init

.gitignore

@@ -0,0 +1,4 @@
+.gradle/
+build/
+.kotlin/
+.idea/

README.md

@@ -0,0 +1,3 @@
+# kswingutil
+
+Kotlin Swing Utilities

build.gradle.kts

@@ -0,0 +1,28 @@
+import org.jetbrains.kotlin.gradle.dsl.JvmTarget
+
+plugins {
+    kotlin("jvm") version "2.1.10"
+    `maven-publish` // for publishToMavenLocal
+}
+
+group = "net.eksb"
+
+dependencies {}
+
+java {
+    targetCompatibility = JavaVersion.VERSION_17
+    sourceCompatibility = JavaVersion.VERSION_17
+}
+kotlin {
+    compilerOptions {
+        jvmTarget.set(JvmTarget.JVM_17)
+    }
+}
+
+publishing {
+    publications {
+        create<MavenPublication>("maven") {
+            from(components["java"])
+        }
+    }
+}

gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,7 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.12.1-bin.zip
+networkTimeout=10000
+validateDistributionUrl=true
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists

gradlew

@@ -0,0 +1,249 @@
+#!/bin/sh
+
+#
+# Copyright © 2015-2021 the original authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+##############################################################################
+#
+#   Gradle start up script for POSIX generated by Gradle.
+#
+#   Important for running:
+#
+#   (1) You need a POSIX-compliant shell to run this script. If your /bin/sh is
+#       noncompliant, but you have some other compliant shell such as ksh or
+#       bash, then to run this script, type that shell name before the whole
+#       command line, like:
+#
+#           ksh Gradle
+#
+#       Busybox and similar reduced shells will NOT work, because this script
+#       requires all of these POSIX shell features:
+#         * functions;
+#         * expansions «$var», «${var}», «${var:-default}», «${var+SET}»,
+#           «${var#prefix}», «${var%suffix}», and «$( cmd )»;
+#         * compound commands having a testable exit status, especially «case»;
+#         * various built-in commands including «command», «set», and «ulimit».
+#
+#   Important for patching:
+#
+#   (2) This script targets any POSIX shell, so it avoids extensions provided
+#       by Bash, Ksh, etc; in particular arrays are avoided.
+#
+#       The "traditional" practice of packing multiple parameters into a
+#       space-separated string is a well documented source of bugs and security
+#       problems, so this is (mostly) avoided, by progressively accumulating
+#       options in "$@", and eventually passing that to Java.
+#
+#       Where the inherited environment variables (DEFAULT_JVM_OPTS, JAVA_OPTS,
+#       and GRADLE_OPTS) rely on word-splitting, this is performed explicitly;
+#       see the in-line comments for details.
+#
+#       There are tweaks for specific operating systems such as AIX, CygWin,
+#       Darwin, MinGW, and NonStop.
+#
+#   (3) This script is generated from the Groovy template
+#       https://github.com/gradle/gradle/blob/HEAD/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       within the Gradle project.
+#
+#       You can find Gradle at https://github.com/gradle/gradle/.
+#
+##############################################################################
+
+# Attempt to set APP_HOME
+
+# Resolve links: $0 may be a link
+app_path=$0
+
+# Need this for daisy-chained symlinks.
+while
+    APP_HOME=${app_path%"${app_path##*/}"}  # leaves a trailing /; empty if no leading path
+    [ -h "$app_path" ]
+do
+    ls=$( ls -ld "$app_path" )
+    link=${ls#*' -> '}
+    case $link in             #(
+      /*)   app_path=$link ;; #(
+      *)    app_path=$APP_HOME$link ;;
+    esac
+done
+
+# This is normally unused
+# shellcheck disable=SC2034
+APP_BASE_NAME=${0##*/}
+# Discard cd standard output in case $CDPATH is set (https://github.com/gradle/gradle/issues/25036)
+APP_HOME=$( cd "${APP_HOME:-./}" > /dev/null && pwd -P ) || exit
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD=maximum
+
+warn () {
+    echo "$*"
+} >&2
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+} >&2
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "$( uname )" in                #(
+  CYGWIN* )         cygwin=true  ;; #(
+  Darwin* )         darwin=true  ;; #(
+  MSYS* | MINGW* )  msys=true    ;; #(
