Implement comment brightness configuration feature

GH-48

README.md

@@ -20,6 +20,7 @@ Nord Vim is a 16 colorspace theme build to run in GUI- and terminal mode with su
     - [Activation](#activation)
   - [Configuration](#configuration)
     - [Italic comments](#italic-comments)
+    - [Comment contrast](#comment-contrast)
   - [Plugin Support](#plugin-support)
     - [UI Plugins](#ui-plugins)
     - [Language Plugins](#language-plugins)
@@ -110,10 +111,27 @@ Enable to use italic font for all comments.
 
 To adhere to the Nord style guide this option is disabled by default.
 It can be enabled by setting the `g:nord_italic_comments` variable to `1`. 
+
 ```vim
 let g:nord_italic_comments = 1
 ```
 
+### Comment contrast
+**This option should only be enabled if your terminal emulator supports 24bit true color (16 million colors)!**
+
+This option is only visible if `termguicolors` is enabled in your `~/.vimrc` or set via `:set termguicolors`!
+
+The comment brightness can be increased by 1 - 20 percent. It can be enabled by setting the `g:nord_comment_brightness`
+variable to a number between `1` and `20`.
+
+```vim
+let g:nord_comment_brightness = 12
+```
+
+To adhere to the Nord style guide this option uses `nord3` by default.
+
+More information about true color and the support in various terminals can be found in [this gist][gist-true-color].
+
 ## Plugin Support
 Nord Vim provides support for many third-party language- and the UI plugins.  
 
@@ -159,9 +177,9 @@ Please report issues/bugs, feature requests and suggestions for improvements to
 
 <p align="center"><a href="http://www.apache.org/licenses/LICENSE-2.0"><img src="https://img.shields.io/badge/License-Apache_2.0-5E81AC.svg?style=flat-square"/></a> <a href="https://creativecommons.org/licenses/by-sa/4.0"><img src="https://img.shields.io/badge/License-CC_BY--SA_4.0-5E81AC.svg?style=flat-square"/></a></p>
 
+[gist-true-color]: https://gist.github.com/XVilka/8346728
 [scrot-readme-default-profile]: https://raw.githubusercontent.com/arcticicestudio/nord-vim/develop/src/assets/scrot-readme-default-profile.png
 [scrot-readme-lazy-profile-change]: https://raw.githubusercontent.com/arcticicestudio/nord-vim/develop/src/assets/scrot-readme-lazy-profile-change.png
-
 [scrot-lang-c]: https://raw.githubusercontent.com/arcticicestudio/nord-vim/develop/assets/scrot-lang-c.png
 [scrot-lang-css]: https://raw.githubusercontent.com/arcticicestudio/nord-vim/develop/assets/scrot-lang-css.png
 [scrot-lang-html]: https://raw.githubusercontent.com/arcticicestudio/nord-vim/develop/assets/scrot-lang-html.png

colors/nord.vim

@@ -48,10 +48,38 @@ let s:nord13_term = "3"
 let s:nord14_term = "2"
 let s:nord15_term = "5"
 
-if !exists('g:nord_italic_comments')
+let s:nord3_gui_brightened = [
+  \ s:nord3_gui,
+  \ "#4e586d",
+  \ "#505b70",
+  \ "#525d73",
+  \ "#556076",
+  \ "#576279",
+  \ "#59647c",
+  \ "#5b677f",
+  \ "#5d6982",
+  \ "#5f6c85",
+  \ "#616e88",
+  \ "#63718b",
+  \ "#66738e",
+  \ "#687591",
+  \ "#6a7894",
+  \ "#6d7a96",
+  \ "#6f7d98",
+  \ "#72809a",
+  \ "#75829c",
+  \ "#78859e",
+  \ "#7b88a1",
+\ ]
+
+if !exists("g:nord_italic_comments")
   let g:nord_italic_comments = 0
 endif
 
+if !exists("g:nord_comment_brightness")
+  let g:nord_comment_brightness = 0
+endif
+
 function! s:hi(group, guifg, guibg, ctermfg, ctermbg, attr, guisp)
   let l:attr = a:attr
   if g:nord_italic_comments == 0 && l:attr ==? 'italic'
@@ -150,7 +178,7 @@ call s:hi("VertSplit", s:nord2_gui, s:nord1_gui, s:nord3_term, s:nord1_term, "NO
 "+----------------------+
 call s:hi("Boolean", s:nord9_gui, "", s:nord9_term, "", "", "")
 call s:hi("Character", s:nord14_gui, "", s:nord14_term, "", "", "")
-call s:hi("Comment", s:nord3_gui, "", s:nord3_term, "", "italic", "")
+call s:hi("Comment", s:nord3_gui_brightened[g:nord_comment_brightness], "", s:nord3_term, "", "italic", "")
 call s:hi("Conditional", s:nord9_gui, "", s:nord9_term, "", "", "")
 call s:hi("Constant", s:nord4_gui, "", "NONE", "", "", "")
 call s:hi("Define", s:nord9_gui, "", s:nord9_term, "", "", "")