Fix https://forum.plantuml.net/17043/transparent-background-colours-on-alt-else-elements

src/net/sourceforge/plantuml/asciiart/TextSkin.java

@@ -135,7 +135,7 @@ public class TextSkin extends Rose {
 		if (type == ComponentType.DIVIDER)
 			return new ComponentTextDivider(type, stringsToDisplay, fileFormat);
 
-		if (type == ComponentType.GROUPING_HEADER)
+		if (type == ComponentType.GROUPING_HEADER_LEGACY || type == ComponentType.GROUPING_HEADER_TEOZ)
 			return new ComponentTextGroupingHeader(type, stringsToDisplay, fileFormat);
 
 		if (type == ComponentType.GROUPING_SPACE)

src/net/sourceforge/plantuml/sequencediagram/GroupingLeaf.java

@@ -78,9 +78,9 @@ final public class GroupingLeaf extends Grouping implements EventWithDeactivate
 
 	@Override
 	public final HColor getBackColorGeneral() {
-		if (backColorGeneral == null) {
+		if (backColorGeneral == null)
 			return start.getBackColorGeneral();
-		}
+
 		return backColorGeneral;
 	}
 

src/net/sourceforge/plantuml/sequencediagram/GroupingStart.java

@@ -62,9 +62,9 @@ public class GroupingStart extends Grouping {
 
 	public Style[] getUsedStyles() {
 		final Style[] result = super.getUsedStyles();
-		if (result[0] != null) {
+		if (result[0] != null)
 			result[0] = result[0].eventuallyOverride(PName.BackGroundColor, backColorGeneral);
-		}
+
 		return result;
 	}
 
@@ -77,9 +77,9 @@ public class GroupingStart extends Grouping {
 	}
 
 	public int getLevel() {
-		if (parent == null) {
+		if (parent == null)
 			return 0;
-		}
+
 		return parent.getLevel() + 1;
 	}
 

src/net/sourceforge/plantuml/sequencediagram/graphic/DrawableSetInitializer.java

@@ -361,7 +361,7 @@ class DrawableSetInitializer {
 		final Display strings = start.getTitle().equals("group") ? Display.create(start.getComment())
 				: Display.create(start.getTitle(), start.getComment());
 		final Component header = drawableSet.getSkin().createComponent(start.getUsedStyles(),
-				ComponentType.GROUPING_HEADER, null, skinParam, strings);
+				ComponentType.GROUPING_HEADER_LEGACY, null, skinParam, strings);
 		final ParticipantBox veryfirst = drawableSet.getVeryfirst();
 		final InGroupableList inGroupableList = new InGroupableList(veryfirst, start, freeY2.getFreeY(range));
 		inGroupableStack.addList(inGroupableList);

