Should be similar in spirit to the UIScrollView in that it can move the contents of the subviews

Work in Progress in ScrollView

We are currently reporting the mouse movement events, but it looks like the terminal via curses
is not sending us the events we need when the mouse is clicked and then moved.

It is currently sitting in an instance of the TextField and should instead be accessible to all fields and future entries.

Should unprocessed cursor key events trigger focus? -> Yes, we should. More discoverable than tab/shifttab

Currently does conversions from string to ustring and should use ustring methods, when those are implemented (and ustringbuilder)

And allow for yank operetions

Rows and columns, multi-row/column spanning for specific cells, etc.

Merely a control that draws a frame with a label

It should render more detail depending on the height. 1 line, current design; 2 progress plus percentage; 3 framed; 4 frame with progress; 6 frame wothnprogress padded

We should have a system to define keyboard chords as well as a Command system, to not rely nor be limieted by the function keys.

This would allow things like "C-x C-s" to be defined easily.

Can use the work-in-progress XtermSharp and mono/pty-sharp

as it currently prevents the library from working there.

Currently the only backend in use for gui.cs is the ncurses backend. There is a partial implementation of a System.Console based driver but it is not complete.

Currently we use mainloop.cs to monitor input on standard input and wake up the mainloop to read the input. We need a variant that works for Windows, likely using Console.ReadKey and using some AutoResetEvent to wake up the thread.

Generally, we can either make mainloop.cs fully cross platform, or we could surface Windows/Unix codepaths, and let the consumer (in this case, gui.cs) deal with it.

In addition to that, the backend itself needs to be completed.

Would be good to have a way of toggling a way to draw a box around boundaries on views.

• Control-L does not redraw everything when there are many toplevels running

• Redraw (Control-L) handler needs to do a painter's paint job, currently
  only Application.Top gets the SetNeedsDisplay(), but this needs to apply
  on Control-L to the entire stack.

  Repro: activate dialog box, press esc, and this clears the dialog contents.

To make it simpler to add a splash of color to the UI.

Some thoughts:

• Attributed strings should allow overlapping attributes
• Attributed strings should have an HTML-like input system for ease of creation.

Tags:

• <b> - bold
• <u> - underline
• <r> - reverse

Colors:

• <red>, <green>, <yellow> etc

I can type anywhere, characters are just printed on top of the views.
Typing a non-alpha character makes the next character overwrite the previous etc.

Trying to compile this on Windows it wants "Unix" something?

Severity Code Description Project File Line Suppression State
Error CS0234 The type or namespace name 'Unix' does not exist in the namespace 'Mono' (are you missing an assembly reference?) Terminal.Gui V:\Downloads\gui.cs-master\gui.cs-master\Terminal.Gui\MonoCurses\mainloop.cs 28 Active
Error CS0246 The type or namespace name 'Pollfd' could not be found (are you missing a using directive or an assembly reference?) Terminal.Gui V:\Downloads\gui.cs-master\gui.cs-master\Terminal.Gui\MonoCurses\mainloop.cs 86 Active
Error CS0246 The type or namespace name 'PollEvents' could not be found (are you missing a using directive or an assembly reference?) Terminal.Gui V:\Downloads\gui.cs-master\gui.cs-master\Terminal.Gui\MonoCurses\mainloop.cs 217 Active
Error CS0006 Metadata file 'V:\Downloads\gui.cs-master\gui.cs-master\Terminal.Gui\bin\Debug\Terminal.Gui.dll' could not be found Terminal V:\Downloads\gui.cs-master\gui.cs-master\CSC 1 Active

Pondering: should it support attributed text?

This is the function bar at the bottom of the screen that provides a visual cue for the available commands.

There is a partial implementation in the old gui.cs:

https://github.com/mono/mono-curses/blob/master/gui.cs

A hotlabel, is just a label but it has the following properties:

• It uses hot-strings so that the hot-letter can be used as a hotkey
• Is linked to another View that can be focused
• Responds to the hotkey and when pressed, focuses the provided view.

