Merge #6816 'TUI improvements'

Removed these commits (test-suite changes):
e2fba01910
7c809c4bc7
18e7cd9e97

runtime/doc/eval.txt

@@ -1852,10 +1852,11 @@ v:t_number	Value of Number type.  Read-only.  See: |type()|
 v:t_string	Value of String type.  Read-only.  See: |type()|
 
 				*v:termresponse* *termresponse-variable*
-v:termresponse	The escape sequence returned by the terminal for the |t_RV|
-		termcap entry.	It is set when Vim receives an escape sequence
-		that starts with ESC [ or CSI and ends in a 'c', with only
-		digits, ';' and '.' in between.
+v:termresponse	The escape sequence returned by the terminal for the DA
+		(request primary device attributes) control sequence.  It is
+		set when Vim receives an escape sequence that starts with ESC
+		[ or CSI and ends in a 'c', with only digits, ';' and '.' in
+		between.
 		When this option is set, the TermResponse autocommand event is
 		fired, so that you can react to the response from the
 		terminal.

runtime/doc/intro.txt

@@ -442,8 +442,8 @@ available on a few terminals.
 
 Note: There are two codes for the delete key.  127 is the decimal ASCII value
 for the delete key, which is always recognized.  Some delete keys send another
-value, in which case this value is obtained from the termcap entry "kD".  Both
-values have the same effect.
+value, in which case this value is obtained from the |terminfo| entry "key_dc".
+Both values have the same effect.
 
 Note: The keypad keys are used in the same way as the corresponding "normal"
 keys.  For example, <kHome> has the same effect as <Home>.  If a keypad key

runtime/doc/map.txt

@@ -443,8 +443,8 @@ There are two ways to map a special key:
 1. The Vi-compatible method: Map the key code.  Often this is a sequence that
    starts with <Esc>.  To enter a mapping like this you type ":map " and then
    you have to type CTRL-V before hitting the function key.  Note that when
-   the key code for the key is in the termcap, it will automatically be
-   translated into the internal code and become the second way of mapping
+   the key code for the key is in the |terminfo| entry, it will automatically
+   be translated into the internal code and become the second way of mapping
    (unless the 'k' flag is included in 'cpoptions').
 2. The second method is to use the internal code for the function key.  To
    enter such a mapping type CTRL-K and then hit the function key, or use

runtime/doc/options.txt

@@ -24,10 +24,7 @@ achieve special effects.  These options come in three forms:
 
 :se[t] all		Show all but terminal options.
 
-:se[t] termcap		Show all terminal options.  Note that in the GUI the
-			key codes are not shown, because they are generated
-			internally and can't be changed.  Changing the terminal
-			codes in the GUI is not useful either...
+:se[t] termcap		Do nothing.  Nvim uses |terminfo|.
 
 								*E518* *E519*
 :se[t] {option}?	Show value of {option}.
@@ -2756,14 +2753,10 @@ A jump table for the options with a short description can be found at |Q_op|.
 			*'guicursor'* *'gcr'* *E545* *E546* *E548* *E549*
 'guicursor' 'gcr'	string	(default "n-v-c-sm:block,i-ci-ve:ver25,r-cr-o:hor20")
 			global
-	Configures the cursor style for each mode. Works in the GUI and some
-	terminals.
+	Configures the cursor style for each mode. Works in the GUI and many
+	terminals.  See |cursor-shape| for details.
 
-	With tmux you might need this in ~/.tmux.conf (see terminal-overrides
-	in the tmux(1) manual page): >
-		set -ga terminal-overrides ',*:Ss=\E[%p1%d q:Se=\E[2 q'
-
-<	To disable cursor-styling, reset the option: >
+	To disable cursor-styling, reset the option: >
 		:set guicursor=
 
 <	To enable mode shapes, "Cursor" highlight, and blinking: >

runtime/doc/quickref.txt

@@ -571,8 +571,8 @@ In Insert or Command-line mode:
 *Q_op*		Options
 
 |:set|		:se[t]			  show all modified options
-|:set|		:se[t] all		  show all non-termcap options
-|:set|		:se[t] termcap		  show all termcap options
+|:set|		:se[t] all		  show all options
+|:set|		:se[t] termcap		  Do nothing. (|terminfo|)
 |:set|		:se[t] {option}		  set boolean option (switch it on),
 					  show string or number option
 |:set|		:se[t] no{option}	  reset boolean option (switch it off)

runtime/doc/starting.txt

@@ -214,7 +214,7 @@ argument.
 			:set      to display option values.
 		When 'verbose' is non-zero messages are printed (for
 		debugging, to stderr).
-		$TERM is not used.
+		$TERM (see |TERM|) is not used.
 		If Vim appears to be stuck try typing "qa!<Enter>".  You don't
 		get a prompt thus you can't see Vim is waiting for you to type
 		something.
@@ -355,7 +355,7 @@ argument.
 At startup, Vim checks environment variables and files and sets values
 accordingly.  Vim proceeds in this order:
 
