Add EndOfBuffer hl group for ~ lines after the last line in buffers

This makes it possible to highlight the lines starting with ~ at the end
of buffers and other elements highlighted using NonText.

As proposed by mhinz at
https://groups.google.com/forum/#!topic/vim_dev/p3de1iU1GXI/discussion

runtime/doc/options.txt

@@ -3784,17 +3784,16 @@ A jump table for the options with a short description can be found at |Q_op|.
 
 						*'highlight'* *'hl'*
 'highlight' 'hl'	string	(default (as a single string):
-				     "8:SpecialKey,@:NonText,d:Directory,
+				     "8:SpecialKey,~:EndOfBuffer,@:NonText,i
-				     e:ErrorMsg,i:IncSearch,l:Search,m:MoreMsg,
+				     d:Directory,e:ErrorMsg,i:IncSearch,
-				     M:ModeMsg,n:LineNr,N:CursorLineNr,
+				     l:Search,m:MoreMsg,M:ModeMsg,n:LineNr,
-				     r:Question,s:StatusLine,S:StatusLineNC,
+				     N:CursorLineNr,r:Question,s:StatusLine,
-				     c:VertSplit, t:Title,v:Visual,
+				     S:StatusLineNC,c:VertSplit,t:Title,
-				     w:WarningMsg,W:WildMenu,
+				     v:Visual,w:WarningMsg,W:WildMenu,f:Folded,
-				     f:Folded,F:FoldColumn,A:DiffAdd,
+				     F:FoldColumn,A:DiffAdd,C:DiffChange,
-				     C:DiffChange,D:DiffDelete,T:DiffText,
+				     D:DiffDelete,T:DiffText,>:SignColumn,
-				     >:SignColumn,B:SpellBad,P:SpellCap,
+				     B:SpellBad,P:SpellCap,R:SpellRare,
-				     R:SpellRare,L:SpellLocal,-:Conceal,
+				     L:SpellLocal,-:Conceal,+:Pmenu,=:PmenuSel,
-				     +:Pmenu,=:PmenuSel,
 				     x:PmenuSbar,X:PmenuThumb")
 			global
 			{not in Vi}
@@ -3803,7 +3802,8 @@ A jump table for the options with a short description can be found at |Q_op|.
 	first character in a pair gives the occasion, the second the mode to
 	use for that occasion.  The occasions are:
 	|hl-SpecialKey|	 8  Meta and special keys listed with ":map"
-	|hl-NonText|	 @  '~' and '@' at the end of the window and
+	|hl-EndOfBuffer|      ~ lines after the last line in the buffer
+	|hl-NonText|	 @  '@' at the end of the window and
 			    characters from 'showbreak'
 	|hl-Directory|	 d  directories in CTRL-D listing and other special
 			    things in listings

runtime/doc/syntax.txt

@@ -4761,6 +4761,9 @@ DiffChange	diff mode: Changed line |diff.txt|
 DiffDelete	diff mode: Deleted line |diff.txt|
 							*hl-DiffText*
 DiffText	diff mode: Changed text within a changed line |diff.txt|
+							*hl-EndOfBuffer*
+EndOfBuffer	filler lines (~) after the end of the buffer.
+		By default, this is highlighted like |hl-NonText|.
 							*hl-ErrorMsg*
 ErrorMsg	error messages on the command line
 							*hl-VertSplit*
@@ -4789,10 +4792,10 @@ ModeMsg		'showmode' message (e.g., "-- INSERT --")
 							*hl-MoreMsg*
 MoreMsg		|more-prompt|
 							*hl-NonText*
-NonText		'~' and '@' at the end of the window, characters from
+NonText		'@' at the end of the window, characters from 'showbreak' 
-		'showbreak' and other characters that do not really exist in
+		and other characters that do not really exist in the text 
-		the text (e.g., ">" displayed when a double-wide character
+		(e.g., ">" displayed when a double-wide character doesn't 
-		doesn't fit at the end of the line).
+		fit at the end of the line). See also |hl-EndOfBuffer|.
 							*hl-Normal*
 Normal		normal text
 							*hl-Pmenu*

runtime/syntax/vim.vim

@@ -68,7 +68,7 @@ syn keyword vimAutoEvent contained	BufAdd BufCreate BufDelete BufEnter BufFilePo
 syn keyword vimGroup contained	Comment Constant String Character Number Boolean Float Identifier Function Statement Conditional Repeat Label Operator Keyword Exception PreProc Include Define Macro PreCondit Type StorageClass Structure Typedef Special SpecialChar Tag Delimiter SpecialComment Debug Underlined Ignore Error Todo 
 