Should this just be folded into the regular Label?

Many characters that take up two slots are not properly rendered as we render those two, but do not fully fill the requested region. Need to use Rune.ColumnWidth to compute the current position.

[x] Setup documentation extracting process
[x] Publish API docs
[ ] Public guideline docs

The issue is that we are not finding a valid view, due to our offset code.

Repro: run the sample, and try clicking on the radio at the end of the word "Personal", it only works if you click on the first few characters.

Need to make a .NET Standard 2 library out of a this, and a NuGet package.

Desired:

[x] Link the mono-curses files directly, to reduce dependencies
[x] Link Mainloop directly, same reason

Challenges:

• Moving to .NET Standard means the main application will end up pulling some 99 assemblies, unless we switch it to .NET Core. Either option is slower.

• There is a bug in P/Invoke against poll that renders the results of poll unusable.

It would be great to support .NET Core.

Should include other color themes, currently we have the Norton-esque theme, we could include a TurboVision-esque theme. The support is already in place, it is a matter of allocating new colors in each driver.

We could likely have a simple listview that relies on text being returned, and a more complicated one, that allows users to provide a full view to be rendered in place - to allow colors and other features.

Implemented as ListView, some features missing:

• Mouse support
• Ponder: Should it show scrollbars?
• Should it support multiple-columns?

Scrollviews should take the focus for any focusable controls and show allow for the key navigation keystrokes to control where the focus goes.

Additionally, we probably should make "PositionCursor" return the Point where the cursor would be in a View, instead of manually positioning it. The caller would place the cursor in the right place.

This would allow us to figure out where the cursor should go in a scrollview and scroll to the right location on those scenarios.

This needs to exist:

https://twitter.com/jessfraz/status/962034432541519873

Currently at best, we have LayoutSubviews, but there is no support for anchoring, springs or any other layout system.

Should consider what options we have.

Perhaps Views could have a LayoutManager in charge of laying things out. Would be desirable to have a layout manager that can work by default with Add, and the question is whether attributes of how a view should be laid out should live in the view itself, or should be an attached property when they are added to the parent.

It seems that with layout managers, we could have general purpose pones like Grid, or Flex, and convenience View subclasses like HBox/VBox to finetune the layout.

Terminal Colors

There exists common confusion about terminal colors. This is what we have right now:

• Plain ASCII
• ANSI escape codes: 16 color codes with bold/italic and background
• 256 color palette: 216 colors + 16 ANSI + 24 gray (colors are 24-bit)
• 24-bit true color: "888" colors (aka 16 milion)

printf "\x1b[${bg};2;${red};${green};${blue}m\n"

The 256-color palette is configured at start and is a 666-cube of colors,
each of them defined as a 24-bit (888 rgb) color.

This means that current support can only display 256 different colors in the
terminal while "true color" means that you can display 16 million different
colors at the same time.

Truecolor escape codes do not use a color palette. They just specify the
color itself.

This is a good test case:

printf "\x1b[38;2;255;100;0mTRUECOLOR\x1b[0m\n"

• or
  https://raw.githubusercontent.com/JohnMorales/dotfiles/master/colors/24-bit-color.sh
• or http://github.com/robertknight/konsole/tree/master/tests/color-spaces.pl
• or https://git.gnome.org/browse/vte/tree/perf/img.sh
• or just run this:

awk 'BEGIN{
    s="/\\/\\/\\/\\/\\"; s=s s s s s s s s;
    for (colnum = 0; colnum<77; colnum++) {
        r = 255-(colnum*255/76);
        g = (colnum*510/76);
        b = (colnum*255/76);
        if (g>255) g = 510-g;
        printf "\033[48;2;%d;%d;%dm", r,g,b;
        printf "\033[38;2;%d;%d;%dm", 255-r,255-g,255-b;
        printf "%s\033[0m", substr(s,colnum+1,1);
    }
    printf "\n";
}'

Keep in mind that it is possible to use both ';' and ':' as Control Sequence
Introducer delimiters.