-1. Set the 'shell' option		*SHELL* *COMSPEC* *TERM*
+1. Set the 'shell' option			*SHELL* *COMSPEC*
 	The environment variable SHELL, if it exists, is used to set the
 	'shell' option.  On Windows, the COMSPEC variable is used
 	if SHELL is not set.

runtime/doc/syntax.txt

@@ -4696,7 +4696,7 @@ cterm={attr-list}					*highlight-cterm*
 ctermfg={color-nr}				*highlight-ctermfg* *E421*
 ctermbg={color-nr}				*highlight-ctermbg*
 	The {color-nr} argument is a color number.  Its range is zero to
-	(not including) the number given by the termcap entry "Co".
+	(not including) the number of |terminfo-colors| available.
 	The actual color with this number depends on the type of terminal
 	and its settings.  Sometimes the color also depends on the settings of
 	"cterm".  For example, on some systems "cterm=bold ctermfg=3" gives
@@ -4768,9 +4768,8 @@ ctermbg={color-nr}				*highlight-ctermbg*
 	delete the "g:colors_name" variable when you don't want this.
 
 	When you have set "ctermfg" or "ctermbg" for the Normal group, Vim
-	needs to reset the color when exiting.	This is done with the "op"
-	termcap entry |t_op|.  If this doesn't work correctly, try setting the
-	't_op' option in your vimrc.
+	needs to reset the color when exiting.	This is done with the
+	"orig_pair" |terminfo| entry.
 							*E419* *E420*
 	When Vim knows the normal foreground and background colors, "fg" and
 	"bg" can be used as color names.  This only works after setting the
@@ -5207,10 +5206,7 @@ To test your color setup, a file has been included in the Vim distribution.
 To use it, execute this command: >
    :runtime syntax/colortest.vim
 
-Some versions of xterm (and other terminals, like the Linux console) can
-output lighter foreground colors, even though the number of colors is defined
-at 8.  Therefore Vim sets the "cterm=bold" attribute for light foreground
-colors, when 't_Co' is 8.
+Nvim uses |256-color| and |true-color| terminal capabilities whereever possible.
 
 ==============================================================================
 18. When syntax is slow						*:syntime*

runtime/doc/term.txt

@@ -20,21 +20,183 @@ Startup						*startup-terminal*
 When Vim is started a default terminal type is assumed.  for MS-DOS this is
 the pc terminal, for Unix an ansi terminal.
 
