Base theming for views

- Control is now aware of active theme name and resolver.
- Theme some settings in BoxView, ListView and MenuView.
- Overhaul scenario system to make it work with themes.
- Add new "background" StyleSetting.
- Relates #824

spring-shell-core/src/main/java/org/springframework/shell/component/view/control/AbstractView.java

@@ -27,13 +27,14 @@ import reactor.core.Disposables;
 
 import org.springframework.lang.Nullable;
 import org.springframework.messaging.Message;
+import org.springframework.shell.component.view.control.cell.AbstractControl;
 import org.springframework.shell.component.view.event.EventLoop;
 import org.springframework.shell.component.view.event.KeyBindingConsumer;
 import org.springframework.shell.component.view.event.KeyBindingConsumerArgs;
 import org.springframework.shell.component.view.event.KeyEvent;
 import org.springframework.shell.component.view.event.KeyHandler;
-import org.springframework.shell.component.view.event.MouseBindingConsumerArgs;
 import org.springframework.shell.component.view.event.MouseBindingConsumer;
+import org.springframework.shell.component.view.event.MouseBindingConsumerArgs;
 import org.springframework.shell.component.view.event.MouseEvent;
 import org.springframework.shell.component.view.event.MouseHandler;
 import org.springframework.shell.component.view.geom.Rectangle;
@@ -46,14 +47,10 @@ import org.springframework.shell.component.view.screen.Screen;
  *
  * @author Janne Valkealahti
  */
-public abstract class AbstractView implements View {
+public abstract class AbstractView extends AbstractControl implements View {
 
 	private final static Logger log = LoggerFactory.getLogger(AbstractView.class);
 	private final Disposable.Composite disposables = Disposables.composite();
-	private int x = 0;
-	private int y = 0;
-	private int width = 0;
-	private int height = 0;
 	private BiFunction<Screen, Rectangle, Rectangle> drawFunction;
 	private boolean hasFocus;
 	private int layer;
@@ -99,19 +96,6 @@ public abstract class AbstractView implements View {
 	protected void initInternal() {
 	}
 
-	@Override
-	public void setRect(int x, int y, int width, int height) {
-		this.x = x;
-		this.y = y;
-		this.width = width;
-		this.height = height;
-	}
-
-	@Override
-	public Rectangle getRect() {
-		return new Rectangle(x, y, width, height);
-	}
-
 	@Override
 	public void setLayer(int index) {
 		this.layer = index;

spring-shell-core/src/main/java/org/springframework/shell/component/view/control/AppView.java

@@ -22,6 +22,7 @@ import org.springframework.shell.component.view.event.MouseHandler;
 import org.springframework.shell.component.view.geom.Rectangle;
 import org.springframework.shell.component.view.message.ShellMessageBuilder;
 import org.springframework.shell.component.view.screen.Screen;
+import org.springframework.shell.style.ThemeResolver;
 import org.springframework.util.Assert;
 
 /**
@@ -49,6 +50,22 @@ public class AppView extends BoxView {
 		initLayout();
 	}
 
+	@Override
+	public void setThemeName(String themeName) {
+		super.setThemeName(themeName);
+		main.setThemeName(themeName);
+		menu.setThemeName(themeName);
+		status.setThemeName(themeName);
+	}
+
+	@Override
+	public void setThemeResolver(ThemeResolver themeResolver) {
+		super.setThemeResolver(themeResolver);
+		main.setThemeResolver(themeResolver);
+		menu.setThemeResolver(themeResolver);
+		status.setThemeResolver(themeResolver);
+	}
+
 	private void initLayout() {
 		grid = new GridView();
 		grid.setRowSize(1, 0, 1);

spring-shell-core/src/main/java/org/springframework/shell/component/view/control/BoxView.java

@@ -18,11 +18,11 @@ package org.springframework.shell.component.view.control;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import org.springframework.lang.Nullable;
 import org.springframework.shell.component.view.geom.HorizontalAlign;
 import org.springframework.shell.component.view.geom.Rectangle;
 import org.springframework.shell.component.view.geom.VerticalAlign;
 import org.springframework.shell.component.view.screen.Screen;
+import org.springframework.shell.style.StyleSettings;
 import org.springframework.util.StringUtils;
 
