Scala example source code file (LayoutContainer.scala)

This example Scala source code file (LayoutContainer.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Scala tags/keywords

anyref, anyref, boolean, component, component, constraints, constraints, gui, illegalargumentexception, iterator, layoutcontainer, map, map, option, string, swing

The Scala LayoutContainer.scala source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2007-2011, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */



package scala.swing

import javax.swing.JComponent
import scala.collection.mutable.Map

/** <p>
 *    A container that associates layout constraints of member type
 *    <code>Constraints with its children. See GridBagPanel
 *    for an example container with custom constraints. 
 *  </p>
 *
 *  @note [Java Swing] In scala.swing, panels and layout managers are 
 *  combined into subclasses of this base class. This approach allows for typed
 *  component constraints.
 */
trait LayoutContainer extends Container.Wrapper {
  /**
   * The type of component constraints for this container.
   */
  type Constraints <: AnyRef
  
  /**
   * Obtains the constraints for the given component from the underlying
   * Swing layout manager.
   */
  protected def constraintsFor(c: Component): Constraints
  /**
   * Checks whether the given constraints are valid. Additionally returns
   * an error string that is only fetched if the constraints aren't valid.
   */
  protected def areValid(c: Constraints): (Boolean, String)
  /**
   * Adds a component with the given constraints to the underlying layout 
   * manager and the component peer. This method needs to interact properly 
   * with method `constraintsFor`, i.e., it might need to remove previously
   * held components in order to maintain layout consistency. See `BorderPanel`
   * for an example.
   */
  protected def add(comp: Component, c: Constraints)
  
  /**
   * A map of components to the associated layout constraints.
   * Any element in this map is automatically added to the contents of this 
   * panel. Therefore, specifying the layout of a component via 
   * 
   * layout(myComponent) = myConstraints
   * 
   * also ensures that myComponent is properly added to this container.
   */
  def layout: Map[Component, Constraints] = new Map[Component, Constraints] {
    def -= (c: Component): this.type = { _contents -= c; this }
    def += (cl: (Component, Constraints)): this.type = { update(cl._1, cl._2); this }
    override def update (c: Component, l: Constraints) {
      val (v, msg) = areValid(l)
      if (!v) throw new IllegalArgumentException(msg)
      add(c, l)
      this
    }
    def get(c: Component) = Option(constraintsFor(c))
    override def size = peer.getComponentCount
    def iterator: Iterator[(Component, Constraints)] = 
      peer.getComponents.iterator.map { c => 
        val comp = UIElement.cachedWrapper[Component](c.asInstanceOf[JComponent])
        (comp, constraintsFor(comp))
      }
  }
}