fix(ui-ext): "scroll_delta" handle topfill and skipcol (#24249)

5 files changed, 414 insertions, 40 deletions

diff --git a/src/nvim/buffer_defs.h b/src/nvim/buffer_defs.h
index d92d425ed5..5e9652792a 100644
--- a/src/nvim/buffer_defs.h
+++ b/src/nvim/buffer_defs.h
@@ -1226,6 +1226,8 @@ struct window_S {
 
   bool w_viewport_invalid;
   linenr_T w_viewport_last_topline;  // topline when the viewport was last updated
+  linenr_T w_viewport_last_topfill;  // topfill when the viewport was last updated
+  linenr_T w_viewport_last_skipcol;  // skipcol when the viewport was last updated
 
   // w_cline_height is the number of physical lines taken by the buffer line
   // that the cursor is on.  We use this to avoid extra calls to plines_win().
diff --git a/src/nvim/plines.c b/src/nvim/plines.c
index eb1ae540a4..46bbbeeb07 100644
--- a/src/nvim/plines.c
+++ b/src/nvim/plines.c
@@ -595,3 +595,52 @@ static int win_nolbr_chartabsize(chartabsize_T *cts, int *headp)
   }
   return n;
 }
+
+int64_t win_get_text_height(win_T *const wp, const linenr_T first, const linenr_T last,
+                            const int64_t start_vcol, const int64_t end_vcol)
+{
+  int width1 = 0;
+  int width2 = 0;
+  if (start_vcol >= 0 || end_vcol >= 0) {
+    width1 = wp->w_width_inner - win_col_off(wp);
+    width2 = width1 + win_col_off2(wp);
+    width1 = MAX(width1, 0);
+    width2 = MAX(width2, 0);
+  }
+
+  int64_t size = 0;
+  int64_t height_nofill = 0;
+  linenr_T lnum = first;
+
+  if (start_vcol >= 0) {
+    linenr_T lnum_next = lnum;
+    const bool folded = hasFoldingWin(wp, lnum, &lnum, &lnum_next, true, NULL);
+    height_nofill = folded ? 1 : plines_win_nofill(wp, lnum, false);
+    size += height_nofill;
+    const int64_t row_off = (start_vcol < width1 || width2 <= 0)
+                            ? 0
+                            : 1 + (start_vcol - width1) / width2;
+    size -= MIN(row_off, height_nofill);
+    lnum = lnum_next + 1;
+  }
+
+  while (lnum <= last) {
+    linenr_T lnum_next = lnum;
+    const bool folded = hasFoldingWin(wp, lnum, &lnum, &lnum_next, true, NULL);
+    height_nofill = folded ? 1 : plines_win_nofill(wp, lnum, false);
+    size += win_get_fill(wp, lnum) + height_nofill;
+    lnum = lnum_next + 1;
+  }
+
+  if (end_vcol >= 0) {
+    size -= height_nofill;
+    const int64_t row_off = end_vcol == 0
+                            ? 0
+                            : (end_vcol <= width1 || width2 <= 0)
+                              ? 1
+                              : 1 + (end_vcol - width1 + width2 - 1) / width2;
+    size += MIN(row_off, height_nofill);
+  }
+
+  return size;
+}
diff --git a/src/nvim/window.c b/src/nvim/window.c
index 20e9dfec07..f5533db385 100644
--- a/src/nvim/window.c
+++ b/src/nvim/window.c
@@ -1037,22 +1037,31 @@ void ui_ext_win_viewport(win_T *wp)
       // interact with incomplete final line? Diff filler lines?
       botline = wp->w_buffer->b_ml.ml_line_count;
     }
-    int scroll_delta = 0;
-    if (wp->w_viewport_last_topline > line_count) {
-      scroll_delta -= wp->w_viewport_last_topline - line_count;
-      wp->w_viewport_last_topline = line_count;
-    }
-    if (wp->w_topline < wp->w_viewport_last_topline) {
-      scroll_delta -= plines_m_win(wp, wp->w_topline, wp->w_viewport_last_topline - 1);
-    } else if (wp->w_topline > wp->w_viewport_last_topline
-               && wp->w_topline <= line_count) {
-      scroll_delta += plines_m_win(wp, wp->w_viewport_last_topline, wp->w_topline - 1);
-    }
-    ui_call_win_viewport(wp->w_grid_alloc.handle, wp->handle, wp->w_topline - 1,
-                         botline, wp->w_cursor.lnum - 1, wp->w_cursor.col,
-                         line_count, scroll_delta);
+    int64_t delta = 0;
+    linenr_T last_topline = wp->w_viewport_last_topline;
+    int last_topfill = wp->w_viewport_last_topfill;
+    int64_t last_skipcol = wp->w_viewport_last_skipcol;
+    if (last_topline > line_count) {
+      delta -= last_topline - line_count;
+      last_topline = line_count;
+      last_topfill = 0;
+      last_skipcol = MAXCOL;
+    }
+    if (wp->w_topline < last_topline
+        || (wp->w_topline == last_topline && wp->w_skipcol < last_skipcol)) {
+      delta -= win_get_text_height(wp, wp->w_topline, last_topline, wp->w_skipcol, last_skipcol);
+    } else if ((wp->w_topline > last_topline && wp->w_topline <= line_count)
+               || (wp->w_topline == last_topline && wp->w_skipcol > last_skipcol)) {
+      delta += win_get_text_height(wp, last_topline, wp->w_topline, last_skipcol, wp->w_skipcol);
+    }
+    delta += last_topfill;
+    delta -= wp->w_topfill;
+    ui_call_win_viewport(wp->w_grid_alloc.handle, wp->handle, wp->w_topline - 1, botline,
+                         wp->w_cursor.lnum - 1, wp->w_cursor.col, line_count, delta);
     wp->w_viewport_invalid = false;
     wp->w_viewport_last_topline = wp->w_topline;
+    wp->w_viewport_last_topfill = wp->w_topfill;
+    wp->w_viewport_last_skipcol = wp->w_skipcol;
   }
 }
 
