From 5874b7a76f223d577a97f46b8d9ef9b04478d3bb Mon Sep 17 00:00:00 2001
From: Aliaksandr Kalenik <kalenik.aliaksandr@gmail.com>
Date: Thu, 3 Jul 2025 21:28:49 +0200
Subject: [PATCH] LibWeb: Skip `update_associated_selection()` when there's no
 selection

This change fixes at least two issues:
- `update_associated_selection()` is responsible for selectionchange
  dispatch, and we were incorrectly dispatching this event on ranges
  that were not associated with a selection.
- `Range::get_client_rects()` was using `update_associated_selection()`
  to refresh the selection state in the paintable tree for the current
  range, but since a range might not be associated with a selection,
  this could make the painted selection reflect the state of an
  arbitrary range instead of the actual selection range.

Fixes a bug on Discord where any text typed into the message input would
get selected.
---
 Libraries/LibWeb/DOM/Range.cpp                | 16 ++++++++--
 .../LibWeb/Painting/PaintableFragment.cpp     | 18 +++++------
 Libraries/LibWeb/Painting/PaintableFragment.h |  2 +-
 ...th-selection-should-not-affect-it-ref.html | 17 ++++++++++
 ...d-with-selection-should-not-affect-it.html | 32 +++++++++++++++++++
 5 files changed, 73 insertions(+), 12 deletions(-)
 create mode 100644 Tests/LibWeb/Ref/expected/range-not-assiciated-with-selection-should-not-affect-it-ref.html
 create mode 100644 Tests/LibWeb/Ref/input/range-not-assiciated-with-selection-should-not-affect-it.html

diff --git a/Libraries/LibWeb/DOM/Range.cpp b/Libraries/LibWeb/DOM/Range.cpp
index 00be8803ec5..5cfdb380699 100644
--- a/Libraries/LibWeb/DOM/Range.cpp
+++ b/Libraries/LibWeb/DOM/Range.cpp
@@ -3,6 +3,7 @@
  * Copyright (c) 2022, Luke Wilde <lukew@serenityos.org>
  * Copyright (c) 2022-2023, Andreas Kling <andreas@ladybird.org>
  * Copyright (c) 2024-2025, Jelle Raaijmakers <jelle@ladybird.org>
+ * Copyright (c) 2024-2025, Aliaksandr Kalenik <kalenik.aliaksandr@gmail.com>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -99,6 +100,9 @@ void Range::set_associated_selection(Badge<Selection::Selection>, GC::Ptr<Select
 
 void Range::update_associated_selection()
 {
+    if (!m_associated_selection)
+        return;
+
     auto& document = m_start_container->document();
     if (auto* viewport = document.paintable()) {
         viewport->recompute_selection_states(*this);
@@ -1143,7 +1147,6 @@ GC::Ref<Geometry::DOMRectList> Range::get_client_rects()
         return Geometry::DOMRectList::create(realm(), {});
 
