Strange behavior on Debian linux with any terminal except xterm-color

[MiklosPathy]

Describe the bug
Barely see anything absolutely no colors, sometimes something flashes up, otherwise mostly black screen. Menu "works", if you can figure out where you are.

To Reproduce
Steps to reproduce the behavior:

1. Install the latest Debian on a Hyper-V virtual machine. Only install SSH.
2. Install the latest dotnet 6.0 runtime on the machine.
3. Install libncursesw6, because it will be necessary.
4. Copy a Release build of the Example to the virtual machine.
5. Try to run it thru SSH with Putty
6. Try to run it thru Hyper-V Virtual Machine Connection.

Expected behavior
Works exacly like on Windows.

Screenshots

[MiklosPathy]

Exactly the same problem with the latest official Microsoft Dotnet Docker image, and with the Docker Desktop terminal.

[tznind]

Hi, thanks for getting in touch. Looks like the colors are not being recognized by the curses driver. What is your $TERM variable? Try setting it to xterm-256color

export TERM=xterm-256color

Another option is to use Application.UseSystemConsole = true (must be set before Init). In the UICatalog samples app this can be done at runtime with -usc.

If you are using a remoting technology e.g. PuTTY then you might need to set this TERM variable in that too, see: #1455

[MiklosPathy]

Hi, thank you for you answer.

I played a little with the $TERM variable values. Default is linux in debian. In case of Putty, it is xterm.

On the system console, if i set it to anything else (xterm-16color, xterm-256color, konsole-16color, konsole-256color) the folowing happens:

Only highlighted colors, the menu cursor cannot be seen. Also Midnight Commander has only higlighted colors with these settings, so this spoils another applications.

However, xterm-16color and xterm-256color are working in Putty.

Just by a lucky educated guess, i tried on the system console the linux-16colors parameter. This looks the best solution. No highlighted colors only problem, and Midnight Commander also works well.

The Application.UseSystemConsole = true solution works on Windows, and in Putty. In linux sytem console forcibly results the highlighted color problem.

Somehow Midninght Commander uses the right colors even if the seting is linux or xterm. Maybe they are using some heuristics in this case?

Best Regards,

[MiklosPathy]

Interesting.
In Docker Desktop on Windows 10, the best solution is Application.UseSystemConsole = true
The next best solutions are xterm-16color and xterm-256color. However these, results strange menu and window borders.

Fascinating.

[tznind]

Strange. If Midnight Commander works ok out of the box then it should be possible to improve things. At the very least we could look for TERM variables that we know are not going to work and override them to ncurses (hopefully).

[tig]

Two things relative to this:

1. The coming ConfigurationManager feature (Fixes #2181 - Adds configuration manager #2284) will enable forcing the use of NetDriver (aka System Console) via an external config file for cases where that's the only way to make Terminal.Gui apps work.
2. Should we consider adding a check to CursesDriver for TERM=xterm-256color and either setting it ourselves, or at least providing a Console.Writeline in Shutdown that highlights that it's not set?

[tznind]

Should we consider adding a check to CursesDriver for TERM=xterm-256color and either setting it ourselves, or at least providing a Console.Writeline in Shutdown that highlights that it's not set?

I think this is a great idea!

SetEnvironmentVariable(String, String) makes changes for the current process only. So there is no harm in forcing xterm-256color in situations where we know the value the user currently has wont work (e.g. it is blank or linux or one of the other values curses does not understand)