vim-patch:9.0.0751: 'scrolloff' does not work well with 'smoothscroll'

Problem:    'scrolloff' does not work well with 'smoothscroll'.
Solution:   Make positioning the cursor a bit better.  Rename functions.

c9121f798f

Co-authored-by: Bram Moolenaar <Bram@vim.org>

src/nvim/cursor.c

@@ -115,7 +115,7 @@ static int coladvance2(pos_T *pos, bool addspaces, bool finetune, colnr_T wcol_a
     col = wcol;
 
     if ((addspaces || finetune) && !VIsual_active) {
-      curwin->w_curswant = linetabsize(line) + one_more;
+      curwin->w_curswant = linetabsize_str(line) + one_more;
       if (curwin->w_curswant > 0) {
         curwin->w_curswant--;
       }
@@ -129,7 +129,7 @@ static int coladvance2(pos_T *pos, bool addspaces, bool finetune, colnr_T wcol_a
         && curwin->w_width_inner != 0
         && wcol >= (colnr_T)width
         && width > 0) {
-      csize = linetabsize(line);
+      csize = linetabsize_str(line);
       if (csize > 0) {
         csize--;
       }

src/nvim/edit.c

@@ -193,7 +193,7 @@ static void insert_enter(InsertState *s)
     }
   }
 
-  Insstart_textlen = (colnr_T)linetabsize(get_cursor_line_ptr());
+  Insstart_textlen = linetabsize_str(get_cursor_line_ptr());
   Insstart_blank_vcol = MAXCOL;
 
   if (!did_ai) {
@@ -2251,7 +2251,7 @@ int stop_arrow(void)
       // right, except when nothing was inserted yet.
       update_Insstart_orig = false;
     }
-    Insstart_textlen = (colnr_T)linetabsize(get_cursor_line_ptr());
+    Insstart_textlen = linetabsize_str(get_cursor_line_ptr());
 
     if (u_save_cursor() == OK) {
       arrow_used = false;

src/nvim/ex_cmds.c

@@ -346,10 +346,8 @@ static int linelen(int *has_tab)
        last > first && ascii_iswhite(last[-1]); last--) {}
   char save = *last;
   *last = NUL;
-  // Get line length.
-  len = linetabsize(line);
-  // Check for embedded TAB.
-  if (has_tab != NULL) {
+  len = linetabsize_str(line);  // Get line length.
+  if (has_tab != NULL) {        // Check for embedded TAB.
     *has_tab = vim_strchr(first, TAB) != NULL;
   }
   *last = save;

src/nvim/move.c

@@ -1238,7 +1238,7 @@ bool scrolldown(long line_count, int byfold)
   }
 
   if (curwin->w_cursor.lnum == curwin->w_topline && do_sms) {
-    long so = curwin->w_p_so >= 0 ? curwin->w_p_so : p_so;
+    long so = get_scrolloff_value(curwin);
     long scrolloff_cols = so == 0 ? 0 : width1 + (so - 1) * width2;
 
     // make sure the cursor is in the visible text
@@ -1274,12 +1274,11 @@ bool scrollup(long line_count, int byfold)
   if (do_sms || (byfold && hasAnyFolding(curwin)) || win_may_fill(curwin)) {
     int width1 = curwin->w_width - curwin_col_off();
     int width2 = width1 + curwin_col_off2();
-    int size = 0;
+    unsigned size = 0;
     linenr_T prev_topline = curwin->w_topline;
 
     if (do_sms) {
-      size = (int)win_linetabsize(curwin, curwin->w_topline,
-                                  ml_get(curwin->w_topline), (colnr_T)MAXCOL);
+      size = linetabsize(curwin, curwin->w_topline);
     }
 
     // diff mode: first consume "topfill"
@@ -1300,7 +1299,7 @@ bool scrollup(long line_count, int byfold)
           // the end of the line, then advance to the next line.
           int add = curwin->w_skipcol > 0 ? width2 : width1;
           curwin->w_skipcol += add;
-          if (curwin->w_skipcol >= size) {
+          if ((unsigned)curwin->w_skipcol >= size) {
             if (lnum == curbuf->b_ml.ml_line_count) {
               // at the last screen line, can't scroll further
               curwin->w_skipcol -= add;
@@ -1322,8 +1321,7 @@ bool scrollup(long line_count, int byfold)
           curwin->w_topfill = win_get_fill(curwin, lnum);
           curwin->w_skipcol = 0;
           if (todo > 1 && do_sms) {
-            size = (int)win_linetabsize(curwin, curwin->w_topline,
-                                        ml_get(curwin->w_topline), (colnr_T)MAXCOL);
+            size = linetabsize(curwin, curwin->w_topline);
           }
         }
       }
@@ -1363,11 +1361,16 @@ bool scrollup(long line_count, int byfold)
   if (curwin->w_cursor.lnum == curwin->w_topline && do_sms && curwin->w_skipcol > 0) {
     int width1 = curwin->w_width - curwin_col_off();
     int width2 = width1 + curwin_col_off2();
-    long so = curwin->w_p_so >= 0 ? curwin->w_p_so : p_so;
+    long so = get_scrolloff_value(curwin);
     long scrolloff_cols = so == 0 ? 0 : width1 + (so - 1) * width2;
+    int space_cols = (curwin->w_height - 1) * width2;
 
