src/main/scala/li/cil/oc/server/component/GraphicsCard.scala - minecraft/opencomputers - Rivoreo Source Code Repositories

 package li.cil.oc.server.component

 import li.cil.oc.api.Network
 import li.cil.oc.api.network._
 import li.cil.oc.common.component.Buffer
 import li.cil.oc.common.tileentity
 import li.cil.oc.Settings
 import li.cil.oc.util.PackedColor
 import net.minecraft.nbt.NBTTagCompound
 import net.minecraft.util.StatCollector

 abstract class GraphicsCard extends ManagedComponent {
   val node = Network.newNode(this, Visibility.Neighbors).
     withComponent("gpu").
     withConnector().
     create()

   val maxResolution: (Int, Int)

   val maxDepth: PackedColor.Depth.Value

   private var screenAddress: Option[String] = None

   private var screenInstance: Option[Buffer] = None

   private def screen(f: (Buffer) => Array[AnyRef]) = screenInstance match {
     case Some(screen) => screen.synchronized(f(screen))
     case _ => Array(Unit, "no screen")
   }

   // ----------------------------------------------------------------------- //

   override val canUpdate = true

   override def update() {
     super.update()
     if (node.network != null && screenInstance.isEmpty && screenAddress.isDefined) {
       Option(node.network.node(screenAddress.get)) match {
         case Some(node: Node) if node.host.isInstanceOf[Buffer] =>
           screenInstance = Some(node.host.asInstanceOf[Buffer])
         case _ =>
           // This could theoretically happen after loading an old address, but
           // if the screen either disappeared between saving and now or changed
           // type. The first scenario is more likely, and could happen if the
           // chunk the screen is in isn't loaded when the chunk the GPU is in
           // gets loaded.
           screenAddress = None
       }
     }
   }

   @Callback
   def bind(context: Context, args: Arguments): Array[AnyRef] = {
     val address = args.checkString(0)
     node.network.node(address) match {
       case null => result(Unit, "invalid address")
       case node: Node if node.host.isInstanceOf[Buffer] =>
         screenAddress = Option(address)
         screenInstance = Some(node.host.asInstanceOf[Buffer])
         screen(s => {
           val (gmw, gmh) = maxResolution
           val (smw, smh) = s.maxResolution
           s.resolution = (math.min(gmw, smw), math.min(gmh, smh))
           s.format = PackedColor.Depth.format(PackedColor.Depth(math.min(maxDepth.id, s.maxDepth.id)))
           s.foreground = PackedColor.Color(0xFFFFFF)
           s.background = PackedColor.Color(0x000000)
           result(true)
         })
       case _ => result(Unit, "not a screen")
     }
   }

   @Callback(direct = true)
   def getBackground(context: Context, args: Arguments): Array[AnyRef] =
     screen(s => result(s.background.value, s.background.isPalette))

   def setBackground(context: Context, args: Arguments): Array[AnyRef] = {
     val color = args.checkInteger(0)
     screen(s => {
       val background = s.background = PackedColor.Color(color, args.count > 1 && args.checkBoolean(1))
       result(background.value, background.isPalette)
     })
   }

   @Callback(direct = true)
   def getForeground(context: Context, args: Arguments): Array[AnyRef] =
     screen(s => result(s.foreground.value, s.foreground.isPalette))

   def setForeground(context: Context, args: Arguments): Array[AnyRef] = {
     val color = args.checkInteger(0)
     screen(s => {
       val foreground = s.foreground = PackedColor.Color(color, args.count > 1 && args.checkBoolean(1))
       result(foreground.value, foreground.isPalette)
     })
   }

   @Callback(direct = true)
   def getPaletteColor(context: Context, args: Arguments): Array[AnyRef] = {
     val index = args.checkInteger(0)
     screen(s => result(s.getPalette(index)))
   }

   @Callback
   def setPaletteColor(context: Context, args: Arguments): Array[AnyRef] = {
     val index = args.checkInteger(0)
     val color = args.checkInteger(1)
     context.pause(0.1)
     screen(s => result(s.setPalette(index, color)))
   }

