clipboard: keep track of ownership and cache clipboard data locally

Helped-By: Justin M. Keyes <justinkz@gmail.com>

runtime/autoload/provider/clipboard.vim

@@ -1,9 +1,23 @@
 " The clipboard provider uses shell commands to communicate with the clipboard.
-" The provider function will only be registered if one of the supported
+" The provider function will only be registered if a supported command is
-" commands are available.
+" available.
 let s:copy = {}
 let s:paste = {}
 
+" When caching is enabled, store the jobid of the xclip/xsel process keeping
+" ownership of the selection, so we know how long the cache is valid.
+let s:selection = { 'owner': 0, 'data': [] }
+
+function! s:selection.on_exit(jobid, data, event)
+  " At this point this nvim instance might already have launched
+  " a new provider instance. Don't drop ownership in this case.
+  if self.owner == a:jobid
+    let self.owner = 0
+  endif
+endfunction
+
+let s:selections = { '*': s:selection, '+': copy(s:selection)}
+
 function! s:try_cmd(cmd, ...)
   let argv = split(a:cmd, " ")
   let out = a:0 ? systemlist(argv, a:1, 1) : systemlist(argv, [''], 1)
@@ -14,20 +28,23 @@ function! s:try_cmd(cmd, ...)
   return out
 endfunction
 
+let s:cache_enabled = 1
+
 if executable('pbcopy')
   let s:copy['+'] = 'pbcopy'
   let s:paste['+'] = 'pbpaste'
   let s:copy['*'] = s:copy['+']
   let s:paste['*'] = s:paste['+']
+  let s:cache_enabled = 0
 elseif executable('xclip')
-  let s:copy['+'] = 'xclip -i -selection clipboard'
+  let s:copy['+'] = 'xclip -quiet -i -selection clipboard'
   let s:paste['+'] = 'xclip -o -selection clipboard'
-  let s:copy['*'] = 'xclip -i -selection primary'
+  let s:copy['*'] = 'xclip -quiet -i -selection primary'
   let s:paste['*'] = 'xclip -o -selection primary'
 elseif executable('xsel')
-  let s:copy['+'] = 'xsel -i -b'
+  let s:copy['+'] = 'xsel --nodetach -i -b'
   let s:paste['+'] = 'xsel -o -b'
-  let s:copy['*'] = 'xsel -i -p'
+  let s:copy['*'] = 'xsel --nodetach -i -p'
   let s:paste['*'] = 'xsel -o -p'
 else
   echom 'clipboard: No shell command for communicating with the clipboard found.'
@@ -37,11 +54,36 @@ endif
 let s:clipboard = {}
 
 function! s:clipboard.get(reg)
+  if s:selections[a:reg].owner > 0
+    return s:selections[a:reg].data
+  end
   return s:try_cmd(s:paste[a:reg])
 endfunction
 
 function! s:clipboard.set(lines, regtype, reg)
-  call s:try_cmd(s:copy[a:reg], a:lines)
+  if s:cache_enabled == 0
+    call s:try_cmd(s:copy[a:reg], a:lines)
+    return 0
+  end
+
+  let selection = s:selections[a:reg]
+  if selection.owner > 0
+    " The previous provider instance should exit when the new one takes
+    " ownership, but kill it to be sure we don't fill up the job table.
+    call jobstop(selection.owner)
+  end
+  let selection.data = [a:lines, a:regtype]
+  let argv = split(s:copy[a:reg], " ")
+  let jobid = jobstart(argv, selection)
+  if jobid <= 0
+    echohl WarningMsg
+    echo "clipboard: error when invoking provider"
+    echohl None
+    return 0
+  endif
+  call jobsend(jobid, a:lines)
+  call jobclose(jobid, 'stdin')
+  let selection.owner = jobid
 endfunction
 
 function! provider#clipboard#Call(method, args)