-				*termcap* *terminfo* *E557* *E558* *E559*
-On Unix the terminfo database or termcap file is used.  This is referred to as
-"termcap" in all the documentation.
+					*terminfo* *E557* *E558* *E559*
+On Unix the terminfo database is used.  There is no access to the terminfo
+settings with |:set|.
+
+The Unibilium library (used by Nvim to read terminfo) allows you to override
+an out-of-date system terminfo database with one in your $HOME/.terminfo/
+directory, in part or in whole.
+
+Building your own up-to-date terminfo database is usually as simple as running
+this as a non-superuser:
+>
+  wget http://invisible-island.net/datafiles/current/terminfo.src.gz
+  gunzip terminfo.src.gz
+  tic terminfo.src
+<
+								*TERM*
+If you experience terminal difficulties, first ensure that you have set the
+correct terminal type in your $TERM environment variable so that Nvim is
+pulling the correct entry from the terminfo database in the first place.
+
+Per the terminfo source file from ncurses:
+
+ For these terminals          Set $TERM to                |builtin-terms|?
+
+  iTerm.app                "iterm" or "iTerm.app"                Y
+  anything libvte based    "vte" or "vte-256color"               Y
+   (e.g. GNOME Terminal)   ("gnome" and "gnome-256color" are
+                            available as aliases for these)
+  tmux                     "tmux" or "tmux-256color"             Y
+  screen                   "screen" or "screen-256color"         Y
+  PuTTY                    "putty" or "putty-256color"           Y
+  Terminal.app             "nsterm"                              N
+  Linux virtual terminal   "linux" or "linux-256color"           Y
+
+Describing any of these as "xterm" or "xterm-256colour" will not describe the
+terminal correctly to Nvim, and will cause various kinds of problematic
+behaviours.
+
+Setting your $TERM environment variable to the correct value also avoids the
+problem that SSH does not mirror arbitrary client-end environment variables
+such as $COLORTERM, $XTERM_VERSION, $VTE_VERSION, $KONSOLE_PROFILE_NAME, and
+$TERM_PROGRAM to the server end, whereas it does send the $TERM environment
+variable.
+
+See |terminfo| for dealing with out of date terminfo databases.
+
+					*builtin-terms* *builtin_terms*
+If a |terminfo| database is not available, or no entry for the terminal type is
+found in that database, Nvim will look up the terminal type in a compiled-in
+mini-database of terminfo entries for "xterm", "putty", "screen", "tmux",
+"rxvt", "iterm", "interix", "linux", "st", "vte", "gnome", and "ansi".
+
+The lookup matches the initial portion of the terminal type, so (for example)
+"putty-256color" and "putty" will both be mapped to the built-in "putty"
+entry.  The built-in terminfo entries describe the terminal as 256-colour
+capable if possible.  See |termcap-colors|.
+
+If no built-in terminfo record matches the terminal type, the built-in "ansi"
+terminfo record is used as a final fallback.
+
+The built-in mini-database is not combined with an external terminfo database,
+nor can it be used in preference to one.  You can thus entirely override any
+omissions or out-of-date information in the built-in terminfo database by
+supplying an external one with entries for the terminal type.
 
 Settings depending on terminal			*term-dependent-settings*
 
 If you want to set options or mappings, depending on the terminal name, you
-can do this best in your vimrc.  Example: >
+can do this best in your init.vim.  Example: >
 
