* Extract common functionality to UGraphicNo class

* Simplify subclass constructors
* Remove dpiFactor() methods which became redundant a while ago

src/net/sourceforge/plantuml/activitydiagram3/ftile/CollisionDetector.java

@@ -35,6 +35,8 @@
  */
 package net.sourceforge.plantuml.activitydiagram3.ftile;
 
+import static net.sourceforge.plantuml.utils.ObjectUtils.instanceOfAny;
+
 import java.awt.geom.Line2D;
 import java.util.ArrayList;
 import java.util.List;
@@ -46,36 +48,41 @@ import net.sourceforge.plantuml.ugraphic.UChange;
 import net.sourceforge.plantuml.ugraphic.UGraphic;
 import net.sourceforge.plantuml.ugraphic.UGraphicNo;
 import net.sourceforge.plantuml.ugraphic.ULine;
-import net.sourceforge.plantuml.ugraphic.UParam;
-import net.sourceforge.plantuml.ugraphic.UParamNull;
 import net.sourceforge.plantuml.ugraphic.UPolygon;
 import net.sourceforge.plantuml.ugraphic.URectangle;
 import net.sourceforge.plantuml.ugraphic.UShape;
 import net.sourceforge.plantuml.ugraphic.UStroke;
 import net.sourceforge.plantuml.ugraphic.UTranslate;
-import net.sourceforge.plantuml.ugraphic.color.ColorMapper;
 import net.sourceforge.plantuml.ugraphic.color.HColor;
 import net.sourceforge.plantuml.ugraphic.color.HColorUtils;
 
-public class CollisionDetector extends UGraphicNo implements UGraphic {
+public class CollisionDetector extends UGraphicNo {
 
+	@Override
 	public UGraphic apply(UChange change) {
-		if (change instanceof UTranslate) {
+		return new CollisionDetector(this, change);
-			return new CollisionDetector(stringBounder, translate.compose((UTranslate) change), this.context);
-		} else if (change instanceof UStroke) {
-			return new CollisionDetector(this);
-		} else if (change instanceof UBackground) {
-			return new CollisionDetector(this);
-		} else if (change instanceof HColor) {
-			return new CollisionDetector(this);
-		}
-		throw new UnsupportedOperationException();
 	}
 
-	private final StringBounder stringBounder;
-	private final UTranslate translate;
 	private final Context context;
 
+	public CollisionDetector(StringBounder stringBounder) {
+		super(stringBounder);
+		this.context = new Context();
+	}
+
+	private CollisionDetector(CollisionDetector other, UChange change) {
+		super(other, change);
+		if (!instanceOfAny(change,
+				UBackground.class,
+				HColor.class,
+				UStroke.class,
+				UTranslate.class
+		)) {
+			throw new UnsupportedOperationException(change.getClass().toString());
+		}
+		this.context = other.context;
+	}
+	
 	static class Context {
 		private final List<MinMax> rectangles = new ArrayList<>();
 		private final List<Snake> snakes = new ArrayList<>();
@@ -146,28 +153,6 @@ public class CollisionDetector extends UGraphicNo implements UGraphic {
 		return true;
 	}
 
-	public CollisionDetector(StringBounder stringBounder) {
-		this(stringBounder, new UTranslate(), new Context());
-	}
-
-	private CollisionDetector(StringBounder stringBounder, UTranslate translate, Context context) {
-		this.stringBounder = stringBounder;
-		this.translate = translate;
-		this.context = context;
-	}
-
-	private CollisionDetector(CollisionDetector other) {
-		this(other.stringBounder, other.translate, other.context);
-	}
-
-	public StringBounder getStringBounder() {
-		return stringBounder;
-	}
-
-	public UParam getParam() {
-		return new UParamNull();
-	}
-
 	public void draw(UShape shape) {
 		if (shape instanceof UPolygon) {
 			drawPolygone((UPolygon) shape);
@@ -182,24 +167,17 @@ public class CollisionDetector extends UGraphicNo implements UGraphic {
 
 	private void drawSnake(Snake shape) {
 		if (context.manageSnakes) {
-			context.snakes.add(shape.translate(translate));
+			context.snakes.add(shape.translate(getTranslate()));
 		}
 