diff --git a/test/functional/ui/fold_spec.lua b/test/functional/ui/fold_spec.lua
index 71b9e49d2f..2c8455753e 100644
--- a/test/functional/ui/fold_spec.lua
+++ b/test/functional/ui/fold_spec.lua
@@ -1923,7 +1923,7 @@ describe("folded lines", function()
       meths.buf_set_extmark(0, ns, 2, 0, { virt_lines_above = true, virt_lines = {{{"virt_line above line 3", ""}}} })
       meths.buf_set_extmark(0, ns, 3, 0, { virt_lines = {{{"virt_line below line 4", ""}}} })
       if multigrid then
-        screen:expect([[
+        screen:expect{grid=[[
         ## grid 1
           [2:---------------------------------------------]|
           [2:---------------------------------------------]|
@@ -1943,7 +1943,9 @@ describe("folded lines", function()
           {1:~                                            }|
         ## grid 3
                                                        |
-        ]])
+        ]], win_viewport={
+          [2] = {win = {id = 1000}, topline = 0, botline = 5, curline = 0, curcol = 0, linecount = 4, sum_scroll_delta = 0};
+        }}
       else
         screen:expect([[
           {5:^+--  2 lines: line 1·························}|
@@ -1959,7 +1961,7 @@ describe("folded lines", function()
 
