Update docs

- Some new docs for theming.
- Relates #433

spring-shell-docs/src/main/asciidoc/appendices-techical-intro-theming.adoc

@@ -0,0 +1,60 @@
+[#appendix-tech-intro-theming]
+=== Theming
+ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
+
+Styling in a theming is provided by a use of a _AttributedString_ from `JLine`.
+Unfortunately styling in `JLine` is mostly undocumented but we try to go through
+some of its features here.
+
+In `JLine` a style spec is a string having a special format. Spec can be given
+multiple times if separated by a comma. A spec will either define a color for
+foreground, background or its mode. Special format `<spec>:=<spec>` allows to
+define a default within latter spec if former for some reason is invalid.
+
+If spec contains a colon its former part indicates either foreground or background
+and possible values are `foreground`, `fg`, `f`, `background`, `bg`, `b`, `foreground-rgb`,
+`fg-rgb`, `f-rgb`, `background-rgb`, `bg-rgb` or `b-rgb`. Without rbg a color value
+is name from an allowable colors `black`, `red`, `green`, `yellow`, `blue`, `magenta`,
+`cyan` or `white`. Colors have their short formats `k`, `r`, `g`, `y`, `b`, `m`, `c` and `w`
+respectively. If color is prefixed with either `!` or `bright-`, bright mode is automatically
+applied. Prefixing with `~` will resolve from JLine internal bsd color table.
+
+If rgb format is expected and prefixed with either `x` or `#` a normal
+hex format is used.
+
+====
+[source, text]
+----
+fg-red
+fg-r
+fg-rgb:red
+fg-rgb:xff3333
+fg-rgb:#ff3333
+----
+====
+
+If spec contains special names `default`, `bold`, `faint`, `italic`, `underline`, `blink`,
+`inverse`, `inverse-neg`, `inverseneg`, `conceal`, `crossed-out`, `crossedout` or `hidden`
+a style is changed accordingly with an existing color.
+
+====
+[source, text]
+----
+bold
+bold,fg:red
+----
+====
+
+If spec is a number or numbers separated with semicolon, format is a plain part of an ansi
+ascii codes.
+
+====
+[source, text]
+----
+31
+31;1
+----
+====
+
+NOTE: JLine special mapping format which would resolve spec starting with dot can't be
+used as we don't yet map those into Spring Shell styling names.

spring-shell-docs/src/main/asciidoc/appendices-techical-intro.adoc

@@ -13,3 +13,5 @@ include::appendices-techical-intro-execution.adoc[]
 include::appendices-techical-intro-commandcontext.adoc[]
 
 include::appendices-techical-intro-commandcatalog.adoc[]
+
+include::appendices-techical-intro-theming.adoc[]

spring-shell-docs/src/main/asciidoc/using-shell-customization-styling.adoc

@@ -1,49 +1,68 @@
-[[styling]]
-==== Styling
+[[theming]]
+==== Theming
+ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
 
-Version 2.1.x introduced support for centrally handling styling and theming.
-You can change the default theme (named `default`)by setting the
-`spring.shell.theme.name` property.
+Current terminal implementations are rich in features and can usually show
+something else that just plain text. For example a text can be styled to be
+_bold_ or have different colors. It's also common for terminals to be able
+to show various characters from an unicode table like emoji's which are usually
+used to make shell output more pretty.
 
-To create a new theme, register a new `Theme` bean with custom `ThemeSettings`. This new bean
-lets you tweak styles. The following example shows how to do so:
+Spring Shell supports these via it's theming framework which contains two parts,
+firstly _styling_ can be used to change text type and secondly _figures_ how
+some characters are shown. These two are then combined together as a _theme_.
+
+More about _theming_ internals, see <<appendix-tech-intro-theming>>.
+
+NOTE: Default theme is named `default` but can be change using property
+`spring.shell.theme.name`. Other built-in theme named `dump` uses
+no styling for colors and tries to not use any special figures.
+
+Modify existing style by overriding settings.
 