   @Callback(direct = true)
   def getDepth(context: Context, args: Arguments): Array[AnyRef] =
     screen(s => result(PackedColor.Depth.bits(s.format.depth)))

   @Callback
   def setDepth(context: Context, args: Arguments): Array[AnyRef] = {
     val depth = args.checkInteger(0)
     screen(s => result(s.format = depth match {
       case 1 => PackedColor.Depth.format(PackedColor.Depth.OneBit)
       case 4 if maxDepth >= PackedColor.Depth.FourBit => PackedColor.Depth.format(PackedColor.Depth.FourBit)
       case 8 if maxDepth >= PackedColor.Depth.EightBit => PackedColor.Depth.format(PackedColor.Depth.EightBit)
       case _ => throw new IllegalArgumentException("unsupported depth")
     }))
   }

   @Callback(direct = true)
   def maxDepth(context: Context, args: Arguments): Array[AnyRef] =
     screen(s => result(PackedColor.Depth(math.min(maxDepth.id, s.maxDepth.id)) match {
       case PackedColor.Depth.OneBit => 1
       case PackedColor.Depth.FourBit => 4
       case PackedColor.Depth.EightBit => 8
     }))

   @Callback(direct = true)
   def getResolution(context: Context, args: Arguments): Array[AnyRef] =
     screen(s => {
       val (w, h) = s.resolution
       result(w, h)
     })

   @Callback
   def setResolution(context: Context, args: Arguments): Array[AnyRef] = {
     val w = args.checkInteger(0)
     val h = args.checkInteger(1)
     val (mw, mh) = maxResolution
     // Even though the buffer itself checks this again, we need this here for
     // the minimum of screen and GPU resolution.
     if (w < 1 || h < 1 || w > mw || h > mw || h * w > mw * mh)
       throw new IllegalArgumentException("unsupported resolution")
     screen(s => result(s.resolution = (w, h)))
   }

   @Callback(direct = true)
   def maxResolution(context: Context, args: Arguments): Array[AnyRef] =
     screen(s => {
       val (gmw, gmh) = maxResolution
       val (smw, smh) = s.maxResolution
       result(math.min(gmw, smw), math.min(gmh, smh))
     })

   @Callback
   def getSize(context: Context, args: Arguments): Array[AnyRef] =
     screen(s => s.owner match {
       case screen: tileentity.Screen => result(screen.width, screen.height)
       case _ => result(1, 1)
     })

   @Callback(direct = true)
   def get(context: Context, args: Arguments): Array[AnyRef] = {
     val x = args.checkInteger(0) - 1
     val y = args.checkInteger(1) - 1
     screen(s => {
       val char = s.get(x, y)
       val color = s.color(y)(x)
       val format = s.format
       val foreground = PackedColor.unpackForeground(color, format)
       val background = PackedColor.unpackBackground(color, format)
       result(char, foreground, background)
     })
   }

   def set(context: Context, args: Arguments): Array[AnyRef] = {
     val x = args.checkInteger(0) - 1
     val y = args.checkInteger(1) - 1
     val value = args.checkString(2)

     screen(s => {
       if (consumePower(value.length, Settings.get.gpuSetCost)) {
         s.set(x, y, value)
         result(true)
       }
       else result(Unit, "not enough energy")
     })
   }

   def copy(context: Context, args: Arguments): Array[AnyRef] = {
     val x = args.checkInteger(0) - 1
     val y = args.checkInteger(1) - 1
     val w = args.checkInteger(2)
     val h = args.checkInteger(3)
     val tx = args.checkInteger(4)
     val ty = args.checkInteger(5)
     screen(s => {
       if (consumePower(w * h, Settings.get.gpuCopyCost)) {
         s.copy(x, y, w, h, tx, ty)
         result(true)
       }
       else result(Unit, "not enough energy")
     })
   }

   def fill(context: Context, args: Arguments): Array[AnyRef] = {
     val x = args.checkInteger(0) - 1
     val y = args.checkInteger(1) - 1
     val w = args.checkInteger(2)
     val h = args.checkInteger(3)
     val value = args.checkString(4)
     if (value.length == 1) screen(s => {
       val c = value.charAt(0)
       val cost = if (c == ' ') Settings.get.gpuClearCost else Settings.get.gpuFillCost
       if (consumePower(w * h, cost)) {
         s.fill(x, y, w, h, value.charAt(0))
         result(true)
       }
       else {
         result(Unit, "not enough energy")
       }
     })
     else throw new Exception("invalid fill value")
   }

   private def consumePower(n: Double, cost: Double) = node.tryChangeBuffer(-n * cost)