       feed('jzfj')
       if multigrid then
-        screen:expect([[
+        screen:expect{grid=[[
         ## grid 1
           [2:---------------------------------------------]|
           [2:---------------------------------------------]|
@@ -1979,7 +1981,9 @@ describe("folded lines", function()
           {1:~                                            }|
         ## grid 3
                                                        |
-        ]])
+        ]], win_viewport={
+          [2] = {win = {id = 1000}, topline = 0, botline = 5, curline = 2, curcol = 0, linecount = 4, sum_scroll_delta = 0};
+        }}
       else
         screen:expect([[
           {5:+--  2 lines: line 1·························}|
@@ -1996,7 +2000,7 @@ describe("folded lines", function()
       feed('kzo<C-Y>')
       funcs.setline(5, 'line 5')
       if multigrid then
-        screen:expect([[
+        screen:expect{grid=[[
         ## grid 1
           [2:---------------------------------------------]|
           [2:---------------------------------------------]|
@@ -2016,7 +2020,9 @@ describe("folded lines", function()
           {1:~                                            }|
         ## grid 3
                                                        |
-        ]])
+        ]], win_viewport={
+          [2] = {win = {id = 1000}, topline = 0, botline = 6, curline = 0, curcol = 0, linecount = 5, sum_scroll_delta = -1};
+        }}
       else
         screen:expect([[
           virt_line above line 1                       |
@@ -2044,7 +2050,7 @@ describe("folded lines", function()
       meths.buf_set_extmark(0, ns, 1, 0, { virt_lines = {{{"more virt_line below line 2", ""}}} })
       feed('G<C-E>')
       if multigrid then
-        screen:expect([[
+        screen:expect{grid=[[
         ## grid 1
           [2:---------------------------------------------]|
           [2:---------------------------------------------]|
@@ -2064,7 +2070,9 @@ describe("folded lines", function()
           {1:~                                            }|
         ## grid 3
                                                        |
-        ]])
+        ]], win_viewport={
+          [2] = {win = {id = 1000}, topline = 0, botline = 6, curline = 4, curcol = 0, linecount = 5, sum_scroll_delta = 0};
+        }}
       else
         screen:expect([[
           line 1                                       |
@@ -2080,7 +2088,7 @@ describe("folded lines", function()
 
       feed('<C-E>')
       if multigrid then
-        screen:expect([[
+        screen:expect{grid=[[
         ## grid 1
           [2:---------------------------------------------]|
           [2:---------------------------------------------]|
@@ -2100,7 +2108,9 @@ describe("folded lines", function()
           {1:~                                            }|
         ## grid 3
                                                        |
-        ]])
+        ]], win_viewport={
+          [2] = {win = {id = 1000}, topline = 1, botline = 6, curline = 4, curcol = 0, linecount = 5, sum_scroll_delta = 1};
+        }}
       else
         screen:expect([[
           line 2                                       |
@@ -2116,7 +2126,7 @@ describe("folded lines", function()
 
       feed('<C-E>')
       if multigrid then
-        screen:expect([[
+        screen:expect{grid=[[
         ## grid 1
           [2:---------------------------------------------]|
           [2:---------------------------------------------]|
@@ -2136,7 +2146,9 @@ describe("folded lines", function()
           {1:~                                            }|
         ## grid 3
                                                        |
-        ]])
+        ]], win_viewport={
+          [2] = {win = {id = 1000}, topline = 2, botline = 6, curline = 4, curcol = 0, linecount = 5, sum_scroll_delta = 2};
+        }}
       else
         screen:expect([[
           virt_line below line 2                       |
@@ -2152,7 +2164,7 @@ describe("folded lines", function()
 
       feed('<C-E>')
       if multigrid then
-        screen:expect([[
+        screen:expect{grid=[[
         ## grid 1
           [2:---------------------------------------------]|
           [2:---------------------------------------------]|
@@ -2172,7 +2184,9 @@ describe("folded lines", function()
           {1:~                                            }|
         ## grid 3
                                                        |
-        ]])
+        ]], win_viewport={
+          [2] = {win = {id = 1000}, topline = 2, botline = 6, curline = 4, curcol = 0, linecount = 5, sum_scroll_delta = 3};
+        }}
       else
         screen:expect([[
           more virt_line below line 2                  |
@@ -2188,7 +2202,7 @@ describe("folded lines", function()
 