 	}
 
 	private void drawRectangle(URectangle shape) {
-		context.rectangles.add(shape.getMinMax().translate(translate));
+		context.rectangles.add(shape.getMinMax().translate(getTranslate()));
 	}
 
 	private void drawPolygone(UPolygon shape) {
-		context.rectangles.add(shape.getMinMax().translate(translate));
+		context.rectangles.add(shape.getMinMax().translate(getTranslate()));
-	}
-
-	public ColorMapper getColorMapper() {
-		throw new UnsupportedOperationException();
-	}
-
-	public void flushUg() {
 	}
 
 	public void drawDebug(UGraphic ug) {
@@ -210,12 +188,4 @@ public class CollisionDetector extends UGraphicNo implements UGraphic {
 		this.context.manageSnakes = manageSnakes;
 	}
 
-	public boolean matchesProperty(String propertyName) {
-		return false;
-	}
-
-	public double dpiFactor() {
-		return 1;
-	}
-
 }

src/net/sourceforge/plantuml/activitydiagram3/ftile/ZadBuilder.java

@@ -35,38 +35,26 @@
  */
 package net.sourceforge.plantuml.activitydiagram3.ftile;
 
+import static net.sourceforge.plantuml.utils.ObjectUtils.instanceOfAny;
 import net.sourceforge.plantuml.graphic.StringBounder;
 import net.sourceforge.plantuml.ugraphic.MinMax;
 import net.sourceforge.plantuml.ugraphic.UBackground;
 import net.sourceforge.plantuml.ugraphic.UChange;
 import net.sourceforge.plantuml.ugraphic.UGraphic;
 import net.sourceforge.plantuml.ugraphic.UGraphicNo;
-import net.sourceforge.plantuml.ugraphic.UParam;
-import net.sourceforge.plantuml.ugraphic.UParamNull;
 import net.sourceforge.plantuml.ugraphic.URectangle;
 import net.sourceforge.plantuml.ugraphic.UShape;
 import net.sourceforge.plantuml.ugraphic.UStroke;
 import net.sourceforge.plantuml.ugraphic.UTranslate;
-import net.sourceforge.plantuml.ugraphic.color.ColorMapper;
 import net.sourceforge.plantuml.ugraphic.color.HColor;
 
-public class ZadBuilder extends UGraphicNo implements UGraphic {
+public class ZadBuilder extends UGraphicNo {
 
+	@Override
 	public UGraphic apply(UChange change) {
-		if (change instanceof UTranslate) {
+		return new ZadBuilder(this, change);
-			return new ZadBuilder(stringBounder, translate.compose((UTranslate) change), this.context);
-		} else if (change instanceof UStroke) {
-			return new ZadBuilder(this);
-		} else if (change instanceof UBackground) {
-			return new ZadBuilder(this);
-		} else if (change instanceof HColor) {
-			return new ZadBuilder(this);
-		}
-		throw new UnsupportedOperationException();
 	}
 
-	private final StringBounder stringBounder;
-	private final UTranslate translate;
 	private final Context context;
 
 	static class Context {
@@ -74,25 +62,21 @@ public class ZadBuilder extends UGraphicNo implements UGraphic {
 	}
 
 	public ZadBuilder(StringBounder stringBounder) {
-		this(stringBounder, new UTranslate(), new Context());
+		super(stringBounder);
+		this.context = new Context();
 	}
 
-	private ZadBuilder(StringBounder stringBounder, UTranslate translate, Context context) {
+	private ZadBuilder(ZadBuilder other, UChange change) {
-		this.stringBounder = stringBounder;
+		super(other, change);
-		this.translate = translate;
+		if (!instanceOfAny(change,
-		this.context = context;
+				UBackground.class,
-	}
+				HColor.class,
-
+				UStroke.class,
-	private ZadBuilder(ZadBuilder other) {
+				UTranslate.class
-		this(other.stringBounder, other.translate, other.context);
+		)) {
-	}
+			throw new UnsupportedOperationException(change.getClass().toString());
-
+		}
-	public StringBounder getStringBounder() {
+		this.context = other.context;
-		return stringBounder;
-	}
-
-	public UParam getParam() {
-		return new UParamNull();
 	}
 
 	public void draw(UShape shape) {
@@ -102,26 +86,11 @@ public class ZadBuilder extends UGraphicNo implements UGraphic {
 	}
 
 	private void drawRectangle(URectangle shape) {
-		final MinMax area = shape.getMinMax().translate(translate);
+		final MinMax area = shape.getMinMax().translate(getTranslate());
 		// System.err.println("ZadBuilder " + shape + " " + area);
 		context.zad.add(area);
 	}
 