-   if &term == "xterm"
-     ... xterm maps and settings ...
-   elseif &term =~ "vt10."
-     ... vt100, vt102 maps and settings ...
+    if $TERM =~ '^\(rxvt\|screen\)\(\|-.*\)'
+        set notermguicolors
+    elseif $TERM =~ '^\(xterm\|tmux\)\(\|-.*\)'
+        set termguicolors
+    elseif $TERM =~ ...
+	... and so forth ...
     endif
 <
+					*scroll-region* *xterm-scroll-region*
+Where possible, Nvim will use the terminal's ability to set a scroll region in
+order to redraw faster when a window is scrolled.  If the terminal's terminfo
+description describes an ability to set top and bottom scroll margins, that is
+used.
+
+This will not speed up scrolling in a window that is not the full width of the
+terminal.  Xterm has an extra ability, not described by terminfo, to set left
+and right scroll margins as well.  If Nvim detects that the terminal is Xterm,
+it will make use of this ability to speed up scrolling that is not the full
+width of the terminal.
+
+This ability is only present in genuine Xterm, not in the many terminal
+emulators that incorrectly describe themselves as xterm.  Nvim's detection of
+genuine Xterm will not work over an SSH connection, because the environment
+variable, set by genuine Xterm, that it looks for is not automatically
+replicated over an SSH login session.
+
+					*256-color* *terminfo-colors* *termcap-colors*
+Nvim can make use of 256-colour terminals and tries to do so whereever it can.
+
+If the |terminfo| description of the terminal says that it supports fewer
+colours, Nvim will override this for many terminal types, including "linux"
+(whose virtual terminals have had 256-colour support since version 4.8) and
+anything (even if falsely) claiming to be "xterm".  It will also set 256
+colours when the COLORTERM or TERM environment variables contain the string
+"256" somewhere.
+
+Nvim similarly assumes that any terminal emulator that sets the COLORTERM
+environment variable at all, to anything, is capable of at least 16-colour
+operation; and it will override |terminfo| saying that it has fewer colours
+available.
+
+						*true-color* *xterm-true-color*
+Nvim supports using true (24-bit) colours in the terminal, on terminals that
+support it.  It uses the same |terminfo| extensions that were proposed by
+Rüdiger Sonderfeld in 2013 for this: "setrgbf" and "setrgbb".  If your
+terminfo definition specifies these, then nothing more is required.
+
+If your terminfo definition is missing them, then Nvim will decide whether to
+add them to your terminfo definition, using the ISO 8613-6:1994/ITU T.416:1993
+control sequences for setting RGB colours, but modified to use semicolons
+instead of colons unless the terminal is known to follow the standard.
+(Semicolons cause ambiguities that the standard avoided by specifying colons
+as a sub-parameter delimiter.  A historical misunderstanding meant that many
+terminal emulators ended up using semicolons for many years, though.)
+
+A new convention, pioneered in 2016 by tmux, is the "Tc" terminfo extension.
+If your terminal's terminfo definition has this flag, Nvim will add
+constructed "setrgbf" and "setrgbb" capabilities as if they had been in the
+terminfo definition.
+
+If your terminal's terminfo definition does not (yet) have this flag, Nvim
+will fall back to looking at the TERM and other environment variables.  For
+the "rxvt", "linux", "st", and "iterm" terminal types, or when Konsole,
+genuine Xterm, or a terminal emulator that sets the COLORTERM environment
+variable to "truecolor" is detected, it will also add constructed "setrgbf"
+and "setrgbb" capabilities.
+
+							*xterm-resize*
+Nvim can resize the terminal display on some terminals that implement an
+extension pioneered by the dtterm program.  |terminfo| does not have a flag
+for this extension.  So Nvim simply assumes that (all) "dtterm", "xterm",
+"teraterm", "rxvt" terminal types, and Konsole, are capable of this.
+
+			*cursor-shape* *terminfo-cursor-shape* *termcap-cursor-shape*
+Nvim will adjust the shape of the cursor from a block to a line when in insert
+mode (or as specified by the 'guicursor' option), on terminals that support
+it.  It uses the same |terminfo| extensions that were pioneered by tmux for
+this: "Ss" and "Se".  If your terminfo definition specifies these, as some
+(such as those based upon "xterm+tmux") do, then nothing more is required.
+
+If your terminfo definition is missing them, then Nvim will decide whether to
+add them to your terminfo definition, by looking at the TERM and other
+environment variables.  For the "rxvt", "putty", "linux", "screen",
+"teraterm", and "iterm" terminal types, or when Konsole, a libvte-based
+terminal emulator, or genuine Xterm are detected, it will add constructed
+"Ss" and "Se" capabilities.
+
+Note: Sometimes it will appear that Nvim when run within tmux is not changing
+the cursor, but in fact it is tmux receiving instructions from Nvim to change
+the cursor and not knowing what to do in turn.  tmux has to translate what it
+receives from Nvim into whatever control sequence is appropriate for the
+terminal that it is outputting to.  It shares a common mechanism with Nvim, of
+using the "Ss" and "Se" capabilities from terminfo (for the output terminal)
+if they are present.  Unlike Nvim, if they are not present in terminfo you
+will have to add them by setting the tmux "terminal-overrides" setting in
+$HOME/.tmux.conf .
+
+See the tmux(1) manual page for the details of how and what to do in the tmux
+configuration file.  It will look something like: >
+
+		set -ga terminal-overrides '*:Ss=\E[%p1%d q:Se=\E[ q'
+<or (alas!) for Konsole specifically, something more complex like: >
+	set -ga terminal-overrides \
+        'xterm*:\E]50;CursorShape=%?%p1%{3}%<%t%{0}%e%{1}%;%d\007'
+<but these are only rough examples that do not include all of the other stuff
+that occurs in that setting.
+
 							*cs7-problem*
 Note: If the terminal settings are changed after running Vim, you might have
 an illegal combination of settings.  This has been reported on Solaris 2.5
@@ -69,20 +231,6 @@ them as a cursor key.  When you type you normally are not that fast, so they
 are recognized as individual typed commands, even though Vim receives the same
 sequence of bytes.
 
