Best Practices

Spectre.Console works hard to make writing console applications easier for developers. It is designed to be easy to use and to be flexible, but there are some things that can be a bit tricky.

Output

Spectre.Console has a number of output methods and functions, but they rely on the user's console to render.

Many things make up what a console can render.

  • It's output encoding.
  • The console font.
  • The size of the windows.
  • The codepage.
  • The terminal itself.
  • The console's background color.

Many of these items can be auto-detected by Spectre.Console. Some of these items can only be configured by the user and cannot be detected automatically.

Spectre.Console can detect the following items:

  • Output encoding: the built-in widgets will use the encoding that is detected to fallback when needed when UTF-8 is not detected e.g. if a Table is configured to use a rounded border, but a user's output encoding does not support the extended ASCII characters then a fallback set of characters will be used.
  • Size of the windows: at the time of writing to the screen, Spectre.Console will know the number of characters when writing full-width widths.
  • Most terminals: Spectre.Console will try to detect the running Console and match their capabilities.

Things that cannot be detected automatically:

  • Console font: Spectre.Console will assume a relatively modern and fixed width font. If a user's console font is not fixed width, then the output for some items such as Table will be incorrect. The supported characters can also vary between fonts, especially with some modern features like Powerline characters and NerdFonts.
  • The background color and configured foreground colors.

Output Best Practices

Do test your application in multiple terminals. On Windows machines, the built-in cmd.exe and Windows Terminal both work well for a variety of capabilities.

Do not hard-code emojis and extended unicode characters in your code as default output strings. There is no guarantee that the user's console will support them and Spectre.Console will not be able to fall back automatically. To ensure the widest level of support for various terminals, allow users to either opt in to the use of extended unicode characters or, depending on the type of application, allow the user to customize the output and configure those characters by hand.

Do not assume a user's background color is black. It can be any color, including white. While Spectre.Console allows you to use up to 24-bit colors, don't assume they'll look good when displayed on the user's console. If you stick to the standard 16 ANSI colors, Spectre.Console will tell your terminal to use the color that is configured in the user's terminal theme. If you are using an 8 or 24-bit color for the foreground text, it is recommended that you also set an appropriate background color to match.

Do escape data when outputting any user input or any external data via Markup using the Markup.Escape method on the data. Any user input containing [ or ] will likely cause a runtime error while rendering otherwise.

Consider replacing Markup and MarkupLine with MarkupInterpolated and MarkupLineInterpolated. Both these methods will automatically escape all data in the interpolated string holes. When working with widgets such as the Table and Tree, consider using Markup.FromInterpolated to generate an IRenderable from an interpolated string.

Live-Rendering Best Practices

Spectre.Console has a variety of live-rendering capabilities widgets. These widgets can be used to display data that are updated and refreshed on the user's console. To do so, the widget rendering has a render loop that writes to the screen and then erases the previous output before writing again.

Do keep your rendering logic as simple as possible on a single thread. Rendering additional content while a live rendering is in progress can cause the rendering to be corrupted.

Do not use multiple live-rendering widgets simultaneously. Like the previous tip, displaying a Status control and a Progress is not supported and can cause rendering corruption.

Do create additional work threads within the Start method, but render on the main thread. For items such as a progress bar, multiple threads or tasks can be created from the Start method for concurrent execution. To ensure proper rendering, ensure that calls to update the widgets are done on the main thread.

Unit Testing Best Practices

For testing of console output, Spectre.Console has IAnsiConsole that can be injected into your application. The Spectre.Console.Test contains a set of utilities for capturing the output for verification, either manually or via a tool such as Verify.

Analyzer for Best Practices

Spectre.Console has an analyzer that helps prevent some common errors in writing console output from above such as using multiple live rendering widgets simultaneously, or using the static AnsiConsole class when IAnsiConsole is available.

Configuring the Windows Terminal For Unicode and Emoji Support

Windows Terminal supports Unicode and Emoji. However, the shells such as Powershell and cmd.exe do not. For the difference between the two, see What's the difference between a console, a terminal and a shell.

For PowerShell, the following command will enable Unicode and Emoji support. You can add this to your profile.ps1 file:

[console]::InputEncoding = [console]::OutputEncoding = [System.Text.UTF8Encoding]::new()

For cmd.exe, the following steps are required to enable Unicode and Emoji support.

  1. Run intl.cpl.
  2. Click the Administrative tab
  3. Click the Change system locale button.
  4. Check the "Use Unicode UTF-8 for worldwide language support" checkbox.
  5. Reboot.

You will also need to ensure that your Console application is configured to use a font that supports Unicode and Emoji, such as Cascadia Code.