Add LSClientShowHover

Closes natebosch#24

- Add a utility method to show some lines acting like a preview window
- Add hook to call `textDocument/hover` and wrap it up in a command

CHANGELOG.md

@@ -7,6 +7,7 @@
   recursion to a while loop.
 - Add `LSClientDisable`, `LSClientEnable` to disable or re-enable the client
   for the current filetype during a session.
+- Add `LSClientShowHover` to display hover information in a preview window.
 
 # 0.2.2
 

README.md

@@ -86,3 +86,8 @@ the response will be ignored.
 
 While the cursor is on any identifier call `LSClientFindReferences` to populate
 the quickfix list with usage locations.
+
+### Hover
+
+While the cursor is on any identifier call `LSClientShowHover` to request hover
+text and show it in a preview window.

autoload/lsc/reference.vim

@@ -99,3 +99,19 @@ function! s:goTo(file, line, character) abort
     exec 'normal! '.a:line.'G'.a:character.'|'
   endif
 endfunction
+
+function! lsc#reference#hover() abort
+  call lsc#file#flushChanges()
+  let params = s:TextDocumentPositionParams()
+  call lsc#server#call(&filetype, 'textDocument/hover',
+      \ params, function('<SID>showHover'))
+endfunction
+
+function! s:showHover(result) abort
+  if empty(a:result) || empty(a:result.contents)
+    echom 'No hover information'
+    return
+  endif
+  let lines = split(a:result.contents, "\n")
+  call lsc#util#displayAsPreview(lines)
+endfunction

autoload/lsc/util.vim

@@ -92,3 +92,22 @@ function! s:QuickFixFilename(item) abort
   endif
   return bufname(a:item.bufnr)
 endfunction
+
+" Populate a hidden buffer with [lines] and show it as a preview window.
+function! lsc#util#displayAsPreview(lines) abort
+  let view = winsaveview()
+  let alternate=@#
+  silent! pclose
+  sp __lsc_preview__
+  execute 'resize '.min([len(a:lines), &previewheight])
+  set previewwindow
+  setlocal bufhidden=hide
+  setlocal nobuflisted
+  setlocal buftype=nofile
+  setlocal noswapfile
+  %d
+  call setline(1, a:lines)
+  execute "normal \<c-w>p"
+  call winrestview(view)
+  let @#=alternate
+endfunction

plugin/lsc.vim

@@ -16,6 +16,7 @@ endif
 
 command! LSClientGoToDefinition call lsc#reference#goToDefinition()
 command! LSClientFindReferences call lsc#reference#findReferences()
+command! LSClientShowHover call lsc#reference#hover()
 command! LSClientRestartServer call <SID>IfEnabled('lsc#server#restart')
 command! LSClientDisable call <SID>Disable()
 command! LSClientEnable call <SID>Enable()