-						*xterm-8bit* *xterm-8-bit*
-Xterm can be run in a mode where it uses 8-bit escape sequences.  The CSI code
-is used instead of <Esc>[.  The advantage is that an <Esc> can quickly be
-recognized in Insert mode, because it can't be confused with the start of a
-special key.
-For the builtin termcap entries, Vim checks if the 'term' option contains
-"8bit" anywhere.  It then uses 8-bit characters for the termcap entries, the
-mouse and a few other things.  You would normally set $TERM in your shell to
-"xterm-8bit" and Vim picks this up and adjusts to the 8-bit setting
-automatically.
-When Vim receives a response to the "request version" sequence and it
-starts with CSI, it assumes that the terminal is in 8-bit mode and will
-convert all key sequences to their 8-bit variants.
-
 ==============================================================================
 Window size						*window-size*
 
@@ -93,7 +241,7 @@ On Unix systems, three methods are tried to get the window size:
 
 - an ioctl call (TIOCGSIZE or TIOCGWINSZ, depends on your system)
 - the environment variables "LINES" and "COLUMNS"
-- from the termcap entries "li" and "co"
+- from the |terminfo| entries "lines" and "columns"
 
 If everything fails a default size of 24 lines and 80 columns is assumed.  If
 a window-resize signal is received the size will be set again.  If the window
@@ -116,30 +264,27 @@ cursor position is shown in the status line.  If you are using horizontal
 scrolling ('wrap' option off) consider setting 'sidescroll' to a small
 number.
 
-If you have a slow terminal you may want to reset the 'showcmd' option.
-The command characters will not be shown in the status line.  If the terminal
-scrolls very slowly, set the 'scrolljump' to 5 or so.  If the cursor is moved
-off the screen (e.g., with "j") Vim will scroll 5 lines at a time.  Another
-possibility is to reduce the number of lines that Vim uses with the command
-"z{height}<CR>".
+If you have a slow terminal you may want to reset the 'showcmd' and 'ruler'
+options.  The command characters and cursor positions will not be shown in the
+status line (which involves a lot of cursor motions and attribute changes for
+every keypress or movement).  If the terminal scrolls very slowly, set the
+'scrolljump' to 5 or so.  If the cursor is moved off the screen (e.g., with
+"j") Vim will scroll 5 lines at a time.  Another possibility is to reduce the
+number of lines that Vim uses with the command "z{height}<CR>".
 
 If the characters from the terminal are arriving with more than 1 second
 between them you might want to set the 'timeout' and/or 'ttimeout' option.
 See the "Options" chapter |options|.
 
-If you are using a color terminal that is slow, use this command: >
+If you are using a color terminal that is slow when displaying lines beyond
+the end of a buffer, this is because Nvim is drawing the whitespace twice, in
+two sets of colours and attributes.  To prevent this, use this command: >
 	hi NonText cterm=NONE ctermfg=NONE
-This avoids that spaces are sent when they have different attributes.  On most
-terminals you can't see this anyway.
-
-If you are using Vim over a slow serial line, you might want to try running
-Vim inside the "screen" program.  Screen will optimize the terminal I/O quite
-a bit.
-
-If you are testing termcap options, but you cannot see what is happening,
-you might want to set the 'writedelay' option.  When non-zero, one character
-is sent to the terminal at a time (does not work for MS-DOS).  This makes the
-screen updating a lot slower, making it possible to see what is happening.
+This draws the spaces with the default colours and attributes, which allows the
+second pass of drawing to be optimized away.  Note: Although in theory the
+colours of whitespace are immaterial, in practice they change the colours of
+cursors and selections that cross them.  This may have a visible, but minor,
+effect on some UIs.
 
 ==============================================================================
 Using the mouse						*mouse-using*

runtime/doc/vim_diff.txt

@@ -156,6 +156,15 @@ are always available and may be used simultaneously in separate plugins.  The
 `neovim` pip package must be installed to use Python plugins in Nvim (see
 |provider-python|).
 
+Because of general |256-color| usage whereever possible, Nvim will even use
+256-colour capability on Linux virtual terminals.  Vim uses only 8 colours
+plus bright foreground on Linux VTs.
+
+Vim combines what is in its |builtin-terms| with what it reads from termcap,
+and has a |ttybuiltin| setting to control how that combination works.  Nvim
+uses either one or the other of an external |terminfo| entry or the built-in
+one.  It does not attempt to mix data from the two.
+
 |:!| does not support "interactive" commands. Use |:terminal| instead.
 (GUI Vim has a similar limitation, see ":help gui-pty" in Vim.)
 
@@ -283,6 +292,19 @@ Nvim does not have special `t_XX` options nor <t_XX> keycodes to configure
 terminal capabilities. Instead Nvim treats the terminal as any other UI. For
 example, 'guicursor' sets the terminal cursor style if possible.
 
