From 846cde53b3dd7c2dd79034cb0ef2e214228c976a Mon Sep 17 00:00:00 2001
From: Opelkuh <25430283+Opelkuh@users.noreply.github.com>
Date: Sat, 18 Sep 2021 22:54:12 +0200
Subject: [PATCH] Add `RelativePositionAxes` support

---
 .../Gameplay/TestSceneParticleSpewer.cs       | 25 +++++++++-----
 osu.Game/Graphics/ParticleSpewer.cs           | 33 ++++++++++++++-----
 2 files changed, 41 insertions(+), 17 deletions(-)

diff --git a/osu.Game.Tests/Visual/Gameplay/TestSceneParticleSpewer.cs b/osu.Game.Tests/Visual/Gameplay/TestSceneParticleSpewer.cs
index c259718a7a..31cc505a0d 100644
--- a/osu.Game.Tests/Visual/Gameplay/TestSceneParticleSpewer.cs
+++ b/osu.Game.Tests/Visual/Gameplay/TestSceneParticleSpewer.cs
@@ -28,8 +28,12 @@ namespace osu.Game.Tests.Visual.Gameplay
             Child = spewer = createSpewer();
 
             AddToggleStep("toggle spawning", value => spewer.Active.Value = value);
-            AddSliderStep("particle gravity", 0f, 250f, 0f, value => spewer.Gravity = value);
-            AddSliderStep("particle velocity", 0f, 500f, 250f, value => spewer.MaxVelocity = value);
+            AddSliderStep("particle gravity", 0f, 1f, 0f, value => spewer.Gravity = value);
+            AddSliderStep("particle velocity", 0f, 1f, 0.25f, value => spewer.MaxVelocity = value);
+            AddStep("move to new location", () =>
+            {
+                spewer.TransformTo(nameof(spewer.SpawnPosition), new Vector2(RNG.NextSingle(), RNG.NextSingle()), 1000, Easing.Out);
+            });
         }
 
         [SetUpSteps]
@@ -51,14 +55,15 @@ namespace osu.Game.Tests.Visual.Gameplay
             AddAssert("is not present", () => !spewer.IsPresent);
         }
 
-        private TestParticleSpewer createSpewer()
-        {
-            return new TestParticleSpewer(skinManager.DefaultLegacySkin.GetTexture("star2"))
+        private TestParticleSpewer createSpewer() =>
+            new TestParticleSpewer(skinManager.DefaultLegacySkin.GetTexture("star2"))
             {
-                Anchor = Anchor.Centre,
                 Origin = Anchor.Centre,
+                RelativePositionAxes = Axes.Both,
+                RelativeSizeAxes = Axes.Both,
+                Position = new Vector2(0.5f),
+                Size = new Vector2(0.5f),
             };
-        }
 
         private class TestParticleSpewer : ParticleSpewer
         {
@@ -66,7 +71,10 @@ namespace osu.Game.Tests.Visual.Gameplay
             private const int rate = 250;
 
             public float Gravity;
-            public float MaxVelocity = 250;
+
+            public float MaxVelocity = 0.25f;
+
+            public Vector2 SpawnPosition { get; set; } = new Vector2(0.5f);
 
             protected override float ParticleGravity => Gravity;
 
@@ -82,6 +90,7 @@ namespace osu.Game.Tests.Visual.Gameplay
                         RNG.NextSingle(-MaxVelocity, MaxVelocity),
                         RNG.NextSingle(-MaxVelocity, MaxVelocity)
                     ),
+                    StartPosition = SpawnPosition,
                     Duration = RNG.NextSingle(lifetime),
                     StartAngle = RNG.NextSingle(MathF.PI * 2),
                     EndAngle = RNG.NextSingle(MathF.PI * 2),
diff --git a/osu.Game/Graphics/ParticleSpewer.cs b/osu.Game/Graphics/ParticleSpewer.cs
index c022fd4598..6bf9bff05a 100644
--- a/osu.Game/Graphics/ParticleSpewer.cs
+++ b/osu.Game/Graphics/ParticleSpewer.cs
@@ -3,6 +3,7 @@
 
 using System;
 using osu.Framework.Bindables;
+using osu.Framework.Extensions.EnumExtensions;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.OpenGL.Vertices;
 using osu.Framework.Graphics.Primitives;
@@ -83,6 +84,8 @@ namespace osu.Game.Graphics
 
             private float currentTime;
             private float gravity;
+            private Axes relativePositionAxes;
+            private Vector2 sourceSize;
 
             public ParticleSpewerDrawNode(Sprite source)
                 : base(source)
@@ -98,6 +101,8 @@ namespace osu.Game.Graphics
 
                 currentTime = (float)Source.Time.Current;
                 gravity = Source.ParticleGravity;
+                relativePositionAxes = Source.RelativePositionAxes;
+                sourceSize = Source.DrawSize;
             }
 
             protected override void Blit(Action<TexturedVertex2D> vertexAction)
@@ -116,18 +121,11 @@ namespace osu.Game.Graphics
                     var alpha = p.AlphaAtTime(timeSinceStart);
                     if (alpha <= 0) continue;
 
-                    var scale = p.ScaleAtTime(timeSinceStart);
                     var pos = p.PositionAtTime(timeSinceStart, gravity);
+                    var scale = p.ScaleAtTime(timeSinceStart);
                     var angle = p.AngleAtTime(timeSinceStart);
 
-                    var width = Texture.DisplayWidth * scale;
-                    var height = Texture.DisplayHeight * scale;
-
-                    var rect = new RectangleF(
-                        pos.X - width / 2,
-                        pos.Y - height / 2,
-                        width,
-                        height);
+                    var rect = createDrawRect(pos, scale);
 
                     var quad = new Quad(
                         transformPosition(rect.TopLeft, rect.Centre, angle),
@@ -142,6 +140,23 @@ namespace osu.Game.Graphics
                 }
             }
 
+            private RectangleF createDrawRect(Vector2 position, float scale)
+            {
+                var width = Texture.DisplayWidth * scale;
+                var height = Texture.DisplayHeight * scale;
+
+                if (relativePositionAxes.HasFlagFast(Axes.X))
+                    position.X *= sourceSize.X;
+                if (relativePositionAxes.HasFlagFast(Axes.Y))
+                    position.Y *= sourceSize.Y;
+
+                return new RectangleF(
+                    position.X - width / 2,
+                    position.Y - height / 2,
+                    width,
+                    height);
+            }
+
             private Vector2 transformPosition(Vector2 pos, Vector2 centre, float angle)
             {
                 float cos = MathF.Cos(angle);