--- a/src/name/blackcap/exifwasher/Misc.kt	Wed Apr 08 21:31:30 2020 -0700
+++ b/src/name/blackcap/exifwasher/Misc.kt	Thu Apr 09 18:20:34 2020 -0700
@@ -9,7 +9,7 @@
 import javax.swing.*
 import kotlin.annotation.*
 import kotlin.properties.ReadWriteProperty
-import kotlin.reflect.KProperty
+import kotlin.reflect.*
 
 /**
  * Delegate that makes a var that can only be set once. This is commonly
@@ -17,22 +17,22 @@
  * outer levels but initialized in the Swing event dispatch thread.
  */
 class SetOnce<T: Any>: ReadWriteProperty<Any?,T> {
-    private var value: T? = null
+    private var setOnceValue: T? = null
 
     override operator fun getValue(thisRef: Any?, property: KProperty<*>): T {
-        if (value == null) {
+        if (setOnceValue == null) {
             throw RuntimeException("${property.name} has not been initialized")
         } else {
-            return value!!
+            return setOnceValue!!
         }
     }
 
     @Synchronized
-    override operator fun setValue(thisRef: Any?, property: KProperty<*>, newValue: T): Unit {
-        if (value != null) {
+    override operator fun setValue(thisRef: Any?, property: KProperty<*>, value: T): Unit {
+        if (setOnceValue != null) {
             throw RuntimeException("${property.name} has already been initialized")
         }
-        value = newValue
+        setOnceValue = value
     }
 }
 
@@ -82,14 +82,14 @@
  * Change to the standard wait cursor.
  */
 fun Component.useWaitCursor() {
-    this.cursor = Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR))
+    this.cursor = Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR)
 }
 
 /**
  * Return back to the normal cursor().
  */
 fun Component.useNormalCursor() {
-    this.cursor = Cursor.defaultCursor
+    this.cursor = Cursor.getDefaultCursor()
 }
 
 /**
@@ -105,10 +105,10 @@
  * @param T Type returned by inBackground (Java doInBackground) task.
  */
 class SwingWorkerBuilder<T>: SwingWorker<T,Unit>() {
-    private var inBackgroundLambda: (SwingWorkerBuilder.() -> T)? = null
-    private var whenDoneLambda: (SwingWorkerBuilder.() -> Unit)? = null
+    private var inBackgroundLambda: (SwingWorkerBuilder<T>.() -> T)? = null
+    private var whenDoneLambda: (SwingWorkerBuilder<T>.() -> Unit)? = null
 
-    private fun setOnce<U>(prop: KMutableProperty<(SwingWorkerBuilder.() -> U)?>, value: SwingWorkerBuilder.() -> U) {
+    private fun <U> setOnce(prop: KMutableProperty0<(SwingWorkerBuilder<T>.() -> U)?>, value: SwingWorkerBuilder<T>.() -> U) {
         if (prop.get() != null) {
             throw SwingWorkerException(prop.name.removeSuffix("Lambda") + " already defined!")
         }
@@ -118,38 +118,40 @@
     /**
      * Define the inBackground task.
      */
-    fun inBackground(lambda: SwingWorkerBuilder.() -> T): Unit {
+    fun inBackground(lambda: SwingWorkerBuilder<T>.() -> T): Unit {
         setOnce<T>(::inBackgroundLambda, lambda)
     }
 
     /**
      * Define the whenDone task.
      */
-    fun whenDone(lambda: SwingWorkerBuilder.() -> Unit): Unit {
+    fun whenDone(lambda: SwingWorkerBuilder<T>.() -> Unit): Unit {
         setOnce<Unit>(::whenDoneLambda, lambda)
     }
 
+    /**
+     * Validates we've been properly initialized.
+     */
+    fun validate(): Unit {
+        if (inBackgroundLambda == null) {
+            throw SwingWorkerException("inBackground not defined!")
+        }
+    }
+
     /* standard overrides for SwingWorker follow */
 
-    override fun doInBackground(): T = inBackgroundLambda?.invoke(this)
-
-    override fun done(): Unit = whenDoneLambda?.invoke(this)
+    override fun doInBackground(): T = inBackgroundLambda!!.invoke(this)
 
-    override fun execute(): Unit {
-        if (inBackgroundLambda == null) {
-            throw SwingWorkerException("inBackground not defined!")
-        } else {
-            super.execute()
-        }
-    }
+    override fun done(): Unit = whenDoneLambda?.invoke(this) ?: Unit
 }
 
 /**
  * Provides for an outer swingWorker block to contain the DSL.
  */
-fun swingWorker<T>(initializer: SwingWorkerBuilder.() -> Unit): Unit {
+fun <T> swingWorker(initializer: SwingWorkerBuilder<T>.() -> Unit): Unit {
     SwingWorkerBuilder<T>().run {
         initializer()
+        validate()
         execute()
     }
 }