src/net/sourceforge/plantuml/sequencediagram/teoz/Blotter.java

@@ -0,0 +1,97 @@
+/* ========================================================================
+ * PlantUML : a free UML diagram generator
+ * ========================================================================
+ *
+ * (C) Copyright 2009-2023, Arnaud Roques
+ *
+ * Project Info:  http://plantuml.com
+ * 
+ * If you like this project or if you find it useful, you can support us at:
+ * 
+ * http://plantuml.com/patreon (only 1$ per month!)
+ * http://plantuml.com/paypal
+ * 
+ * This file is part of PlantUML.
+ *
+ * PlantUML is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * PlantUML distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
+ * License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,
+ * USA.
+ *
+ *
+ * Original Author:  Arnaud Roques
+ * 
+ *
+ */
+package net.sourceforge.plantuml.sequencediagram.teoz;
+
+import java.util.Map.Entry;
+import java.util.SortedMap;
+import java.util.TreeMap;
+
+import net.sourceforge.plantuml.awt.geom.XDimension2D;
+import net.sourceforge.plantuml.graphic.UDrawable;
+import net.sourceforge.plantuml.ugraphic.UGraphic;
+import net.sourceforge.plantuml.ugraphic.URectangle;
+import net.sourceforge.plantuml.ugraphic.UTranslate;
+import net.sourceforge.plantuml.ugraphic.color.HColor;
+import net.sourceforge.plantuml.ugraphic.color.HColors;
+
+public class Blotter implements UDrawable {
+
+	private final XDimension2D dim;
+	private final HColor defaultBackcolor;
+	private HColor last;
+	private final SortedMap<Double, HColor> changes = new TreeMap<>();
+
+	public Blotter(XDimension2D dim, HColor defaultBackcolor) {
+		if (defaultBackcolor == null)
+			defaultBackcolor = HColors.transparent();
+		this.dim = dim;
+		this.defaultBackcolor = defaultBackcolor;
+		this.last = defaultBackcolor;
+	}
+
+	@Override
+	public String toString() {
+		return "" + dim + " " + defaultBackcolor;
+	}
+
+	@Override
+	public void drawU(UGraphic ug) {
+		HColor current = defaultBackcolor;
+		double y = 0;
+		for (Entry<Double, HColor> ent : changes.entrySet()) {
+			if (current.isTransparent() == false) {
+				final URectangle rect = new URectangle(dim.getWidth(), ent.getKey() - y);
+				ug.apply(current).apply(current.bg()).apply(UTranslate.dy(y)).draw(rect);
+			}
+			y = ent.getKey();
+			current = ent.getValue();
+		}
+	}
+
+	public void closeChanges() {
+		changes.put(dim.getHeight(), defaultBackcolor);
+	}
+
+	public void addChange(double ypos, HColor color) {
+		if (color == null)
+			color = HColors.transparent();
+		if (color.equals(last))
+			return;
+		changes.put(ypos, color);
+		last = color;
+	}
+
+}

src/net/sourceforge/plantuml/sequencediagram/teoz/ElseTile.java

@@ -50,6 +50,7 @@ import net.sourceforge.plantuml.skin.Context2D;
 import net.sourceforge.plantuml.skin.rose.Rose;
 import net.sourceforge.plantuml.ugraphic.UGraphic;
 import net.sourceforge.plantuml.ugraphic.UTranslate;
+import net.sourceforge.plantuml.ugraphic.color.HColor;
 
 public class ElseTile extends AbstractTile {
 
@@ -82,6 +83,10 @@ public class ElseTile extends AbstractTile {
 		return yGauge;
 	}
 
+	public final HColor getBackColorGeneral() {
+		return anElse.getBackColorGeneral();
+	}
+
 	public Component getComponent(StringBounder stringBounder) {
 		// final Display display = Display.create(anElse.getTitle());
 		final ISkinParam tmp = new SkinParamBackcolored(skinParam, anElse.getBackColorElement(),

src/net/sourceforge/plantuml/sequencediagram/teoz/GroupingTile.java

@@ -57,8 +57,10 @@ import net.sourceforge.plantuml.skin.Component;
 import net.sourceforge.plantuml.skin.ComponentType;
 import net.sourceforge.plantuml.skin.Context2D;
 import net.sourceforge.plantuml.skin.rose.Rose;
+import net.sourceforge.plantuml.style.PName;
 import net.sourceforge.plantuml.ugraphic.UGraphic;
 import net.sourceforge.plantuml.ugraphic.UTranslate;
+import net.sourceforge.plantuml.ugraphic.color.HColor;
 
 public class GroupingTile extends AbstractTile {
 
@@ -156,7 +158,7 @@ public class GroupingTile extends AbstractTile {
 	}
 
 	private Component getComponent(StringBounder stringBounder) {
-		final Component comp = skin.createComponent(start.getUsedStyles(), ComponentType.GROUPING_HEADER, null,
+		final Component comp = skin.createComponent(start.getUsedStyles(), ComponentType.GROUPING_HEADER_TEOZ, null,
 				skinParam, display);
 		return comp;
 	}
@@ -168,14 +170,19 @@ public class GroupingTile extends AbstractTile {
 	public void drawU(UGraphic ug) {
 		final StringBounder stringBounder = ug.getStringBounder();
 