 /**
@@ -45,7 +45,8 @@ public class BoxView extends AbstractView {
 	private int paddingBottom;
 	private int paddingLeft;
 	private int paddingRight;
-	private Integer backgroundColor = -1;
+	private boolean transparent = true;
+	private int backgroundColor = -1;
 	private int titleColor = -1;
 	private int titleStyle = -1;
 	private int focusedTitleColor = -1;
@@ -110,7 +111,7 @@ public class BoxView extends AbstractView {
 	 *
 	 * @param backgroundColor the background color
 	 */
-	public void setBackgroundColor(@Nullable Integer backgroundColor) {
+	public void setBackgroundColor(int backgroundColor) {
 		this.backgroundColor = backgroundColor;
 	}
 
@@ -161,6 +162,24 @@ public class BoxView extends AbstractView {
 		this.titleAlign = titleAlign;
 	}
 
+	/**
+	 * Sets if box should be transparent, {@code true} by default.
+	 *
+	 * @param transparent a transparency flag
+	 */
+	public void setTransparent(boolean transparent) {
+		this.transparent = transparent;
+	}
+
+	/**
+	 * Is box transparent.
+	 *
+	 * @return box transparency
+	 */
+	protected boolean isTransparent() {
+		return transparent;
+	}
+
 	/**
 	 * Possibly draws a box around this view and title in a box top boundary. Also
 	 * calls a {@code draw function} if defined.
@@ -173,12 +192,14 @@ public class BoxView extends AbstractView {
 		if (rect.width() <= 0 || rect.height() <= 0) {
 			return;
 		}
-		if (backgroundColor == null) {
-			screen.writerBuilder().layer(getLayer()).build().background(rect, -1);
+		int bgColor;
+		if (isTransparent()) {
+			bgColor = backgroundColor > -1 ? backgroundColor : -1;
 		}
-		else if (backgroundColor > -1) {
-			screen.writerBuilder().layer(getLayer()).build().background(rect, backgroundColor);
+		else {
+			bgColor = resolveThemeBackground(StyleSettings.TAG_BACKGROUND, backgroundColor, -1);
 		}
+		screen.writerBuilder().layer(getLayer()).build().background(rect, bgColor);
 		if (showBorder && rect.width() >= 2 && rect.height() >= 2) {
 			screen.writerBuilder().layer(getLayer()).build().border(rect.x(), rect.y(), rect.width(), rect.height());
 			if (StringUtils.hasText(title)) {

spring-shell-core/src/main/java/org/springframework/shell/component/view/control/Control.java

@@ -15,8 +15,10 @@
  */
 package org.springframework.shell.component.view.control;
 
+import org.springframework.lang.Nullable;
 import org.springframework.shell.component.view.geom.Rectangle;
 import org.springframework.shell.component.view.screen.Screen;
+import org.springframework.shell.style.ThemeResolver;
 
 /**
  * Base interface for all controls. {@link Control} is able to define a
@@ -51,4 +53,19 @@ public interface Control {
 	 * @param height a height of a bounded box
 	 */
 	void setRect(int x, int y, int width, int height);
+
+	/**
+	 * Sets a {@link ThemeResolver}.
+	 *
+	 * @param themeResolver the theme resolver
+	 */
+	void setThemeResolver(@Nullable ThemeResolver themeResolver);
+
+	/**
+	 * Sets a theme name to use.
+	 *
+	 * @param themeName the theme name
+	 */
+	void setThemeName(@Nullable String themeName);
+
 }

spring-shell-core/src/main/java/org/springframework/shell/component/view/control/ListView.java

@@ -26,6 +26,7 @@ import org.springframework.shell.component.view.geom.Rectangle;
 import org.springframework.shell.component.view.message.ShellMessageBuilder;
 import org.springframework.shell.component.view.screen.Screen;
 import org.springframework.shell.component.view.screen.ScreenItem;
+import org.springframework.shell.style.StyleSettings;
 
 /**
  * {@link ListView} shows {@code list items} vertically.
@@ -51,12 +52,13 @@ public class ListView<T> extends BoxView {
 		Rectangle rect = getInnerRect();
 		int y = rect.y();
 