     start_container()->document().update_layout(DOM::UpdateLayoutReason::RangeGetClientRects);
-    update_associated_selection();
     Vector<GC::Root<Geometry::DOMRect>> rects;
     // FIXME: take Range collapsed into consideration
     // 2. Iterate the node included in Range
@@ -1159,6 +1162,15 @@ GC::Ref<Geometry::DOMRectList> Range::get_client_rects()
         end_node = *end_node->child_at_index(m_end_offset - 1);
     }
     for (GC::Ptr<Node> node = start_node; node && node != end_node->next_in_pre_order(); node = node->next_in_pre_order()) {
+        auto selection_state = Painting::Paintable::SelectionState::Full;
+        if (node == start_node && node == end_node) {
+            selection_state = Painting::Paintable::SelectionState::StartAndEnd;
+        } else if (node == start_node) {
+            selection_state = Painting::Paintable::SelectionState::Start;
+        } else if (node == end_node) {
+            selection_state = Painting::Paintable::SelectionState::End;
+        }
+
         auto node_type = static_cast<NodeType>(node->node_type());
         if (node_type == NodeType::ELEMENT_NODE) {
             // 1. For each element selected by the range, whose parent is not selected by the range, include the border
@@ -1181,7 +1193,7 @@ GC::Ref<Geometry::DOMRectList> Range::get_client_rects()
                     auto const& paintable_lines = static_cast<Painting::PaintableWithLines const&>(*containing_block);
                     auto fragments = paintable_lines.fragments();
                     for (auto frag = fragments.begin(); frag != fragments.end(); frag++) {
-                        auto rect = frag->range_rect(start_offset(), end_offset());
+                        auto rect = frag->range_rect(selection_state, start_offset(), end_offset());
                         if (rect.is_empty())
                             continue;
                         rects.append(Geometry::DOMRect::create(realm(),
diff --git a/Libraries/LibWeb/Painting/PaintableFragment.cpp b/Libraries/LibWeb/Painting/PaintableFragment.cpp
index 5992695146a..00541bb278a 100644
--- a/Libraries/LibWeb/Painting/PaintableFragment.cpp
+++ b/Libraries/LibWeb/Painting/PaintableFragment.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2024, Aliaksandr Kalenik <kalenik.aliaksandr@gmail.com>
+ * Copyright (c) 2024-2025, Aliaksandr Kalenik <kalenik.aliaksandr@gmail.com>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -81,12 +81,12 @@ size_t PaintableFragment::index_in_node_for_point(CSSPixelPoint position) const
     return utf16_view().code_unit_offset_of(code_point_offset - 1);
 }
 
-CSSPixelRect PaintableFragment::range_rect(size_t start_offset_in_code_units, size_t end_offset_in_code_units) const
+CSSPixelRect PaintableFragment::range_rect(Paintable::SelectionState selection_state, size_t start_offset_in_code_units, size_t end_offset_in_code_units) const
 {
-    if (paintable().selection_state() == Paintable::SelectionState::None)
+    if (selection_state == Paintable::SelectionState::None)
         return {};
 
-    if (paintable().selection_state() == Paintable::SelectionState::Full)
+    if (selection_state == Paintable::SelectionState::Full)
         return absolute_rect();
 
     auto const& font = glyph_run() ? glyph_run()->font() : layout_node().first_available_font();
@@ -110,7 +110,7 @@ CSSPixelRect PaintableFragment::range_rect(size_t start_offset_in_code_units, si
     // We operate on the UTF-8 string that is part of this fragment.
     auto text = utf8_view().substring_view(m_start_byte_offset, m_length_in_bytes);
 
-    if (paintable().selection_state() == Paintable::SelectionState::StartAndEnd) {
+    if (selection_state == Paintable::SelectionState::StartAndEnd) {
         auto selection_start_in_this_fragment = code_unit_to_byte_offset(start_offset_in_code_units);
         auto selection_end_in_this_fragment = code_unit_to_byte_offset(end_offset_in_code_units);
 
@@ -141,7 +141,7 @@ CSSPixelRect PaintableFragment::range_rect(size_t start_offset_in_code_units, si
 
         return rect;
     }
-    if (paintable().selection_state() == Paintable::SelectionState::Start) {
+    if (selection_state == Paintable::SelectionState::Start) {
         auto selection_start_in_this_fragment = code_unit_to_byte_offset(start_offset_in_code_units);
         auto selection_end_in_this_fragment = m_length_in_bytes;
 
@@ -168,7 +168,7 @@ CSSPixelRect PaintableFragment::range_rect(size_t start_offset_in_code_units, si
 
         return rect;
     }
-    if (paintable().selection_state() == Paintable::SelectionState::End) {
+    if (selection_state == Paintable::SelectionState::End) {
         auto selection_start_in_this_fragment = 0u;
         auto selection_end_in_this_fragment = code_unit_to_byte_offset(end_offset_in_code_units);
 