+		final Area area = Area.create(max.getCurrentValue() - min.getCurrentValue(), getTotalHeight(stringBounder));
+
 		final Component comp = getComponent(stringBounder);
 		final XDimension2D dim1 = getPreferredDimensionIfEmpty(stringBounder);
-		final Area area = Area.create(max.getCurrentValue() - min.getCurrentValue(), getTotalHeight(stringBounder));
 
 		if (YGauge.USE_ME) {
 			comp.drawU(ug.apply(new UTranslate(min.getCurrentValue(), getYGauge().getMin().getCurrentValue())), area,
 					(Context2D) ug);
 		} else {
+			if (((Context2D) ug).isBackground()) {
+				drawBackground(ug, area);
+				return;
+			}
 			comp.drawU(ug.apply(UTranslate.dx(min.getCurrentValue())), area, (Context2D) ug);
 			drawAllElses(ug);
 		}
@@ -191,6 +198,36 @@ public class GroupingTile extends AbstractTile {
 		}
 	}
 
+	private void drawBackground(UGraphic ug, Area area) {
+		final HColor back = start.getUsedStyles()[0].value(PName.BackGroundColor).asColor(skinParam.getIHtmlColorSet());
+		final XDimension2D dimensionToUse = area.getDimensionToUse();
+		final Blotter blotter = new Blotter(dimensionToUse, back);
+
+		for (Tile tile : tiles)
+			if (tile instanceof ElseTile) {
+				final ElseTile elseTile = (ElseTile) tile;
+				final double ypos = elseTile.getTimeHook().getValue() - getTimeHook().getValue() + MARGINY_MAGIC / 2;
+				blotter.addChange(ypos, elseTile.getBackColorGeneral());
+			}
+
+		blotter.closeChanges();
+		blotter.drawU(ug.apply(UTranslate.dx(min.getCurrentValue())));
+
+		final StringBounder stringBounder = ug.getStringBounder();
+
+		final XDimension2D dim1 = getPreferredDimensionIfEmpty(stringBounder);
+		double h = dim1.getHeight() + MARGINY_MAGIC / 2;
+		for (Tile tile : tiles) {
+			if (YGauge.USE_ME)
+				((UDrawable) tile).drawU(ug);
+			else
+				((UDrawable) tile).drawU(ug.apply(UTranslate.dy(h)));
+			final double preferredHeight = tile.getPreferredHeight();
+			h += preferredHeight;
+		}
+
+	}
+
 	private double getTotalHeight(StringBounder stringBounder) {
 		final XDimension2D dimIfEmpty = getPreferredDimensionIfEmpty(stringBounder);
 		return bodyHeight + dimIfEmpty.getHeight() + MARGINY_MAGIC / 2;
@@ -198,7 +235,6 @@ public class GroupingTile extends AbstractTile {
 
 	private void drawAllElses(UGraphic ug) {
 		final StringBounder stringBounder = ug.getStringBounder();
-		final double totalHeight = getTotalHeight(stringBounder);
 
 		final List<Double> ys = new ArrayList<>();
 		for (Tile tile : tiles) {
@@ -213,6 +249,7 @@ public class GroupingTile extends AbstractTile {
 				ys.add(ypos);
 			}
 		}
+		final double totalHeight = getTotalHeight(stringBounder);
 		ys.add(totalHeight);
 		int i = 0;
 		for (Tile tile : tiles) {

src/net/sourceforge/plantuml/skin/ComponentType.java

@@ -56,7 +56,7 @@ public enum ComponentType implements Styleable {
 	DELAY_LINE, PARTICIPANT_LINE, CONTINUE_LINE,
 