   // ----------------------------------------------------------------------- //

   override def onMessage(message: Message) {
     super.onMessage(message)
     if (message.name == "computer.stopped" && node.isNeighborOf(message.source)) {
       screenInstance match {
         case Some(buffer) => buffer.synchronized {
           val (w, h) = buffer.resolution
           buffer.foreground = PackedColor.Color(0xFFFFFF)
           message.source.host match {
             case machine: machine.Machine if machine.lastError != null =>
               if (buffer.format.depth > PackedColor.Depth.OneBit) buffer.background = PackedColor.Color(0x0000FF)
               else buffer.background = PackedColor.Color(0x000000)
               if (buffer.buffer.fill(0, 0, w, h, ' ')) {
                 buffer.owner.onScreenFill(0, 0, w, h, ' ')
               }
               try {
                 val message = "Unrecoverable error:\n" + StatCollector.translateToLocal(machine.lastError) + "\n"
                 val wrapRegEx = s"(.{1,${math.max(1, w - 2)}})\\s".r
                 val lines = wrapRegEx.replaceAllIn(message, m => m.group(1) + "\n").lines.toArray
                 for ((line, idx) <- lines.zipWithIndex) {
                   val col = (w - line.length) / 2
                   val row = (h - lines.length) / 2 + idx
                   buffer.buffer.set(col, row, line)
                   buffer.owner.onScreenSet(col, row, line)
                 }
               }
               catch {
                 case t: Throwable => t.printStackTrace()
               }
             case _ =>
               buffer.background = PackedColor.Color(0x000000)
               if (buffer.buffer.fill(0, 0, w, h, ' ')) {
                 buffer.owner.onScreenFill(0, 0, w, h, ' ')
               }
           }
         }
         case _ =>
       }
     }
   }

   override def onDisconnect(node: Node) {
     super.onDisconnect(node)
     if (node == this.node || screenAddress.exists(_ == node.address)) {
       screenAddress = None
       screenInstance = None
     }
   }

   // ----------------------------------------------------------------------- //

   override def load(nbt: NBTTagCompound) {
     super.load(nbt)

     if (nbt.hasKey("screen")) {
       nbt.getString("screen") match {
         case screen: String if !screen.isEmpty => screenAddress = Some(screen)
         case _ => screenAddress = None
       }
       screenInstance = None
     }
   }

   override def save(nbt: NBTTagCompound) {
     super.save(nbt)

     if (screenAddress.isDefined) {
       nbt.setString("screen", screenAddress.get)
     }
   }
 }

 object GraphicsCard {

   // IMPORTANT: usually methods with side effects should *not* be direct
   // callbacks to avoid the massive headache synchronizing them ensues, in
   // particular when it comes to world saving. I'm making an exception for
   // screens, though since they'd be painfully sluggish otherwise. This also
   // means we have to use a somewhat nasty trick in common.component.Buffer's
   // save function: we wait for all computers in the same network to finish
   // their current execution and then pause them, to ensure the state of the
   // buffer is "clean", meaning the computer has the correct state when it is
   // saved in turn. If we didn't, a computer might change a screen after it was
   // saved, but before the computer was saved, leading to mismatching states in
   // the save file - a Bad Thing (TM).

   class Tier1 extends GraphicsCard {
     val maxDepth = Settings.screenDepthsByTier(0)
     val maxResolution = Settings.screenResolutionsByTier(0)

     @Callback(direct = true, limit = 1)
     override def copy(context: Context, args: Arguments) = super.copy(context, args)