       feed('<C-E>')
       if multigrid then
-        screen:expect([[
+        screen:expect{grid=[[
         ## grid 1
           [2:---------------------------------------------]|
           [2:---------------------------------------------]|
@@ -2208,7 +2222,9 @@ describe("folded lines", function()
           {1:~                                            }|
         ## grid 3
                                                        |
-        ]])
+        ]], win_viewport={
+          [2] = {win = {id = 1000}, topline = 2, botline = 6, curline = 4, curcol = 0, linecount = 5, sum_scroll_delta = 4};
+        }}
       else
         screen:expect([[
           {5:+--  2 lines: line 3·························}|
@@ -2224,7 +2240,7 @@ describe("folded lines", function()
 
       feed('<C-E>')
       if multigrid then
-        screen:expect([[
+        screen:expect{grid=[[
         ## grid 1
           [2:---------------------------------------------]|
           [2:---------------------------------------------]|
@@ -2244,7 +2260,9 @@ describe("folded lines", function()
           {1:~                                            }|
         ## grid 3
                                                        |
-        ]])
+        ]], win_viewport={
+          [2] = {win = {id = 1000}, topline = 4, botline = 6, curline = 4, curcol = 0, linecount = 5, sum_scroll_delta = 5};
+        }}
       else
         screen:expect([[
           ^line 5                                       |
@@ -2260,7 +2278,7 @@ describe("folded lines", function()
 
       feed('3<C-Y>')
       if multigrid then
-        screen:expect([[
+        screen:expect{grid=[[
         ## grid 1
           [2:---------------------------------------------]|
           [2:---------------------------------------------]|
@@ -2280,7 +2298,9 @@ describe("folded lines", function()
           {1:~                                            }|
         ## grid 3
                                                        |
-        ]])
+        ]], win_viewport={
+          [2] = {win = {id = 1000}, topline = 2, botline = 6, curline = 4, curcol = 0, linecount = 5, sum_scroll_delta = 2};
+        }}
       else
         screen:expect([[
           virt_line below line 2                       |
@@ -2296,7 +2316,7 @@ describe("folded lines", function()
 
       meths.input_mouse('left', 'press', '3', multigrid and 2 or 0, 3, 0)
       if multigrid then
-        screen:expect([[
+        screen:expect{grid=[[
         ## grid 1
           [2:---------------------------------------------]|
           [2:---------------------------------------------]|
@@ -2316,7 +2336,9 @@ describe("folded lines", function()
           {1:~                                            }|
         ## grid 3
           {11:-- VISUAL LINE --}                            |
-        ]])
+        ]], win_viewport={
+          [2] = {win = {id = 1000}, topline = 2, botline = 6, curline = 4, curcol = 0, linecount = 5, sum_scroll_delta = 2};
+        }}
       else
         screen:expect([[
           virt_line below line 2                       |
@@ -2332,7 +2354,7 @@ describe("folded lines", function()
 
       meths.input_mouse('left', 'drag', '3', multigrid and 2 or 0, 7, 0)
       if multigrid then
-        screen:expect([[
+        screen:expect{grid=[[
         ## grid 1
           [2:---------------------------------------------]|
           [2:---------------------------------------------]|
@@ -2352,7 +2374,9 @@ describe("folded lines", function()
           {1:~                                            }|
         ## grid 3
           {11:-- VISUAL LINE --}                            |
-        ]])
+        ]], win_viewport={
+          [2] = {win = {id = 1000}, topline = 2, botline = 6, curline = 4, curcol = 0, linecount = 5, sum_scroll_delta = 3};
+        }}
       else
         screen:expect([[
           more virt_line below line 2                  |
@@ -2368,7 +2392,7 @@ describe("folded lines", function()
 
