Update screen contents once per tick

Fixes #117. Closes #103.

src/main/scala/ocelot/desktop/node/nodes/ScreenNode.scala

@@ -7,7 +7,7 @@ import ocelot.desktop.node.Node.{HighlightThickness, NoHighlightSize, Size}
 import ocelot.desktop.node.nodes.ScreenNode.{BorderSize, FontHeight, FontWidth}
 import ocelot.desktop.node.{EntityNode, LabeledEntityNode, WindowedNode}
 import ocelot.desktop.ui.event.ClickEvent
-import ocelot.desktop.ui.widget.ScreenAspectRatioDialog
+import ocelot.desktop.ui.widget.{ScreenAspectRatioDialog, TickUpdatable}
 import ocelot.desktop.ui.widget.contextmenu.{ContextMenu, ContextMenuEntry}
 import ocelot.desktop.util.TierColor
 import ocelot.desktop.windows.ScreenWindow
@@ -16,7 +16,12 @@ import totoro.ocelot.brain.entity.{Keyboard, Screen}
 import totoro.ocelot.brain.nbt.NBTTagCompound
 import totoro.ocelot.brain.util.PackedColor
 
-class ScreenNode(val screen: Screen) extends EntityNode(screen) with LabeledEntityNode with WindowedNode[ScreenWindow] {
+class ScreenNode(val screen: Screen)
+  extends EntityNode(screen)
+    with LabeledEntityNode
+    with WindowedNode[ScreenWindow]
+    with TickUpdatable {
+
   override def minimumSize: Size2D = Size2D(
     Size * screen.aspectRatio._1,
     Size * screen.aspectRatio._2
@@ -28,6 +33,11 @@ class ScreenNode(val screen: Screen) extends EntityNode(screen) with LabeledEnti
 
   private val viewport = new ScreenViewport(160 * 8, 160 * 8)
 
+  // the cached contents of the screen, updated every tick to synchronize with the TPS rate
+  private var colorBuffer = Array.fill[Short](screen.getHeight, screen.getWidth)(0)
+  private var textBuffer = Array.fill[Int](screen.getHeight, screen.getWidth)(0x20)
+  private var bufferRendered = false
+
   private var keyboard: Option[Keyboard] = None
   private val keyboardNBTKey: String = "keyboard"
 
@@ -105,7 +115,8 @@ class ScreenNode(val screen: Screen) extends EntityNode(screen) with LabeledEnti
   }
 
   private def drawScreenTexture(): Unit = {
-    // TODO: cache
+    if (bufferRendered) return
+
     val width = (screen.getWidth * FontWidth).toInt
     val height = (screen.getHeight * FontHeight).toInt
 
@@ -126,6 +137,8 @@ class ScreenNode(val screen: Screen) extends EntityNode(screen) with LabeledEnti
       }
     }
 
+    bufferRendered = true
+
     viewport.flush()
   }
 
@@ -352,6 +365,29 @@ class ScreenNode(val screen: Screen) extends EntityNode(screen) with LabeledEnti
     }
   }
 
+  override def tickUpdate(): Unit = {
+    super.tickUpdate()
+
+    val newWidth = screen.getWidth
+    val newHeight = screen.getHeight
+
+    if (textBuffer.length != newHeight || textBuffer(0).length != newWidth) {
+      // create new arrays
+      colorBuffer = Array.tabulate(newHeight, newWidth)((y, x) => screen.data.color(y)(x))
+      textBuffer = Array.tabulate(newHeight, newWidth)((y, x) => screen.data.buffer(y)(x))
+    } else {
+      // reuse existing arrays
+      for (y <- 0 until newHeight) {
+        for (x <- 0 until newWidth) {
+          colorBuffer(y)(x) = screen.data.color(y)(x)
+          textBuffer(y)(x) = screen.data.buffer(y)(x)
+        }
+      }
+    }
+
+    bufferRendered = false
+  }
+
   override def createWindow(): ScreenWindow = new ScreenWindow(this)
 }