According to Wikipedia[1], this behavior is only supported by xterm and konsole.

[1] https://en.wikipedia.org/wiki/ANSI_color

Since
ncurses-6.0-20180121,
terminfo began to support the 24-bit True Color capability under the name of
"RGB". You need to use the "setaf" and "setab" commands to set the foreground
and background respectively.

True Color Detection

There will be no reliable way to detect the "RGB" flag until the new release of
terminfo/ncurses. S-Lang author added a check for $COLORTERM containing either
"truecolor" or "24bit" (case sensitive). In addition,
VTE,
Konsole and
iTerm2 set this variable to
"truecolor". It has been in VTE for a while and but is relatively new, being
still git-only in Konsole and iTerm2).

This is obviously not a reliable method, and is not forwarded via sudo, SSH etc.
However, whenever it errs, it errs on the safe side. It does not advertise
support when it is actually unsupported. App developers can freely choose to
check for this same variable, or introduce their own method (e.g. an option in
their config file). They should use whichever method best matches the overall
design of their app. Checking $COLORTERM is recommended though since it will
lead to a more seamless desktop experience where only one variable needs to be
set. This would be system-wide so that the user would not need to set it
separately for each app.

Querying The Terminal

A more reliable method in an interactive program which can read terminal
responses, and one that is transparent to things like sudo, SSH, etc.. is to
simply try setting a truecolor value and then query the terminal to ask what
color it currently has. If the response replies the same color that was set
then it indicates truecolor is supported.

$ (echo -e '\e[48:2:1:2:3m\eP$qm\e\\' ; xxd)

^[P1$r48:2:1:2:3m^[\
00000000: 1b50 3124 7234 383a 323a 313a 323a 336d  .P1$r48:2:1:2:3m

Here we ask to set the background color to RGB(1,2,3) - an unlikely default
choice - and request the value that we just set. The response comes back that
the request was understood (1), and that the color is indeed 48:2:1:2:3.
This tells us also that the terminal supports the colon delimiter. If instead,
the terminal did not support truecolor we might see a response like

^[P1$r40m^[\
00000000: 1b50 3124 7234 306d 1b5c 0a              .P1$r40m.\.

This terminal replied the color is 40 - it has not accepted our request to
set 48:2:1:2:3.

^[P0$r^[\
00000000: 1b50 3024 721b 5c0a                      .P0$r.\.

This terminal did not even understand the DECRQSS request - its response was
0$r. We do not learn if it managed to set the color, but since it doesn't
understand how to reply to our request it is unlikely to support truecolor
either.