 	//
-	GROUPING_ELSE_LEGACY, GROUPING_ELSE_TEOZ, GROUPING_HEADER, GROUPING_SPACE,
+	GROUPING_ELSE_LEGACY, GROUPING_ELSE_TEOZ, GROUPING_HEADER_LEGACY, GROUPING_HEADER_TEOZ, GROUPING_SPACE,
 	//
 	NEWPAGE, NOTE, NOTE_HEXAGONAL, NOTE_BOX, DIVIDER, REFERENCE, ENGLOBER,
 

src/net/sourceforge/plantuml/skin/rose/ComponentRoseGroupingElse.java

@@ -67,7 +67,8 @@ public class ComponentRoseGroupingElse extends AbstractTextualComponent {
 		this.teoz = teoz;
 		this.roundCorner = style.value(PName.RoundCorner).asInt();
 		this.groupBorder = style.value(PName.LineColor).asColor(getIHtmlColorSet());
-		this.backgroundColor = style.value(PName.BackGroundColor).asColor(getIHtmlColorSet());
+		this.backgroundColor = teoz ? HColors.transparent()
+				: style.value(PName.BackGroundColor).asColor(getIHtmlColorSet());
 	}
 
 	@Override

src/net/sourceforge/plantuml/skin/rose/ComponentRoseGroupingHeader.java

@@ -56,6 +56,7 @@ import net.sourceforge.plantuml.ugraphic.URectangle;
 import net.sourceforge.plantuml.ugraphic.UStroke;
 import net.sourceforge.plantuml.ugraphic.UTranslate;
 import net.sourceforge.plantuml.ugraphic.color.HColor;
+import net.sourceforge.plantuml.ugraphic.color.HColors;
 
 public class ComponentRoseGroupingHeader extends AbstractTextualComponent {
 
@@ -69,11 +70,12 @@ public class ComponentRoseGroupingHeader extends AbstractTextualComponent {
 	private final SymbolContext symbolContextCorner;
 	private final double roundCorner;
 
-	public ComponentRoseGroupingHeader(Style style, Style styleHeader, Display strings, ISkinSimple spriteContainer) {
+	public ComponentRoseGroupingHeader(boolean teoz, Style style, Style styleHeader, Display strings,
+			ISkinSimple spriteContainer) {
 		super(styleHeader, LineBreakStrategy.NONE, 15, 30, 1, spriteContainer, strings.get(0));
 
 		this.roundCorner = style.value(PName.RoundCorner).asInt();
-		this.background = style.value(PName.BackGroundColor).asColor(getIHtmlColorSet());
+		this.background = teoz ? HColors.transparent() : style.value(PName.BackGroundColor).asColor(getIHtmlColorSet());
 		this.symbolContext = style.getSymbolContext(getIHtmlColorSet());
 		this.symbolContextCorner = styleHeader.getSymbolContext(getIHtmlColorSet());
 

src/net/sourceforge/plantuml/skin/rose/Rose.java

@@ -208,8 +208,11 @@ public class Rose {
 		if (type == ComponentType.NOTE_BOX)
 			throw new UnsupportedOperationException();
 
-		if (type == ComponentType.GROUPING_HEADER)
+		if (type == ComponentType.GROUPING_HEADER_LEGACY)
-			return new ComponentRoseGroupingHeader(styles[0], styles[1], stringsToDisplay, param);
+			return new ComponentRoseGroupingHeader(false, styles[0], styles[1], stringsToDisplay, param);
+
+		if (type == ComponentType.GROUPING_HEADER_TEOZ)
+			return new ComponentRoseGroupingHeader(true, styles[0], styles[1], stringsToDisplay, param);
 
 		if (type == ComponentType.GROUPING_ELSE_LEGACY)
 			return new ComponentRoseGroupingElse(false, styles[0], stringsToDisplay.get(0), param);

src/net/sourceforge/plantuml/version/Version.java

@@ -81,7 +81,7 @@ public class Version {
 	}
 
 	public static int beta() {
-		final int beta = 3;
+		final int beta = 4;
 		return beta;
 	}