Remove manual width calculation and handle horizontal scroll

autoload/jedi.vim

@@ -168,9 +168,9 @@ endfunction
 " Determine where the current window is on the screen for displaying call
 " signatures in the correct column.
 function! s:save_first_col()
-    let gutterwidth = &fdc + &number * max([&numberwidth, len(line('$')) + 1])
-    if bufname('%') ==# '[Command Line]' | return gutterwidth + 1 | endif
-    if winnr('$') == 1 | return gutterwidth | endif
+    if bufname('%') ==# '[Command Line]' || winnr('$') == 1
+        return 0
+    endif
 
     let l:eventignore = &eventignore
     set eventignore=all
@@ -182,7 +182,7 @@ function! s:save_first_col()
         wincmd h
         let win_on_left = winnr() == startwin
         if win_on_left
-            return gutterwidth
+            return 0
         else
             " Walk left and count up window widths until hitting the edge
             execute startwin."wincmd w"
@@ -194,7 +194,7 @@ function! s:save_first_col()
                 let winnr = winnr()
                 wincmd h
             endwhile
-            return width + gutterwidth
+            return width
         endif
     finally
         let &eventignore = l:eventignore

jedi_vim.py

@@ -341,7 +341,8 @@ def cmdline_call_signatures(signatures):
     if max_num_spaces < 0:
         return  # No room for the message
     _, column = signatures[0].bracket_start
-    num_spaces = min(int(vim_eval('g:jedi#first_col')) +
+    num_spaces = min(int(vim_eval('g:jedi#first_col +'
+                     'wincol() - col(".")')) +
                      column - len(signatures[0].call_name),
                      max_num_spaces)
     spaces = ' ' * num_spaces