-	public ColorMapper getColorMapper() {
-		throw new UnsupportedOperationException();
-	}
-
-	public void flushUg() {
-	}
-
-	public boolean matchesProperty(String propertyName) {
-		return false;
-	}
-
-	public double dpiFactor() {
-		return 1;
-	}
-
 	public Zad getZad() {
 		return context.zad;
 	}

src/net/sourceforge/plantuml/svek/image/Footprint.java

@@ -35,6 +35,8 @@
  */
 package net.sourceforge.plantuml.svek.image;
 
+import static net.sourceforge.plantuml.utils.ObjectUtils.instanceOfAny;
+
 import java.awt.geom.Dimension2D;
 import java.awt.geom.Point2D;
 import java.util.ArrayList;
@@ -50,8 +52,6 @@ import net.sourceforge.plantuml.ugraphic.UGraphicNo;
 import net.sourceforge.plantuml.ugraphic.UHorizontalLine;
 import net.sourceforge.plantuml.ugraphic.UImage;
 import net.sourceforge.plantuml.ugraphic.ULine;
-import net.sourceforge.plantuml.ugraphic.UParam;
-import net.sourceforge.plantuml.ugraphic.UParamNull;
 import net.sourceforge.plantuml.ugraphic.UPath;
 import net.sourceforge.plantuml.ugraphic.URectangle;
 import net.sourceforge.plantuml.ugraphic.UShape;
@@ -71,48 +71,35 @@ public class Footprint {
 
 	}
 
-	class MyUGraphic extends UGraphicNo implements UGraphic {
+	class MyUGraphic extends UGraphicNo {
 
-		private final UTranslate translate;
 		private final List<Point2D.Double> all;
 
-		public double dpiFactor() {
-			return 1;
-		}
-
-		private MyUGraphic(List<Point2D.Double> all, UTranslate translate) {
-			this.all = all;
-			this.translate = translate;
-		}
-
-		public boolean matchesProperty(String propertyName) {
-			return false;
-		}
-
 		public MyUGraphic() {
-			this(new ArrayList<Point2D.Double>(), new UTranslate());
+			super(stringBounder);
+			this.all = new ArrayList<>();
+		}
+
+		private MyUGraphic(MyUGraphic other, UChange change) {
+			super(other, change);
+			if (!instanceOfAny(change,
+					UBackground.class,
+					HColor.class,
+					UStroke.class,
+					UTranslate.class
+			)) {
+				throw new UnsupportedOperationException(change.getClass().toString());
+			}
+			this.all = other.all;
 		}
 
 		public UGraphic apply(UChange change) {
-			if (change instanceof UTranslate) {
+			return new MyUGraphic(this, change);
-				return new MyUGraphic(all, translate.compose((UTranslate) change));
-			} else if (change instanceof UStroke || change instanceof HColor || change instanceof UBackground) {
-				return new MyUGraphic(all, translate);
-			}
-			throw new UnsupportedOperationException();
-		}
-
-		public StringBounder getStringBounder() {
-			return stringBounder;
-		}
-
-		public UParam getParam() {
-			return new UParamNull();
 		}
 
 		public void draw(UShape shape) {
-			final double x = translate.getDx();
+			final double x = getTranslate().getDx();
-			final double y = translate.getDy();
+			final double y = getTranslate().getDy();
 			if (shape instanceof UText) {
 				drawText(x, y, (UText) shape);
 			} else if (shape instanceof UHorizontalLine) {
@@ -142,7 +129,7 @@ public class Footprint {
 		}
 