     @Callback(direct = true, limit = 1)
     override def fill(context: Context, args: Arguments) = super.fill(context, args)

     @Callback(direct = true, limit = 4)
     override def set(context: Context, args: Arguments) = super.set(context, args)

     @Callback(direct = true, limit = 2)
     override def setBackground(context: Context, args: Arguments) = super.setBackground(context, args)

     @Callback(direct = true, limit = 2)
     override def setForeground(context: Context, args: Arguments) = super.setForeground(context, args)
   }

   class Tier2 extends GraphicsCard {
     val maxDepth = Settings.screenDepthsByTier(1)
     val maxResolution = Settings.screenResolutionsByTier(1)

     @Callback(direct = true, limit = 2)
     override def copy(context: Context, args: Arguments) = super.copy(context, args)

     @Callback(direct = true, limit = 4)
     override def fill(context: Context, args: Arguments) = super.fill(context, args)

     @Callback(direct = true, limit = 8)
     override def set(context: Context, args: Arguments) = super.set(context, args)

     @Callback(direct = true, limit = 4)
     override def setBackground(context: Context, args: Arguments) = super.setBackground(context, args)

     @Callback(direct = true, limit = 4)
     override def setForeground(context: Context, args: Arguments) = super.setForeground(context, args)
   }

   class Tier3 extends GraphicsCard {
     val maxDepth = Settings.screenDepthsByTier(2)
     val maxResolution = Settings.screenResolutionsByTier(2)

     @Callback(direct = true, limit = 4)
     override def copy(context: Context, args: Arguments) = super.copy(context, args)

     @Callback(direct = true, limit = 8)
     override def fill(context: Context, args: Arguments) = super.fill(context, args)

     @Callback(direct = true, limit = 16)
     override def set(context: Context, args: Arguments) = super.set(context, args)

     @Callback(direct = true, limit = 8)
     override def setBackground(context: Context, args: Arguments) = super.setBackground(context, args)

     @Callback(direct = true, limit = 8)
     override def setForeground(context: Context, args: Arguments) = super.setForeground(context, args)
   }

 }
	package li.cil.oc.server.component

	import li.cil.oc.api.Network
	import li.cil.oc.api.network._
	import li.cil.oc.common.component.Buffer
	import li.cil.oc.common.tileentity
	import li.cil.oc.Settings
	import li.cil.oc.util.PackedColor
	import net.minecraft.nbt.NBTTagCompound
	import net.minecraft.util.StatCollector

	abstract class GraphicsCard extends ManagedComponent {
	val node = Network.newNode(this, Visibility.Neighbors).
	withComponent("gpu").
	withConnector().
	create()

	val maxResolution: (Int, Int)

	val maxDepth: PackedColor.Depth.Value

	private var screenAddress: Option[String] = None

	private var screenInstance: Option[Buffer] = None

	private def screen(f: (Buffer) => Array[AnyRef]) = screenInstance match {
	case Some(screen) => screen.synchronized(f(screen))
	case _ => Array(Unit, "no screen")
	}

	// ----------------------------------------------------------------------- //

	override val canUpdate = true

	override def update() {
	super.update()
	if (node.network != null && screenInstance.isEmpty && screenAddress.isDefined) {
	Option(node.network.node(screenAddress.get)) match {
	case Some(node: Node) if node.host.isInstanceOf[Buffer] =>
	screenInstance = Some(node.host.asInstanceOf[Buffer])
	case _ =>
	// This could theoretically happen after loading an old address, but
	// if the screen either disappeared between saving and now or changed
	// type. The first scenario is more likely, and could happen if the
	// chunk the screen is in isn't loaded when the chunk the GPU is in
	// gets loaded.
	screenAddress = None
	}
	}
	}

