LibWeb: Add support for range deletion.

Author: https://github.com/asynts
Commit: 43dc47a494
Pull-request: https://github.com/SerenityOS/serenity/pull/4318
Reviewed-by: https://github.com/Lubrsi
Reviewed-by: https://github.com/awesomekling
Reviewed-by: https://github.com/linusg

Libraries/LibWeb/Page/EventHandler.cpp

@@ -345,16 +345,33 @@ bool EventHandler::handle_keydown(KeyCode key, unsigned modifiers, u32 code_poin
             return focus_next_element();
     }
 
+    if (layout_root()->selection().is_valid()) {
+        auto range = layout_root()->selection().to_dom_range();
+
+        if (key == KeyCode::Key_Backspace) {
+            if (range.start().node()->is_editable()) {
+                m_edit_event_handler->handle_delete(range);
+                return true;
+            }
+        }
+
+        // FIXME: Check if this code point is in the printable character range.
+
+        m_edit_event_handler->handle_delete(range);
+        m_edit_event_handler->handle_insert(m_frame.cursor_position(), code_point);
+        return true;
+    }
+
     if (m_frame.cursor_position().is_valid() && m_frame.cursor_position().node()->is_editable()) {
         if (key == KeyCode::Key_Backspace) {
             m_edit_event_handler->handle_delete(m_frame.cursor_position());
             return true;
         }
 
-        if (code_point) {
-            m_edit_event_handler->handle_insert(m_frame.cursor_position(), code_point);
-            return true;
-        }
+        // FIXME: Check if this code point is in the printable character range.
+
+        m_edit_event_handler->handle_insert(m_frame.cursor_position(), code_point);
+        return true;
     }
 
     return false;