vim-patch:8.2.4707: redrawing could be a bit more efficient (#18022)

Problem:    Redrawing could be a bit more efficient.
Solution:   Optimize redrawing. (closes vim/vim#10105)
https://github.com/vim/vim/commit/8c9796085071950f9a03ca0fe116608e4f86aac2

4 files changed, 54 insertions, 23 deletions

diff --git a/src/nvim/change.c b/src/nvim/change.c
index 0644b1d601..44abd69733 100644
--- a/src/nvim/change.c
+++ b/src/nvim/change.c
@@ -286,9 +286,11 @@ static void changed_common(linenr_T lnum, colnr_T col, linenr_T lnume, long xtra
         set_topline(wp, wp->w_topline);
       }
 
-      // Relative numbering may require updating more.
+      // If lines have been added or removed, relative numbering always
+      // requires a redraw.
       if (wp->w_p_rnu && xtra != 0) {
-        redraw_later(wp, SOME_VALID);
+        wp->w_last_cursor_lnum_rnu = 0;
+        redraw_later(wp, VALID);
       }
 
       // Cursor line highlighting probably need to be updated with
diff --git a/src/nvim/edit.c b/src/nvim/edit.c
index da0b577056..3ab176b2a3 100644
--- a/src/nvim/edit.c
+++ b/src/nvim/edit.c
@@ -390,12 +390,9 @@ static void insert_enter(InsertState *s)
   trigger_modechanged();
   stop_insert_mode = false;
 
-  // Need to recompute the cursor position, it might move when the cursor
-  // is on a TAB or special character.
-  // ptr2cells() treats a TAB character as double-width.
-  if (ptr2cells(get_cursor_pos_ptr()) > 1) {
-    curwin->w_valid &= ~VALID_VIRTCOL;
-    curs_columns(curwin, true);
+  // need to position cursor again when on a TAB
+  if (gchar_cursor() == TAB) {
+    curwin->w_valid &= ~(VALID_WROW|VALID_WCOL|VALID_VIRTCOL);
   }
 
   // Enable langmap or IME, indicated by 'iminsert'.
@@ -7330,21 +7327,21 @@ static void mb_replace_pop_ins(int cc)
       // Not a multi-byte char, put it back.
       replace_push(c);
       break;
+    }
+
+    buf[0] = c;
+    assert(n > 1);
+    for (i = 1; i < n; i++) {
+      buf[i] = replace_pop();
+    }
+    if (utf_iscomposing(utf_ptr2char(buf))) {
+      ins_bytes_len(buf, n);
     } else {
-      buf[0] = c;
-      assert(n > 1);
-      for (i = 1; i < n; i++) {
-        buf[i] = replace_pop();
-      }
-      if (utf_iscomposing(utf_ptr2char(buf))) {
-        ins_bytes_len(buf, n);
-      } else {
-        // Not a composing char, put it back.
-        for (i = n - 1; i >= 0; i--) {
-          replace_push(buf[i]);
-        }
-        break;
+      // Not a composing char, put it back.
+      for (i = n - 1; i >= 0; i--) {
+        replace_push(buf[i]);
       }
+      break;
     }
   }
 }
@@ -8054,8 +8051,10 @@ static bool ins_esc(long *count, int cmdchar, bool nomove)
 
   State = NORMAL;
   trigger_modechanged();
-  // need to position cursor again (e.g. when on a TAB )
-  changed_cline_bef_curs();
+  // need to position cursor again when on a TAB
+  if (gchar_cursor() == TAB) {
+    curwin->w_valid &= ~(VALID_WROW|VALID_WCOL|VALID_VIRTCOL);
+  }
 
   setmouse();
   ui_cursor_shape();            // may show different cursor shape
diff --git a/src/nvim/testdir/test_highlight.vim b/src/nvim/testdir/test_highlight.vim
index 5588e515e1..efdf44a0d6 100644
--- a/src/nvim/testdir/test_highlight.vim
+++ b/src/nvim/testdir/test_highlight.vim
@@ -615,6 +615,14 @@ func Test_cursorcolumn_insert_on_tab()
   call TermWait(buf)
   call VerifyScreenDump(buf, 'Test_cursorcolumn_insert_on_tab_2', {})
 
+  call term_sendkeys(buf, "\<C-O>")
+  call TermWait(buf)
+  call VerifyScreenDump(buf, 'Test_cursorcolumn_insert_on_tab_3', {})
+
+  call term_sendkeys(buf, 'i')
+  call TermWait(buf)
+  call VerifyScreenDump(buf, 'Test_cursorcolumn_insert_on_tab_2', {})
+
   call StopVimInTerminal(buf)
   call delete('Xcuc_insert_on_tab')
 endfunc
diff --git a/test/functional/ui/highlight_spec.lua b/test/functional/ui/highlight_spec.lua
index 4b63b09a5b..8afc69a649 100644
--- a/test/functional/ui/highlight_spec.lua
+++ b/test/functional/ui/highlight_spec.lua
@@ -1345,6 +1345,28 @@ describe('CursorColumn highlight', function()
       {2:~                                                 }|
       {3:-- INSERT --}                                      |
     ]])
+    feed('<C-O>')
+    screen:expect([[
+      1234567{1:8}9                                         |
+      a      ^ b                                         |
+      {2:~                                                 }|
+      {2:~                                                 }|
+      {2:~                                                 }|
+      {2:~                                                 }|
+      {2:~                                                 }|
+      {3:-- (insert) --}                                    |
+    ]])
+    feed('i')
+    screen:expect([[
+      1{1:2}3456789                                         |
+      a^       b                                         |
+      {2:~                                                 }|
+      {2:~                                                 }|
+      {2:~                                                 }|
+      {2:~                                                 }|
+      {2:~                                                 }|
+      {3:-- INSERT --}                                      |
+    ]])
   end)
 
   it('is updated if cursor is moved from timer', function()