+		int selectedStyle = resolveThemeStyle(StyleSettings.TAG_HIGHLIGHT, ScreenItem.STYLE_BOLD);
 		int i = 0;
 		for (ListCell<T> c : cells) {
 			c.setRect(rect.x(), y++, rect.width(), 1);
 			if (i == selected) {
 				c.updateSelected(true);
-				c.setStyle(ScreenItem.STYLE_BOLD);
+				c.setStyle(selectedStyle);
 			}
 			else {
 				c.updateSelected(false);

spring-shell-core/src/main/java/org/springframework/shell/component/view/control/MenuBarView.java

@@ -35,6 +35,7 @@ import org.springframework.shell.component.view.geom.Dimension;
 import org.springframework.shell.component.view.geom.Rectangle;
 import org.springframework.shell.component.view.screen.Screen;
 import org.springframework.shell.component.view.screen.Screen.Writer;
+import org.springframework.shell.style.ThemeResolver;
 import org.springframework.shell.component.view.screen.ScreenItem;
 
 /**
@@ -201,6 +202,18 @@ public class MenuBarView extends BoxView {
 		checkMenuView();
 	}
 
+	@Override
+	public void setThemeName(String themeName) {
+		super.setThemeName(themeName);
+		menuViews.values().forEach(view -> view.setThemeName(themeName));
+	}
+
+	@Override
+	public void setThemeResolver(ThemeResolver themeResolver) {
+		super.setThemeResolver(themeResolver);
+		menuViews.values().forEach(view -> view.setThemeResolver(themeResolver));
+	}
+
 	private void checkMenuView() {
 		if (activeItemIndex < 0) {
 			closeCurrentMenuView();
@@ -218,8 +231,10 @@ public class MenuBarView extends BoxView {
 	private MenuView buildMenuView(MenuBarItem item) {
 		MenuView menuView = new MenuView(item.getItems());
 		menuView.setEventLoop(getEventLoop());
+		menuView.setThemeResolver(getThemeResolver());
+		menuView.setThemeName(getThemeName());
 		menuView.setShowBorder(true);
-		menuView.setBackgroundColor(null);
+		menuView.setTransparent(false);
 		menuView.setLayer(1);
 		Rectangle rect = getInnerRect();
 		int x = positionAtIndex(activeItemIndex);

spring-shell-core/src/main/java/org/springframework/shell/component/view/control/MenuView.java

@@ -33,6 +33,7 @@ import org.springframework.shell.component.view.geom.Rectangle;
 import org.springframework.shell.component.view.message.ShellMessageBuilder;
 import org.springframework.shell.component.view.screen.Screen;
 import org.springframework.shell.component.view.screen.Screen.Writer;
+import org.springframework.shell.style.StyleSettings;
 import org.springframework.shell.component.view.screen.ScreenItem;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
@@ -143,7 +144,8 @@ public class MenuView extends BoxView {
 		Rectangle rect = getInnerRect();
 		int y = rect.y();
 		Writer writer = screen.writerBuilder().layer(getLayer()).build();
-		Writer writer2 = screen.writerBuilder().layer(getLayer()).style(ScreenItem.STYLE_BOLD).build();
+		int themeStyle = resolveThemeStyle(StyleSettings.TAG_HIGHLIGHT, ScreenItem.STYLE_BOLD);
+		Writer writer2 = screen.writerBuilder().layer(getLayer()).style(themeStyle).build();
 		int i = 0;
 		boolean hasCheck = false;
 		for (MenuItem item : items) {

spring-shell-core/src/main/java/org/springframework/shell/component/view/control/cell/AbstractControl.java

@@ -15,8 +15,15 @@
  */
 package org.springframework.shell.component.view.control.cell;
 
+import java.util.Optional;
+
+import org.jline.utils.AttributedStyle;
+
+import org.springframework.lang.Nullable;
 import org.springframework.shell.component.view.control.Control;
 import org.springframework.shell.component.view.geom.Rectangle;
+import org.springframework.shell.style.ThemeResolver;
+import org.springframework.shell.style.ThemeResolver.ResolvedValues;
 