	@Callback
	def bind(context: Context, args: Arguments): Array[AnyRef] = {
	val address = args.checkString(0)
	node.network.node(address) match {
	case null => result(Unit, "invalid address")
	case node: Node if node.host.isInstanceOf[Buffer] =>
	screenAddress = Option(address)
	screenInstance = Some(node.host.asInstanceOf[Buffer])
	screen(s => {
	val (gmw, gmh) = maxResolution
	val (smw, smh) = s.maxResolution
	s.resolution = (math.min(gmw, smw), math.min(gmh, smh))
	s.format = PackedColor.Depth.format(PackedColor.Depth(math.min(maxDepth.id, s.maxDepth.id)))
	s.foreground = PackedColor.Color(0xFFFFFF)
	s.background = PackedColor.Color(0x000000)
	result(true)
	})
	case _ => result(Unit, "not a screen")
	}
	}

	@Callback(direct = true)
	def getBackground(context: Context, args: Arguments): Array[AnyRef] =
	screen(s => result(s.background.value, s.background.isPalette))

	def setBackground(context: Context, args: Arguments): Array[AnyRef] = {
	val color = args.checkInteger(0)
	screen(s => {
	val background = s.background = PackedColor.Color(color, args.count > 1 && args.checkBoolean(1))
	result(background.value, background.isPalette)
	})
	}

	@Callback(direct = true)
	def getForeground(context: Context, args: Arguments): Array[AnyRef] =
	screen(s => result(s.foreground.value, s.foreground.isPalette))

	def setForeground(context: Context, args: Arguments): Array[AnyRef] = {
	val color = args.checkInteger(0)
	screen(s => {
	val foreground = s.foreground = PackedColor.Color(color, args.count > 1 && args.checkBoolean(1))
	result(foreground.value, foreground.isPalette)
	})
	}

	@Callback(direct = true)
	def getPaletteColor(context: Context, args: Arguments): Array[AnyRef] = {
	val index = args.checkInteger(0)
	screen(s => result(s.getPalette(index)))
	}

	@Callback
	def setPaletteColor(context: Context, args: Arguments): Array[AnyRef] = {
	val index = args.checkInteger(0)
	val color = args.checkInteger(1)
	context.pause(0.1)
	screen(s => result(s.setPalette(index, color)))
	}

	@Callback(direct = true)
	def getDepth(context: Context, args: Arguments): Array[AnyRef] =
	screen(s => result(PackedColor.Depth.bits(s.format.depth)))

	@Callback
	def setDepth(context: Context, args: Arguments): Array[AnyRef] = {
	val depth = args.checkInteger(0)
	screen(s => result(s.format = depth match {
	case 1 => PackedColor.Depth.format(PackedColor.Depth.OneBit)
	case 4 if maxDepth >= PackedColor.Depth.FourBit => PackedColor.Depth.format(PackedColor.Depth.FourBit)
	case 8 if maxDepth >= PackedColor.Depth.EightBit => PackedColor.Depth.format(PackedColor.Depth.EightBit)
	case _ => throw new IllegalArgumentException("unsupported depth")
	}))
	}

	@Callback(direct = true)
	def maxDepth(context: Context, args: Arguments): Array[AnyRef] =
	screen(s => result(PackedColor.Depth(math.min(maxDepth.id, s.maxDepth.id)) match {
	case PackedColor.Depth.OneBit => 1
	case PackedColor.Depth.FourBit => 4
	case PackedColor.Depth.EightBit => 8
	}))

	@Callback(direct = true)
	def getResolution(context: Context, args: Arguments): Array[AnyRef] =
	screen(s => {
	val (w, h) = s.resolution
	result(w, h)
	})

	@Callback
	def setResolution(context: Context, args: Arguments): Array[AnyRef] = {
	val w = args.checkInteger(0)
	val h = args.checkInteger(1)
	val (mw, mh) = maxResolution
	// Even though the buffer itself checks this again, we need this here for
	// the minimum of screen and GPU resolution.
	if (w < 1 \|\| h < 1 \|\| w > mw \|\| h > mw \|\| h * w > mw * mh)
	throw new IllegalArgumentException("unsupported resolution")
	screen(s => result(s.resolution = (w, h)))
	}

	@Callback(direct = true)
	def maxResolution(context: Context, args: Arguments): Array[AnyRef] =
	screen(s => {
	val (gmw, gmh) = maxResolution
	val (smw, smh) = s.maxResolution
	result(math.min(gmw, smw), math.min(gmh, smh))
	})