Terminals + True Color

Now Supporting True Color

• st (from suckless) [delimeter: semicolon] -
  http://lists.suckless.org/dev/1307/16688.html
• xst - fork of st
• konsole [delimeter: colon,
  semicolon] - https://bugs.kde.org/show_bug.cgi?id=107487
• iTerm2 [delimeter: colon, semicolon] - since v3
  version
• Therm [delimeter: colon, semicolon] - fork
  of iTerm2
• qterminal [delimeter: semicolon] - > 0.14.1 versions (issue #78)
• alacritty [delimeter: semicolon] -
  written in Rust
• kitty [delimeter: colon,semicolon] -
  uses OpenGL
• cool-retro-term [delimeter:
  semicolon]
• mosh (Mobile SHell) [delimeter: semicolon] - since commit 6cfa4aef598146cfbde7f7a4a83438c3769a2835
• pangoterm [delimeter:
  colon, semicolon]
• Termux [delimeter: semicolon] - Android platform
• ConnectBot - Android platform - since 3bcc75ccedaf2136b04c5932c81a5155f29dc3b5 commit.
• Black Screen [delimeter:
  semicolon] - crossplatform, HTML/CSS/JS-based
• hterm -
  HTML/CSS/JS-based (ChromeOS)
• PuTTY -
  landed
  in git (patched version [3] {xterm-like approximation to 256 colors} and [4]
  {real true colors} available) - Windows platform
• Tera Term [delimeter: colon,
  semicolon] - Windows platform
• ConEmu [delimeter: semicolon] -
  Windows platform
• Windows
  Powershell
  [delimeter: semicolon] - aka Powershell 5.x and below Windows 10
• Powershell Core [delimeter:
  semicolon] aka Powershell 6+ Windows 10
• cmd.exe [delimeter:
  semicolon] Builtin Windows shell that is mostly unchanged since DOS Windows 10
• FinalTerm [delimeter: semicolon] -
  abandoned, iTerm2
  borrowing it's ideas and features.
• MacTerm [delimeter: semicolon] - Mac
  OS X platform
• mintty [delimeter: semicolon] Cygwin and
  MSYS/MSYS2 since commit 43f0ed8a46c6549cb9a3ea27abc057b5abe13bdb
  (2.0.1 release) - Windows platform
• MobaXterm Windows platform - closed
  source (run lscolors to see a truecolor test)
• ZOC Windows/OS X platform - closed
  source since
  7.19.0 version
• upterm Windows/Macos/Linux Electron -
  A terminal emulator for the 21st century.
• Windows 10 bash console, since
  Windows Insiders build 14931
• All libvte based terminals
  (since 0.36 version) [delimeter: colon, semicolon] -
  https://bugzilla.gnome.org/show_bug.cgi?id=704449
  • libvte-based
    Gnome Terminal
  • libvte-based sakura
  • libvte-based
    xfce4-terminal - since
    0.6.90
    release, if compiled with GTK+3
  • libvte-based
    Terminator -
    since 1.90 release
  • libvte-based Tilix - written in D.
    Similar user interface as for Terminator.
  • libvte-based Lilyterm - since commit 72536e7ba448ad9ef1126ce45fbde3a3407a271b
  • libvte-based ROXTerm
  • libvte-based evilvte - no release yet,
    version from git https://github.com/caleb-/evilvte
  • libvte-based Termit
  • libvte-based Termite
  • libvte-based Tilda
  • libvte-based tinyterm
  • libvte-based
    Pantheon Terminal
  • libvte-based lxterminal - with
    --enable-gtk3 configure flag.
  • libvte-based guake - A top-down terminal for GNOME
• All xterm.js based terminals (since v3.13, v4.3 for webgl) [delimeter: semicolon]
  • VS Code's integrated terminal
  • Terminus: highly configurable terminal emulator for Windows, macOS and Linux

There are a bunch of libvte-based terminals for GTK2, so they are listed in the
another section.

Also, while this one is not a terminal, but a terminal replayer, it is
still worth mentioning:

• asciinema player:
  https://github.com/asciinema/asciinema-player

Improper Support for True Color

• mlterm - built with --with-gtk=3.0
  configure flag. Approximates colors to 512 embedded palette
  (https://sourceforge.net/p/mlterm/bugs/74/)

Terminals that parse ANSI color sequences, but approximate them to 256 palette

• xterm (but doing it wrong: "it uses nearest color in RGB color space,
  with a usual false assumption about orthogonal axes")
• urxvt aka rxvt-unicode -
  since
  Revision 1.570
  http://lists.schmorp.de/pipermail/rxvt-unicode/2016q2/002261.html (Note there
  is a restriction of colors count still)
• linux console (fbcon), since v3.16 - https://bugzilla.kernel.org/show_bug.cgi?id=79551 (downgraded to 16 foregrounds and 8 backgrounds)
• Hyper.app [delimeter: semicolon] - crossplatform, HTML/CSS/JS-based (Electron) vercel/hyper#2294

Note about color differences:
a) RGB axes are not orthogonal, so you cannot use
sqrt(R^2+G^2+B^2) formula
b) for color differences there is more correct (but
much more complex)
CIEDE2000 formula
(which may easily blow up performance if used blindly) [2].

