Move blueprint validity conditions to allow more correct external usage of EndPlacement

Until now, these were haphazardly enforce inline in blueprint
implementations. The only thing stopping complete breakage is that
`EndPlacement` wasn't called (too much) from outside the blueprint,
leaving them responsible for their own placement.

By moving this conditional out of the provided paramters to
`EndPlacement`, it allows more flexible usage of that method externally.
Coming in a future PR.

osu.Game.Rulesets.Catch/Edit/Blueprints/BananaShowerPlacementBlueprint.cs

@@ -17,6 +17,8 @@ namespace osu.Game.Rulesets.Catch.Edit.Blueprints
         private double placementStartTime;
         private double placementEndTime;
 
+        protected override bool IsValidForPlacement => HitObject.Duration > 0;
+
         public BananaShowerPlacementBlueprint()
         {
             InternalChild = outline = new TimeSpanOutline();
@@ -49,7 +51,7 @@ namespace osu.Game.Rulesets.Catch.Edit.Blueprints
                 case PlacementState.Active:
                     if (e.Button != MouseButton.Right) break;
 
-                    EndPlacement(HitObject.Duration > 0);
+                    EndPlacement(true);
                     return true;
             }
 

osu.Game.Rulesets.Catch/Edit/Blueprints/JuiceStreamPlacementBlueprint.cs

@@ -24,6 +24,8 @@ namespace osu.Game.Rulesets.Catch.Edit.Blueprints
 
         private InputManager inputManager = null!;
 
+        protected override bool IsValidForPlacement => HitObject.Duration > 0;
+
         public JuiceStreamPlacementBlueprint()
         {
             InternalChildren = new Drawable[]
@@ -70,7 +72,7 @@ namespace osu.Game.Rulesets.Catch.Edit.Blueprints
                             return true;
 
                         case MouseButton.Right:
-                            EndPlacement(HitObject.Duration > 0);
+                            EndPlacement(true);
                             return true;
                     }
 

osu.Game.Rulesets.Mania/Edit/Blueprints/HoldNotePlacementBlueprint.cs

@@ -25,6 +25,8 @@ namespace osu.Game.Rulesets.Mania.Edit.Blueprints
         [Resolved]
         private IScrollingInfo scrollingInfo { get; set; }
 
+        protected override bool IsValidForPlacement => HitObject.Duration > 0;
+
         public HoldNotePlacementBlueprint()
             : base(new HoldNote())
         {
@@ -75,7 +77,7 @@ namespace osu.Game.Rulesets.Mania.Edit.Blueprints
                 return;
 
             base.OnMouseUp(e);
-            EndPlacement(HitObject.Duration > 0);
+            EndPlacement(true);
         }
 
         private double originalStartTime;

osu.Game.Rulesets.Osu/Edit/Blueprints/Sliders/SliderPlacementBlueprint.cs

@@ -41,6 +41,8 @@ namespace osu.Game.Rulesets.Osu.Edit.Blueprints.Sliders
         [Resolved(CanBeNull = true)]
         private IDistanceSnapProvider snapProvider { get; set; }
 
+        protected override bool IsValidForPlacement => HitObject.Path.HasValidLength;
+
         public SliderPlacementBlueprint()
             : base(new Slider())
         {
@@ -150,7 +152,7 @@ namespace osu.Game.Rulesets.Osu.Edit.Blueprints.Sliders
         private void endCurve()
         {
             updateSlider();
-            EndPlacement(HitObject.Path.HasValidLength);
+            EndPlacement(true);
         }
 
         protected override void Update()

osu.Game.Rulesets.Taiko/Edit/Blueprints/TaikoSpanPlacementBlueprint.cs

@@ -25,6 +25,8 @@ namespace osu.Game.Rulesets.Taiko.Edit.Blueprints
 
         private readonly IHasDuration spanPlacementObject;
 
+        protected override bool IsValidForPlacement => spanPlacementObject.Duration > 0;
+
         public TaikoSpanPlacementBlueprint(HitObject hitObject)
             : base(hitObject)
         {
@@ -73,7 +75,7 @@ namespace osu.Game.Rulesets.Taiko.Edit.Blueprints
                 return;
 
             base.OnMouseUp(e);
-            EndPlacement(spanPlacementObject.Duration > 0);
+            EndPlacement(true);
         }
 
         public override void UpdateTimeAndPosition(SnapResult result)

osu.Game/Rulesets/Edit/PlacementBlueprint.cs

@@ -47,6 +47,15 @@ namespace osu.Game.Rulesets.Edit
         [Resolved]
         private IPlacementHandler placementHandler { get; set; }
 
+        /// <summary>
+        /// Whether this blueprint is currently in a state that can be committed.
+        /// </summary>
+        /// <remarks>
+        /// Override this with any preconditions that should be double-checked on committing.
+        /// If <c>false</c> is returned and a commit is attempted, the blueprint will be destroyed instead.
+        /// </remarks>
+        protected virtual bool IsValidForPlacement => true;
+
         protected PlacementBlueprint(HitObject hitObject)
         {
             HitObject = hitObject;
@@ -88,7 +97,7 @@ namespace osu.Game.Rulesets.Edit
         /// Signals that the placement of <see cref="HitObject"/> has finished.
         /// This will destroy this <see cref="PlacementBlueprint"/>, and add the HitObject.StartTime to the <see cref="Beatmap"/>.
         /// </summary>
-        /// <param name="commit">Whether the object should be committed.</param>
+        /// <param name="commit">Whether the object should be committed. Note that a commit may fail if <see cref="IsValidForPlacement"/> is <c>false</c>.</param>
         public void EndPlacement(bool commit)
         {
             switch (PlacementActive)
@@ -102,7 +111,7 @@ namespace osu.Game.Rulesets.Edit
                     break;
             }
 
-            placementHandler.EndPlacement(HitObject, commit);
+            placementHandler.EndPlacement(HitObject, IsValidForPlacement && commit);
             PlacementActive = PlacementState.Finished;
         }