Mimic Vanilla durability system

Author: ALongStringOfNumbers

src/main/java/gregtech/api/items/toolitem/IGTTool.java

@@ -45,7 +45,13 @@
 import net.minecraft.item.Item;
 import net.minecraft.item.ItemStack;
 import net.minecraft.nbt.NBTTagCompound;
-import net.minecraft.util.*;
+import net.minecraft.util.ActionResult;
+import net.minecraft.util.EnumActionResult;
+import net.minecraft.util.EnumFacing;
+import net.minecraft.util.EnumHand;
+import net.minecraft.util.NonNullList;
+import net.minecraft.util.SoundCategory;
+import net.minecraft.util.SoundEvent;
 import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.math.RayTraceResult;
 import net.minecraft.world.IBlockAccess;
@@ -620,8 +626,7 @@ default AoESymmetrical getAoEDefinition(ItemStack stack) {
     default double definition$getDurabilityForDisplay(ItemStack stack) {
         int damage = stack.getItem().getDamage(stack);
         int maxDamage = stack.getItem().getMaxDamage(stack);
-        if (damage == 0) return 1.0;
-        return (double) (maxDamage - damage) / (double) maxDamage;
+        return (double) damage / (double) maxDamage;
     }
 
     @Nullable

src/main/java/gregtech/client/utils/ToolChargeBarRenderer.java

@@ -165,12 +165,12 @@ private static boolean renderDurabilityBar(ItemStack stack, IItemDurabilityManag
         boolean doDepletedColor = manager.doDamagedStateColors(stack);
         Color left = colors != null ? colors.getLeft() : colorBarLeftDurability;
         Color right = colors != null ? colors.getRight() : colorBarRightDurability;
-        render(level, xPosition, yPosition, 0, true, left, right, doDepletedColor);
+        render(1 - level, xPosition, yPosition, 0, true, left, right, doDepletedColor);
         return true;
     }
 
     private static boolean renderDurabilityBar(double level, int xPosition, int yPosition) {
-        render(level, xPosition, yPosition, 0, true, colorBarLeftDurability, colorBarRightDurability, true);
+        render(1 - level, xPosition, yPosition, 0, true, colorBarLeftDurability, colorBarRightDurability, true);
         return true;
     }