 		private void drawText(double x, double y, UText text) {
-			final Dimension2D dim = stringBounder.calculateDimension(text.getFontConfiguration().getFont(),
+			final Dimension2D dim = getStringBounder().calculateDimension(text.getFontConfiguration().getFont(),
 					text.getText());
 			y -= dim.getHeight() - 1.5;
 			addPoint(x, y);
@@ -172,10 +159,6 @@ public class Footprint {
 			addPoint(x, y);
 			addPoint(x + rect.getWidth(), y + rect.getHeight());
 		}
-
-		public void flushUg() {
-		}
-
 	}
 
 	public ContainingEllipse getEllipse(UDrawable drawable, double alpha) {

src/net/sourceforge/plantuml/ugraphic/LimitFinder.java

@@ -35,6 +35,8 @@
  */
 package net.sourceforge.plantuml.ugraphic;
 
+import static net.sourceforge.plantuml.utils.ObjectUtils.instanceOfAny;
+
 import java.awt.geom.Dimension2D;
 
 import net.sourceforge.plantuml.activitydiagram3.ftile.CenteredText;
@@ -46,66 +48,38 @@ import net.sourceforge.plantuml.ugraphic.color.ColorMapper;
 import net.sourceforge.plantuml.ugraphic.color.ColorMapperIdentity;
 import net.sourceforge.plantuml.ugraphic.color.HColor;
 
-public class LimitFinder extends UGraphicNo implements UGraphic {
+public class LimitFinder extends UGraphicNo {
-
-	public boolean matchesProperty(String propertyName) {
-		return false;
-	}
-
-	public double dpiFactor() {
-		return 1;
-	}
 
+	@Override
 	public UGraphic apply(UChange change) {
-		if (change instanceof UTranslate) {
+		return new LimitFinder(this, change);
-			return new LimitFinder(stringBounder, minmax, translate.compose((UTranslate) change), clip);
-		} else if (change instanceof UStroke) {
-			return new LimitFinder(this);
-		} else if (change instanceof UBackground) {
-			return new LimitFinder(this);
-		} else if (change instanceof HColor) {
-			return new LimitFinder(this);
-		} else if (change instanceof UHidden) {
-			return new LimitFinder(this);
-		} else if (change instanceof UAntiAliasing) {
-			return new LimitFinder(this);
-		} else if (change instanceof UScale) {
-			return new LimitFinder(this);
-		} else if (change instanceof UClip) {
-			final LimitFinder copy = new LimitFinder(this);
-			copy.clip = (UClip) change;
-			copy.clip = copy.clip.translate(translate);
-			return copy;
-		}
-		throw new UnsupportedOperationException(change.getClass().toString());
 	}
 
-	private final StringBounder stringBounder;
-	private final UTranslate translate;
 	private final MinMaxMutable minmax;
-	private UClip clip;
+	private final UClip clip;
 
 	public LimitFinder(StringBounder stringBounder, boolean initToZero) {
-		this(stringBounder, MinMaxMutable.getEmpty(initToZero), new UTranslate(), null);
+		super(stringBounder);
+		this.minmax = MinMaxMutable.getEmpty(initToZero);
+		this.clip = null;
 	}
 
-	private LimitFinder(StringBounder stringBounder, MinMaxMutable minmax, UTranslate translate, UClip clip) {
+	private LimitFinder(LimitFinder other, UChange change) {
-		this.stringBounder = stringBounder;
+		super(other, change);
-		this.minmax = minmax;
+		if (!instanceOfAny(change,
-		this.translate = translate;
+				UAntiAliasing.class,
-		this.clip = clip;
+				UBackground.class,
-	}
+				UClip.class,
-
+				HColor.class,
-	private LimitFinder(LimitFinder other) {
+				UHidden.class,
-		this(other.stringBounder, other.minmax, other.translate, other.clip);
+				UScale.class,
-	}
+				UStroke.class,
-
+				UTranslate.class
-	public StringBounder getStringBounder() {
+		)) {
-		return stringBounder;
+			throw new UnsupportedOperationException(change.getClass().toString());
-	}
+		}
-
+		this.clip = change instanceof UClip ? ((UClip) change).translate(getTranslate()) : other.clip;
-	public UParam getParam() {
+		this.minmax = other.minmax;
-		return new UParamNull();
 	}
 
