fix(ui-ext): backport win_viewport fixes to release-0.9

runtime/doc/ui.txt

@@ -199,7 +199,7 @@ the editor.
 	The following keys are deprecated:
 
 	`hl_id`:	Use `attr_id` instead.
-	`hl_lm`:	Use `attr_id_lm` instead.
+	`id_lm`:	Use `attr_id_lm` instead.
 
 ["option_set", name, value] ~
 	UI-related option changed, where `name` is one of:
@@ -336,7 +336,7 @@ numerical highlight ids to the actual attributes.
 
 	Highlights are always transmitted both for both the RGB format and as
 	terminal 256-color codes, as the `rgb_attr` and `cterm_attr` parameters
-	respectively. The |ui-rgb| option has no effect effect anymore.
+	respectively. The |ui-rgb| option has no effect anymore.
 	Most external UIs will only need to store and use the `rgb_attr`
 	attributes.
 
@@ -352,7 +352,7 @@ numerical highlight ids to the actual attributes.
 	|ui-hlstate| extension explained below.
 
 ["hl_group_set", name, hl_id] ~
-	The bulitin highlight group `name` was set to use the attributes `hl_id`
+	The built-in highlight group `name` was set to use the attributes `hl_id`
 	defined by a previous `hl_attr_define` call. This event is not needed
 	to render the grids which use attribute ids directly, but is useful
 	for a UI who want to render its own elements with consistent
@@ -640,7 +640,8 @@ tabs.
 	the top line of a window moved since `win_viewport` was last emitted.
 	It is intended to be used to implement smooth scrolling. For this
 	purpose it only counts "virtual" or "displayed" lines, so folds
-	only count as one line.
+	only count as one line. When scrolling more than a full screen it is
+	an approximate value.
 
 	All updates, such as `grid_line`, in a batch affects the new viewport,
 	despite the fact that `win_viewport` is received after the updates.
@@ -723,7 +724,7 @@ For command-line 'wildmenu' UI events, activate |ui-popupmenu|.
 	to distinguish different command lines active at the same time. The
 	first invoked command line has level 1, the next recursively-invoked
 	prompt has level 2. A command line invoked from the |cmdline-window|
-	has a higher level than than the edited command line.
+	has a higher level than the edited command line.
 
 ["cmdline_pos", pos, level] ~
 	Change the cursor position in the cmdline.

src/nvim/buffer_defs.h

@@ -1223,6 +1223,9 @@ 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_botline;  // botline 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().

src/nvim/plines.c

@@ -530,3 +530,68 @@ static int win_nolbr_chartabsize(chartabsize_T *cts, int *headp)
   }
   return n;
 }
+
+/// Get the number of screen lines a range of text will take in window "wp".
+///
+/// @param[in] start_lnum  Starting line number, 1-based inclusive.
+/// @param[in] start_vcol  >= 0: Starting virtual column index on "start_lnum",
+///                              0-based inclusive, rounded down to full screen lines.
+///                        < 0:  Count a full "start_lnum", including filler lines above.
+/// @param[in] end_lnum    Ending line number, 1-based inclusive.
+/// @param[in] end_vcol    >= 0: Ending virtual column index on "end_lnum",
+///                              0-based exclusive, rounded up to full screen lines.
+///                        < 0:  Count a full "end_lnum", not including filler lines below.
+/// @param[out] fill       If not NULL, set to the number of filler lines in the range.
+int64_t win_text_height(win_T *const wp, const linenr_T start_lnum, const int64_t start_vcol,
+                        const linenr_T end_lnum, const int64_t end_vcol, int64_t *const fill)
+{
+  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 height_sum_fill = 0;
+  int64_t height_cur_nofill = 0;
+  int64_t height_sum_nofill = 0;
+  linenr_T lnum = start_lnum;
+
+  if (start_vcol >= 0) {
+    linenr_T lnum_next = lnum;
+    const bool folded = hasFoldingWin(wp, lnum, &lnum, &lnum_next, true, NULL);
+    height_cur_nofill = folded ? 1 : plines_win_nofill(wp, lnum, false);
+    height_sum_nofill += height_cur_nofill;
+    const int64_t row_off = (start_vcol < width1 || width2 <= 0)
+                            ? 0
+                            : 1 + (start_vcol - width1) / width2;
+    height_sum_nofill -= MIN(row_off, height_cur_nofill);
+    lnum = lnum_next + 1;
+  }
+
+  while (lnum <= end_lnum) {
+    linenr_T lnum_next = lnum;
+    const bool folded = hasFoldingWin(wp, lnum, &lnum, &lnum_next, true, NULL);
+    height_sum_fill += win_get_fill(wp, lnum);
+    height_cur_nofill = folded ? 1 : plines_win_nofill(wp, lnum, false);
+    height_sum_nofill += height_cur_nofill;
+    lnum = lnum_next + 1;
+  }
+
+  if (end_vcol >= 0) {
+    height_sum_nofill -= height_cur_nofill;
+    const int64_t row_off = end_vcol == 0
+                            ? 0
+                            : (end_vcol <= width1 || width2 <= 0)
+                              ? 1
+                              : 1 + (end_vcol - width1 + width2 - 1) / width2;
+    height_sum_nofill += MIN(row_off, height_cur_nofill);
+  }
+
+  if (fill != NULL) {
+    *fill = height_sum_fill;
+  }
+  return height_sum_fill + height_sum_nofill;
+}

