fix(signs): priority of extmark signs (#19718)

src/nvim/api/extmark.c

@@ -441,8 +441,9 @@ Array nvim_buf_get_extmarks(Buffer buffer, Integer ns_id, Object start, Object e
 ///                   the extmark end position (if it exists) will be shifted
 ///                   in when new text is inserted (true for right, false
 ///                   for left). Defaults to false.
-///               - priority: a priority value for the highlight group. For
-///                   example treesitter highlighting uses a value of 100.
+///               - priority: a priority value for the highlight group or sign
+///                   attribute. For example treesitter highlighting uses a
+///                   value of 100.
 ///               - strict: boolean that indicates extmark should not be placed
 ///                   if the line or column value is past the end of the
 ///                   buffer or end of the line respectively. Defaults to true.

src/nvim/decoration.c

@@ -385,7 +385,7 @@ void decor_redraw_signs(buf_T *buf, int row, int *num_signs, sign_attrs_T sattrs
 
     int j;
     for (j = (*num_signs); j > 0; j--) {
-      if (sattrs[j].sat_prio <= decor->priority) {
+      if (sattrs[j - 1].sat_prio >= decor->priority) {
         break;
       }
       sattrs[j] = sattrs[j - 1];