Incorrect highlighting with termguicolors, cursorline and spell

[puremourning]

Issue

When the termguicolors, spell and cursorline are set and the Normal highlight group sets a background colour, misspelled words are rendered incorrectly when they appear outside of another highlighting group and the cursor is on that line.

Steps to reproduce

• Create a file vimrc_hl_test with the following contents:

set termguicolors
set cursorline
syntax clear
highlight clear
hi! Normal cterm=NONE gui=NONE ctermfg=12 guifg=white ctermbg=8 guibg=black
hi! SpellBad cterm=NONE,undercurl gui=NONE,undercurl ctermfg=NONE guifg=NONE ctermbg=NONE guibg=NONE guisp=#d33682
syntax enable
syntax on
syn spell toplevel
set spell

• Edit a file with the following command: vim -Nu vimrc_hl_test and type Slpelling error.<ESC>j

Expected behaviour

The word Slpelling is rendered underlined with a foreground colour of 'white'

Actual behaviour

The word Slpelling is rendered underlined, but with a foreground colour of 'black'.

Follow-ups

• Variations of guifg and guibg on the Normal group do not change the behaviour. It appears still rendered as black.
• set notermguicolors - The text is rendered as expected (or at least the same colour as the other text)

Installed versions, environment etc.

OS: macOS
Vim: master as of today (c4bfeda)
True color terminal: iterm2

:version
VIM - Vi IMproved 8.0 (2016 Sep 12, compiled Dec 29 2016 20:42:18)
MacOS X (unix) version
Included patches: 1-134
Compiled by ben@Bens-MacBook-Pro.local
Huge version without GUI.  Features included (+) or not (-):
+acl             +cindent         +cryptv          -ebcdic          +float           +job             +listcmds        +mouse_dec       +multi_byte      +persistent_undo +rightleft       +syntax          +textobjects     +visualextra     -xfontset
+arabic          -clientserver    -cscope          +emacs_tags      +folding         +jumplist        +localmap        -mouse_gpm       +multi_lang      +postscript      +ruby/dyn        +tag_binary      +timers          +viminfo         -xim
+autocmd         +clipboard       +cursorbind      +eval            -footer          +keymap          -lua             -mouse_jsbterm   -mzscheme        +printer         +scrollbind      +tag_old_static  +title           +vreplace        -xpm
-balloon_eval    +cmdline_compl   +cursorshape     +ex_extra        +fork()          +lambda          +menu            +mouse_netterm   +netbeans_intg   +profile         +signs           -tag_any_white   -toolbar         +wildignore      -xsmp
-browse          +cmdline_hist    +dialog_con      +extra_search    -gettext         +langmap         +mksession       +mouse_sgr       +num64           -python          +smartindent     -tcl             +user_commands   +wildmenu        -xterm_clipboard
++builtin_terms  +cmdline_info    +diff            +farsi           -hangul_input    +libcall         +modify_fname    -mouse_sysmouse  +packages        +python3         +startuptime     +termguicolors   +vertsplit       +windows         -xterm_save
+byte_offset     +comments        +digraphs        +file_in_path    +iconv           +linebreak       +mouse           +mouse_urxvt     +path_extra      +quickfix        +statusline      +terminfo        +virtualedit     +writebackup
+channel         +conceal         -dnd             +find_in_path    +insert_expand   +lispindent      -mouseshape      +mouse_xterm     -perl            +reltime         -sun_workshop    +termresponse    +visual          -X11
   system vimrc file: "$VIM/vimrc"
     user vimrc file: "$HOME/.vimrc"
 2nd user vimrc file: "~/.vim/vimrc"
      user exrc file: "$HOME/.exrc"
       defaults file: "$VIMRUNTIME/defaults.vim"
  fall-back for $VIM: "/Users/ben/Development/vim2-root/share/vim"
Compilation: gcc -c -I. -Iproto -DHAVE_CONFIG_H   -DMACOS_X_UNIX  -g -O2 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1
Linking: gcc   -L. -fstack-protector -L/usr/local/lib -L/usr/local/opt/libyaml/lib -L/usr/local/opt/openssl/lib -L/usr/local/opt/readline/lib  -L/usr/local/lib -o vim        -lm -lncurses  -liconv -framework Cocoa     -L/usr/local/Cellar/python3/3.5.1/Frameworks/Python.fr
amework/Versions/3.5/lib/python3.5/config-3.5m -lpython3.5m -framework CoreFoundation

Please don't hesitate to ask if further information is required. I'm afraid I don't currently have a true colour xterm to test in for a more canonical environment.

[puremourning]

OK I have a fix for this.

Bens-MacBook-Pro:vim2 ben$ git diff
diff --git a/src/syntax.c b/src/syntax.c
index 75ede361c..ef0e45791 100644
--- a/src/syntax.c
+++ b/src/syntax.c
@@ -8765,6 +8765,8 @@ hl_combine_attr(int char_attr, int prim_attr)
        else
        {
            vim_memset(&new_en, 0, sizeof(new_en));
+           new_en.ae_u.cterm.bg_rgb = INVALCOLOR;
+           new_en.ae_u.cterm.fg_rgb = INVALCOLOR;
            if (char_attr <= HL_ALL)
                new_en.ae_attr = char_attr;
        }

PR incoming.

[puremourning]

I have a test case which shows this is not restricted to just spell. Any highlighting group is affected if it doesn't explicitly set a foreground or background colour.

• create the following file as vimrc_test:

set termguicolors
set cursorline
syntax clear
highlight clear

syntax enable
syntax on

function! s:Setup()
    syntax keyword Test Splelling
    hi! Normal cterm=NONE gui=NONE ctermfg=12 guifg=white ctermbg=8 guibg=black
    "hi! SpellBad cterm=NONE,undercurl gui=NONE,undercurl ctermfg=NONE guifg=NONE ctermbg=NONE guibg=NONE guisp=#d33682
    hi! Comment cterm=NONE,undercurl gui=NONE,undercurl ctermfg=NONE guifg=NONE ctermbg=NONE guibg=NONE guisp=#d33682
    hi link Test Comment
endfunction

autocmd BufReadPost * call s:Setup()

• create a file with the contents "Splelling" (e.g. echo Slpelling > test.txt)

• vim -Nu vimrc_test test.txt

• Observe that the word Splelling has black foreground colour, should be white.

• With the fix, observe that it is white.

[puremourning]

Fixed by #1344 (review) / 0cdb72a