Re-organize all projects (#4166)

Content.Shared/DragDrop/IDragDropOn.cs

@@ -0,0 +1,35 @@
+#nullable enable
+using Robust.Shared.Analyzers;
+
+namespace Content.Shared.DragDrop
+{
+    /// <summary>
+    ///     This interface allows the component's entity to be dragged and dropped
+    ///     onto by another entity and gives it behavior when that occurs.
+    /// </summary>
+    [RequiresExplicitImplementation]
+    public interface IDragDropOn
+    {
+        /// <summary>
+        ///     Invoked when another entity is being dragged and dropped
+        ///     onto this one before invoking <see cref="DragDropOn"/>.
+        ///     Note that other drag and drop interactions may be attempted if
+        ///     this one fails.
+        /// </summary>
+        /// <param name="eventArgs"></param>
+        /// <returns>true if <see cref="eventArgs"/> is valid, false otherwise.</returns>
+        bool CanDragDropOn(DragDropEvent eventArgs);
+
+        /// <summary>
+        ///     Invoked server-side when another entity is being dragged and dropped
+        ///     onto this one before invoking <see cref="DragDropOn"/>
+        ///     Note that other drag and drop interactions may be attempted if
+        ///     this one fails.
+        /// </summary>
+        /// <returns>
+        ///     true if an interaction occurred and no further interaction should
+        ///     be processed for this drop.
+        /// </returns>
+        bool DragDropOn(DragDropEvent eventArgs);
+    }
+}