       meths.input_mouse('left', 'drag', '3', multigrid and 2 or 0, 7, 5)
       if multigrid then
-        screen:expect([[
+        screen:expect{grid=[[
         ## grid 1
           [2:---------------------------------------------]|
           [2:---------------------------------------------]|
@@ -2388,7 +2412,9 @@ describe("folded lines", function()
           {1:~                                            }|
         ## grid 3
           {11:-- VISUAL LINE --}                            |
-        ]])
+        ]], win_viewport={
+          [2] = {win = {id = 1000}, topline = 2, botline = 6, curline = 4, curcol = 5, linecount = 5, sum_scroll_delta = 4};
+        }}
       else
         screen:expect([[
           {5:+--  2 lines: line 3·························}|
diff --git a/test/functional/ui/multigrid_spec.lua b/test/functional/ui/multigrid_spec.lua
index 8918c46de6..d643a77be7 100644
--- a/test/functional/ui/multigrid_spec.lua
+++ b/test/functional/ui/multigrid_spec.lua
@@ -3341,6 +3341,294 @@ describe('ext_multigrid', function()
       [2] = {win = {id = 1000}, topline = 0, botline = 3, curline = 0, curcol = 10, linecount = 11, sum_scroll_delta = 0},
       [4] = {win = {id = 1001}, topline = 6, botline = 10, curline = 6, curcol = 0, linecount = 11, sum_scroll_delta = 5},
     }}
+
+    command('close | 21vsplit | setlocal number smoothscroll')
+    screen:expect{grid=[[
+    ## grid 1
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      {11:[No Name] [+]         }{12:[No Name] [+]             }|
+      [3:------------------------------------------------]|
+    ## grid 2
+      Lorem ipsum dolor sit amet|
+      , consectetur             |
+      adipisicing elit, sed do e|
+      iusmod tempor             |
+      incididunt ut labore et do|
+      lore magna aliqua.        |
+    ## grid 3
+                                                      |
+    ## grid 5
+      {19:  1 }Lorem ipsu^m dolor|
+      {19:    } sit amet, consec|
+      {19:    }tetur            |
+      {19:  2 }adipisicing elit,|
+      {19:    } sed do eiusmod t|
+      {19:    }empor            |
+    ]], win_viewport={
+      [2] = {win = {id = 1000}, topline = 0, botline = 4, curline = 0, curcol = 10, linecount = 11, sum_scroll_delta = 0};
+      [5] = {win = {id = 1002}, topline = 0, botline = 3, curline = 0, curcol = 10, linecount = 11, sum_scroll_delta = 0};
+    }}
+
+    feed('5<C-E>')
+    screen:expect{grid=[[
+    ## grid 1
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      {11:[No Name] [+]         }{12:[No Name] [+]             }|
+      [3:------------------------------------------------]|
+    ## grid 2
+      Lorem ipsum dolor sit amet|
+      , consectetur             |
+      adipisicing elit, sed do e|
+      iusmod tempor             |
+      incididunt ut labore et do|
+      lore magna aliqua.        |
+    ## grid 3
+                                                      |
+    ## grid 5
+      {1:<<<}{19: }empo^r            |
+      {19:  3 }incididunt ut lab|
+      {19:    }ore et dolore mag|
+      {19:    }na aliqua.       |
+      {19:  4 }Ut enim ad minim |
+      {19:    }veniam, quis n{1:@@@}|
+    ]], win_viewport={
+      [2] = {win = {id = 1000}, topline = 0, botline = 4, curline = 0, curcol = 10, linecount = 11, sum_scroll_delta = 0};
+      [5] = {win = {id = 1002}, topline = 1, botline = 4, curline = 1, curcol = 38, linecount = 11, sum_scroll_delta = 5};
+    }}
+
+    feed('<C-Y>')
+    screen:expect{grid=[[
+    ## grid 1
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      {11:[No Name] [+]         }{12:[No Name] [+]             }|