	@Callback
	def getSize(context: Context, args: Arguments): Array[AnyRef] =
	screen(s => s.owner match {
	case screen: tileentity.Screen => result(screen.width, screen.height)
	case _ => result(1, 1)
	})

	@Callback(direct = true)
	def get(context: Context, args: Arguments): Array[AnyRef] = {
	val x = args.checkInteger(0) - 1
	val y = args.checkInteger(1) - 1
	screen(s => {
	val char = s.get(x, y)
	val color = s.color(y)(x)
	val format = s.format
	val foreground = PackedColor.unpackForeground(color, format)
	val background = PackedColor.unpackBackground(color, format)
	result(char, foreground, background)
	})
	}

	def set(context: Context, args: Arguments): Array[AnyRef] = {
	val x = args.checkInteger(0) - 1
	val y = args.checkInteger(1) - 1
	val value = args.checkString(2)

	screen(s => {
	if (consumePower(value.length, Settings.get.gpuSetCost)) {
	s.set(x, y, value)
	result(true)
	}
	else result(Unit, "not enough energy")
	})
	}

	def copy(context: Context, args: Arguments): Array[AnyRef] = {
	val x = args.checkInteger(0) - 1
	val y = args.checkInteger(1) - 1
	val w = args.checkInteger(2)
	val h = args.checkInteger(3)
	val tx = args.checkInteger(4)
	val ty = args.checkInteger(5)
	screen(s => {
	if (consumePower(w * h, Settings.get.gpuCopyCost)) {
	s.copy(x, y, w, h, tx, ty)
	result(true)
	}
	else result(Unit, "not enough energy")
	})
	}

	def fill(context: Context, args: Arguments): Array[AnyRef] = {
	val x = args.checkInteger(0) - 1
	val y = args.checkInteger(1) - 1
	val w = args.checkInteger(2)
	val h = args.checkInteger(3)
	val value = args.checkString(4)
	if (value.length == 1) screen(s => {
	val c = value.charAt(0)
	val cost = if (c == ' ') Settings.get.gpuClearCost else Settings.get.gpuFillCost
	if (consumePower(w * h, cost)) {
	s.fill(x, y, w, h, value.charAt(0))
	result(true)
	}
	else {
	result(Unit, "not enough energy")
	}
	})
	else throw new Exception("invalid fill value")
	}

	private def consumePower(n: Double, cost: Double) = node.tryChangeBuffer(-n * cost)

	// ----------------------------------------------------------------------- //

	override def onMessage(message: Message) {
	super.onMessage(message)
	if (message.name == "computer.stopped" && node.isNeighborOf(message.source)) {
	screenInstance match {
	case Some(buffer) => buffer.synchronized {
	val (w, h) = buffer.resolution
	buffer.foreground = PackedColor.Color(0xFFFFFF)
	message.source.host match {
	case machine: machine.Machine if machine.lastError != null =>
	if (buffer.format.depth > PackedColor.Depth.OneBit) buffer.background = PackedColor.Color(0x0000FF)
	else buffer.background = PackedColor.Color(0x000000)
	if (buffer.buffer.fill(0, 0, w, h, ' ')) {
	buffer.owner.onScreenFill(0, 0, w, h, ' ')
	}
	try {
	val message = "Unrecoverable error:\n" + StatCollector.translateToLocal(machine.lastError) + "\n"
	val wrapRegEx = s"(.{1,${math.max(1, w - 2)}})\\s".r
	val lines = wrapRegEx.replaceAllIn(message, m => m.group(1) + "\n").lines.toArray
	for ((line, idx) <- lines.zipWithIndex) {
	val col = (w - line.length) / 2
	val row = (h - lines.length) / 2 + idx
	buffer.buffer.set(col, row, line)
	buffer.owner.onScreenSet(col, row, line)
	}
	}
	catch {
	case t: Throwable => t.printStackTrace()
	}
	case _ =>
	buffer.background = PackedColor.Color(0x000000)
	if (buffer.buffer.fill(0, 0, w, h, ' ')) {
	buffer.owner.onScreenFill(0, 0, w, h, ' ')
	}
	}
	}
	case _ =>
	}
	}
	}

	override def onDisconnect(node: Node) {
	super.onDisconnect(node)
	if (node == this.node \|\| screenAddress.exists(_ == node.address)) {
	screenAddress = None
	screenInstance = None
	}
	}

