vim-patch:9.1.0430: getregionpos() doesn't handle one char selection (#28924)

Problem:  getregionpos() doesn't handle one char selection.
Solution: Handle startspaces differently when is_oneChar is set.
          Also add a test for an exclusive charwise selection with
          multibyte chars (zeertzjq)

closes: vim/vim#14825

https://github.com/vim/vim/commit/52a6f348874778cf315b47d9e8b5f818f4b97277

1 files changed, 17 insertions, 3 deletions

diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index 1d01f3ad98..7453bbb601 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -3041,7 +3041,6 @@ static void f_getregionpos(typval_T *argvars, typval_T *rettv, EvalFuncData fptr
   }
 
   for (linenr_T lnum = p1.lnum; lnum <= p2.lnum; lnum++) {
-    struct block_def bd;
     pos_T ret_p1, ret_p2;
 
     if (region_type == kMTLineWise) {
@@ -3050,19 +3049,34 @@ static void f_getregionpos(typval_T *argvars, typval_T *rettv, EvalFuncData fptr
       ret_p2.col = MAXCOL;
       ret_p2.coladd = 0;
     } else {
+      struct block_def bd;
+
       if (region_type == kMTBlockWise) {
         block_prep(&oa, &bd, lnum, false);
       } else {
         charwise_block_prep(p1, p2, &bd, lnum, inclusive);
       }
-      if (bd.startspaces > 0) {
+
+      if (bd.is_oneChar) {  // selection entirely inside one char
+        if (region_type == kMTBlockWise) {
+          ret_p1.col = bd.textcol;
+          ret_p1.coladd = bd.start_char_vcols - (bd.start_vcol - oa.start_vcol);
+        } else {
+          ret_p1.col = p1.col + 1;
+          ret_p1.coladd = p1.coladd;
+        }
+      } else if (bd.startspaces > 0) {
         ret_p1.col = bd.textcol;
         ret_p1.coladd = bd.start_char_vcols - bd.startspaces;
       } else {
         ret_p1.col = bd.textcol + 1;
         ret_p1.coladd = 0;
       }
-      if (bd.endspaces > 0) {
+
+      if (bd.is_oneChar) {  // selection entirely inside one char
+        ret_p2.col = ret_p1.col;
+        ret_p2.coladd = ret_p1.coladd + bd.startspaces;
+      } else if (bd.endspaces > 0) {
         ret_p2.col = bd.textcol + bd.textlen + 1;
         ret_p2.coladd = bd.endspaces;
       } else {