+								*termcap*
+Nvim never uses the termcap database and only uses |terminfo|.  See
+|builtin-terms| for what happens on operating systems without a terminfo
+database.
+
+						*xterm-8bit* *xterm-8-bit*
+Xterm can be run in a mode where it uses true 8-bit CSI.  Supporting this
+requires autodetection of whether the terminal is in UTF-8 mode or non-UTF-8
+mode, as the 8-bit CSI character has to be written differently in each case.
+Vim issues a "request version" sequence to the terminal at startup and looks
+at how the terminal is sending CSI.  Nvim does not issue such a sequence and
+always uses 7-bit control sequences.
+
 'ttyfast':
   ":set ttyfast" is ignored
   ":set nottyfast" is an error

runtime/doc/windows.txt

@@ -117,7 +117,7 @@ check if the 'highlight' option contains "si".  In version 3.0, this meant to
 invert the status line.  Now it should be "sr", reverse the status line, as
 "si" now stands for italic!  If italic is not available on your terminal, the
 status line is inverted anyway; you will only see this problem on terminals
-that have termcap codes for italics.
+that have |terminfo| capabilities for italics.
 
 ==============================================================================
 3. Opening and closing a window				*opening-window* *E36*

src/nvim/option.c

@@ -969,10 +969,13 @@ void set_init_2(bool headless)
     p_window = Rows - 1;
   }
   set_number_default("window", Rows - 1);
+#if 0
+  // This bodges around problems that should be fixed in the TUI layer.
   if (!headless && !os_term_is_nice()) {
     set_string_option_direct((char_u *)"guicursor", -1, (char_u *)"",
                              OPT_GLOBAL, SID_NONE);
   }
+#endif
   parse_shape_opt(SHAPE_CURSOR);   // set cursor shapes from 'guicursor'
   (void)parse_printoptions();      // parse 'printoptions' default value
 }

src/nvim/screen.c

@@ -4230,7 +4230,6 @@ win_line (
          * (regardless of the xn,am settings).
          * Only do this if the cursor is on the current line
          * (something has been written in it).
-         * Don't do this for the GUI.
          * Don't do this for double-width characters.
          * Don't do this for a window not at the right screen border.
          */
@@ -5846,12 +5845,12 @@ static void screen_char(unsigned off, int row, int col)
   if (row >= screen_Rows || col >= screen_Columns)
     return;
 
-  /* Outputting the last character on the screen may scrollup the screen.
-   * Don't to it!  Mark the character invalid (update it when scrolled up) */
+  // Outputting the last character on the screen may scrollup the screen.
+  // Don't to it!  Mark the character invalid (update it when scrolled up)
+  // FIXME: The premise here is not actually true (cf. deferred wrap).
   if (row == screen_Rows - 1 && col == screen_Columns - 1
-      /* account for first command-line character in rightleft mode */
-      && !cmdmsg_rl
-      ) {
+      // account for first command-line character in rightleft mode
+      && !cmdmsg_rl) {
     ScreenAttrs[off] = (sattr_T)-1;
     return;
   }

src/nvim/tui/terminfo.h

@@ -0,0 +1,10 @@
+#ifndef NVIM_TUI_TERMINFO_H
+#define NVIM_TUI_TERMINFO_H
+
+#include <unibilium.h>
+
+#ifdef INCLUDE_GENERATED_DECLARATIONS
+# include "tui/terminfo.h.generated.h"
+#endif
+
+#endif  // NVIM_TUI_TERMINFO_H

test/functional/terminal/tui_spec.lua

@@ -318,6 +318,7 @@ end)
 describe("tui 't_Co' (terminal colors)", function()
   local screen
   local is_linux = (helpers.eval("system('uname') =~? 'linux'") == 1)
+  local is_freebsd = (helpers.eval("system('uname') =~? 'FreeBSD'") == 1)
 
   local function assert_term_colors(term, colorterm, maxcolors)
     helpers.clear({env={TERM=term}, args={}})
@@ -332,7 +333,7 @@ describe("tui 't_Co' (terminal colors)", function()
     thelpers.feed_data(":echo &t_Co\n")
     helpers.wait()
     local tline
-    if maxcolors == 8 then
+    if maxcolors == 8 or maxcolors == 16 then
       tline = "~                                                 "
     else
       tline = "{4:~                                                 }"
@@ -348,35 +349,79 @@ describe("tui 't_Co' (terminal colors)", function()
     ]], tline, tline, tline, tostring(maxcolors and maxcolors or "")))
   end
 