+  NONSTOP* )        nonstop=true ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD=$JAVA_HOME/jre/sh/java
+    else
+        JAVACMD=$JAVA_HOME/bin/java
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD=java
+    if ! command -v java >/dev/null 2>&1
+    then
+        die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+fi
+
+# Increase the maximum file descriptors if we can.
+if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
+    case $MAX_FD in #(
+      max*)
+        # In POSIX sh, ulimit -H is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC3045
+        MAX_FD=$( ulimit -H -n ) ||
+            warn "Could not query maximum file descriptor limit"
+    esac
+    case $MAX_FD in  #(
+      '' | soft) :;; #(
+      *)
+        # In POSIX sh, ulimit -n is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC3045
+        ulimit -n "$MAX_FD" ||
+            warn "Could not set maximum file descriptor limit to $MAX_FD"
+    esac
+fi
+
+# Collect all arguments for the java command, stacking in reverse order:
+#   * args from the command line
+#   * the main class name
+#   * -classpath
+#   * -D...appname settings
+#   * --module-path (only if needed)
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and GRADLE_OPTS environment variables.
+
+# For Cygwin or MSYS, switch paths to Windows format before running java
+if "$cygwin" || "$msys" ; then
+    APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
+    CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )
+
+    JAVACMD=$( cygpath --unix "$JAVACMD" )
+
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    for arg do
+        if
+            case $arg in                                #(
+              -*)   false ;;                            # don't mess with options #(
+              /?*)  t=${arg#/} t=/${t%%/*}              # looks like a POSIX filepath
+                    [ -e "$t" ] ;;                      #(
+              *)    false ;;
+            esac
+        then
+            arg=$( cygpath --path --ignore --mixed "$arg" )
+        fi
+        # Roll the args list around exactly as many times as the number of
+        # args, so each arg winds up back in the position where it started, but
+        # possibly modified.
+        #
+        # NB: a `for` loop captures its iteration list before it begins, so
+        # changing the positional parameters here affects neither the number of
+        # iterations, nor the values presented in `arg`.
+        shift                   # remove old arg
+        set -- "$@" "$arg"      # push replacement arg
+    done
+fi
+
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Collect all arguments for the java command;
+#   * $DEFAULT_JVM_OPTS, $JAVA_OPTS, and $GRADLE_OPTS can contain fragments of
+#     shell script including quotes and variable substitutions, so put them in
+#     double quotes to make sure that they get re-expanded; and
+#   * put everything else in single quotes, so that it's not re-expanded.
+
+set -- \
+        "-Dorg.gradle.appname=$APP_BASE_NAME" \
+        -classpath "$CLASSPATH" \
+        org.gradle.wrapper.GradleWrapperMain \
+        "$@"
+
+# Stop when "xargs" is not available.
+if ! command -v xargs >/dev/null 2>&1
+then
+    die "xargs is not available"
+fi
+
+# Use "xargs" to parse quoted args.
+#
+# With -n1 it outputs one arg per line, with the quotes and backslashes removed.
+#
+# In Bash we could simply go:
+#
+#   readarray ARGS < <( xargs -n1 <<<"$var" ) &&
+#   set -- "${ARGS[@]}" "$@"
+#
+# but POSIX shell has neither arrays nor command substitution, so instead we
+# post-process each arg (as a line of input to sed) to backslash-escape any
+# character that might be a shell metacharacter, then use eval to reverse
+# that process (while maintaining the separation between arguments), and wrap
+# the whole thing up as a single "set" statement.
+#
+# This will of course break if any of these variables contains a newline or
+# an unmatched quote.
+#
+
+eval "set -- $(
+        printf '%s\n' "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" |
+        xargs -n1 |
+        sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; ' |
+        tr '\n' ' '
+    )" '"$@"'
+
+exec "$JAVACMD" "$@"

