offset = focus_node->length();
+                }
+                // NOTE: Prevents this from being handled again further down
+                user_select = CSS::UserSelect::Contain;
+            }
+        }
+    }
+
+    switch (user_select) {
+    case CSS::UserSelect::None:
+        // https://drafts.csswg.org/css-ui/#valdef-user-select-none
+
+        // The UA must not allow selections to be started in this element.
+        if (anchor_node == focus_node) {
+            return;
+        }
+
+        // A selection started outside of this element must not end in this element. If the user attempts to create such a
+        // selection, the UA must instead end the selection range at the element boundary.
+        if (focus_node->is_before(*anchor_node)) {
+            do {
+                focus_node = focus_node->next_in_pre_order();
+            } while (focus_node->layout_node()->user_select_used_value() == CSS::UserSelect::None);
+            focus_offset = 0;
+        } else {
+            do {
+                focus_node = focus_node->previous_in_pre_order();
+            } while (focus_node->layout_node()->user_select_used_value() == CSS::UserSelect::None);
+            focus_offset = focus_node->length();
+        }
+        break;
+    case CSS::UserSelect::All:
+        // https://drafts.csswg.org/css-ui/#valdef-user-select-all
+
+        // The content of the element must be selected atomically: If a selection would contain part of the element,
+        // then the selection must contain the entire element including all its descendants. If the element is selected
+        // and the used value of 'user-select' on its parent is 'all', then the parent must be included in the selection,
+        // recursively.
+        while (focus_node->parent() && focus_node->parent()->layout_node()->user_select_used_value() == CSS::UserSelect::All) {
+            if (anchor_node == focus_node) {
+                anchor_node = focus_node->parent();
+            }
+            focus_node = focus_node->parent();
+        }
+
+        if (focus_node == anchor_node) {
+            if (anchor_offset > focus_offset) {
+                anchor_offset = focus_node->length();
+                focus_offset = 0;
+            } else {
+                anchor_offset = 0;
+                focus_offset = focus_node->length();
+            }
+        } else if (focus_node->is_before(*anchor_node)) {
+            focus_offset = 0;
+        } else {
+            focus_offset = focus_node->length();
+        }
+        break;
+    case CSS::UserSelect::Contain:
+        // NOTE: This is handled at the start of this function
+        break;
+    case CSS::UserSelect::Text:
+        // https://drafts.csswg.org/css-ui/#valdef-user-select-text
+
+        // The element imposes no constraint on the selection.
+        break;
+    case CSS::UserSelect::Auto:
+        VERIFY_NOT_REACHED();
+        break;
+    }
+
+    (void)selection->set_base_and_extent(*anchor_node, anchor_offset, *focus_node, focus_offset);
+}
+
 EventHandler::EventHandler(Badge<HTML::Navigable>, HTML::Navigable& navigable)
     : m_navigable(navigable)
     , m_drag_and_drop_event_handler(make<DragAndDropEventHandler>())
@@ -502,23 +633,29 @@ EventResult EventHandler::handle_mousedown(CSSPixelPoint viewport_position, CSSP
                 else if (auto* focused_element = document->focused_element())
                     HTML::run_unfocusing_steps(focused_element);
 
-                auto target = document->active_input_events_target();
-                if (target) {
-                    m_in_mouse_selection = true;
-                    m_mouse_selection_target = target;
-                    if (modifiers & UIEvents::KeyModifier::Mod_Shift) {
-                        target->set_selection_focus(*dom_node, result->index_in_node);
-                    } else {
-                        target->set_selection_anchor(*dom_node, result->index_in_node);
-                    }
-                } else if (!focus_candidate) {
-                    m_in_mouse_selection = true;
-                    if (auto selection = document->get_selection()) {
-                        auto anchor_node = selection->anchor_node();
-                        if (anchor_node && modifiers & UIEvents::KeyModifier::Mod_Shift) {
-                            (void)selection->set_base_and_extent(*anchor_node, selection->anchor_offset(), *dom_node, result->index_in_node);
+                // https://drafts.csswg.org/css-ui/#valdef-user-select-none
+                // Attempting to start a selection in an element where user-select is none, such as by clicking in it or starting
+                // a drag in it, must not cause a pre-existing selection to become unselected or to be affected in any way.
+                auto user_select = paintable->layout_node().user_select_used_value();
+                if (user_select != CSS::UserSelect::None) {
+                    auto target = document->active_input_events_target();
+                    if (target) {
+                        m_in_mouse_selection = true;
+                        m_mouse_selection_target = target;
+                        if (modifiers & UIEvents::KeyModifier::Mod_Shift) {
+                            target->set_selection_focus(*dom_node, result->index_in_node);
                         } else {
-                            (void)selection->set_base_and_extent(*dom_node, result->index_in_node, *dom_node, result->index_in_node);
+                            target->set_selection_anchor(*dom_node, result->index_in_node);
+                        }
+                    } else if (!focus_candidate) {
+                        m_in_mouse_selection = true;
+                        if (auto selection = document->get_selection()) {
+                            auto anchor_node = selection->anchor_node();
+                            if (anchor_node && modifiers & UIEvents::KeyModifier::Mod_Shift) {
+                                set_user_selection(*anchor_node, selection->anchor_offset(), *dom_node, result->index_in_node, selection, user_select);
+                            } else {
+                                set_user_selection(*dom_node, result->index_in_node, *dom_node, result->index_in_node, selection, user_select);
+                            }
                         }
                     }
                 }
@@ -635,9 +772,9 @@ EventResult EventHandler::handle_mousemove(CSSPixelPoint viewport_position, CSSP
                         auto anchor_node = selection->anchor_node();
                         if (anchor_node) {
                             if (&anchor_node->root() == &hit->dom_node()->root())
-                                (void)selection->set_base_and_extent(*anchor_node, selection->anchor_offset(), *hit->paintable->dom_node(), hit->index_in_node);
+                                set_user_selection(*anchor_node, selection->anchor_offset(), *hit->paintable->dom_node(), hit->index_in_node, selection, hit->paintable->layout_node().user_select_used_value());
                         } else {
-                            (void)selection->set_base_and_extent(*hit->paintable->dom_node(), hit->index_in_node, *hit->paintable->dom_node(), hit->index_in_node);
+                            set_user_selection(*hit->paintable->dom_node(), hit->index_in_node, *hit->paintable->dom_node(), hit->index_in_node, selection, hit->paintable->layout_node().user_select_used_value());
                         }
                     }
 
@@ -751,7 +888,7 @@ EventResult EventHandler::handle_doubleclick(CSSPixelPoint viewport_position, CS
                 target->set_selection_anchor(hit_dom_node, previous_boundary);
                 target->set_selection_focus(hit_dom_node, next_boundary);
             } else if (auto selection = node->document().get_selection()) {
-                (void)selection->set_base_and_extent(hit_dom_node, previous_boundary, hit_dom_node, next_boundary);
+                set_user_selection(hit_dom_node, previous_boundary, hit_dom_node, next_boundary, selection, hit_paintable.layout_node().user_select_used_value());
             }
         }
     }