[2] neovim/neovim#793 (comment)

Terminal multiplexers

• tmux - starting from version 2.2 (support since
  427b820...)
• screen - has support in
  'master' branch, need to be enabled (see 'truecolor' option)
• pymux - tmux clone in pure Python
  (to enable truecolor run pymux with --truecolor option)
• dvtm - not yet supporting True Color
  martanne/dvtm#10

NOT Supporting True Color

• Terminal.app: Macos Terminal builtin
• Terminology
  (Enlightenment) - https://phab.enlightenment.org/T746
• Cmder: Portable console emulator for Windows,
  based on ConEmu.
• mrxvt (looks abandoned) -
  https://sourceforge.net/p/materm/feature-requests/41/
• aterm (looks abandoned) -
  https://sourceforge.net/p/aterm/feature-requests/23/
• FreeBSD console - https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=191652
• yaft framebuffer terminal - issue #12
• KiTTY - Windows platform
• MTPuTTY - Windows platform
• mRemoteNG - Windows platform - issue #717
• JuiceSSH - Adroid platform, closed source
• Termius - Linux, Windows, OS X platforms,
  closed source
• SmarTTY - Windows platform - closed source
  (sent them a request)
• Netsarang XShell -
  closed source (sent them an email)
• libvte and GTK2 - based:
  • libvte-based GTKTerm2
  • libvte-based stjerm (looks abandoned) - issue #39

Console Programs + True Color

Console Programs Supporting True Color

• s-lang
  library - (since pre2.3.1-35, for 64bit systems)
• ncurses library - since 6.1 version
• Eternal Terminal - automatically
  reconnecting shell
• mc - since
  682a5....
  See also ticket #3724 for
  truecolor themes.
• irssi - since
  PR #48
• neovim - since commit
  8dd415e887923f99ab5daaeba9f0303e173dd1aa;
  need to set
  termguicolors to
  enable true color.
• vim - (from 7.4.1770); need to set
  termguicolors
  to enable true color.
• joe - (from
  4.5
  version)
• emacs - since
  26.1 release
• micro editor
• elinks -
  configure.in:1410
  (./configure --enable-true-color)
• tcell library for Go language
• timg - Terminal Image Viewer
• tv - tool to quickly view high-resolution
  multi-band imagery directly in terminal
• termimage - terminal image
  viewer
• explosion - terminal image viewer
• ls-icons - fork of coreutils with
  ls program that supports icons
• mpv - video player with support of
  console-only output (since 0.22 version)
• radare2 - reverse engineering franework;
  since 0.9.6 version.

Console Programs Not Supporting True Color

• mutt (email client) - http://dev.mutt.org/trac/ticket/3674
• neomutt (email client) - issue #58
• termbox library - issue #37 (there is a fork termbox_next with the support
• https://bitbucket.org/McKael/mcabber-crew (jabber client) - issue #126
• tig (git TUI) - issue #227
• cmus (music player) - issue #799
• weechat (chat client) - issue #1364
• scim (spreadsheet program) - issue #306
• gui.cs Terminal UI toolkit for .NET (curses-like) - issue #48

See the repository https://github.com/termstandard/colors

Or the gist and discussion here: https://gist.github.com/XVilka/8346728

Reusable scrollbars.

Work-in progress in ScrollBarView

Perhaps dialog containers need to set a general style for the child widgets,so that when we set a dialog, or error box, all the children added get the right set of default colors.

Widgets should not use Colors.Base or Colors.Dialog, they should likely use the colors defined in the toplevel container, so that the Dialog vs Toplevel colors are set there only.

Resizing of the toplevel windows, and message boxes should be relatively easy, but there is no support to relayout the views. As we do not currently have a layout system, beyond the absolute positioning system.

Update The https://github.com/migueldeicaza/gui.cs/tree/layout branch now contains a C# port of the Xamarin Flex engine that Stephane Delcroix did, while the port is complete, it is completely untested, that needs to be done.