 /**
  * Base implementation of a {@link Control}.
@@ -29,6 +36,8 @@ public abstract class AbstractControl implements Control {
 	private int y = 0;
 	private int width = 0;
 	private int height = 0;
+	private ThemeResolver themeResolver;
+	private String themeName;
 
 	@Override
 	public void setRect(int x, int y, int width, int height) {
@@ -43,4 +52,98 @@ public abstract class AbstractControl implements Control {
 		return new Rectangle(x, y, width, height);
 	}
 
+	/**
+	 * Sets a {@link ThemeResolver}.
+	 *
+	 * @param themeResolver the theme resolver
+	 */
+	public void setThemeResolver(@Nullable ThemeResolver themeResolver) {
+		this.themeResolver = themeResolver;
+	}
+
+	/**
+	 * Gets a {@link ThemeResolver}.
+	 *
+	 * @return a theme resolver
+	 */
+	@Nullable
+	protected ThemeResolver getThemeResolver() {
+		return themeResolver;
+	}
+
+	/**
+	 * Sets a theme name to use.
+	 *
+	 * @param themeName the theme name
+	 */
+	public void setThemeName(@Nullable String themeName) {
+		this.themeName = themeName;
+	}
+
+	/**
+	 * Gets a theme name.
+	 *
+	 * @return a theme name
+	 */
+	@Nullable
+	protected String getThemeName() {
+		return themeName;
+	}
+
+	private Optional<ResolvedValues> getThemeResolvedValues(String tag) {
+		ThemeResolver themeResolver = getThemeResolver();
+		if (themeResolver != null) {
+			String styleTag = themeResolver.resolveStyleTag(tag, getThemeName());
+			AttributedStyle attributedStyle = themeResolver.resolveStyle(styleTag);
+			return Optional.of(themeResolver.resolveValues(attributedStyle));
+		}
+		return Optional.empty();
+	}
+
+	/**
+	 * Resolve style using existing {@link ThemeResolver} and {@code theme name}.
+	 * Use {@code defaultStyle} if resolving cannot happen.
+	 *
+	 * @param tag the style tag to use
+	 * @param defaultStyle the default style to use
+	 * @return resolved style
+	 */
+	protected int resolveThemeStyle(String tag, int defaultStyle) {
+		return getThemeResolvedValues(tag).map(ResolvedValues::style).orElse(defaultStyle);
+	}
+
+	/**
+	 * Resolve foreground color using existing {@link ThemeResolver} and {@code theme name}.
+	 * {@code defaultColor} is used if it's value is not negative. {@code fallbackColor} is
+	 * used if theme resolver cannot be used.
+	 *
+	 * @param tag the style tag to use
+	 * @param defaultColor the default foreground color to use
+	 * @param fallbackColor the fallback foreground color to use
+	 * @return resolved foreground color
+	 */
+	protected int resolveThemeForeground(String tag, int defaultColor, int fallbackColor) {
+		if (defaultColor > -1) {
+			return defaultColor;
+		}
+		return getThemeResolvedValues(tag).map(ResolvedValues::foreground).orElse(fallbackColor);
+	}
+
+	/**
+	 * Resolve background color using existing {@link ThemeResolver} and {@code theme name}.
+	 * {@code defaultColor} is used if it's value is not negative. {@code fallbackColor} is
+	 * used if theme resolver cannot be used.
+	 *
+	 * @param tag the style tag to use
+	 * @param defaultColor the default background color to use
+	 * @param fallbackColor the fallback background color to use
+	 * @return resolved background color
+	 */
+	protected int resolveThemeBackground(String tag, int defaultColor, int fallbackColor) {
+		if (defaultColor > -1) {
+			return defaultColor;
+		}
+		return getThemeResolvedValues(tag).map(ResolvedValues::background).orElse(fallbackColor);
+	}
+
 }

spring-shell-core/src/main/java/org/springframework/shell/component/view/screen/DefaultScreen.java

@@ -257,10 +257,15 @@ public class DefaultScreen implements Screen, DisplayLines {
 			// if (items[y] == null) {
 			// 	items[y] = new DefaultScreenItem[columns];
 			// }
-			if (items[y][x] == null) {
-				items[y][x] = new DefaultScreenItem();
+			if (y < rows && x < columns) {
+				if (items[y][x] == null) {
+					items[y][x] = new DefaultScreenItem();
+				}
+				return items[y][x];
+			}
+			else {
+				return null;
 			}
-			return items[y][x];
 		}
 	}
 
