Support copying nerd stats from item list

src/main/kotlin/moe/nea/firmament/util/HoveredItemStack.kt

@@ -0,0 +1,35 @@
+/*
+ * SPDX-FileCopyrightText: 2023 Linnea Gräf <nea@nea.moe>
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+package moe.nea.firmament.util
+
+import me.shedaniel.math.impl.PointHelper
+import me.shedaniel.rei.api.client.REIRuntime
+import me.shedaniel.rei.api.client.gui.widgets.Slot
+import me.shedaniel.rei.api.client.registry.screen.ScreenRegistry
+import net.minecraft.client.gui.Element
+import net.minecraft.client.gui.ParentElement
+import net.minecraft.client.gui.screen.ingame.HandledScreen
+import net.minecraft.item.ItemStack
+import moe.nea.firmament.mixins.accessor.AccessorHandledScreen
+
+
+val HandledScreen<*>.focusedItemStack: ItemStack?
+    get() {
+        this as AccessorHandledScreen
+        val vanillaSlot = this.focusedSlot_Firmament?.stack
+        if (vanillaSlot != null) return vanillaSlot
+        val focusedSlot = ScreenRegistry.getInstance().getFocusedStack(this, PointHelper.ofMouse())
+        if (focusedSlot != null) return focusedSlot.cheatsAs().value
+        var baseElement: Element? = REIRuntime.getInstance().overlay.orElse(null)
+        val mx = PointHelper.getMouseFloatingX()
+        val my = PointHelper.getMouseFloatingY()
+        while (true) {
+            if (baseElement is Slot) return baseElement.currentEntry.cheatsAs().value
+            if (baseElement !is ParentElement) return null
+            baseElement = baseElement.hoveredElement(mx, my).orElse(null)
+        }
+    }