src/nvim/window.c

@@ -990,29 +990,56 @@ void ui_ext_win_viewport(win_T *wp)
   // NOTE: The win_viewport command is delayed until the next flush when there are pending updates.
   // This ensures that the updates and the viewport are sent together.
   if ((wp == curwin || ui_has(kUIMultigrid)) && wp->w_viewport_invalid && wp->w_redr_type == 0) {
-    int botline = wp->w_botline;
+    const linenr_T line_count = wp->w_buffer->b_ml.ml_line_count;
-    int line_count = wp->w_buffer->b_ml.ml_line_count;
+    // Avoid ml_get errors when producing "scroll_delta".
-    if (botline == line_count + 1 && wp->w_empty_rows == 0) {
+    const linenr_T cur_topline = MIN(wp->w_topline, line_count);
+    const linenr_T cur_botline = MIN(wp->w_botline, line_count);
+    int64_t delta = 0;
+    linenr_T last_topline = wp->w_viewport_last_topline;
+    linenr_T last_botline = wp->w_viewport_last_botline;
+    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;
+    }
+    last_botline = MIN(last_botline, line_count);
+    if (cur_topline < last_topline
+        || (cur_topline == last_topline && wp->w_skipcol < last_skipcol)) {
+      if (last_topline > 0 && cur_botline < last_topline) {
+        // Scrolling too many lines: only give an approximate "scroll_delta".
+        delta -= win_text_height(wp, cur_topline, wp->w_skipcol, cur_botline, 0, NULL);
+        delta -= last_topline - cur_botline;
+      } else {
+        delta -= win_text_height(wp, cur_topline, wp->w_skipcol, last_topline, last_skipcol, NULL);
+      }
+    } else if (cur_topline > last_topline
+               || (cur_topline == last_topline && wp->w_skipcol > last_skipcol)) {
+      if (last_botline > 0 && cur_topline > last_botline) {
+        // Scrolling too many lines: only give an approximate "scroll_delta".
+        delta += win_text_height(wp, last_topline, last_skipcol, last_botline, 0, NULL);
+        delta += cur_topline - last_botline;
+      } else {
+        delta += win_text_height(wp, last_topline, last_skipcol, cur_topline, wp->w_skipcol, NULL);
+      }
+    }
+    delta += last_topfill;
+    delta -= wp->w_topfill;
+    linenr_T ev_botline = wp->w_botline;
+    if (ev_botline == line_count + 1 && wp->w_empty_rows == 0) {
       // TODO(bfredl): The might be more cases to consider, like how does this
       // interact with incomplete final line? Diff filler lines?
-      botline = wp->w_buffer->b_ml.ml_line_count;
+      ev_botline = line_count;
     }
-    int scroll_delta = 0;
+    ui_call_win_viewport(wp->w_grid_alloc.handle, wp->handle, wp->w_topline - 1, ev_botline,
-    if (wp->w_viewport_last_topline > line_count) {
+                         wp->w_cursor.lnum - 1, wp->w_cursor.col, line_count, delta);
-      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);
     wp->w_viewport_invalid = false;
     wp->w_viewport_last_topline = wp->w_topline;
+    wp->w_viewport_last_botline = wp->w_botline;
+    wp->w_viewport_last_topfill = wp->w_topfill;
+    wp->w_viewport_last_skipcol = wp->w_skipcol;
   }
 }
 

test/functional/ui/fold_spec.lua

@@ -1904,7 +1904,7 @@ 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:---------------------------------------------]|
@@ -1924,7 +1924,9 @@ 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·························}|
@@ -1940,7 +1942,7 @@ describe("folded lines", function()
 
       feed('jzfj')
       if multigrid then
-        screen:expect([[
+        screen:expect{grid=[[
         ## grid 1
           [2:---------------------------------------------]|
           [2:---------------------------------------------]|
@@ -1960,7 +1962,9 @@ 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·························}|
@@ -1977,7 +1981,7 @@ 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:---------------------------------------------]|
@@ -1997,7 +2001,9 @@ 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                       |
@@ -2025,7 +2031,7 @@ 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:---------------------------------------------]|
@@ -2045,7 +2051,9 @@ 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                                       |
@@ -2061,7 +2069,7 @@ describe("folded lines", function()
 
       feed('<C-E>')
       if multigrid then
-        screen:expect([[
+        screen:expect{grid=[[
         ## grid 1
           [2:---------------------------------------------]|
           [2:---------------------------------------------]|
@@ -2081,7 +2089,9 @@ 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                                       |
@@ -2097,7 +2107,7 @@ describe("folded lines", function()
 
       feed('<C-E>')
       if multigrid then
-        screen:expect([[
+        screen:expect{grid=[[
         ## grid 1
           [2:---------------------------------------------]|
           [2:---------------------------------------------]|
@@ -2117,7 +2127,9 @@ 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                       |
@@ -2133,7 +2145,7 @@ describe("folded lines", function()
 
