vim-patch:9.0.0646: with 'smoothscroll' CTRL-E is wrong when 'foldmethod' set

Problem:    with 'smoothscroll' set CTRL-E does not work properly when
            'foldmethod' is set to "indent". (Yee Cheng Chin)
Solution:   Merge the code for scroling with folds and 'smoothscroll'.
            (closes vim/vim#11262)

6b2d4ff714

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

src/nvim/move.c

@@ -707,8 +707,8 @@ int curwin_col_off(void)
 }
 
 // Return the difference in column offset for the second screen line of a
-// wrapped line.  It's 8 if 'number' or 'relativenumber' is on and 'n' is in
+// wrapped line.  It's positive if 'number' or 'relativenumber' is on and 'n'
-// 'cpoptions'.
+// is in 'cpoptions'.
 int win_col_off2(win_T *wp)
 {
   if ((wp->w_p_nu || wp->w_p_rnu) && vim_strchr(p_cpo, CPO_NUMCOL) != NULL) {
@@ -1097,7 +1097,7 @@ bool scrolldown(long line_count, int byfold)
 
   if (curwin->w_p_wrap && curwin->w_p_sms) {
     width1 = curwin->w_width - curwin_col_off();
-    width2 = width1 - curwin_col_off2();
+    width2 = width1 + curwin_col_off2();
   }
 
   // Make sure w_topline is at the first of a sequence of folded lines.
@@ -1209,55 +1209,66 @@ bool scrollup(long line_count, int byfold)
 {
   linenr_T topline = curwin->w_topline;
   linenr_T botline = curwin->w_botline;
+  int do_smoothscroll = curwin->w_p_wrap && curwin->w_p_sms;
 
-  if ((byfold && hasAnyFolding(curwin))
+  if (do_smoothscroll || (byfold && hasAnyFolding(curwin)) || win_may_fill(curwin)) {
-      || win_may_fill(curwin)) {
+    int width1 = curwin->w_width - curwin_col_off();
-    // count each sequence of folded lines as one logical line
+    int width2 = width1 + curwin_col_off2();
-    linenr_T lnum = curwin->w_topline;
+    int size = 0;
-    while (line_count--) {
+    linenr_T prev_topline = curwin->w_topline;
+
+    if (do_smoothscroll) {
+      size = (int)win_linetabsize(curwin, curwin->w_topline,
+                                  ml_get(curwin->w_topline), (colnr_T)MAXCOL);
+    }
+
+    // diff mode: first consume "topfill"
+    // 'smoothscroll': increase "w_skipcol" until it goes over the end of
+    // the line, then advance to the next line.
+    // folding: count each sequence of folded lines as one logical line.
+    for (long todo = line_count; todo > 0; todo--) {
       if (curwin->w_topfill > 0) {
         curwin->w_topfill--;
       } else {
+        linenr_T lnum = curwin->w_topline;
         if (byfold) {
+          // for a closed fold: go to the last line in the fold
           (void)hasFolding(lnum, NULL, &lnum);
         }
+        if (lnum == curwin->w_topline && curwin->w_p_wrap && curwin->w_p_sms) {
+          // 'smoothscroll': increase "w_skipcol" until it goes over
+          // 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 (lnum == curbuf->b_ml.ml_line_count) {
+              // at the last screen line, can't scroll further
+              curwin->w_skipcol -= add;
+              break;
+            }
+            lnum++;
+          }
+        } else {
           if (lnum >= curbuf->b_ml.ml_line_count) {
             break;
           }
           lnum++;
-        curwin->w_topfill = win_get_fill(curwin, lnum);
-      }
         }
+
+        if (lnum > curwin->w_topline) {
           // approximate w_botline
           curwin->w_botline += lnum - curwin->w_topline;
           curwin->w_topline = lnum;
-  } else if (curwin->w_p_wrap && curwin->w_p_sms) {
+          curwin->w_topfill = win_get_fill(curwin, lnum);
-    int off1 = curwin_col_off();
-    int off2 = off1 + curwin_col_off2();
-    int add;
-    int size = (int)win_linetabsize(curwin, curwin->w_topline,
-                                    ml_get(curwin->w_topline), (colnr_T)MAXCOL);
-    linenr_T prev_topline = curwin->w_topline;
-
-    // 'smoothscroll': increase "w_skipcol" until it goes over the end of
-    // the line, then advance to the next line.
-    for (long todo = line_count; todo > 0; todo--) {
-      add = curwin->w_width - (curwin->w_skipcol > 0 ? off2 : off1);
-      curwin->w_skipcol += add;
-      if (curwin->w_skipcol >= size) {
-        if (curwin->w_topline == curbuf->b_ml.ml_line_count) {
-          curwin->w_skipcol -= add;
-          break;
-        }
-        curwin->w_topline++;
-        curwin->w_botline++;    // approximate w_botline
           curwin->w_skipcol = 0;
-        if (todo > 1) {
+          if (todo > 1 && do_smoothscroll) {
             size = (int)win_linetabsize(curwin, curwin->w_topline,
                                         ml_get(curwin->w_topline), (colnr_T)MAXCOL);
           }
         }
       }
+    }
+
     if (curwin->w_topline == prev_topline) {
       // need to redraw even though w_topline didn't change
       redraw_later(curwin, UPD_NOT_VALID);

