provide configuration option to set max signal queue size

closes #3084

src/main/resources/application.conf

@@ -268,6 +268,15 @@ opencomputers {
       # IN PARTICULAR, DO NOT REPORT ISSUES AFTER MESSING WITH THIS!
       maxTotalRam: 67108864
     }
+
+    # The maximum depth a machine will queue signals before dropping them
+    # A machine state should be pulling signals via computer.pullSignal
+    # As the machine receives signals they are queued for pulling, and
+    # this maximum defines the max queue size. All signals recieved when
+    # the queue is full are discarded. Note that clipboard text creates
+    # a signal for each line of text. Thus client are limited to pasting
+    # text of this many lines. The default (and minimum) is 256
+    maxSignalQueueSize: 256
   }
 
   # Robot related settings, what they may do and general balancing.

src/main/scala/li/cil/oc/Settings.scala

@@ -338,7 +338,6 @@ class Settings(val config: Config) {
   val maxScreenWidth = config.getInt("misc.maxScreenWidth") max 1
   val maxScreenHeight = config.getInt("misc.maxScreenHeight") max 1
   val inputUsername = config.getBoolean("misc.inputUsername")
-  val maxClipboard = config.getInt("misc.maxClipboard") max 0
   val maxNetworkPacketSize = config.getInt("misc.maxNetworkPacketSize") max 0
   // Need at least 4 for nanomachine protocol. Because I can!
   val maxNetworkPacketParts = config.getInt("misc.maxNetworkPacketParts") max 4
@@ -465,6 +464,9 @@ class Settings(val config: Config) {
 
   val registerLuaJArchitecture = config.getBoolean("debug.registerLuaJArchitecture")
   val disableLocaleChanging = config.getBoolean("debug.disableLocaleChanging")
+
+  // >= 1.7.4
+  val maxSignalQueueSize: Int = (if (config.hasPath("computer.maxSignalQueueSize")) config.getInt("computer.maxSignalQueueSize") else 256) min 256
 }
 
 object Settings {

src/main/scala/li/cil/oc/server/machine/Machine.scala

@@ -102,6 +102,8 @@ class Machine(val host: MachineHost) extends prefab.ManagedEnvironment with mach
 
   private var cost = Settings.get.computerCost * Settings.get.tickFrequency
 
+  private val maxSignalQueueSize = Settings.get.maxSignalQueueSize
+
   // ----------------------------------------------------------------------- //
 
   override def onHostChanged(): Unit = {
@@ -311,7 +313,7 @@ class Machine(val host: MachineHost) extends prefab.ManagedEnvironment with mach
     state.synchronized(state.top match {
       case Machine.State.Stopped | Machine.State.Stopping => return false
       case _ => signals.synchronized {
-        if (signals.size >= 256) return false
+        if (signals.size >= maxSignalQueueSize) return false
         else if (args == null) {
           signals.enqueue(new Machine.Signal(name, Array.empty))
         }