 " Default highlighting groups {{{2
-syn keyword vimHLGroup contained	ColorColumn Cursor CursorColumn CursorIM CursorLine CursorLineNr DiffAdd DiffChange DiffDelete DiffText Directory ErrorMsg FoldColumn Folded IncSearch LineNr MatchParen Menu ModeMsg MoreMsg NonText Normal Pmenu PmenuSbar PmenuSel PmenuThumb Question Scrollbar Search SignColumn SpecialKey SpellBad SpellCap SpellLocal SpellRare StatusLine StatusLineNC TabLine TabLineFill TabLineSel Title Tooltip VertSplit Visual VisualNOS WarningMsg WildMenu 
+syn keyword vimHLGroup contained	ColorColumn Cursor CursorColumn CursorIM CursorLine CursorLineNr DiffAdd DiffChange DiffDelete DiffText Directory EndOfBuffer ErrorMsg FoldColumn Folded IncSearch LineNr MatchParen Menu ModeMsg MoreMsg NonText Normal Pmenu PmenuSbar PmenuSel PmenuThumb Question Scrollbar Search SignColumn SpecialKey SpellBad SpellCap SpellLocal SpellRare StatusLine StatusLineNC TabLine TabLineFill TabLineSel Title Tooltip VertSplit Visual VisualNOS WarningMsg WildMenu 
 syn match vimHLGroup contained	"Conceal"
 syn case match
 

src/nvim/globals.h

@@ -405,7 +405,8 @@ EXTERN int no_check_timestamps INIT(= 0);       /* Don't check timestamps */
 typedef enum {
   HLF_8 = 0         /* Meta & special keys listed with ":map", text that is
                        displayed different from what it is */
-  , HLF_AT          /* @ and ~ characters at end of screen, characters that
+  , HLF_EOB         // after the last line in the buffer
+  , HLF_AT          /* @ characters at end of screen, characters that
                        don't really exist in the text */
   , HLF_D           /* directories in CTRL-D listing */
   , HLF_E           /* error messages */
@@ -451,10 +452,10 @@ typedef enum {
 
 /* The HL_FLAGS must be in the same order as the HLF_ enums!
  * When changing this also adjust the default for 'highlight'. */
-#define HL_FLAGS {'8', '@', 'd', 'e', 'i', 'l', 'm', 'M', 'n', 'N', 'r', 's', \
+#define HL_FLAGS {'8', '~', '@', 'd', 'e', 'i', 'l', 'm', 'M', 'n', 'N', 'r', \
-                  'S', 'c', 't', 'v', 'V', 'w', 'W', 'f', 'F', 'A', 'C', 'D', \
+                  's', 'S', 'c', 't', 'v', 'V', 'w', 'W', 'f', 'F', 'A', 'C', \
-                  'T', '-', '>', 'B', 'P', 'R', 'L', '+', '=', 'x', 'X', '*', \
+                  'D', 'T', '-', '>', 'B', 'P', 'R', 'L', '+', '=', 'x', 'X', \
-                  '#', '_', '!', '.', 'o'}
+                  '*', '#', '_', '!', '.', 'o'}
 
 EXTERN int highlight_attr[HLF_COUNT];       /* Highl. attr for each context. */
 # define USER_HIGHLIGHT

src/nvim/option.c

@@ -365,8 +365,8 @@ typedef struct vimoption {
 # define ISP_LATIN1 (char_u *)"@,161-255"
 
 #define HIGHLIGHT_INIT \
-  "8:SpecialKey,@:NonText,d:Directory,e:ErrorMsg,i:IncSearch,l:Search," \
+  "8:SpecialKey,~:EndOfBuffer,@:NonText,d:Directory,e:ErrorMsg,i:IncSearch," \
-  "m:MoreMsg,M:ModeMsg,n:LineNr,N:CursorLineNr,r:Question,s:StatusLine," \
+  "l:Search,m:MoreMsg,M:ModeMsg,n:LineNr,N:CursorLineNr,r:Question,s:StatusLine," \
   "S:StatusLineNC,c:VertSplit,t:Title,v:Visual,V:VisualNOS,w:WarningMsg," \
   "W:WildMenu,f:Folded,F:FoldColumn,A:DiffAdd,C:DiffChange,D:DiffDelete," \
   "T:DiffText,>:SignColumn,-:Conceal,B:SpellBad,P:SpellCap,R:SpellRare," \

src/nvim/screen.c

@@ -1651,7 +1651,7 @@ static void win_update(win_T *wp)
 
     /* make sure the rest of the screen is blank */
     /* put '~'s on rows that aren't part of the file. */
-    win_draw_end(wp, '~', ' ', row, wp->w_height, HLF_AT);
+    win_draw_end(wp, '~', ' ', row, wp->w_height, HLF_EOB);
   }
 
   /* Reset the type of redrawing required, the window has been updated. */

src/nvim/syntax.c

@@ -5781,6 +5781,7 @@ static char *(highlight_init_both[]) =
       "StatusLine term=reverse,bold cterm=reverse,bold gui=reverse,bold"),
   CENT("StatusLineNC term=reverse cterm=reverse",
       "StatusLineNC term=reverse cterm=reverse gui=reverse"),
+  "default link EndOfBuffer NonText",
   CENT("VertSplit term=reverse cterm=reverse",
       "VertSplit term=reverse cterm=reverse gui=reverse"),
   CENT("DiffText term=reverse cterm=bold ctermbg=Red",