LibWeb: Add LayoutRange::normalized()

We use this to ensure that we're always working with a selection where
the start() is before the end() in document order. That simplifies all
the logic around this.

Libraries/LibWeb/CMakeLists.txt

@@ -77,6 +77,7 @@ set(SOURCES
     Layout/LayoutListItem.cpp
     Layout/LayoutListItemMarker.cpp
     Layout/LayoutNode.cpp
+    Layout/LayoutPosition.cpp
     Layout/LayoutReplaced.cpp
     Layout/LayoutTable.cpp
     Layout/LayoutTableCell.cpp

Libraries/LibWeb/Layout/LayoutPosition.cpp

@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <LibWeb/Layout/LayoutNode.h>
+#include <LibWeb/Layout/LayoutPosition.h>
+
+namespace Web {
+
+LayoutRange LayoutRange::normalized() const
+{
+    if (!is_valid())
+        return {};
+    if (m_start.layout_node == m_end.layout_node) {
+        if (m_start.index_in_node < m_end.index_in_node)
+            return *this;
+        return { m_end, m_start };
+    }
+    if (m_start.layout_node->is_before(*m_end.layout_node))
+        return *this;
+    return { m_end, m_start };
+}
+
+}

Libraries/LibWeb/Layout/LayoutPosition.h

@@ -78,6 +78,8 @@ public:
     const LayoutPosition& start() const { return m_start; }
     const LayoutPosition& end() const { return m_end; }
 
+    LayoutRange normalized() const;
+
 private:
     LayoutPosition m_start;
     LayoutPosition m_end;

Libraries/LibWeb/Layout/LineBoxFragment.cpp

@@ -97,7 +97,7 @@ int LineBoxFragment::text_index_at(float x) const
 
 Gfx::FloatRect LineBoxFragment::selection_rect(const Gfx::Font& font) const
 {
-    auto& selection = layout_node().root().selection();
+    auto selection = layout_node().root().selection().normalized();
     if (!selection.is_valid())
         return {};
     if (!layout_node().is_text())

Libraries/LibWeb/TreeNode.h

@@ -136,6 +136,17 @@ public:
         return const_cast<TreeNode*>(this)->next_in_pre_order();
     }
 
+    bool is_before(const T& other) const
+    {
+        if (this == &other)
+            return false;
+        for (auto* node = this; node; node = node->next_in_pre_order()) {
+            if (node == &other)
+                return true;
+        }
+        return false;
+    }
+
     template<typename Callback>
     IterationDecision for_each_in_subtree(Callback callback) const
     {