Add new functionality to the `=` marker in the STL

This new functionality is explained in the documentation.

Also, many tests have been added to the buffer_spec.lua file

3 files changed, 53 insertions, 26 deletions

diff --git a/src/nvim/buffer.c b/src/nvim/buffer.c
index 71ec20c788..72724b0ffd 100644
--- a/src/nvim/buffer.c
+++ b/src/nvim/buffer.c
@@ -2849,7 +2849,7 @@ typedef enum {
 /// is "curwin".
 ///
 /// Items are drawn interspersed with the text that surrounds it
-/// Specials: %-<wid>(xxx%) => group, %= => middle marker, %< => truncation
+/// Specials: %-<wid>(xxx%) => group, %= => separation marker, %< => truncation
 /// Item: %-<minwid>.<maxwid><itemch> All but <itemch> are optional
 ///
 /// If maxwidth is not zero, the string will be filled at any middle marker
@@ -2893,7 +2893,7 @@ int build_stl_str_hl(
       Normal,
       Empty,
       Group,
-      Middle,
+      Separate,
       Highlight,
       TabPage,
       ClickFunc,
@@ -2994,14 +2994,14 @@ int build_stl_str_hl(
       continue;
     }
 
-    // STL_MIDDLEMARK: Separation place between left and right aligned items.
-    if (*fmt_p == STL_MIDDLEMARK) {
+    // STL_SEPARATE: Separation place between left and right aligned items.
+    if (*fmt_p == STL_SEPARATE) {
       fmt_p++;
       // Ignored when we are inside of a grouping
       if (groupdepth > 0) {
         continue;
       }
-      item[curitem].type = Middle;
+      item[curitem].type = Separate;
       item[curitem++].start = out_p;
       continue;
     }
@@ -3840,27 +3840,53 @@ int build_stl_str_hl(
     width = maxwidth;
 
   // If there is room left in our statusline, and room left in our buffer,
-  // add characters at the middle marker (if there is one) to
+  // add characters at the separate marker (if there is one) to
   // fill up the available space.
   } else if (width < maxwidth
-               && STRLEN(out) + maxwidth - width + 1 < outlen) {
-    for (int item_idx = 0; item_idx < itemcnt; item_idx++) {
-      if (item[item_idx].type == Middle) {
-        // Move the statusline to make room for the middle characters
-        char_u *middle_end = item[item_idx].start + (maxwidth - width);
-        STRMOVE(middle_end, item[item_idx].start);
-
-        // Fill the middle section with our fill character
-        for (char_u *s = item[item_idx].start; s < middle_end; s++)
-          *s = fillchar;
+             && STRLEN(out) + maxwidth - width + 1 < outlen) {
+    // Find how many separators there are, which we will use when
+    // figuring out how many groups there are.
+    int num_separators = 0;
+    for (int i = 0; i < itemcnt; i++) {
+      if (item[i].type == Separate) {
+        num_separators++;
+      }
+    }
 
-        // Adjust the offset of any items after the middle
-        for (item_idx++; item_idx < itemcnt; item_idx++)
-          item[item_idx].start += maxwidth - width;
+    // If we have separated groups, then we deal with it now
+    if (num_separators) {
+      // Create an array of the start location for each
+      // separator mark.
+      int separator_locations[STL_MAX_ITEM];
+      int index = 0;
+      for (int i = 0; i < itemcnt; i++) {
+        if (item[i].type == Separate) {
+          separator_locations[index] = i;
+          index++;
+        }
+      }
 
-        width = maxwidth;
-        break;
+      int standard_spaces = (maxwidth - width) / num_separators;
+      int final_spaces = (maxwidth - width) -
+        standard_spaces * (num_separators - 1);
+
+      for (int i = 0; i < num_separators; i++) {
+        int dislocation = (i == (num_separators - 1)) ?
+          final_spaces : standard_spaces;
+        char_u *sep_loc = item[separator_locations[i]].start + dislocation;
+        STRMOVE(sep_loc, item[separator_locations[i]].start);
+        for (char_u *s = item[separator_locations[i]].start; s < sep_loc; s++) {
+          *s = fillchar;
+        }
+
+        for (int item_idx = separator_locations[i] + 1;
+             item_idx < itemcnt;
+             item_idx++) {
+          item[item_idx].start += dislocation;
+        }
       }
+
+      width = maxwidth;
     }
   }
 
diff --git a/src/nvim/option.c b/src/nvim/option.c
index ac906d82ad..52a1fd8558 100644
--- a/src/nvim/option.c
+++ b/src/nvim/option.c
@@ -3403,9 +3403,10 @@ char_u *check_stl_option(char_u *s)
     if (!*s)
       break;
     s++;
-    if (*s != '%' && *s != ')')
-      ++itemcnt;
-    if (*s == '%' || *s == STL_TRUNCMARK || *s == STL_MIDDLEMARK) {
+    if (*s != '%' && *s != ')') {
+      itemcnt++;
+    }
+    if (*s == '%' || *s == STL_TRUNCMARK || *s == STL_SEPARATE) {
       s++;
       continue;
     }
diff --git a/src/nvim/option_defs.h b/src/nvim/option_defs.h
index 904e97f8ca..b1a2b00bdb 100644
--- a/src/nvim/option_defs.h
+++ b/src/nvim/option_defs.h
@@ -258,7 +258,7 @@ enum {
   STL_ARGLISTSTAT     = 'a',  ///< Argument list status as (x of y).
   STL_PAGENUM         = 'N',  ///< Page number (when printing).
   STL_VIM_EXPR        = '{',  ///< Start of expression to substitute.
-  STL_MIDDLEMARK      = '=',  ///< Separation between left and right.
+  STL_SEPARATE        = '=',  ///< Separation between alignment sections.
   STL_TRUNCMARK       = '<',  ///< Truncation mark if line is too long.
   STL_USER_HL         = '*',  ///< Highlight from (User)1..9 or 0.
   STL_HIGHLIGHT       = '#',  ///< Highlight name.
@@ -274,7 +274,7 @@ enum {
   STL_HELPFLAG, STL_HELPFLAG_ALT, STL_FILETYPE, STL_FILETYPE_ALT, \
   STL_PREVIEWFLAG, STL_PREVIEWFLAG_ALT, STL_MODIFIED, STL_MODIFIED_ALT, \
   STL_QUICKFIX, STL_PERCENTAGE, STL_ALTPERCENT, STL_ARGLISTSTAT, STL_PAGENUM, \
-  STL_VIM_EXPR, STL_MIDDLEMARK, STL_TRUNCMARK, STL_USER_HL, STL_HIGHLIGHT, \
+  STL_VIM_EXPR, STL_SEPARATE, STL_TRUNCMARK, STL_USER_HL, STL_HIGHLIGHT, \
   STL_TABPAGENR, STL_TABCLOSENR, STL_CLICK_FUNC, \
   0, \
 })