@@ -343,7 +348,9 @@ public class DefaultScreen implements Screen, DisplayLines {
 			for (int i = rect.y(); i < rect.y() + rect.height(); i++) {
 				for (int j = rect.x(); j < rect.x() + rect.width(); j++) {
 					DefaultScreenItem item = layer.getScreenItem(j, i);
-					item.background = color;
+					if (item != null) {
+						item.background = color;
+					}
 				}
 			}
 		}

spring-shell-core/src/main/java/org/springframework/shell/style/StyleSettings.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2022 the original author or authors.
+ * Copyright 2022-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -91,6 +91,11 @@ public abstract class StyleSettings {
 	 */
 	public final static String TAG_HIGHLIGHT = "style-highlight";
 
+	/**
+	 * Styling for something which has a background.
+	 */
+	public final static String TAG_BACKGROUND = "style-background";
+
 	public String title() {
 		return "bold";
 	}
@@ -143,6 +148,10 @@ public abstract class StyleSettings {
 		return "bold";
 	}
 
+	public String background() {
+		return "default";
+	}
+
 	/**
 	 * Resolve a theme setting from a given tag.
 	 *
@@ -177,6 +186,8 @@ public abstract class StyleSettings {
 				return itemSelector();
 			case TAG_HIGHLIGHT:
 				return highlight();
+			case TAG_BACKGROUND:
+				return background();
 		}
 		throw new IllegalArgumentException(String.format("Unknown tag '%s'", tag));
 	}
@@ -213,7 +224,8 @@ public abstract class StyleSettings {
 				TAG_ITEM_SELECTED,
 				TAG_ITEM_UNSELECTED,
 				TAG_ITEM_SELECTOR,
-				TAG_HIGHLIGHT
+				TAG_HIGHLIGHT,
+				TAG_BACKGROUND
 		};
 	}
 

spring-shell-core/src/main/java/org/springframework/shell/style/ThemeRegistry.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2022 the original author or authors.
+ * Copyright 2022-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,6 +17,7 @@ package org.springframework.shell.style;
 
 import java.util.HashMap;
 import java.util.Map;
+import java.util.Set;
 
 import org.springframework.util.Assert;
 
@@ -48,4 +49,13 @@ public class ThemeRegistry {
 		Assert.notNull(theme, "theme cannot be null");
 		themes.put(theme.getName(), theme);
 	}
+
+	/**
+	 * Gets all theme names registered.
+	 *
+	 * @return theme names
+	 */
+	public Set<String> getThemeNames() {
+		return themes.keySet();
+	}
 }

spring-shell-core/src/main/java/org/springframework/shell/style/ThemeResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2022 the original author or authors.
+ * Copyright 2022-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -15,12 +15,17 @@
  */
 package org.springframework.shell.style;
 
+import java.util.Set;
+
 import org.jline.style.MemoryStyleSource;
 import org.jline.style.StyleExpression;
 import org.jline.style.StyleResolver;
 import org.jline.style.StyleSource;
 import org.jline.utils.AttributedString;
 import org.jline.utils.AttributedStyle;
+import org.jline.utils.Colors;
+
+import org.springframework.util.StringUtils;
 
 /**
  * Service which helps to do various things with styles.
@@ -32,12 +37,67 @@ public class ThemeResolver {
 	private StyleSource styleSource = new MemoryStyleSource();
 	private StyleResolver styleResolver = new StyleResolver(styleSource, "default");
 	private StyleExpression styleExpression = new StyleExpression(styleResolver);
+	private ThemeRegistry themeRegistry;
 	private final Theme theme;
 
 	public ThemeResolver(ThemeRegistry themeRegistry, String themeName) {
+		this.themeRegistry = themeRegistry;
 		this.theme = themeRegistry.get(themeName);
 	}
 