test/functional/legacy/scroll_opt_spec.lua

@@ -31,23 +31,9 @@ describe('smoothscroll', function()
   it('works with <C-E> and <C-E>', function()
     exec([[
       call setline(1, [ 'line one', 'word '->repeat(20), 'line three', 'long word '->repeat(7), 'line', 'line', 'line', ])
-      set smoothscroll
+      set smoothscroll scrolloff=5
       :5
     ]])
-    local s0 = [[
-      line one                                |
-      word word word word word word word word |
-      word word word word word word word word |
-      word word word word                     |
-      line three                              |
-      long word long word long word long word |
-      long word long word long word           |
-      ^line                                    |
-      line                                    |
-      line                                    |
-      ~                                       |
-                                              |
-    ]]
     local s1 = [[
       word word word word word word word word |
       word word word word word word word word |
@@ -94,13 +80,69 @@ describe('smoothscroll', function()
       line three                              |
       long word long word long word long word |
       long word long word long word           |
+      line                                    |
+      line                                    |
       ^line                                    |
+      ~                                       |
+      ~                                       |
+      ~                                       |
+      ~                                       |
+      ~                                       |
+                                              |
+    ]]
+    local s5 = [[
+      word word word word                     |
+      line three                              |
+      long word long word long word long word |
+      long word long word long word           |
       line                                    |
       line                                    |
+      ^line                                    |
       ~                                       |
       ~                                       |
       ~                                       |
       ~                                       |
+                                              |
+    ]]
+    local s6 = [[
+      word word word word word word word word |
+      word word word word                     |
+      line three                              |
+      long word long word long word long word |
+      long word long word long word           |
+      line                                    |
+      line                                    |
+      ^line                                    |
+      ~                                       |
+      ~                                       |
+      ~                                       |
+                                              |
+    ]]
+    local s7 = [[
+      word word word word word word word word |
+      word word word word word word word word |
+      word word word word                     |
+      line three                              |
+      long word long word long word long word |
+      long word long word long word           |
+      line                                    |
+      line                                    |
+      ^line                                    |
+      ~                                       |
+      ~                                       |
+                                              |
+    ]]
+    local s8 = [[
+      line one                                |
+      word word word word word word word word |
+      word word word word word word word word |
+      word word word word                     |
+      line three                              |
+      long word long word long word long word |
+      long word long word long word           |
+      line                                    |
+      line                                    |
+      ^line                                    |
       ~                                       |
                                               |
     ]]
@@ -113,12 +155,22 @@ describe('smoothscroll', function()
     feed('<C-E>')
     screen:expect(s4)
     feed('<C-Y>')
-    screen:expect(s3)
+    screen:expect(s5)
     feed('<C-Y>')
-    screen:expect(s2)
+    screen:expect(s6)
     feed('<C-Y>')
+    screen:expect(s7)
+    feed('<C-Y>')
+    screen:expect(s8)
+    exec('set foldmethod=indent')
+    -- move the cursor so we can reuse the same dumps
+    feed('5G<C-E>')
     screen:expect(s1)
+    feed('<C-E>')
+    screen:expect(s2)
+    feed('7G<C-Y>')
+    screen:expect(s7)
     feed('<C-Y>')
-    screen:expect(s0)
+    screen:expect(s8)
   end)
 end)

test/old/testdir/test_scroll_opt.vim

@@ -105,6 +105,21 @@ func Test_smoothscroll_CtrlE_CtrlY()
   call term_sendkeys(buf, "\<C-Y>")
   call VerifyScreenDump(buf, 'Test_smoothscroll_8', {})
 
+  if has('folding')
+    call term_sendkeys(buf, ":set foldmethod=indent\<CR>")
+    " move the cursor so we can reuse the same dumps
+    call term_sendkeys(buf, "5G")
+    call term_sendkeys(buf, "\<C-E>")
+    call VerifyScreenDump(buf, 'Test_smoothscroll_1', {})
+    call term_sendkeys(buf, "\<C-E>")
+    call VerifyScreenDump(buf, 'Test_smoothscroll_2', {})
+    call term_sendkeys(buf, "7G")
+    call term_sendkeys(buf, "\<C-Y>")
+    call VerifyScreenDump(buf, 'Test_smoothscroll_7', {})
+    call term_sendkeys(buf, "\<C-Y>")
+    call VerifyScreenDump(buf, 'Test_smoothscroll_8', {})
+  endif
+
   call StopVimInTerminal(buf)
 endfunc