     // Make sure the cursor is in a visible part of the line, taking
     // 'scrolloff' into account, but using screen lines.
+    // If there are not enough screen lines put the cursor in the middle.
+    if (scrolloff_cols > space_cols / 2) {
+      scrolloff_cols = space_cols / 2;
+    }
     validate_virtcol();
     if (curwin->w_virtcol < curwin->w_skipcol + 3 + scrolloff_cols) {
       colnr_T col = curwin->w_virtcol;
@@ -1402,11 +1405,20 @@ void adjust_skipcol(void)
 
   int width1 = curwin->w_width - curwin_col_off();
   int width2 = width1 + curwin_col_off2();
-  long so = curwin->w_p_so >= 0 ? curwin->w_p_so : p_so;
+  long so = get_scrolloff_value(curwin);
   long scrolloff_cols = so == 0 ? 0 : width1 + (so - 1) * width2;
   bool scrolled = false;
 
   validate_virtcol();
+  if (curwin->w_cline_height == curwin->w_height) {
+    // the line just fits in the window, don't scroll
+    if (curwin->w_skipcol != 0) {
+      curwin->w_skipcol = 0;
+      redraw_later(curwin, UPD_NOT_VALID);
+    }
+    return;
+  }
+
   while (curwin->w_skipcol > 0
          && curwin->w_virtcol < curwin->w_skipcol + 3 + scrolloff_cols) {
     // scroll a screen line down
@@ -2071,6 +2083,16 @@ void cursor_correct(void)
     return;
   }
 
+  if (curwin->w_p_sms && !curwin->w_p_wrap) {
+    // 'smoothscroll is active
+    if (curwin->w_cline_height == curwin->w_height) {
+      // The cursor line just fits in the window, don't scroll.
+      curwin->w_skipcol = 0;
+      return;
+    }
+    // TODO(vim): If the cursor line doesn't fit in the window then only adjust w_skipcol.
+  }
+
   // Narrow down the area where the cursor can be put by taking lines from
   // the top and the bottom until:
   // - the desired context lines are found

src/nvim/normal.c

@@ -2432,7 +2432,7 @@ bool find_decl(char *ptr, size_t len, bool locally, bool thisblock, int flags_ar
 /// @return  true if able to move cursor, false otherwise.
 static bool nv_screengo(oparg_T *oap, int dir, long dist)
 {
-  int linelen = linetabsize(get_cursor_line_ptr());
+  int linelen = linetabsize_str(get_cursor_line_ptr());
   bool retval = true;
   bool atend = false;
   int col_off1;                 // margin offset for first screen line
@@ -2494,7 +2494,7 @@ static bool nv_screengo(oparg_T *oap, int dir, long dist)
             retval = false;
             break;
           }
-          linelen = linetabsize(get_cursor_line_ptr());
+          linelen = linetabsize_str(get_cursor_line_ptr());
           if (linelen > width1) {
             int w = (((linelen - width1 - 1) / width2) + 1) * width2;
             assert(curwin->w_curswant <= INT_MAX - w);
@@ -2525,7 +2525,7 @@ static bool nv_screengo(oparg_T *oap, int dir, long dist)
           if (curwin->w_curswant >= width1) {
             curwin->w_curswant -= width2;
           }
-          linelen = linetabsize(get_cursor_line_ptr());
+          linelen = linetabsize_str(get_cursor_line_ptr());
         }
       }
     }
@@ -5497,7 +5497,7 @@ static void nv_g_cmd(cmdarg_T *cap)
   case 'M':
     oap->motion_type = kMTCharWise;
     oap->inclusive = false;
-    i = linetabsize(get_cursor_line_ptr());
+    i = linetabsize_str(get_cursor_line_ptr());
     if (cap->count0 > 0 && cap->count0 <= 100) {
       coladvance((colnr_T)(i * cap->count0 / 100));
     } else {

src/nvim/ops.c

@@ -5503,7 +5503,7 @@ void cursor_pos_info(dict_T *dict)
         validate_virtcol();
         col_print(buf1, sizeof(buf1), (int)curwin->w_cursor.col + 1,
                   (int)curwin->w_virtcol + 1);
-        col_print(buf2, sizeof(buf2), (int)strlen(p), linetabsize(p));
+        col_print(buf2, sizeof(buf2), (int)strlen(p), linetabsize_str(p));
 
         if (char_count_cursor == byte_count_cursor
             && char_count == byte_count) {

src/nvim/plines.c

@@ -243,12 +243,12 @@ int win_chartabsize(win_T *wp, char *p, colnr_T col)
 /// @param s
 ///
 /// @return Number of characters the string will take on the screen.
-int linetabsize(char *s)
+int linetabsize_str(char *s)
 {
   return linetabsize_col(0, s);
 }
 
-/// Like linetabsize(), but "s" starts at column "startcol".
+/// Like linetabsize_str(), but "s" starts at column "startcol".
 ///
 /// @param startcol
 /// @param s
@@ -265,7 +265,7 @@ int linetabsize_col(int startcol, char *s)
   return cts.cts_vcol;
 }
 
-/// Like linetabsize(), but for a given window instead of the current one.
+/// Like linetabsize_str(), but for a given window instead of the current one.
 ///
 /// @param wp
 /// @param line
@@ -284,6 +284,13 @@ unsigned win_linetabsize(win_T *wp, linenr_T lnum, char *line, colnr_T len)
   return (unsigned)cts.cts_vcol;
 }
 
+/// Return the number of cells line "lnum" of window "wp" will take on the
+/// screen, taking into account the size of a tab and text properties.
+unsigned     linetabsize(win_T *wp, linenr_T lnum)
+{
+  return win_linetabsize(wp, lnum, ml_get_buf(wp->w_buffer, lnum, false), (colnr_T)MAXCOL);
+}
+
 /// Prepare the structure passed to chartabsize functions.
 ///
 /// "line" is the start of the line, "ptr" is the first relevant character.