	// ----------------------------------------------------------------------- //

	override def load(nbt: NBTTagCompound) {
	super.load(nbt)

	if (nbt.hasKey("screen")) {
	nbt.getString("screen") match {
	case screen: String if !screen.isEmpty => screenAddress = Some(screen)
	case _ => screenAddress = None
	}
	screenInstance = None
	}
	}

	override def save(nbt: NBTTagCompound) {
	super.save(nbt)

	if (screenAddress.isDefined) {
	nbt.setString("screen", screenAddress.get)
	}
	}
	}

	object GraphicsCard {

	// IMPORTANT: usually methods with side effects should not be direct
	// callbacks to avoid the massive headache synchronizing them ensues, in
	// particular when it comes to world saving. I'm making an exception for
	// screens, though since they'd be painfully sluggish otherwise. This also
	// means we have to use a somewhat nasty trick in common.component.Buffer's
	// save function: we wait for all computers in the same network to finish
	// their current execution and then pause them, to ensure the state of the
	// buffer is "clean", meaning the computer has the correct state when it is
	// saved in turn. If we didn't, a computer might change a screen after it was
	// saved, but before the computer was saved, leading to mismatching states in
	// the save file - a Bad Thing (TM).

	class Tier1 extends GraphicsCard {
	val maxDepth = Settings.screenDepthsByTier(0)
	val maxResolution = Settings.screenResolutionsByTier(0)

	@Callback(direct = true, limit = 1)
	override def copy(context: Context, args: Arguments) = super.copy(context, args)

	@Callback(direct = true, limit = 1)
	override def fill(context: Context, args: Arguments) = super.fill(context, args)

	@Callback(direct = true, limit = 4)
	override def set(context: Context, args: Arguments) = super.set(context, args)

	@Callback(direct = true, limit = 2)
	override def setBackground(context: Context, args: Arguments) = super.setBackground(context, args)

	@Callback(direct = true, limit = 2)
	override def setForeground(context: Context, args: Arguments) = super.setForeground(context, args)
	}

	class Tier2 extends GraphicsCard {
	val maxDepth = Settings.screenDepthsByTier(1)
	val maxResolution = Settings.screenResolutionsByTier(1)

	@Callback(direct = true, limit = 2)
	override def copy(context: Context, args: Arguments) = super.copy(context, args)

	@Callback(direct = true, limit = 4)
	override def fill(context: Context, args: Arguments) = super.fill(context, args)

	@Callback(direct = true, limit = 8)
	override def set(context: Context, args: Arguments) = super.set(context, args)

	@Callback(direct = true, limit = 4)
	override def setBackground(context: Context, args: Arguments) = super.setBackground(context, args)

	@Callback(direct = true, limit = 4)
	override def setForeground(context: Context, args: Arguments) = super.setForeground(context, args)
	}

	class Tier3 extends GraphicsCard {
	val maxDepth = Settings.screenDepthsByTier(2)
	val maxResolution = Settings.screenResolutionsByTier(2)

	@Callback(direct = true, limit = 4)
	override def copy(context: Context, args: Arguments) = super.copy(context, args)

	@Callback(direct = true, limit = 8)
	override def fill(context: Context, args: Arguments) = super.fill(context, args)

	@Callback(direct = true, limit = 16)
	override def set(context: Context, args: Arguments) = super.set(context, args)

	@Callback(direct = true, limit = 8)
	override def setBackground(context: Context, args: Arguments) = super.setBackground(context, args)

	@Callback(direct = true, limit = 8)
	override def setForeground(context: Context, args: Arguments) = super.setForeground(context, args)
	}

	}