gradlew.bat

@@ -0,0 +1,92 @@
+@rem
+@rem Copyright 2015 the original author or authors.
+@rem
+@rem Licensed under the Apache License, Version 2.0 (the "License");
+@rem you may not use this file except in compliance with the License.
+@rem You may obtain a copy of the License at
+@rem
+@rem      https://www.apache.org/licenses/LICENSE-2.0
+@rem
+@rem Unless required by applicable law or agreed to in writing, software
+@rem distributed under the License is distributed on an "AS IS" BASIS,
+@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@rem See the License for the specific language governing permissions and
+@rem limitations under the License.
+@rem
+
+@if "%DEBUG%"=="" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%"=="" set DIRNAME=.
+@rem This is normally unused
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Resolve any "." and ".." in APP_HOME to make it shorter.
+for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if %ERRORLEVEL% equ 0 goto execute
+
+echo.
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto execute
+
+echo.
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %*
+
+:end
+@rem End local scope for the variables with windows NT shell
+if %ERRORLEVEL% equ 0 goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+set EXIT_CODE=%ERRORLEVEL%
+if %EXIT_CODE% equ 0 set EXIT_CODE=1
+if not ""=="%GRADLE_EXIT_CONSOLE%" exit %EXIT_CODE%
+exit /b %EXIT_CODE%
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega

settings.gradle.kts

@@ -0,0 +1 @@
+rootProject.name = "kswingutil"

src/main/kotlin/net/eksb/kswingutil/ext/Bind.kt

@@ -0,0 +1,85 @@
+package net.eksb.kswingutil.ext
+
+import net.eksb.kswingutil.property.MutableProperty
+import net.eksb.kswingutil.property.Property
+import java.awt.Component
+
+/**
+ * One-way bind a [java.awt.Component] to a [Property].
+ * This component's property is immediately set to the property's value.
+ * Then changes to the property are propagated to this component.
+ *
+ * @param property Property to bind from
+ * @param setter lambda to set this component's value.
+ */
+fun <T> Component.bind(property: Property<T>, setter:(T)->Unit ) {
+	val listener = { _:T, new:T -> setter(new) }
+	property.addListener(listener)
+	setter(property.value)
+	onDispose { property.removeListener(listener) }
+}
+
+/**
+ * A change listener that only gives the new value.
+ */
+typealias NewValueListener<T> = (T)->Unit
+
+/**
+ * Run only one block, even if the block calls other blocks recursively.
+ * Not thread safe. Presumably only called from the swing event dispatch thread.
+ */
+class RunOne {
+	private var isRunning = false
+	fun run(block:()->Unit) {
+		if (! isRunning) {
+			try {
+				isRunning = true
+				block.invoke()
+			} finally {
+				isRunning = false
+			}
+		}
+	}
+}
+
+/**
+ * Two-way bind a [Component] to a [Property].
+ * This component's property is immediately set to the property's value (via [setter]).
+ * Then changes to either are propagated to the other.
+ *
+ * @param property Property to bind to
+ * @param setter lambda to set this component value
+ * @param listenerRegister lambda to register a [NewValueListener] with this component
+ */
+fun <T> Component.bind(
+	property: MutableProperty<T>,
+	setter:(T)->Unit,
+	listenerRegister:(NewValueListener<T>)->Unit,
+) {
+
+	val runOne = RunOne() // avoid recursive loop
+
+	// copy from component to property
+	// register change listener with component
+	val componentChangeListener = { value:T ->
+		runOne.run {
+			property.value = value
+		}
+	}
+	listenerRegister.invoke(componentChangeListener)
+
+	// copy from property to component
+	fun propertyToComponent() {
+		runOne.run {
+			setter( property.value )
+		}
+	}
+	val listener = { old:T, new:T -> propertyToComponent() }
+	property.addListener(listener)
+	onDispose {
+		property.removeListener( listener )
+	}
+
+	// initialize component with the property's value
+	propertyToComponent()
+}