 	private void addPoint(double x, double y) {
@@ -115,8 +89,8 @@ public class LimitFinder extends UGraphicNo implements UGraphic {
 	}
 
 	public void draw(UShape shape) {
-		final double x = translate.getDx();
+		final double x = getTranslate().getDx();
-		final double y = translate.getDy();
+		final double y = getTranslate().getDy();
 		if (shape instanceof UText) {
 			drawText(x, y, (UText) shape);
 		} else if (shape instanceof ULine) {
@@ -208,7 +182,7 @@ public class LimitFinder extends UGraphicNo implements UGraphic {
 	}
 
 	private void drawText(double x, double y, UText text) {
-		final Dimension2D dim = stringBounder.calculateDimension(text.getFontConfiguration().getFont(), text.getText());
+		final Dimension2D dim = getStringBounder().calculateDimension(text.getFontConfiguration().getFont(), text.getText());
 		y -= dim.getHeight() - 1.5;
 		addPoint(x, y);
 		addPoint(x, y + dim.getHeight());
@@ -243,7 +217,4 @@ public class LimitFinder extends UGraphicNo implements UGraphic {
 		return MinMax.fromMutable(minmax);
 	}
 
-	public void flushUg() {
-	}
-
 }

src/net/sourceforge/plantuml/ugraphic/TextLimitFinder.java

@@ -35,75 +35,50 @@
  */
 package net.sourceforge.plantuml.ugraphic;
 
+import static net.sourceforge.plantuml.utils.ObjectUtils.instanceOfAny;
+
 import java.awt.geom.Dimension2D;
 
 import net.sourceforge.plantuml.graphic.StringBounder;
-import net.sourceforge.plantuml.ugraphic.color.ColorMapper;
 import net.sourceforge.plantuml.ugraphic.color.HColor;
 
-public class TextLimitFinder extends UGraphicNo implements UGraphic {
+public class TextLimitFinder extends UGraphicNo {
-
-	public boolean matchesProperty(String propertyName) {
-		return false;
-	}
-
-	public double dpiFactor() {
-		return 1;
-	}
 
+	@Override
 	public UGraphic apply(UChange change) {
-		if (change instanceof UTranslate) {
+		return new TextLimitFinder(this, change);
-			return new TextLimitFinder(stringBounder, minmax, translate.compose((UTranslate) change));
-		} else if (change instanceof UStroke) {
-			return new TextLimitFinder(this);
-		} else if (change instanceof UBackground) {
-			return new TextLimitFinder(this);
-		} else if (change instanceof HColor) {
-			return new TextLimitFinder(this);
-		}
-		throw new UnsupportedOperationException();
 	}
 
-	private final StringBounder stringBounder;
-	private final UTranslate translate;
 	private final MinMaxMutable minmax;
 
 	public TextLimitFinder(StringBounder stringBounder, boolean initToZero) {
-		this(stringBounder, MinMaxMutable.getEmpty(initToZero), new UTranslate());
+		super(stringBounder);
+		this.minmax = MinMaxMutable.getEmpty(initToZero);
 	}
 
-	private TextLimitFinder(StringBounder stringBounder, MinMaxMutable minmax, UTranslate translate) {
+	private TextLimitFinder(TextLimitFinder other, UChange change) {
-		this.stringBounder = stringBounder;
+		super(other, change);
-		this.minmax = minmax;
+		if (!instanceOfAny(change,
-		this.translate = translate;
+				UBackground.class,
-	}
+				HColor.class,
-
+				UStroke.class,
-	private TextLimitFinder(TextLimitFinder other) {
+				UTranslate.class
-		this(other.stringBounder, other.minmax, other.translate);
+		)) {
-	}
+			throw new UnsupportedOperationException(change.getClass().toString());
-
+		}
-	public StringBounder getStringBounder() {
+		this.minmax = other.minmax;
-		return stringBounder;
-	}
-
-	public UParam getParam() {
-		return new UParamNull();
 	}
 
 	public void draw(UShape shape) {
 		if (shape instanceof UText) {
-			final double x = translate.getDx();
+			final double x = getTranslate().getDx();
-			final double y = translate.getDy();
+			final double y = getTranslate().getDy();
 			drawText(x, y, (UText) shape);
 		}
 	}
 
