Initial terminal ui implementation

- This commit adds proof of concept work for terminal ui as is.
- Some things work, some don't but we need to start from somewhere.
  Further development continues in a main.
- Essentially we are starting to have enough so that it merits to
  move all this work into a main repo.
- Everything new is kept under org.springframework.shell.component.view
  and will get revisiter later to find correct locations for some classes.
- Catalog sample has been modified to provide "showcase" app for
  terminal ui features. This is a start while it already contains
  some usefull scenarios.
- Relates #800
- Relates #801
- Relates #802
- Relates #803
- Relates #804
- Relates #805
- Relates #806
- Relates #807
- Relates #808
- Relates #809
- Relates #810
- Relates #811

spring-shell-docs/src/main/asciidoc/appendices-tui-catalog.adoc

@@ -0,0 +1,12 @@
+[#appendix-tui-catalog]
+=== Catalog App
+ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
+
+Catalog application is showing various ways how Terminal UI Framework can be used.
+In this section we discuss how this application works. It can be considered to be
+a reference application as it's using most of the features available and tries
+to follow best practices.
+
+==== Create Scenario
+Every `Scenario` essentially is a sample code of a `View` as that's what catalog
+app demonstrates.

spring-shell-docs/src/main/asciidoc/appendices-tui-control.adoc

@@ -0,0 +1,5 @@
+[#appendix-tui-control]
+=== Control
+ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
+
+_Control_ draws something into a screen with a given bounds.

spring-shell-docs/src/main/asciidoc/appendices-tui-eventloop.adoc

@@ -0,0 +1,5 @@
+[#appendix-tui-eventloop]
+=== EventLoop
+ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
+
+_EventLoop_ is a central system handling eventing in a framework.

spring-shell-docs/src/main/asciidoc/appendices-tui-keyhandling.adoc

@@ -0,0 +1,5 @@
+[#appendix-tui-keyhandling]
+=== Key Handling
+ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
+
+Handles incoming key events.

spring-shell-docs/src/main/asciidoc/appendices-tui-mousehandling.adoc

@@ -0,0 +1,5 @@
+[#appendix-tui-mousehandling]
+=== Mouse Handling
+ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
+
+Handles incoming mouse events.

spring-shell-docs/src/main/asciidoc/appendices-tui-screen.adoc

@@ -0,0 +1,6 @@
+[#appendix-tui-screen]
+=== Screen
+ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
+
+_Screen_ is an abstraction providing higher level concept to draw something
+into a terminal.

spring-shell-docs/src/main/asciidoc/appendices-tui-view.adoc

@@ -0,0 +1,5 @@
+[#appendix-tui-view]
+=== View
+ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
+
+_View_ extends _Control_ providing integration into event loop.

spring-shell-docs/src/main/asciidoc/appendices-tui.adoc

@@ -0,0 +1,22 @@
+[appendix]
+[#appendix-tech-intro-tui]
+== Terminal UI
+ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
+
+This is a technical introduction to _UI Framework_.
+
+_UI Framework_ is a toolkit to build rich console apps.
+
+include::appendices-tui-control.adoc[]
+
+include::appendices-tui-view.adoc[]
+
+include::appendices-tui-eventloop.adoc[]
+
+include::appendices-tui-screen.adoc[]
+
+include::appendices-tui-keyhandling.adoc[]
+
+include::appendices-tui-mousehandling.adoc[]
+
+include::appendices-tui-catalog.adoc[]

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

@@ -1,3 +1,5 @@
 include::appendices-techical-intro.adoc[]
 
 include::appendices-debugging.adoc[]
+
+include::appendices-tui.adoc[]

spring-shell-docs/src/main/asciidoc/using-shell-tui-intro.adoc

@@ -0,0 +1,14 @@
+[[using-shell-tui-intro]]
+=== Introduction
+ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
+
+Lets start with a simple app which prints "hello world" in a view.
+====
+[source, java, indent=0]
+----
+include::{snippets}/TerminalUiSnippets.java[tag=snippet1]
+----
+====
+
+There is not much to see here other than `TerminalUI` is a class handling
+all logic aroung views and uses `View` as it's root view.

spring-shell-docs/src/main/asciidoc/using-shell-tui-views-box.adoc

@@ -0,0 +1,6 @@
+[[using-shell-tui-views-box]]
+==== BoxView
+ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
+
+_BoxView_ is a base implementation providing functionality to draw into a
+bounded _Rectancle_.

spring-shell-docs/src/main/asciidoc/using-shell-tui-views-list.adoc

@@ -0,0 +1,5 @@
+[[using-shell-tui-views-list]]
+==== ListView
+ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
+
+_ListView_ is a base implementation providing functionality to draw list of items.

spring-shell-docs/src/main/asciidoc/using-shell-tui-views.adoc

@@ -0,0 +1,11 @@
+[[using-shell-tui-views]]
+=== Views
+ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
+
+Framework provides a build-in views which are documented below.
+
+TIP: To learn more about views, see <<appendix-tui-view>>.
+
+include::using-shell-tui-views-box.adoc[]
+
+include::using-shell-tui-views-list.adoc[]

spring-shell-docs/src/main/asciidoc/using-shell-tui.adoc

@@ -0,0 +1,16 @@
+[[using-shell-tui]]
+== Terminal UI
+
+NOTE: Feature is experimental and subject to breaking changes until foundation
+      and related concepts around framework are getting more stable.
+
+_Terminal UI Framework_ is a toolkit to build rich console apps. This section is
+for those using existing features as is. If you're planning to go deeper possibly
+creating your own components <<appendix-tech-intro-tui>> provides more detailed
+documentation.
+
+TIP: Catalog sample is a good place to study a real application <<appendix-tui-catalog>>.
+
+include::using-shell-tui-intro.adoc[]
+
+include::using-shell-tui-views.adoc[]

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

@@ -10,6 +10,8 @@ include::using-shell-building.adoc[]
 
 include::using-shell-components.adoc[]
 
+include::using-shell-tui.adoc[]
+
 include::using-shell-customization.adoc[]
 
 include::using-shell-execution.adoc[]

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

@@ -0,0 +1,49 @@
+/*
+ * Copyright 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.
+ * 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.terminal.Terminal;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.shell.component.view.TerminalUI;
+import org.springframework.shell.component.view.control.BoxView;
+import org.springframework.shell.component.view.geom.HorizontalAlign;
+import org.springframework.shell.component.view.geom.VerticalAlign;
+
+class TerminalUiSnippets {
+
+	class Sample {
+
+		// tag::snippet1[]
+		@Autowired
+		Terminal terminal;
+
+		void build() {
+			TerminalUI ui = new TerminalUI(terminal);
+			BoxView view = new BoxView();
+			view.setDrawFunction((screen, rect) -> {
+				screen.writerBuilder()
+					.build()
+					.text("Hello World", rect, HorizontalAlign.CENTER, VerticalAlign.CENTER);
+				return rect;
+			});
+			ui.setRoot(view, true);
+			ui.run();
+		}
+		// end::snippet1[]
+	}
+
+}