src/main/kotlin/net/eksb/kswingutil/ext/Component.kt

@@ -0,0 +1,47 @@
+package net.eksb.kswingutil.ext
+
+import net.eksb.kswingutil.property.Property
+import net.eksb.kswingutil.ext.bind
+import java.awt.Component
+import java.awt.Frame
+import java.awt.event.ComponentAdapter
+import java.awt.event.ComponentEvent
+import java.awt.event.WindowAdapter
+import java.awt.event.WindowEvent
+import javax.swing.JFrame
+import javax.swing.SwingUtilities
+import kotlin.system.exitProcess
+
+/**
+ * Bind this component to be enabled when [property] is enabled.
+ */
+fun Component.enabledWhen(property:Property<Boolean>) = bind(property) { isEnabled = it }
+
+fun Component.getFrame(): Frame =
+	this as? Frame ?: SwingUtilities.getAncestorOfClass(Frame::class.java,this) as Frame
+
+fun Component.onDispose(block:()->Unit) {
+	addComponentListener(
+		object: ComponentAdapter() {
+			var registered = false
+			override fun componentShown(e: ComponentEvent) {
+				if (! registered) {
+					getFrame().addWindowListener(
+						object: WindowAdapter() {
+							override fun windowClosed(e: WindowEvent) {
+								block()
+							}
+						})
+					registered = true
+				}
+			}
+		})
+}
+
+fun JFrame.exitOnClose() {
+	addWindowListener(object: WindowAdapter() {
+		override fun windowClosed(e: WindowEvent) {
+			exitProcess(0)
+		}
+	})
+}

src/main/kotlin/net/eksb/kswingutil/ext/Events.kt

@@ -0,0 +1,19 @@
+package net.eksb.kswingutil.ext
+
+import java.awt.Component
+import java.awt.event.MouseAdapter
+import java.awt.event.MouseEvent
+
+fun Component.onClick1(block:(MouseEvent)->Unit) {
+	onClick(MouseEvent.BUTTON1, block)
+}
+
+fun Component.onClick(button:Int?=null, block:(MouseEvent)->Unit) {
+	addMouseListener(object: MouseAdapter() {
+		override fun mouseClicked(event: MouseEvent) {
+			if (button == null || event.button == button) {
+				block(event)
+			}
+		}
+	})
+}

src/main/kotlin/net/eksb/kswingutil/ext/Ext.kt

@@ -0,0 +1,89 @@
+package net.eksb.kswingutil.ext
+
+import net.eksb.kswingutil.property.MutableProperty
+import net.eksb.kswingutil.property.Property
+import net.eksb.kswingutil.ext.bind
+import java.awt.Component
+import java.awt.Container
+import javax.swing.BorderFactory
+import javax.swing.Box
+import javax.swing.DefaultComboBoxModel
+import javax.swing.DefaultListCellRenderer
+import javax.swing.JButton
+import javax.swing.JComboBox
+import javax.swing.JComponent
+import javax.swing.JLabel
+import javax.swing.JList
+import javax.swing.JPanel
+import javax.swing.JSeparator
+
+fun Container.separator(constraints:Any?=null, alignment:Int, block:JSeparator.()->Unit ={}):JSeparator =
+	add(constraints, JSeparator(alignment),block)
+
+fun Container.panel(constraints:Any?=null, block:JPanel.()->Unit ={}):JPanel = add(constraints, JPanel(),block)
+
+fun Container.horizontalGlue():Component = add(Box.createHorizontalGlue())
+
+fun JComponent.emptyBorder(size:Int) {
+	border = BorderFactory.createEmptyBorder(size,size,size,size)
+}
+
+fun Container.label(constraints:Any?=null, text:String?=null, block:JLabel.()->Unit ={}):JLabel = add(constraints,
+	JLabel(text),block)
+
+/**
+ * Bind the supplied [Property] to this [JLabel].
+ * This label's value is immediately set from the property's value.
+ * Then changes to the property are propagated to this label.
+ */
+fun JLabel.bind(prop:Property<String>) {
+	bind(prop) { text = it }
+}
+
+fun <T> Container.combobox(constraints:Any?=null, block:JComboBox<T>.()->Unit = {}):JComboBox<T> = add(constraints,
+	JComboBox<T>(),block)
+
+fun <T> JComboBox<T>.model(values:Array<T>) {
+	model = DefaultComboBoxModel<T>(values)
+}
+
+typealias ListCellRendererLambda<T> = DefaultListCellRenderer.(
+	list:JList<T>,
+	value:T,
+	index:Int,
+	isSelected:Boolean,
+	cellHasFocus:Boolean
+)->Component
+
+inline fun <T> JComboBox<T>.renderer(crossinline block: ListCellRendererLambda<T>) {
+	renderer = object: DefaultListCellRenderer() {
+		override fun getListCellRendererComponent(
+			list:JList<*>, value:Any?, index:Int, isSelected:Boolean, cellHasFocus:Boolean
+		):Component {
+			super.getListCellRendererComponent(list, value, index, isSelected, cellHasFocus)
+			return block(list as JList<T>,value as T,index,isSelected,cellHasFocus)
+		}
+	}
+}
+
+/**
+ * Bind the supplied [MutableProperty] to this [JComboBox].
+ * This combobox's value is immediately set from the property's value.
+ * Then changes to either are propagated to the other.
+ */
+fun <T> JComboBox<T>.bind(property:MutableProperty<T>) {
+	bind(
+		property = property,
+		setter = { value ->
+			selectedItem = value
+		},
+		listenerRegister = { listener ->
+			addActionListener {
+				listener( selectedItem as T )
+			}
+		}
+	)
+}
+
+fun Container.button(constraints:Any?=null, text:String?=null, block:JButton.()->Unit = {}):JButton = add(constraints,
+	JButton(text),block)