-	public ColorMapper getColorMapper() {
-		throw new UnsupportedOperationException();
-	}
-
 	private void drawText(double x, double y, UText text) {
-		final Dimension2D dim = stringBounder.calculateDimension(text.getFontConfiguration().getFont(), text.getText());
+		final Dimension2D dim = getStringBounder().calculateDimension(text.getFontConfiguration().getFont(), text.getText());
 		y -= dim.getHeight() - 1.5;
 		minmax.addPoint(x, y);
 		minmax.addPoint(x, y + dim.getHeight());
@@ -127,7 +102,4 @@ public class TextLimitFinder extends UGraphicNo implements UGraphic {
 		return minmax.getMinY();
 	}
 
-	public void flushUg() {
-	}
-
 }

src/net/sourceforge/plantuml/ugraphic/UGraphicNo.java

@@ -36,25 +36,80 @@
 package net.sourceforge.plantuml.ugraphic;
 
 import net.sourceforge.plantuml.Url;
+import net.sourceforge.plantuml.graphic.StringBounder;
+import net.sourceforge.plantuml.ugraphic.color.ColorMapper;
 import net.sourceforge.plantuml.ugraphic.color.HColor;
 import net.sourceforge.plantuml.ugraphic.color.HColorUtils;
 
-public abstract class UGraphicNo {
+public abstract class UGraphicNo implements UGraphic {
 
+	private final StringBounder stringBounder;
+	private final UTranslate translate;
+
+	public UGraphicNo(StringBounder stringBounder) {
+		this.stringBounder = stringBounder;
+		this.translate = new UTranslate();
+	}
+
+	public UGraphicNo(UGraphicNo other, UChange change) {
+		this.stringBounder = other.stringBounder;
+		this.translate = change instanceof UTranslate ? other.translate.compose((UTranslate) change) : other.translate;
+	}
+
+	//
+	// Implement UGraphic
+	//
+	
+	@Override
 	final public void startUrl(Url url) {
 	}
 
+	@Override
 	public void startGroup(UGroupType type, String ident) {
 	}
 
+	@Override
 	final public void closeUrl() {
 	}
 
+	@Override
 	final public void closeGroup() {
 	}
 
+	@Override
+	public ColorMapper getColorMapper() {
+		throw new UnsupportedOperationException();
+	}
+
+	@Override
 	public HColor getDefaultBackground() {
 		return HColorUtils.BLACK;
 	}
+	
+	@Override
+	public UParam getParam() {
+		return new UParamNull();
+	}
 
+	@Override
+	public StringBounder getStringBounder() {
+		return stringBounder;
+	}
+
+	@Override
+	public void flushUg() {
+	}
+
+	@Override
+	public boolean matchesProperty(String propertyName) {
+		return false;
+	}
+	
+	//
+	// Internal things
+	//
+
+	protected UTranslate getTranslate() {
+		return translate;
+	}
 }

src/net/sourceforge/plantuml/ugraphic/comp/SlotFinder.java

@@ -35,6 +35,7 @@
  */
 package net.sourceforge.plantuml.ugraphic.comp;
 
+import static net.sourceforge.plantuml.utils.ObjectUtils.instanceOfAny;
 import net.sourceforge.plantuml.graphic.StringBounder;
 import net.sourceforge.plantuml.ugraphic.TextLimitFinder;
 import net.sourceforge.plantuml.ugraphic.UBackground;
@@ -43,8 +44,6 @@ import net.sourceforge.plantuml.ugraphic.UEllipse;
 import net.sourceforge.plantuml.ugraphic.UEmpty;
 import net.sourceforge.plantuml.ugraphic.UGraphic;
 import net.sourceforge.plantuml.ugraphic.UGraphicNo;
-import net.sourceforge.plantuml.ugraphic.UParam;
-import net.sourceforge.plantuml.ugraphic.UParamNull;
 import net.sourceforge.plantuml.ugraphic.UPath;
 import net.sourceforge.plantuml.ugraphic.UPolygon;
 import net.sourceforge.plantuml.ugraphic.URectangle;
@@ -57,61 +56,40 @@ import net.sourceforge.plantuml.ugraphic.color.ColorMapper;
 import net.sourceforge.plantuml.ugraphic.color.ColorMapperIdentity;
 import net.sourceforge.plantuml.ugraphic.color.HColor;
 
