Fixed Elytra in 2 Block High Places

Fixed Elytras when you spam jump in a 2 block high area.

src/client/java/com/ztrolix/zlibs/mixin/client/PlayerMixin.java

@@ -0,0 +1,27 @@
+package com.ztrolix.zlibs.mixin.client;
+
+import net.minecraft.entity.player.PlayerEntity;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Unique;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
+
+@Mixin(PlayerEntity.class)
+public class PlayerMixin {
+    @Inject(method = "checkFallFlying", at = @At("HEAD"), cancellable = true)
+    private void injectedStartFallFlying(CallbackInfoReturnable<Boolean> cir) {
+        if (((PlayerEntity) (Object) this).isSneaking()) return;
+        if (((PlayerEntity) (Object) this).isFallFlying()) return;
+        double offset = 4.0 / 16.0;
+        if (((PlayerEntity) (Object) this).isSprinting()) offset = 12.0 / 16.0;
+        if (this.doesCollideY(offset) && this.doesCollideY(-offset)) {
+            cir.setReturnValue(false);
+        }
+    }
+
+    @Unique
+    private boolean doesCollideY(double offsetY) {
+        return !((PlayerEntity) (Object) this).doesNotCollide(0, offsetY, 0);
+    }
+}