From ee220feecf09781876973366ea136b22c6d5b809 Mon Sep 17 00:00:00 2001
From: Derrick Timmermans <derrick.timmermans@outlook.com>
Date: Sun, 18 Jul 2021 16:04:23 +0200
Subject: [PATCH] Avoid using guesses to determine whether inputs blocked

---
 .../Compose/Components/BlueprintContainer.cs  | 12 ++++---
 .../Timeline/TimelineBlueprintContainer.cs    | 33 +++++--------------
 2 files changed, 15 insertions(+), 30 deletions(-)

diff --git a/osu.Game/Screens/Edit/Compose/Components/BlueprintContainer.cs b/osu.Game/Screens/Edit/Compose/Components/BlueprintContainer.cs
index 185f029d14..06cbf7c2e0 100644
--- a/osu.Game/Screens/Edit/Compose/Components/BlueprintContainer.cs
+++ b/osu.Game/Screens/Edit/Compose/Components/BlueprintContainer.cs
@@ -110,9 +110,9 @@ namespace osu.Game.Screens.Edit.Compose.Components
             bool selectionPerformed = performMouseDownActions(e);
 
             // even if a selection didn't occur, a drag event may still move the selection.
-            prepareSelectionMovement();
+            bool movementPossible = prepareSelectionMovement();
 
-            return selectionPerformed || e.Button == MouseButton.Left;
+            return selectionPerformed || movementPossible;
         }
 
         protected SelectionBlueprint<T> ClickedBlueprint { get; private set; }
@@ -427,19 +427,21 @@ namespace osu.Game.Screens.Edit.Compose.Components
         /// <summary>
         /// Attempts to begin the movement of any selected blueprints.
         /// </summary>
-        private void prepareSelectionMovement()
+        /// <returns>Whether a movement is possible.</returns>
+        private bool prepareSelectionMovement()
         {
             if (!SelectionHandler.SelectedBlueprints.Any())
-                return;
+                return false;
 
             // Any selected blueprint that is hovered can begin the movement of the group, however only the first item (according to SortForMovement) is used for movement.
             // A special case is added for when a click selection occurred before the drag
             if (!clickSelectionBegan && !SelectionHandler.SelectedBlueprints.Any(b => b.IsHovered))
-                return;
+                return false;
 
             // Movement is tracked from the blueprint of the earliest item, since it only makes sense to distance snap from that item
             movementBlueprints = SortForMovement(SelectionHandler.SelectedBlueprints).ToArray();
             movementBlueprintOriginalPositions = movementBlueprints.Select(m => m.ScreenSpaceSelectionPoint).ToArray();
+            return true;
         }
 
         /// <summary>
diff --git a/osu.Game/Screens/Edit/Compose/Components/Timeline/TimelineBlueprintContainer.cs b/osu.Game/Screens/Edit/Compose/Components/Timeline/TimelineBlueprintContainer.cs
index abd7f5923c..ae33eaa355 100644
--- a/osu.Game/Screens/Edit/Compose/Components/Timeline/TimelineBlueprintContainer.cs
+++ b/osu.Game/Screens/Edit/Compose/Components/Timeline/TimelineBlueprintContainer.cs
@@ -35,15 +35,10 @@ namespace osu.Game.Screens.Edit.Compose.Components.Timeline
         private Bindable<HitObject> placement;
         private SelectionBlueprint<HitObject> placementBlueprint;
 
-        // We want children to be able to be clicked and dragged
-        public override bool ReceivePositionalInputAt(Vector2 screenSpacePos) => true;
+        private SelectableAreaBackground backgroundBox;
 
-        // This drawable itself should still check whether the mouse is over it
-        private bool shouldHandleInputAt(Vector2 screenSpacePos)
-        {
-            float localY = ToLocalSpace(screenSpacePos).Y;
-            return DrawRectangle.Top <= localY && DrawRectangle.Bottom >= localY;
-        }
+        // We want children to be able to be clicked and dragged, regardless of this drawable's size
+        public override bool ReceivePositionalInputAt(Vector2 screenSpacePos) => true;
 
         public TimelineBlueprintContainer(HitObjectComposer composer)
             : base(composer)
@@ -58,7 +53,7 @@ namespace osu.Game.Screens.Edit.Compose.Components.Timeline
         [BackgroundDependencyLoader]
         private void load()
         {
-            AddInternal(new SelectableAreaBackground
+            AddInternal(backgroundBox = new SelectableAreaBackground
             {
                 Colour = Color4.Black,
                 Depth = float.MaxValue,
@@ -97,25 +92,13 @@ namespace osu.Game.Screens.Edit.Compose.Components.Timeline
 
         protected override Container<SelectionBlueprint<HitObject>> CreateSelectionBlueprintContainer() => new TimelineSelectionBlueprintContainer { RelativeSizeAxes = Axes.Both };
 
-        protected override bool OnMouseDown(MouseDownEvent e)
-        {
-            int selectionCount = SelectedItems.Count;
-
-            // We let BlueprintContainer attempt a HitObject selection
-            // If it fails, we'll pass it this input back to the timeline so it can be dragged
-            // We know it failed if the selection count is unchanged after the selection attempt
-            if (base.OnMouseDown(e) && selectionCount != SelectedItems.Count)
-                return true;
-
-            return false;
-        }
-
         protected override bool OnDragStart(DragStartEvent e)
         {
-            if (!shouldHandleInputAt(e.ScreenSpaceMouseDownPosition))
-                return false;
+            // We should only allow BlueprintContainer to create a drag box if the mouse is within selection bounds
+            if (backgroundBox.ReceivePositionalInputAt(e.ScreenSpaceMouseDownPosition))
+                return base.OnDragStart(e);
 
-            return base.OnDragStart(e);
+            return false;
         }
 
         protected override void OnDrag(DragEvent e)