@@ -226,7 +226,7 @@ CSSPixelRect PaintableFragment::selection_rect() const
         }
         auto selection_start = text_control_element->selection_start();
         auto selection_end = text_control_element->selection_end();
-        return range_rect(selection_start, selection_end);
+        return range_rect(paintable().selection_state(), selection_start, selection_end);
     }
 
     auto selection = paintable().document().get_selection();
@@ -236,7 +236,7 @@ CSSPixelRect PaintableFragment::selection_rect() const
     if (!range)
         return {};
 
-    return range_rect(range->start_offset(), range->end_offset());
+    return range_rect(paintable().selection_state(), range->start_offset(), range->end_offset());
 }
 
 Utf8View PaintableFragment::utf8_view() const
diff --git a/Libraries/LibWeb/Painting/PaintableFragment.h b/Libraries/LibWeb/Painting/PaintableFragment.h
index 91d670d0b47..0bd69235cd8 100644
--- a/Libraries/LibWeb/Painting/PaintableFragment.h
+++ b/Libraries/LibWeb/Painting/PaintableFragment.h
@@ -39,7 +39,7 @@ public:
     Gfx::Orientation orientation() const;
 
     CSSPixelRect selection_rect() const;
-    CSSPixelRect range_rect(size_t start_offset_in_code_units, size_t end_offset_in_code_units) const;
+    CSSPixelRect range_rect(Paintable::SelectionState selection_state, size_t start_offset_in_code_units, size_t end_offset_in_code_units) const;
 
     CSSPixels width() const { return m_size.width(); }
     CSSPixels height() const { return m_size.height(); }
diff --git a/Tests/LibWeb/Ref/expected/range-not-assiciated-with-selection-should-not-affect-it-ref.html b/Tests/LibWeb/Ref/expected/range-not-assiciated-with-selection-should-not-affect-it-ref.html
new file mode 100644
index 00000000000..15d1e1d58b6
--- /dev/null
+++ b/Tests/LibWeb/Ref/expected/range-not-assiciated-with-selection-should-not-affect-it-ref.html
@@ -0,0 +1,17 @@
+<!DOCTYPE html>
+<html>
+    <body>
+        <p id="text">This is a simple sentence used to test range and selection rectangles.</p>
+        <script>
+            const textNode = document.getElementById("text").firstChild;
+
+            const sel = window.getSelection();
+            sel.removeAllRanges();
+
+            const selRange = document.createRange();
+            selRange.setStart(textNode, 5);
+            selRange.setEnd(textNode, 16);
+            sel.addRange(selRange);
+        </script>
+    </body>
+</html>
diff --git a/Tests/LibWeb/Ref/input/range-not-assiciated-with-selection-should-not-affect-it.html b/Tests/LibWeb/Ref/input/range-not-assiciated-with-selection-should-not-affect-it.html
new file mode 100644
index 00000000000..267ca4b33bb
--- /dev/null
+++ b/Tests/LibWeb/Ref/input/range-not-assiciated-with-selection-should-not-affect-it.html
@@ -0,0 +1,32 @@
+<!DOCTYPE html>
+<html class="reftest-wait">
+    <link
+        rel="match"
+        href="../expected/range-not-assiciated-with-selection-should-not-affect-it-ref.html"
+    />
+    <body>
+        <p id="text">This is a simple sentence used to test range and selection rectangles.</p>
+        <script>
+            const textNode = document.getElementById("text").firstChild;
+
+            const sel = window.getSelection();
+            sel.removeAllRanges();
+
+            const selRange = document.createRange();
+            selRange.setStart(textNode, 5);
+            selRange.setEnd(textNode, 16);
+            sel.addRange(selRange);
+
+            requestAnimationFrame(() => {
+                const otherRange = document.createRange();
+                otherRange.setStart(textNode, 0);
+                otherRange.setEnd(textNode, 0);
+
+                // Requesting client rects on a range not associated with selection should not affect selection
+                otherRange.getClientRects();
+
+                document.documentElement.classList.remove("reftest-wait");
+            });
+        </script>
+    </body>
+</html>