gui-cs.Terminal.Gui/docfx/docs/newinv2.md

Terminal.Gui v2

This document provides an overview of the new features and improvements in Terminal.Gui v2.

For information on how to port code from v1 to v2, see the v1 To v2 Migration Guide.

Modern Look & Feel

Apps built with Terminal.Gui now feel modern thanks to these improvements:

• TrueColor support - 24-bit color support for Windows, Mac, and Linux. Legacy 16-color systems are still supported, automatically. See TrueColor for details.
• Enhanced Borders and Padding - Terminal.Gui now supports a Border, Margin, and Padding property on all views. This simplifies View development and enables a sophisticated look and feel. See Adornments for details.
• User Configurable Color Themes - See Color Themes for details.
• Enhanced Unicode/Wide Character support - Terminal.Gui now supports the full range of Unicode/wide characters. See Unicode for details.
• LineCanvas - Terminal.Gui now supports a line canvas enabling high-performance drawing of lines and shapes using box-drawing glyphs. LineCanvas provides auto join, a smart TUI drawing system that automatically selects the correct line/box drawing glyphs for intersections making drawing complex shapes easy. See Line Canvas for details.

Simplified API

The entire library has been reviewed and simplified. As a result, the API is more consistent and uses modern .NET API standards (e.g. for events). This refactoring resulted in the removal of thousands of lines of code, better unit tests, and higher performance than v1. See Simplified API for details.

View Improvements

• View Lifetime Management is Now Deterministic - In v1 the rules ofr lifetime management of View objects was unclear and led to non-dterministic behavior and hard to diagnose bugs. This was particularly acute in the behavior of Application.Run. In v2, the rules are clear and the code and unit test infrastructure tries to enforce them.
  • View and all subclasses support IDisposable and must be disposed (by calling view.Dispose ()) by whatever code owns the instance when the instance is longer needed.
  • To simplify programming, any View added as a Subview another View will have it's lifecycle owned by the Superview; when a View is disposed, it will call Dispose on all the items in the Subviews property. Note this behavior is the same as it was in v1, just clarified.
  • In v1, Application.End called Dispose () on Application.Top (via Runstate.Toplevel). This was incorrect as it meant that after Application.Run returned, Application.Top had been disposed, and any code that wanted to interogate the results of Run by accessing Application.Top only worked by accident. This is because GC had not actually happened; if it had the application would have crashed. In v2 Application.End does NOT call Dispose, and it is the caller to Application.Run who is responsible for disposing the Toplevel that was either passed to Application.Run (View) or created by Application.Run<T> ().
  • Any code that creates a Toplevel, either by using top = new() or by calling either top = Application.Run () or top = ApplicationRun<T>() must call top.Dispose when complete.
  • The exception to this is if top is passed to myView.Add(top) making it a subview of myView. This is because the semantics of Add are that the myView takes over responsibility for the subviews lifetimes. Of course, if someone calls myView.Remove(top) to remove said subview, they then re-take responsbility for top's lifetime and they must call top.Dispose.
• New! Adornments - Adornments are a special form of View that appear outside the Viewport: Margin, Border, and Padding.
• New! Built-in Scrolling/Virtual Content Area - In v1, to have a view a user could scroll required either a bespoke scrolling implementation, inheriting from ScrollView, or managing the complexity of ScrollBarView directly. In v2, the base-View class supports scrolling inherently. The area of a view visible to the user at a given moment was previously a rectangle called Bounds. Bounds.Location was always Point.Empty. In v2 the visible area is a rectangle called Viewport which is a protal into the Views content, which can be bigger (or smaller) than the area visible to the user. Causing a view to scroll is as simple as changing View.Viewport.Location. The View's content described by View.GetContentSize(). See Layout for details.
• New! Dim.Auto - Automatically sizes the view to fitthe view's Text, SubViews, or ContentArea.
• Improved! Pos.AnchorEnd () - New to v2 is Pos.AnchorEnd () (with no parameters) which allows a view to be anchored to the right or bottom of the Superview.
• New! Pos.Align () - Aligns a set of views horizontally or vertically (left, rigth, center, etc...).
• ...
  

New and Improved Built-in Views

• DatePicker - NEW!
• ScrollView - Replaced by built-in scrolling.
• ScrollBar - Replaces ScrollBarView with a much simpler view.
• Slider - NEW!
• Shortcut - NEW! An opinionated (visually & API) View for displaying a command, helptext, key.
• Bar - NEW! Building-block View for containing Shortcuts. Opinionated relative to Orientation but minimially so. The basis for the new StatusBar, MenuBar, and Menu views.
• StatusBar - New implementation based on Bar
• MenuBar - COMING SOON! New implementation based on Bar
• ContextMenu - COMING SOON! New implementation based on Bar
• FileDialog - The new, modern file dialog includes icons (in TUI!) for files/folders, search, and a TreeView.

Configuration Manager

Terminal.Gui now supports a configuration manager enabling library and app settings to be persisted and loaded from the file system. See Configuration Manager for details.

Updated Keyboard API

The API for handling keyboard input is significantly improved. See Keyboard API.

• The Key class replaces the KeyEvent struct and provides a platform-independent abstraction for common keyboard operations. It is used for processing keyboard input and raising keyboard events. This class provides a high-level abstraction with helper methods and properties for common keyboard operations. Use this class instead of the low-level KeyCode enum when possible. See Key for more details.
• The preferred way to handle single keystrokes is to use Key Bindings. Key Bindings map a key press to a Command. A view can declare which commands it supports, and provide a lambda that implements the functionality of the command, using View.AddCommand(). Use the View.Keybindings to configure the key bindings.
• For better consistency and user experience, the default key for closing an app or Toplevel is now Esc (it was previously Ctrl+Q).

Updated Mouse API

The API for mouse input is now internally consistent and easiser to use.

• The MouseEvent class replaces MouseEventEventArgs.
• More granular APIs are provided to ease handling specific mouse actions. See Mouse API.
• Views can use the View.Highlight event to have the view be visibly highlighted on various mouse events.
• Views can set View.WantContinousButtonPresses = true to ahve their Command.Accept command be invoked repeatedly as the user holds a mouse button down on the view.