synchronizing the upgrade installed on robots to clients and checking it in renderer, if present use the item's item renderer to render it in its "equipped" state, which for robot upgrades should take of rendering the upgrade appropriately on its robot; basic generator renderer, still needs syncing of whether its currently active or not to show the appropriate texture

li/cil/oc/client/PacketHandler.scala

@@ -32,6 +32,7 @@ class PacketHandler extends CommonPacketHandler {
       case PacketType.RobotAnimateSwing => onRobotAnimateSwing(p)
       case PacketType.RobotAnimateTurn => onRobotAnimateTurn(p)
       case PacketType.RobotEquippedItemChange => onRobotEquippedItemChange(p)
+      case PacketType.RobotEquippedUpgradeChange => onRobotEquippedUpgradeChange(p)
       case PacketType.RobotMove => onRobotMove(p)
       case PacketType.RobotSelectedSlotChange => onRobotSelectedSlotChange(p)
       case PacketType.RobotXp => onRobotXp(p)
@@ -120,6 +121,12 @@ class PacketHandler extends CommonPacketHandler {
       case _ => // Invalid packet.
     }
 
+  def onRobotEquippedUpgradeChange(p: PacketParser) =
+    p.readTileEntity[RobotProxy]() match {
+      case Some(t) => t.robot.equippedUpgrade = Option(p.readItemStack())
+      case _ => // Invalid packet.
+    }
+
   def onRobotMove(p: PacketParser) =
     p.readTileEntity[RobotProxy]() match {
       case Some(t) => t.robot.move(p.readDirection())

li/cil/oc/client/Proxy.scala

@@ -7,10 +7,12 @@ import cpw.mods.fml.common.registry.TickRegistry
 import cpw.mods.fml.relauncher.Side
 import li.cil.oc.client.renderer.WirelessNetworkDebugRenderer
 import li.cil.oc.client.renderer.block.BlockRenderer
+import li.cil.oc.client.renderer.item.UpgradeRenderer
 import li.cil.oc.client.renderer.tileentity._
 import li.cil.oc.common.tileentity
 import li.cil.oc.common.{Proxy => CommonProxy}
-import li.cil.oc.{Settings, OpenComputers}
+import li.cil.oc.{Items, Settings, OpenComputers}
+import net.minecraftforge.client.MinecraftForgeClient
 import net.minecraftforge.common.MinecraftForge
 
 private[oc] class Proxy extends CommonProxy {
@@ -29,6 +31,8 @@ private[oc] class Proxy extends CommonProxy {
     ClientRegistry.bindTileEntitySpecialRenderer(classOf[tileentity.Screen], ScreenRenderer)
     TickRegistry.registerTickHandler(ScreenRenderer, Side.CLIENT)
 
+    MinecraftForgeClient.registerItemRenderer(Items.multi.itemID, UpgradeRenderer)
+
     MinecraftForge.EVENT_BUS.register(gui.Icons)
   }
 