+      [3:------------------------------------------------]|
+    ## grid 2
+      Lorem ipsum dolor sit amet|
+      , consectetur             |
+      adipisicing elit, sed do e|
+      iusmod tempor             |
+      incididunt ut labore et do|
+      lore magna aliqua.        |
+    ## grid 3
+                                                      |
+    ## grid 5
+      {1:<<<}{19: } sed do eiusmod t|
+      {19:    }empo^r            |
+      {19:  3 }incididunt ut lab|
+      {19:    }ore et dolore mag|
+      {19:    }na aliqua.       |
+      {19:  4 }Ut enim ad min{1:@@@}|
+    ]], win_viewport={
+      [2] = {win = {id = 1000}, topline = 0, botline = 4, curline = 0, curcol = 10, linecount = 11, sum_scroll_delta = 0};
+      [5] = {win = {id = 1002}, topline = 1, botline = 4, curline = 1, curcol = 38, linecount = 11, sum_scroll_delta = 4};
+    }}
+
+    command('set cpoptions+=n')
+    screen:expect{grid=[[
+    ## grid 1
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      {11:[No Name] [+]         }{12:[No Name] [+]             }|
+      [3:------------------------------------------------]|
+    ## grid 2
+      Lorem ipsum dolor sit amet|
+      , consectetur             |
+      adipisicing elit, sed do e|
+      iusmod tempor             |
+      incididunt ut labore et do|
+      lore magna aliqua.        |
+    ## grid 3
+                                                      |
+    ## grid 5
+      {1:<<<}d do eiusmod tempo|
+      ^r                    |
+      {19:  3 }incididunt ut lab|
+      ore et dolore magna a|
+      liqua.               |
+      {19:  4 }Ut enim ad min{1:@@@}|
+    ]], win_viewport={
+      [2] = {win = {id = 1000}, topline = 0, botline = 4, curline = 0, curcol = 10, linecount = 11, sum_scroll_delta = 0};
+      [5] = {win = {id = 1002}, topline = 1, botline = 4, curline = 1, curcol = 38, linecount = 11, sum_scroll_delta = 4};
+    }}
+
+    feed('4<C-E>')
+    screen:expect{grid=[[
+    ## grid 1
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      {11:[No Name] [+]         }{12:[No Name] [+]             }|
+      [3:------------------------------------------------]|
+    ## grid 2
+      Lorem ipsum dolor sit amet|
+      , consectetur             |
+      adipisicing elit, sed do e|
+      iusmod tempor             |
+      incididunt ut labore et do|
+      lore magna aliqua.        |
+    ## grid 3
+                                                      |
+    ## grid 5
+      {1:<<<}ua^.               |
+      {19:  4 }Ut enim ad minim |
+      veniam, quis nostrud |
+      {19:  5 }exercitation ulla|
+      mco laboris nisi ut a|
+      liquip ex            |
+    ]], win_viewport={
+      [2] = {win = {id = 1000}, topline = 0, botline = 4, curline = 0, curcol = 10, linecount = 11, sum_scroll_delta = 0};
+      [5] = {win = {id = 1002}, topline = 2, botline = 6, curline = 2, curcol = 43, linecount = 11, sum_scroll_delta = 8};
+    }}
+
+    feed('2<C-Y>')
+    screen:expect{grid=[[
+    ## grid 1
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      {11:[No Name] [+]         }{12:[No Name] [+]             }|
+      [3:------------------------------------------------]|
+    ## grid 2
+      Lorem ipsum dolor sit amet|
+      , consectetur             |
+      adipisicing elit, sed do e|
+      iusmod tempor             |
+      incididunt ut labore et do|
+      lore magna aliqua.        |
+    ## grid 3
+                                                      |
+    ## grid 5
+      {19:  3 }incididunt ut lab|
+      ore et dolore magna a|
+      liqua^.               |