src/main/kotlin/net/eksb/kswingutil/ext/Layout.kt

@@ -0,0 +1,33 @@
+package net.eksb.kswingutil.ext
+
+import java.awt.BorderLayout
+import java.awt.Component
+import java.awt.Container
+import java.awt.GridBagConstraints
+import java.awt.GridBagLayout
+import javax.swing.BoxLayout
+import javax.swing.JComponent
+import javax.swing.JScrollPane
+
+fun JComponent.borderLayout() {
+	layout = BorderLayout()
+}
+
+fun JComponent.gridBagLayout():GridBagConstraints {
+	layout = GridBagLayout()
+	return GridBagConstraints()
+}
+
+fun JComponent.boxLayoutHoriz() {
+	layout = BoxLayout(this, BoxLayout.X_AXIS)
+}
+
+fun <T:Component> Container.add(constraints:Any?, component:T, block:T.()->Unit):T {
+	block(component)
+	if (this is JScrollPane) {
+		this.viewport.view = component
+	} else {
+		add(component,constraints)
+	}
+	return component
+}

src/main/kotlin/net/eksb/kswingutil/property/MutableProperty.kt

@@ -0,0 +1,41 @@
+package net.eksb.kswingutil.property
+
+/**
+ * A mutable property.
+ *
+ * When used in Swing, modification of value and addition/removal of listeners
+ * should only happen on the event dispatch thread.
+ */
+class MutableProperty<T>(initialValue:T):Property<T> {
+
+	private var _value:T = initialValue
+
+	override var value:T
+		get() {
+			return _value
+		}
+		set(new) {
+			val old = _value
+			this._value = new
+			if (old != new) {
+				notify(old,new)
+			}
+		}
+
+	private val listeners:MutableList<ChangeListener<T>> = mutableListOf()
+
+	override fun addListener(listener:ChangeListener<T>) {
+		listeners.add(listener)
+	}
+	override fun removeListener(listener:ChangeListener<T>) {
+		listeners.remove(listener)
+	}
+
+	private fun notify(old:T, new:T) {
+		listeners.forEach { listener ->
+			try {
+				listener(old,new)
+			} catch (_:Exception) {}
+		}
+	}
+}

src/main/kotlin/net/eksb/kswingutil/property/Property.kt

@@ -0,0 +1,12 @@
+package net.eksb.kswingutil.property
+
+typealias ChangeListener<T> = (T, T)->Unit
+
+/**
+ * A value wrapper that supports change listeners.
+ */
+interface Property<T> {
+	val value:T
+	fun addListener(listener:ChangeListener<T>)
+	fun removeListener(listener:ChangeListener<T>)
+}

src/main/kotlin/net/eksb/kswingutil/property/PropertyExt.kt

@@ -0,0 +1,17 @@
+package net.eksb.kswingutil.property
+
+/**
+ * Map this [Property] to a [Property] via a converter
+ */
+fun <T,R> Property<T>.map(transform:(T)->R):Property<R> =
+	MutableProperty(transform(value))
+		.also { to ->
+			addListener { _, new ->
+				to.value = transform(new)
+			}
+		}
+
+/**
+ * Get a [Property] that is true when this property is not null.
+ */
+fun <T> Property<T>.mapNotNull():Property<Boolean> = map { it != null }