Add repel mod to the osu ruleset

[ggliv]

Initially brought up in #18294.

This mod effectively does the opposite of the existing magnetised mod, pushing hitobjects away from your cursor instead of pulling them toward it. The gradual hitobject repositioning shared between the two mods is implemented in a new abstract class, OsuEaseHitObjectPositionsMod (I am not 100% sure on the naming convention I should use here, please let me know if it should be changed). (No longer abstracted as of 2fe34f1)

OsuHitObjectGenerationUtils.calculatePossibleMovementBounds is exposed to allow the mod to ensure sliders do not move outside of the bounds of the playfield, and a new parameter (defaulted to true) is added to determine whether the returned RectangleF should account for the radius of the slider. (Reverted as of 6e883a6) The slider clamping logic is reused from clampSliderToPlayfield.

repel.mp4

[mk56-spn]

Ive played it a bit and it feels very akward, which i guess its fair enough but the maximum repel strength needs to be cut down to whats currently .75 strength, anything above that is just not really reasonable

[apollo-dw]

I'd personally expect repel to be a checkbox / switch in Magnetised, rather than a whole separate mod

[frenzibyte]

Having it a separate mod is consistent with Grow/Deflate, WindUp/WindDown, etc. I think that's fine for now.

[peppy]

Is it intended that the repulsion gets strong the further away objects are to the cursor? This to be seems counter-intuitive, and hasn't been mentioned anywhere, so I wanted to clarify before going any further.

[ggliv]

I didn't explicitly intend for that to be the case while putting this together, but I think it works well enough gameplay-feel-wise. Using a constant strength makes repulsion while the cursor is close to a hitobject feel jerky, in my opinion, though I could just be used to the original feel at this point.

Here's the diff for constant strength if you want to give it a try.

diff --git a/osu.Game.Rulesets.Osu/Mods/OsuModRepel.cs b/osu.Game.Rulesets.Osu/Mods/OsuModRepel.cs
index 052c7128f6..371e2edfd0 100644
--- a/osu.Game.Rulesets.Osu/Mods/OsuModRepel.cs
+++ b/osu.Game.Rulesets.Osu/Mods/OsuModRepel.cs
@@ -51,24 +51,20 @@ public void Update(Playfield playfield)
 
             foreach (var drawable in playfield.HitObjectContainer.AliveObjects)
             {
-                float x = Math.Clamp(2 * drawable.X - cursorPos.X, 0, OsuPlayfield.BASE_SIZE.X);
-                float y = Math.Clamp(2 * drawable.Y - cursorPos.Y, 0, OsuPlayfield.BASE_SIZE.Y);
+                var destination = drawable.Position - 100 * Vector2.NormalizeFast(cursorPos - drawable.Position);
+                destination = Vector2.Clamp(destination, Vector2.Zero, OsuPlayfield.BASE_SIZE);
 
                 if (drawable.HitObject is Slider thisSlider)
                 {
                     var possibleMovementBounds = OsuHitObjectGenerationUtils.CalculatePossibleMovementBounds(thisSlider);
 
-                    x = possibleMovementBounds.Width < 0
-                        ? x
-                        : Math.Clamp(x, possibleMovementBounds.Left, possibleMovementBounds.Right);
-
-                    y = possibleMovementBounds.Height < 0
-                        ? y
-                        : Math.Clamp(y, possibleMovementBounds.Top, possibleMovementBounds.Bottom);
+                    destination = Vector2.Clamp(
+                        destination,
+                        new Vector2(possibleMovementBounds.Left, possibleMovementBounds.Top),
+                        new Vector2(possibleMovementBounds.Right, possibleMovementBounds.Bottom)
+                    );
                 }
 
-                var destination = new Vector2(x, y);
-
                 switch (drawable)
                 {
                     case DrawableHitCircle circle:

[peppy]

To make it clear, I was implying it should (if going by the physically correct definition) be opposite of what it is right now, not constant.

[ggliv]

I've pushed some commits that correct the repulsion strength. I'm still not 100% sure on the feel of it though, would appreciate some input on that front if you don't think it's currently up to snuff.

[mk56-spn]

I'll give it a play

[mk56-spn]

sorry for the late response, feels really nice now, its smooth and it doesn't sort of get annoying to hit when you get close to the circle. predictable movement, well done. gameplay wise i feel it's good for a merge now

[bdach]

Would be preferable to have all new code have NRT enabled. The problem here is going to be gameplayClock, but I think the way to go here is to annotate it as nullable and then add a Debug.Assert(gameplayClock != null) in easeTo().

[bdach]

This mod is declaring incompatibility with 5 others, but 4 of those 5 are not declaring incompatibility with OsuModRepel themselves in the other direction (OsuModMagnetised being the exception).

[peppy]

You still missed autoplay..

[peppy]

and relax.

[ggliv]

Yikes.

Relax was intentionally excluded though, #17319 isn't an issue when hitobjects are being pushed away. I've opened #19084 to fix.