li/cil/oc/client/renderer/item/UpgradeRenderer.scala

@@ -0,0 +1,72 @@
+package li.cil.oc.client.renderer.item
+
+import li.cil.oc.{Settings, Items}
+import net.minecraft.client.Minecraft
+import net.minecraft.client.renderer.Tessellator
+import net.minecraft.item.ItemStack
+import net.minecraft.util.{ResourceLocation, AxisAlignedBB}
+import net.minecraftforge.client.IItemRenderer
+import net.minecraftforge.client.IItemRenderer.{ItemRendererHelper, ItemRenderType}
+import org.lwjgl.opengl.GL11
+
+object UpgradeRenderer extends IItemRenderer {
+  def handleRenderType(item: ItemStack, renderType: ItemRenderType) = {
+    Items.multi.subItem(item) match {
+      case Some(subItem) if subItem == Items.generator => renderType == ItemRenderType.EQUIPPED
+      case _ => false
+    }
+  }
+
+  def shouldUseRenderHelper(renderType: ItemRenderType, item: ItemStack, helper: ItemRendererHelper) = helper == ItemRendererHelper.EQUIPPED_BLOCK
+
+  def renderItem(renderType: ItemRenderType, item: ItemStack, data: AnyRef*) {
+    val tm = Minecraft.getMinecraft.getTextureManager
+    GL11.glTranslatef(0.5f, 0.5f, 0.5f)
+    val t = Tessellator.instance
+
+    Items.multi.subItem(item) match {
+      case Some(subItem) if subItem == Items.generator =>
+        // TODO display lists?
+        val onOffset = if (true) 0.5 else 0
+        val b = AxisAlignedBB.getAABBPool.getAABB(0.4, 0.2, 0.16, 0.6, 0.4, 0.36)
+        tm.bindTexture(new ResourceLocation(Settings.resourceDomain, "textures/items/upgrade_generator_equipped.png"))
+
+        // Back.
+        t.startDrawingQuads()
+        t.addVertexWithUV(b.minX, b.minY, b.minZ, onOffset, 0.5)
+        t.addVertexWithUV(b.minX, b.maxY, b.minZ, onOffset, 0)
+        t.addVertexWithUV(b.maxX, b.maxY, b.minZ, onOffset + 0.5, 0)
+        t.addVertexWithUV(b.maxX, b.minY, b.minZ, onOffset + 0.5, 0.5)
+        t.setNormal(0, 0, -1)
+        t.draw()
+
+        // Bottom.
+        t.startDrawingQuads()
+        t.addVertexWithUV(b.minX, b.minY, b.minZ, 0.5, 0.5)
+        t.addVertexWithUV(b.maxX, b.minY, b.minZ, 1, 0.5)
+        t.addVertexWithUV(b.maxX, b.minY, b.maxZ, 1, 1)
+        t.addVertexWithUV(b.minX, b.minY, b.maxZ, 0.5, 1)
+        t.setNormal(0, -1, 0)
+        t.draw()
+
+        // Left.
+        t.startDrawingQuads()
+        t.addVertexWithUV(b.maxX, b.minY, b.minZ, 0, 1)
+        t.addVertexWithUV(b.maxX, b.maxY, b.minZ, 0, 0.5)
+        t.addVertexWithUV(b.maxX, b.maxY, b.maxZ, 0.5, 0.5)
+        t.addVertexWithUV(b.maxX, b.minY, b.maxZ, 0.5, 1)
+        t.setNormal(1, 0, 0)
+        t.draw()
+
+        // Right.
+        t.startDrawingQuads()
+        t.addVertexWithUV(b.minX, b.minY, b.minZ, 0, 1)
+        t.addVertexWithUV(b.minX, b.minY, b.maxZ, 0.5, 1)
+        t.addVertexWithUV(b.minX, b.maxY, b.maxZ, 0.5, 0.5)
+        t.addVertexWithUV(b.minX, b.maxY, b.minZ, 0, 0.5)
+        t.setNormal(-1, 0, 0)
+        t.draw()
+      case _ =>
+    }
+  }
+}

li/cil/oc/client/renderer/tileentity/RobotRenderer.scala

@@ -9,6 +9,7 @@ import net.minecraft.client.renderer.tileentity.TileEntitySpecialRenderer
 import net.minecraft.client.renderer.{Tessellator, GLAllocation}
 import net.minecraft.tileentity.TileEntity
 import net.minecraft.util.{Vec3, ResourceLocation}
+import net.minecraftforge.client.IItemRenderer.ItemRenderType
 import net.minecraftforge.client.MinecraftForgeClient
 import net.minecraftforge.common.ForgeDirection
 import org.lwjgl.opengl.GL11
@@ -217,6 +218,7 @@ object RobotRenderer extends TileEntitySpecialRenderer {
 
     robot.equippedItem match {
       case Some(stack) =>
+        GL11.glPushMatrix()
         GL11.glTranslatef(0.1f, 0.25f, 0.75f)
         GL11.glScalef(0.4f, 0.4f, -0.4f)
         if (robot.isAnimatingSwing) {
@@ -225,6 +227,7 @@ object RobotRenderer extends TileEntitySpecialRenderer {
         }
         GL11.glRotatef(-30, 1, 0, 0)
         GL11.glRotatef(40, 0, 1, 0)
+        GL11.glDisable(GL11.GL_CULL_FACE)
         try {
           RenderManager.instance.itemRenderer.renderItem(robot.player(), stack, MinecraftForgeClient.getRenderPass)
         }
@@ -233,6 +236,23 @@ object RobotRenderer extends TileEntitySpecialRenderer {
             OpenComputers.log.log(Level.WARNING, "Failed rendering equipped item.", e)
             robot.equippedItem = None
         }
+        GL11.glEnable(GL11.GL_CULL_FACE)
+        GL11.glPopMatrix()
+      case _ =>
+    }
+
+    robot.equippedUpgrade match {
+      case Some(stack) =>
+        try {
+          if (MinecraftForgeClient.getItemRenderer(stack, ItemRenderType.EQUIPPED) != null) {
+            RenderManager.instance.itemRenderer.renderItem(robot.player(), stack, MinecraftForgeClient.getRenderPass, ItemRenderType.EQUIPPED)
+          }
+        }
+        catch {
+          case e: Throwable =>
+            OpenComputers.log.log(Level.WARNING, "Failed rendering equipped upgrade.", e)
+            robot.equippedUpgrade = None
+        }
       case _ =>
     }
 

li/cil/oc/common/PacketType.scala

@@ -12,6 +12,7 @@ object PacketType extends Enumeration {
   RobotAnimateSwing,
   RobotAnimateTurn,
   RobotEquippedItemChange,
+  RobotEquippedUpgradeChange,
   RobotMove,
   RobotSelectedSlotChange,
   RobotXp,