+	// copied from jline as no public access
+	private static final long F_FOREGROUND_IND = 0x00000100;
+	private static final long F_FOREGROUND_RGB = 0x00000200;
+	private static final long F_FOREGROUND = F_FOREGROUND_IND | F_FOREGROUND_RGB;
+	private static final long F_BACKGROUND_IND = 0x00000400;
+	private static final long F_BACKGROUND_RGB = 0x00000800;
+	private static final long F_BACKGROUND = F_BACKGROUND_IND | F_BACKGROUND_RGB;
+	private static final int FG_COLOR_EXP = 15;
+	private static final int BG_COLOR_EXP = 39;
+	private static final long FG_COLOR = 0xFFFFFFL << FG_COLOR_EXP;
+	private static final long BG_COLOR = 0xFFFFFFL << BG_COLOR_EXP;
+
+	/**
+	 * Stores resolved values for {@link ThemeResolver#resolveValues(AttributedStyle)}.
+	 */
+	public record ResolvedValues(int style, int foreground, int background){}
+
+	/**
+	 * Resolve {@code style}, {@code foreground color} and {@code background color}
+	 * from an {@link AttributedStyle}.
+	 *
+	 * @param attributedStyle the attibuted style
+	 * @return resolved values
+	 */
+	public ResolvedValues resolveValues(AttributedStyle attributedStyle) {
+		long style = attributedStyle.getStyle();
+		long s = style & ~(F_FOREGROUND | F_BACKGROUND);
+		s = (s & 0x00007FFF);
+		int fg = (int) ((style & FG_COLOR) >> FG_COLOR_EXP);
+		int bg = (int) ((style & BG_COLOR) >> BG_COLOR_EXP);
+		// if jline "ind" bit is set, resort to using
+		// same logic as jline.
+		boolean hasFb = (style & F_FOREGROUND_IND) != 0 || (style & F_FOREGROUND_RGB) != 0;
+		if ((style & F_FOREGROUND_IND) != 0) {
+			fg = Colors.DEFAULT_COLORS_256[fg & 0xFF];
+		}
+		boolean hasBg = (style & F_BACKGROUND_IND) != 0 || (style & F_BACKGROUND_RGB) != 0;
+		if ((style & F_BACKGROUND_IND) != 0) {
+			bg = Colors.DEFAULT_COLORS_256[bg & 0xFF];
+		}
+
+		return new ResolvedValues((int)s, hasFb ? fg : -1, hasBg ? bg : -1);
+	}
+
+	/**
+	 * Return all known theme names.
+	 *
+	 * @return all theme names
+	 */
+	public Set<String> themeNames() {
+		return themeRegistry.getThemeNames();
+	}
+
 	/**
 	 * Evaluate expression.
 	 *
@@ -48,6 +108,7 @@ public class ThemeResolver {
 		return styleExpression.evaluate(expression);
 	}
 
+
 	/**
 	 * Resolve style from a tag with activated theme.
 	 *
@@ -58,6 +119,18 @@ public class ThemeResolver {
 		return theme.getSettings().styles().resolveTag(tag);
 	}
 
+	/**
+	 * Resolve style from a tag with given theme.
+	 *
+	 * @param tag the tag
+	 * @param themeName the theme name
+	 * @return a style
+	 */
+	public String resolveStyleTag(String tag, String themeName) {
+		Theme t = StringUtils.hasText(themeName) ? themeRegistry.get(themeName) : theme;
+		return t.getSettings().styles().resolveTag(tag);
+	}
+
 	/**
 	 * Resolve figure from a tag with activated theme.
 	 *

spring-shell-core/src/test/java/org/springframework/shell/style/ThemeResolverTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2022 the original author or authors.
+ * Copyright 2022-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,14 +17,21 @@ package org.springframework.shell.style;
 
 import org.jline.utils.AttributedString;
 import org.jline.utils.AttributedStyle;
+import org.jline.utils.Colors;
+import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
+import org.springframework.shell.component.view.screen.Color;
+import org.springframework.shell.style.ThemeResolver.ResolvedValues;
+
 import static org.assertj.core.api.Assertions.assertThat;
 