-  it("unknown TERM sets empty 't_Co'", function()
-    assert_term_colors("yet-another-term", nil, nil)
+  -- ansi and no terminal type at all:
+
+  it("no TERM uses 8 colors", function()
+    assert_term_colors(nil, nil, 8)
   end)
 
-  it("unknown TERM with COLORTERM=screen-256color uses 256 colors", function()
-    assert_term_colors("yet-another-term", "screen-256color", 256)
+  it("TERM=ansi no COLORTERM uses 8 colors", function()
+    assert_term_colors("ansi", nil, 8)
   end)
 
+  it("TERM=ansi with COLORTERM=anything-no-number uses 16 colors", function()
+    assert_term_colors("ansi", "yet-another-term", 16)
+  end)
+
+  it("unknown TERM COLORTERM with 256 in name uses 256 colors", function()
+    assert_term_colors("ansi", "yet-another-term-256color", 256)
+  end)
+
+  it("TERM=ansi-256color sets 256 colours", function()
+    assert_term_colors("ansi-256color", nil, 256)
+  end)
+
+  -- Unknown terminal types:
+
+  it("unknown TERM no COLORTERM sets 8 colours", function()
+    assert_term_colors("yet-another-term", nil, 8)
+  end)
+
+  it("unknown TERM with COLORTERM=anything-no-number uses 16 colors", function()
+    assert_term_colors("yet-another-term", "yet-another-term", 16)
+  end)
+
+  it("unknown TERM with 256 in name sets 256 colours", function()
+    assert_term_colors("yet-another-term-256color", nil, 256)
+  end)
+
+  it("unknown TERM COLORTERM with 256 in name uses 256 colors", function()
+    assert_term_colors("yet-another-term", "yet-another-term-256color", 256)
+  end)
+
+  -- Linux kernel terminal emulator:
+
   it("TERM=linux uses 256 colors", function()
-    if is_linux then
     assert_term_colors("linux", nil, 256)
-    else
-      pending()
-    end
   end)
 
   it("TERM=linux-16color uses 256 colors", function()
-    if is_linux then
     assert_term_colors("linux-16color", nil, 256)
+  end)
+
+  it("TERM=linux-256color uses 256 colors", function()
+    assert_term_colors("linux-256color", nil, 256)
+  end)
+
+  -- screen:
+  --
+  -- FreeBSD falls back to the built-in screen-256colour entry.
+  -- Linux and MacOS have a screen entry in external terminfo with 8 colours,
+  -- which is raised to 16 by COLORTERM.
+
+  it("TERM=screen no COLORTERM uses 8/256 colors", function()
+    if is_freebsd then
+      assert_term_colors("screen", nil, 256)
     else
-      pending()
+      assert_term_colors("screen", nil, 8)
     end
   end)
 
-  it("TERM=screen uses 8 colors", function()
-    if is_linux then
-      assert_term_colors("screen", nil, 8)
+  it("TERM=screen COLORTERM=screen uses 16/256 colors", function()
+    if is_freebsd then
+      assert_term_colors("screen", "screen", 256)
     else
-      pending()
+      assert_term_colors("screen", "screen", 16)
     end
   end)
 
@@ -384,15 +429,148 @@ describe("tui 't_Co' (terminal colors)", function()
     assert_term_colors("screen", "screen-256color", 256)
   end)
 
-  it("TERM=yet-another-term COLORTERM=screen-256color uses 256 colors", function()
-    assert_term_colors("screen", "screen-256color", 256)
+  it("TERM=screen-256color no COLORTERM uses 256 colors", function()
+    assert_term_colors("screen-256color", nil, 256)
   end)
 
+  -- tmux:
+  --
+  -- FreeBSD and MacOS fall back to the built-in tmux-256colour entry.
+  -- Linux has a tmux entry in external terminfo with 8 colours,
+  -- which is raised to 256.
+
+  it("TERM=tmux no COLORTERM uses 256 colors", function()
+    assert_term_colors("tmux", nil, 256)
+  end)
+
+  it("TERM=tmux COLORTERM=tmux uses 256 colors", function()
+    assert_term_colors("tmux", "tmux", 256)
+  end)
+
+  it("TERM=tmux COLORTERM=tmux-256color uses 256 colors", function()
+    assert_term_colors("tmux", "tmux-256color", 256)
+  end)
+
+  it("TERM=tmux-256color no COLORTERM uses 256 colors", function()
+    assert_term_colors("tmux-256color", nil, 256)
+  end)
+
+  -- xterm and imitators:
+
   it("TERM=xterm uses 256 colors", function()
     assert_term_colors("xterm", nil, 256)
   end)
 
