vim-patch:9.0.1300: 'statusline' only supports one "%=" item (#22218)

Problem:    'statusline' only supports one "%=" item.
Solution:   Add support for multiple "%=" items. (TJ DeVries, Yegappan
            Lakshmanan, closes vim/vim#11970, closes vim/vim#11965)

3ec78f973f

Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>

runtime/doc/options.txt

@@ -6201,8 +6201,10 @@ A jump table for the options with a short description can be found at |Q_op|.
 	         this label.
 	< -   Where to truncate line if too long.  Default is at the start.
 	      No width fields allowed.
-	= -   Separation point between alignment sections. Each section will
+	= -   Separation point between alignment sections.  Each section will
-	      be separated by an equal number of spaces.
+	      be separated by an equal number of spaces.  With one %= what
+	      comes after it will be right-aligned.  With two %= there is a
+	      middle part, with white space left and right of it.
 	      No width fields allowed.
 	# -   Set highlight group.  The name must follow and then a # again.
 	      Thus use %#HLname# for highlight group HLname.  The same

runtime/doc/vim_diff.txt

@@ -267,7 +267,6 @@ Options:
   'pumblend'    pseudo-transparent popupmenu
   'scrollback'
   'signcolumn'  supports up to 9 dynamic/fixed columns
-  'statusline'  supports unlimited alignment sections
   'tabline'     %@Func@foo%X can call any function on mouse-click
   'winblend'    pseudo-transparency in floating windows |api-floatwin|
   'winhighlight' window-local highlights
@@ -292,6 +291,7 @@ These Nvim features were later integrated into Vim.
 - |WinScrolled|
 - |:sign-define| "numhl" argument
 - |:source| works with anonymous (no file) scripts
+- 'statusline' supports unlimited alignment sections
 
 ==============================================================================
 5. Changed features					 *nvim-features-changed*

src/nvim/statusline.c

@@ -1094,7 +1094,7 @@ int build_stl_str_hl(win_T *wp, char *out, size_t outlen, char *fmt, char *opt_n
       continue;
     }
 
-    // STL_SEPARATE: Separation place between left and right aligned items.
+    // STL_SEPARATE: Separation between items, filled with white space.
     if (*fmt_p == STL_SEPARATE) {
       fmt_p++;
       // Ignored when we are inside of a grouping
@@ -2066,8 +2066,7 @@ int build_stl_str_hl(win_T *wp, char *out, size_t outlen, char *fmt, char *opt_n
     int num_separators = 0;
     for (int i = 0; i < itemcnt; i++) {
       if (stl_items[i].type == Separate) {
-        // Create an array of the start location for each
+        // Create an array of the start location for each separator mark.
-        // separator mark.
         stl_separator_locations[num_separators] = i;
         num_separators++;
       }
@@ -2079,17 +2078,17 @@ int build_stl_str_hl(win_T *wp, char *out, size_t outlen, char *fmt, char *opt_n
       int final_spaces = (maxwidth - width) -
                          standard_spaces * (num_separators - 1);
 
-      for (int i = 0; i < num_separators; i++) {
+      for (int l = 0; l < num_separators; l++) {
-        int dislocation = (i == (num_separators - 1)) ? final_spaces : standard_spaces;
+        int dislocation = (l == (num_separators - 1)) ? final_spaces : standard_spaces;
         dislocation *= utf_char2len(fillchar);
-        char *start = stl_items[stl_separator_locations[i]].start;
+        char *start = stl_items[stl_separator_locations[l]].start;
         char *seploc = start + dislocation;
         STRMOVE(seploc, start);
         for (char *s = start; s < seploc;) {
           MB_CHAR2BYTES(fillchar, s);
         }
 
-        for (int item_idx = stl_separator_locations[i] + 1;
+        for (int item_idx = stl_separator_locations[l] + 1;
              item_idx < itemcnt;
              item_idx++) {
           stl_items[item_idx].start += dislocation;

src/nvim/testdir/test_statusline.vim

@@ -231,6 +231,10 @@ func Test_statusline()
   " %=: Separation point between left and right aligned items.
   set statusline=foo%=bar
   call assert_match('^foo\s\+bar\s*$', s:get_statusline())
+  set statusline=foo%=bar%=baz
+  call assert_match('^foo\s\+bar\s\+baz\s*$', s:get_statusline())
+  set statusline=foo%=bar%=baz%=qux
+  call assert_match('^foo\s\+bar\s\+baz\s\+qux\s*$', s:get_statusline())
 
   " Test min/max width, leading zeroes, left/right justify.
   set statusline=%04B