 public class ThemeResolverTests {
 
-	@Test
-	public void test() {
+	private ThemeResolver themeResolver;
+
+	@BeforeEach
+	public void setup() {
 		ThemeRegistry themeRegistry = new ThemeRegistry();
 		themeRegistry.register(new Theme() {
 			@Override
@@ -37,10 +44,55 @@ public class ThemeResolverTests {
 				return ThemeSettings.defaults();
 			}
 		});
-		ThemeResolver themeResolver = new ThemeResolver(themeRegistry, "default");
+		themeResolver = new ThemeResolver(themeRegistry, "default");
+	}
+
+	@Test
+	public void styleExpression() {
 		assertThat(themeResolver.resolveStyleTag(StyleSettings.TAG_TITLE)).isEqualTo("bold");
 		assertThat(themeResolver.resolveStyle("bold")).isEqualTo(AttributedStyle.BOLD);
 		assertThat(themeResolver.evaluateExpression("@{bold foo}"))
 				.isEqualTo(new AttributedString("foo", AttributedStyle.BOLD));
 	}
+
+	@Test
+	public void resolveValuesIndStyle() {
+		AttributedStyle s = AttributedStyle.DEFAULT.background(AttributedStyle.BLUE).foreground(AttributedStyle.RED);
+		ResolvedValues resolvedValues = themeResolver.resolveValues(s);
+		assertThat(resolvedValues.background()).isEqualTo(Colors.DEFAULT_COLORS_256[AttributedStyle.BLUE]);
+		assertThat(resolvedValues.foreground()).isEqualTo(Colors.DEFAULT_COLORS_256[AttributedStyle.RED]);
+	}
+
+	@Test
+	public void resolveValuesRgbStyle() {
+		AttributedStyle s = AttributedStyle.DEFAULT.backgroundRgb(Color.BLUE).foregroundRgb(Color.RED);
+		ResolvedValues resolvedValues = themeResolver.resolveValues(s);
+		assertThat(resolvedValues.background()).isEqualTo(Color.BLUE);
+		assertThat(resolvedValues.foreground()).isEqualTo(Color.RED);
+	}
+
+	@Test
+	public void resolveValuesRgbExp() {
+		AttributedStyle s = themeResolver.resolveStyle("bg-rgb:#0000FF,fg-rgb:#FF0000");
+		ResolvedValues resolvedValues = themeResolver.resolveValues(s);
+		assertThat(resolvedValues.background()).isEqualTo(Color.BLUE);
+		assertThat(resolvedValues.foreground()).isEqualTo(Color.RED);
+	}
+
+	@Test
+	public void resolveValuesIndExp() {
+		AttributedStyle s = themeResolver.resolveStyle("bg:blue,fg:red");
+		ResolvedValues resolvedValues = themeResolver.resolveValues(s);
+		assertThat(resolvedValues.background()).isEqualTo(Colors.DEFAULT_COLORS_256[AttributedStyle.BLUE]);
+		assertThat(resolvedValues.foreground()).isEqualTo(Colors.DEFAULT_COLORS_256[AttributedStyle.RED]);
+	}
+
+	@Test
+	public void resolveValuesNotDefinedExp() {
+		AttributedStyle s = themeResolver.resolveStyle("");
+		ResolvedValues resolvedValues = themeResolver.resolveValues(s);
+		assertThat(resolvedValues.background()).isEqualTo(-1);
+		assertThat(resolvedValues.foreground()).isEqualTo(-1);
+	}
+
 }

spring-shell-core/src/test/java/org/springframework/shell/style/ThemeSettingsTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2022 the original author or authors.
+ * Copyright 2022-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -53,10 +53,11 @@ public class ThemeSettingsTests {
 			StyleSettings.TAG_ITEM_SELECTED,
 			StyleSettings.TAG_ITEM_UNSELECTED,
 			StyleSettings.TAG_ITEM_SELECTOR,
-			StyleSettings.TAG_HIGHLIGHT })
+			StyleSettings.TAG_HIGHLIGHT,
+			StyleSettings.TAG_BACKGROUND })
 	public void testTags(String tag) {
 		ThemeSettings themeSettings = ThemeSettings.defaults();
-		String resolveTag = themeSettings.styles().resolveTag(StyleSettings.TAG_TITLE);
+		String resolveTag = themeSettings.styles().resolveTag(tag);
 		assertThat(resolveTag).isNotNull();
 	}
 }