 ====
-[source, java]
+[source, java, indent=0]
 ----
-@Configuration
-static class CustomThemeConfig {
-
-	@Bean
-	public Theme myTheme() {
-		return new Theme() {
-			@Override
-			public String getName() {
-				return "mytheme";
-			}
-			@Override
-			public ThemeSettings getSettings() {
-				return new MyThemeSettings();
-			}
-		};
-	}
-}
-
-static class MyThemeSettings extends ThemeSettings {
-}
+include::{snippets}/ThemingSnippets.java[tag=custom-style-class]
 ----
 ====
 
-You can use `ThemeResolver` to resolve styles if you want to create
-JLine-styled strings programmatically. The following example shows how to do so:
+Modify existing figures by overriding settings.
 
 ====
-[source, java]
+[source, java, indent=0]
 ----
-@Autowired
-private ThemeResolver themeResolver;
-
-String resolvedStyle = themeResolver.resolveTag(TAG_TITLE);
-AttributedStyle style = themeResolver.resolveStyle(resolvedStyle);
+include::{snippets}/ThemingSnippets.java[tag=custom-figure-class]
+----
+====
+
+To create a new theme, create a `ThemeSettings` and provide your own _style_
+and _figure_ implementations.
+
+====
+[source, java, indent=0]
+----
+include::{snippets}/ThemingSnippets.java[tag=custom-theme-class]
+----
+====
+
+Register a new bean `Theme` where you can return your custom `ThemeSettings`
+and a _theme_ name.
+
+====
+[source, java, indent=0]
+----
+include::{snippets}/ThemingSnippets.java[tag=custom-theme-config]
+----
+====
+
+You can use `ThemeResolver` to resolve _styles_ if you want to create
+JLine-styled strings programmatically and _figures_ if you want to
+theme characters for being more pretty.
+
+====
+[source, java, indent=0]
+----
+include::{snippets}/ThemingSnippets.java[tag=using-theme-resolver]
 ----
 ====

spring-shell-docs/src/test/java/org/springframework/shell/docs/ThemingSnippets.java

@@ -0,0 +1,107 @@
+/*
+ * Copyright 2022 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.
+ * 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.
+ */
+package org.springframework.shell.docs;
+
+import org.jline.utils.AttributedStyle;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.shell.style.FigureSettings;
+import org.springframework.shell.style.StyleSettings;
+import org.springframework.shell.style.Theme;
+import org.springframework.shell.style.ThemeResolver;
+import org.springframework.shell.style.ThemeSettings;
+
+@SuppressWarnings("unused")
+public class ThemingSnippets {
+
+	// tag::custom-style-class[]
+	static class MyStyleSettings extends StyleSettings {
+
+		@Override
+		public String highlight() {
+			return super.highlight();
+		}
+	}
+	// end::custom-style-class[]
+
+	// tag::custom-figure-class[]
+	static class MyFigureSettings extends FigureSettings {
+
+		@Override
+		public String error() {
+			return super.error();
+		}
+	}
+	// end::custom-figure-class[]
+
+	// tag::custom-theme-class[]
+	static class MyThemeSettings extends ThemeSettings {
+
+		@Override
+		public StyleSettings styles() {
+			return new MyStyleSettings();
+		}
+
+		@Override
+		public FigureSettings figures() {
+			return new MyFigureSettings();
+		}
+	}
+	// end::custom-theme-class[]
+
+	// tag::custom-theme-config[]
+	@Configuration
+	static class CustomThemeConfig {
+
+		@Bean
+		Theme myTheme() {
+			return new Theme() {
+				@Override
+				public String getName() {
+					return "mytheme";
+				}
+
+				@Override
+				public ThemeSettings getSettings() {
+					return new MyThemeSettings();
+				}
+			};
+		}
+	}
+	// end::custom-theme-config[]
+
+	class Dump1 {
+
+		// tag::using-theme-resolver[]
+		@Autowired
+		private ThemeResolver resolver;
+
+		void resolve() {
+			String resolvedStyle = resolver.resolveStyleTag(StyleSettings.TAG_TITLE);
+			// bold,fg:bright-white
+
+			AttributedStyle style = resolver.resolveStyle(resolvedStyle);
+			// jline attributed style from expression above
+
+			String resolvedFigure = resolver.resolveFigureTag(FigureSettings.TAG_ERROR);
+			// character i.e. U+2716 Heavy Multiplication X Emoji, cross
+		}
+		// end::using-theme-resolver[]
+	}
+
+}