+  it("TERM=xterm COLORTERM=gnome-terminal uses 256 colors", function()
+    assert_term_colors("xterm", "gnome-terminal", 256)
+  end)
+
+  it("TERM=xterm COLORTERM=mate-terminal uses 256 colors", function()
+    assert_term_colors("xterm", "mate-terminal", 256)
+  end)
+
   it("TERM=xterm-256color uses 256 colors", function()
     assert_term_colors("xterm-256color", nil, 256)
   end)
+
+  -- rxvt and stterm:
+  --
+  -- FreeBSD and MacOS fall back to the built-in rxvt-256color and
+  -- st-256colour entries.
+  -- Linux has an rxvt, an st, and an st-16color entry in external terminfo
+  -- with 8, 8, and 16 colours respectively, which are raised to 256.
+
+  it("TERM=rxvt no COLORTERM uses 256 colors", function()
+    assert_term_colors("rxvt", nil, 256)
+  end)
+
+  it("TERM=rxvt COLORTERM=rxvt uses 256 colors", function()
+    assert_term_colors("rxvt", "rxvt", 256)
+  end)
+
+  it("TERM=rxvt-256color uses 256 colors", function()
+    assert_term_colors("rxvt-256color", nil, 256)
+  end)
+
+  it("TERM=st no COLORTERM uses 256 colors", function()
+    assert_term_colors("st", nil, 256)
+  end)
+
+  it("TERM=st COLORTERM=st uses 256 colors", function()
+    assert_term_colors("st", "st", 256)
+  end)
+
+  it("TERM=st COLORTERM=st-256color uses 256 colors", function()
+    assert_term_colors("st", "st-256color", 256)
+  end)
+
+  it("TERM=st-16color no COLORTERM uses 8/256 colors", function()
+    assert_term_colors("st", nil, 256)
+  end)
+
+  it("TERM=st-16color COLORTERM=st uses 16/256 colors", function()
+    assert_term_colors("st", "st", 256)
+  end)
+
+  it("TERM=st-16color COLORTERM=st-256color uses 256 colors", function()
+    assert_term_colors("st", "st-256color", 256)
+  end)
+
+  it("TERM=st-256color uses 256 colors", function()
+    assert_term_colors("st-256color", nil, 256)
+  end)
+
+  -- gnome and vte:
+  --
+  -- FreeBSD and MacOS fall back to the built-in vte-256color entry.
+  -- Linux has a gnome, a vte, a gnome-256color, and a vte-256color entry in
+  -- external terminfo with 8, 8, 256, and 256 colours respectively, which are
+  -- raised to 256.
+
+  it("TERM=gnome no COLORTERM uses 256 colors", function()
+    assert_term_colors("gnome", nil, 256)
+  end)
+
+  it("TERM=gnome COLORTERM=gnome uses 256 colors", function()
+    assert_term_colors("gnome", "gnome", 256)
+  end)
+
+  it("TERM=gnome COLORTERM=gnome-256color uses 256 colors", function()
+    assert_term_colors("gnome", "gnome-256color", 256)
+  end)
+
+  it("TERM=gnome-256color uses 256 colors", function()
+    assert_term_colors("gnome-256color", nil, 256)
+  end)
+
+  it("TERM=vte no COLORTERM uses 256 colors", function()
+    assert_term_colors("vte", nil, 256)
+  end)
+
+  it("TERM=vte COLORTERM=vte uses 256 colors", function()
+    assert_term_colors("vte", "vte", 256)
+  end)
+
+  it("TERM=vte COLORTERM=vte-256color uses 256 colors", function()
+    assert_term_colors("vte", "vte-256color", 256)
+  end)
+
+  it("TERM=vte-256color uses 256 colors", function()
+    assert_term_colors("vte-256color", nil, 256)
+  end)
+
+  -- others:
+
+  it("TERM=interix uses 8 colors", function()
+    assert_term_colors("interix", nil, 8)
+  end)
+
+  it("TERM=iTerm.app uses 256 colors", function()
+    assert_term_colors("iTerm.app", nil, 256)
+  end)
+
+  it("TERM=iterm uses 256 colors", function()
+    assert_term_colors("iterm", nil, 256)
+  end)
+
 end)