Fix :GoSameIds for light background, GUI, and after changing colour schemes

[arp242]

This does three things:

• For light backgrounds the "highlighted" text is typically the same colour as
  the normal text:
  So use the background setting to set a more appropriate colour.
  I know I can set my own colour, but it would IMHO be better if it just
  works by default.

• The second issue is that most (if not all) colour schemes do this at the
  start:

    " Remove all existing highlighting and set the defaults.
    hi clear
  

  Which resets all custom highlight groups (except for :hi link). So just
  using a "bare" :hi ctermfg=... won't work after changing colour schemes:

    :hi goSameId
    goSameId       xxx term=bold cterm=bold ctermfg=0 ctermbg=121
  
    :colorscheme default
  
    :hi goSameId
    goSameId       xxx cleared
  

  The solution is to hook into the ColorScheme autocommand.

• And it sets the guifg/guibg parameters, otherwise nothing gets highlighted when using Gvim...

[fatih]

Not sure we apply ColorScheme to all files? And why do we have it?

[arp242]

The pattern for the ColorScheme autocommand is matched against the colour scheme name, not the file name (see :help ColorScheme).

[fatih]

Alrigth, back to my question. Why do we need to call this automatically?

[arp242]

It's needed because using :colorscheme foo will reset all custom highlight groups − see the message above:

  :hi goSameId
  goSameId       xxx term=bold cterm=bold ctermfg=0 ctermbg=121

  :colorscheme default

  :hi goSameId
  goSameId       xxx cleared

It's a bit ugly, but as far as I know there's no "clean" way to avoid this...

[fatih]

I'm trying to understand the case. So you mean we have to add this for users who override it? colorscheme is only called once in vimrc. Or is this for people who dynamically change the colorscheme ?

[arp242]

There are a few different scenarios:

• Perhaps the most common case is when you reload the vimrc file with :source ~/.vim/vimrc. This will run the colorscheme command but won't re-run the syntax files (you can use :e to fix this though, but it's annoying).
• I've seen some people use different colour schemes for different filetypes − this autocommand will be run after the syntax file and there is no real way to fix this other than than the above ColorScheme autocommand.
• As you mentioned, it helps people who change colour schemes while Vim is running. I know some people who like to switch between a dark and light version depending on ambient light conditions. Again, :e will fix this, but it's annoying.

[bhcleek]

This would be great. I change my colorscheme using :colorscheme often to accommodate people that are looking at my screen for one reason or another.

[fatih]

Thanks @Carpetsmoker