li/cil/oc/common/tileentity/Robot.scala

@@ -66,6 +66,8 @@ class Robot(isRemote: Boolean) extends Computer(isRemote) with ISidedInventory w
 
   var equippedItem: Option[ItemStack] = None
 
+  var equippedUpgrade: Option[ItemStack] = None
+
   var animationTicksLeft = 0
 
   var animationTicksTotal = 0
@@ -332,6 +334,9 @@ class Robot(isRemote: Boolean) extends Computer(isRemote) with ISidedInventory w
     if (nbt.hasKey("equipped")) {
       equippedItem = Option(ItemStack.loadItemStackFromNBT(nbt.getCompoundTag("equipped")))
     }
+    if (nbt.hasKey("upgrade")) {
+      equippedUpgrade = Option(ItemStack.loadItemStackFromNBT(nbt.getCompoundTag("upgrade")))
+    }
     xp = nbt.getDouble(Settings.namespace + "xp")
     updateXpInfo()
     animationTicksTotal = nbt.getInteger("animationTicksTotal")
@@ -351,6 +356,9 @@ class Robot(isRemote: Boolean) extends Computer(isRemote) with ISidedInventory w
     if (getStackInSlot(0) != null) {
       nbt.setNewCompoundTag("equipped", getStackInSlot(0).writeToNBT)
     }
+    if (getStackInSlot(3) != null) {
+      nbt.setNewCompoundTag("upgrade", getStackInSlot(3).writeToNBT)
+    }
     nbt.setDouble(Settings.namespace + "xp", xp)
     if (isAnimatingMove || isAnimatingSwing || isAnimatingTurn) {
       nbt.setInteger("animationTicksTotal", animationTicksTotal)
@@ -389,11 +397,14 @@ class Robot(isRemote: Boolean) extends Computer(isRemote) with ISidedInventory w
   override protected def onItemRemoved(slot: Int, stack: ItemStack) {
     super.onItemRemoved(slot, stack)
     if (isServer) {
-      if (slot == 0) {
+      if (isToolSlot(slot)) {
         player_.getAttributeMap.removeAttributeModifiers(stack.getAttributeModifiers)
         ServerPacketSender.sendRobotEquippedItemChange(this, null)
       }
-      else if (slot >= actualSlot(0)) {
+      if (isUpgradeSlot(slot)) {
+        ServerPacketSender.sendRobotEquippedUpgradeChange(this, null)
+      }
+      if (isInventorySlot(slot)) {
         computer.signal("inventory_changed", Int.box(slot - actualSlot(0) + 1))
       }
     }
@@ -401,14 +412,17 @@ class Robot(isRemote: Boolean) extends Computer(isRemote) with ISidedInventory w
 
   override protected def onItemAdded(slot: Int, stack: ItemStack) {
     if (isServer) {
-      if (slot == 0) {
+      if (isToolSlot(slot)) {
         player_.getAttributeMap.applyAttributeModifiers(stack.getAttributeModifiers)
-        ServerPacketSender.sendRobotEquippedItemChange(this, getStackInSlot(0))
+        ServerPacketSender.sendRobotEquippedItemChange(this, getStackInSlot(slot))
       }
-      else if (isComponentSlot(slot)) {
+      if (isUpgradeSlot(slot)) {
+        ServerPacketSender.sendRobotEquippedUpgradeChange(this, getStackInSlot(slot))
+      }
+      if (isComponentSlot(slot)) {
         super.onItemAdded(slot, stack)
       }
-      else if (slot >= actualSlot(0)) {
+      if (isInventorySlot(slot)) {
         computer.signal("inventory_changed", Int.box(slot - actualSlot(0) + 1))
       }
     }
@@ -416,6 +430,12 @@ class Robot(isRemote: Boolean) extends Computer(isRemote) with ISidedInventory w
 
   override protected def isComponentSlot(slot: Int) = slot > 0 && slot < actualSlot(0)
 
+  private def isInventorySlot(slot: Int) = slot >= actualSlot(0)
+
+  private def isToolSlot(slot: Int) = slot == 0
+
+  private def isUpgradeSlot(slot: Int) = slot == 3
+
   // ----------------------------------------------------------------------- //
 
   override def installedMemory = 64 * 1024

li/cil/oc/server/PacketSender.scala

@@ -123,6 +123,15 @@ object PacketSender {
     pb.sendToNearbyPlayers(t)
   }
 
+  def sendRobotEquippedUpgradeChange(t: Robot, stack: ItemStack) {
+    val pb = new PacketBuilder(PacketType.RobotEquippedUpgradeChange)
+
+    pb.writeTileEntity(t.proxy)
+    pb.writeItemStack(stack)
+
+    pb.sendToNearbyPlayers(t)
+  }
+
   def sendRobotSelectedSlotChange(t: Robot) {
     val pb = new PacketBuilder(PacketType.RobotSelectedSlotChange)