+      {19:  4 }Ut enim ad minim |
+      veniam, quis nostrud |
+      {19:  5 }exercitation u{1:@@@}|
+    ]], win_viewport={
+      [2] = {win = {id = 1000}, topline = 0, botline = 4, curline = 0, curcol = 10, linecount = 11, sum_scroll_delta = 0};
+      [5] = {win = {id = 1002}, topline = 2, botline = 5, curline = 2, curcol = 43, linecount = 11, sum_scroll_delta = 6};
+    }}
+
+    command('setlocal numberwidth=12')
+    screen:expect{grid=[[
+    ## grid 1
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      {11:[No Name] [+]         }{12:[No Name] [+]             }|
+      [3:------------------------------------------------]|
+    ## grid 2
+      Lorem ipsum dolor sit amet|
+      , consectetur             |
+      adipisicing elit, sed do e|
+      iusmod tempor             |
+      incididunt ut labore et do|
+      lore magna aliqua.        |
+    ## grid 3
+                                                      |
+    ## grid 5
+      {19:          3 }incididun|
+      t ut labore et dolore|
+       magna aliqua^.       |
+      {19:          4 }Ut enim a|
+      d minim veniam, quis |
+      nostrud              |
+    ]], win_viewport={
+      [2] = {win = {id = 1000}, topline = 0, botline = 4, curline = 0, curcol = 10, linecount = 11, sum_scroll_delta = 0};
+      [5] = {win = {id = 1002}, topline = 2, botline = 5, curline = 2, curcol = 43, linecount = 11, sum_scroll_delta = 6};
+    }}
+
+    feed('2<C-E>')
+    screen:expect{grid=[[
+    ## grid 1
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      {11:[No Name] [+]         }{12:[No Name] [+]             }|
+      [3:------------------------------------------------]|
+    ## grid 2
+      Lorem ipsum dolor sit amet|
+      , consectetur             |
+      adipisicing elit, sed do e|
+      iusmod tempor             |
+      incididunt ut labore et do|
+      lore magna aliqua.        |
+    ## grid 3
+                                                      |
+    ## grid 5
+      {1:<<<}gna aliqua^.       |
+      {19:          4 }Ut enim a|
+      d minim veniam, quis |
+      nostrud              |
+      {19:          5 }exercitat|
+      ion ullamco labori{1:@@@}|
+    ]], win_viewport={
+      [2] = {win = {id = 1000}, topline = 0, botline = 4, curline = 0, curcol = 10, linecount = 11, sum_scroll_delta = 0};
+      [5] = {win = {id = 1002}, topline = 2, botline = 5, curline = 2, curcol = 43, linecount = 11, sum_scroll_delta = 8};
+    }}
+
+    feed('<C-E>')
+    screen:expect{grid=[[
+    ## grid 1
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      [5:---------------------]│[2:--------------------------]|
+      {11:[No Name] [+]         }{12:[No Name] [+]             }|
+      [3:------------------------------------------------]|
+    ## grid 2
+      Lorem ipsum dolor sit amet|
+      , consectetur             |
+      adipisicing elit, sed do e|
+      iusmod tempor             |
+      incididunt ut labore et do|
+      lore magna aliqua.        |
+    ## grid 3
+                                                      |
+    ## grid 5
+      {19:          4 }Ut enim a|
+      d minim veniam, quis |
+      nostru^d              |
+      {19:          5 }exercitat|
+      ion ullamco laboris n|
+      isi ut aliquip ex    |
+    ]], win_viewport={
+      [2] = {win = {id = 1000}, topline = 0, botline = 4, curline = 0, curcol = 10, linecount = 11, sum_scroll_delta = 0};
+      [5] = {win = {id = 1002}, topline = 3, botline = 6, curline = 3, curcol = 36, linecount = 11, sum_scroll_delta = 9};
+    }}
   end)
 
   it('does not crash when dragging mouse across grid boundary', function()