A helper for making dialog button bars

JavaFX & ScalaFX already have one of these, but this handles padding
and automatically set up the apply, ok, cancel trilogy (though you can
disable any of these).

src/main/scala/org/gerweck/scalafx/util/control/DialogButtons.scala

@@ -0,0 +1,87 @@
+package org.gerweck.scalafx.util
+package control
+
+import org.log4s._
+
+import scalafx.Includes._
+import scalafx.event.ActionEvent
+import scalafx.event.ActionEvent
+import scalafx.geometry.Insets
+import scalafx.scene.control._
+import scalafx.scene.layout._
+import scalafx.stage.Stage
+import javafx.scene.{ Node => JNode }
+import javafx.scene.layout.{ Region => JRegion }
+import scalafx.delegate.SFXDelegate
+
+/** A standard button bar with the major dialog buttons.
+  *
+  * This will show the Okay, Cancel and Apply buttons, as well as optionally
+  * including a separator.
+  */
+class DialogButtons(stage: Stage, showOk: Boolean = true, showApply: Boolean = true, showCancel: Boolean = true) extends Region(new DialogButtons.DialogButtonsJFXRegion) {
+  protected[this] val logger = getLogger
+
+  def insetSize = 10d
+  def buttonInsets = Insets(insetSize)
+
+  def applyChanges(): Unit = {}
+
+  protected[this] def typedButton(bt: ButtonType) = {
+    val b = new Button(bt.text) {
+      padding = buttonInsets
+    }
+    ButtonBar.setButtonData(b, bt.buttonData)
+    b
+  }
+  lazy val okButton = {
+    val b = typedButton(ButtonType.OK)
+    b.onAction = { ae: ActionEvent =>
+      logger.debug(s"OK button pressed")
+      applyChanges()
+      stage.close()
+    }
+    b
+  }
+  lazy val cancelButton = {
+    val b = typedButton(ButtonType.Close)
+    b.onAction = { ae: ActionEvent =>
+      logger.debug("Cancel button pressed")
+      stage.close()
+    }
+    b
+  }
+  lazy val applyButton = {
+    val b = typedButton(ButtonType.Apply)
+    b.onAction = { ae: ActionEvent =>
+      logger.debug("Apply button pressed")
+      applyChanges()
+    }
+    b
+  }
+  private[this] def seqIf[A](gate: Boolean, a: => A): Seq[A] = {
+    if (gate) Seq(a) else Seq.empty
+  }
+  def bar = new ButtonBar {
+    padding = buttonInsets
+    buttons = {
+      seqIf(showApply, applyButton) ++
+      seqIf(showOk, okButton) ++
+      seqIf(showCancel, cancelButton)
+    }
+  }
+
+  protected[this] def mainLayout = new VBox(Separators.horizontal, bar) {
+    hgrow = Priority.Always
+  }
+
+  delegate.asInstanceOf[DialogButtons.DialogButtonsJFXRegion].addChild(mainLayout)
+}
+
+private object DialogButtons {
+  class DialogButtonsJFXRegion extends JRegion {
+    protected[control] def addChild(n: JNode) = {
+      getChildren.add(n)
+    }
+  }
+}