-public class SlotFinder extends UGraphicNo implements UGraphic {
+public class SlotFinder extends UGraphicNo {
-
-	public boolean matchesProperty(String propertyName) {
-		return false;
-	}
-
-	public double dpiFactor() {
-		return 1;
-	}
 
+	@Override
 	public UGraphic apply(UChange change) {
-		if (change instanceof UTranslate) {
+		return new SlotFinder(this, change);
-			return new SlotFinder(mode, stringBounder, slot, translate.compose((UTranslate) change));
-		} else if (change instanceof UStroke) {
-			return new SlotFinder(this);
-		} else if (change instanceof UBackground) {
-			return new SlotFinder(this);
-		} else if (change instanceof HColor) {
-			return new SlotFinder(this);
-		}
-		throw new UnsupportedOperationException();
 	}
 
 	private final SlotSet slot;
 
-	private final StringBounder stringBounder;
-	private final UTranslate translate;
 	private final CompressionMode mode;
 
 	public SlotFinder(CompressionMode mode, StringBounder stringBounder) {
-		this(mode, stringBounder, new SlotSet(), new UTranslate());
+		super(stringBounder);
-	}
+		this.slot = new SlotSet();
-
-	private SlotFinder(CompressionMode mode, StringBounder stringBounder, SlotSet slot, UTranslate translate) {
-		this.stringBounder = stringBounder;
-		this.slot = slot;
-		this.translate = translate;
 		this.mode = mode;
 	}
 
-	private SlotFinder(SlotFinder other) {
+	private SlotFinder(SlotFinder other, UChange change) {
-		this(other.mode, other.stringBounder, other.slot, other.translate);
+		super(other, change);
-	}
+		if (!instanceOfAny(change,
-
+				UBackground.class,
-	public StringBounder getStringBounder() {
+				HColor.class,
-		return stringBounder;
+				UStroke.class,
-	}
+				UTranslate.class
-
+		)) {
-	public UParam getParam() {
+			throw new UnsupportedOperationException(change.getClass().toString());
-		return new UParamNull();
+		}
+		this.mode = other.mode;
+		this.slot = other.slot;
 	}
 
 	public void draw(UShape sh) {
-		final double x = translate.getDx();
+		final double x = getTranslate().getDx();
-		final double y = translate.getDy();
+		final double y = getTranslate().getDy();
 		if (sh instanceof UShapeIgnorableForCompression) {
 			final UShapeIgnorableForCompression shape = (UShapeIgnorableForCompression) sh;
 			if (shape.isIgnoreForCompressionOn(mode)) {
@@ -154,7 +132,7 @@ public class SlotFinder extends UGraphicNo implements UGraphic {
 	}
 
 	private void drawText(double x, double y, UText shape) {
-		final TextLimitFinder finder = new TextLimitFinder(stringBounder, false);
+		final TextLimitFinder finder = new TextLimitFinder(getStringBounder(), false);
 		finder.apply(new UTranslate(x, y)).draw(shape);
 		if (mode == CompressionMode.ON_X) {
 			slot.addSlot(finder.getMinX(), finder.getMaxX());
@@ -198,7 +176,4 @@ public class SlotFinder extends UGraphicNo implements UGraphic {
 		return slot;
 	}
 
-	public void flushUg() {
-	}
-
 }

src/net/sourceforge/plantuml/utils/ObjectUtils.java

@@ -0,0 +1,13 @@
+package net.sourceforge.plantuml.utils;
+
+public class ObjectUtils {
+
+	public static boolean instanceOfAny(Object object, Class<?>... classes) {
+		for (Class<?> c : classes) {
+			if (c.isInstance(object)) {
+				return true;
+			}
+		}
+		return false;
+	}
+}