       feed('<C-E>')
       if multigrid then
-        screen:expect([[
+        screen:expect{grid=[[
         ## grid 1
           [2:---------------------------------------------]|
           [2:---------------------------------------------]|
@@ -2153,7 +2165,9 @@ 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                  |
@@ -2169,7 +2183,7 @@ describe("folded lines", function()
 
       feed('<C-E>')
       if multigrid then
-        screen:expect([[
+        screen:expect{grid=[[
         ## grid 1
           [2:---------------------------------------------]|
           [2:---------------------------------------------]|
@@ -2189,7 +2203,9 @@ 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·························}|
@@ -2205,7 +2221,7 @@ describe("folded lines", function()
 
       feed('<C-E>')
       if multigrid then
-        screen:expect([[
+        screen:expect{grid=[[
         ## grid 1
           [2:---------------------------------------------]|
           [2:---------------------------------------------]|
@@ -2225,7 +2241,9 @@ 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                                       |
@@ -2241,7 +2259,7 @@ describe("folded lines", function()
 
       feed('3<C-Y>')
       if multigrid then
-        screen:expect([[
+        screen:expect{grid=[[
         ## grid 1
           [2:---------------------------------------------]|
           [2:---------------------------------------------]|
@@ -2261,7 +2279,9 @@ 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                       |
@@ -2277,7 +2297,7 @@ 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:---------------------------------------------]|
@@ -2297,7 +2317,9 @@ 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                       |
@@ -2313,7 +2335,7 @@ 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:---------------------------------------------]|
@@ -2333,7 +2355,9 @@ 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                  |
@@ -2349,7 +2373,7 @@ 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:---------------------------------------------]|
@@ -2369,7 +2393,9 @@ 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·························}|

test/functional/ui/multigrid_spec.lua

@@ -3343,6 +3343,220 @@ describe('ext_multigrid', function()
     }}
   end)
 
+  it('scroll_delta is approximated reasonably when scrolling many lines #24234', function()
+    command('setlocal number nowrap')
+    command('edit test/functional/fixtures/bigfile.txt')
+    screen:expect{grid=[[
+    ## grid 1
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      {11:test/functional/fixtures/bigfile.txt                 }|
+      [3:-----------------------------------------------------]|
+    ## grid 2
+      {19:    1 }^0000;<control>;Cc;0;BN;;;;;N;NULL;;;;          |
+      {19:    2 }0001;<control>;Cc;0;BN;;;;;N;START OF HEADING;;|
+      {19:    3 }0002;<control>;Cc;0;BN;;;;;N;START OF TEXT;;;; |
+      {19:    4 }0003;<control>;Cc;0;BN;;;;;N;END OF TEXT;;;;   |
+      {19:    5 }0004;<control>;Cc;0;BN;;;;;N;END OF TRANSMISSIO|
+      {19:    6 }0005;<control>;Cc;0;BN;;;;;N;ENQUIRY;;;;       |
+      {19:    7 }0006;<control>;Cc;0;BN;;;;;N;ACKNOWLEDGE;;;;   |
+      {19:    8 }0007;<control>;Cc;0;BN;;;;;N;BELL;;;;          |
+      {19:    9 }0008;<control>;Cc;0;BN;;;;;N;BACKSPACE;;;;     |
+      {19:   10 }0009;<control>;Cc;0;S;;;;;N;CHARACTER TABULATIO|
+      {19:   11 }000A;<control>;Cc;0;B;;;;;N;LINE FEED (LF);;;; |
+      {19:   12 }000B;<control>;Cc;0;S;;;;;N;LINE TABULATION;;;;|
+    ## grid 3
+                                                           |
+    ]], win_viewport={
+      [2] = {win = {id = 1000}, topline = 0, botline = 13, curline = 0, curcol = 0, linecount = 30592, sum_scroll_delta = 0};
+    }}
+    feed('G')
+    screen:expect{grid=[[
+    ## grid 1
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      {11:test/functional/fixtures/bigfile.txt                 }|
+      [3:-----------------------------------------------------]|
+    ## grid 2
+      {19:30581 }E01E8;VARIATION SELECTOR-249;Mn;0;NSM;;;;;N;;;;|
+      {19:30582 }E01E9;VARIATION SELECTOR-250;Mn;0;NSM;;;;;N;;;;|
+      {19:30583 }E01EA;VARIATION SELECTOR-251;Mn;0;NSM;;;;;N;;;;|
+      {19:30584 }E01EB;VARIATION SELECTOR-252;Mn;0;NSM;;;;;N;;;;|
+      {19:30585 }E01EC;VARIATION SELECTOR-253;Mn;0;NSM;;;;;N;;;;|
+      {19:30586 }E01ED;VARIATION SELECTOR-254;Mn;0;NSM;;;;;N;;;;|
+      {19:30587 }E01EE;VARIATION SELECTOR-255;Mn;0;NSM;;;;;N;;;;|
+      {19:30588 }E01EF;VARIATION SELECTOR-256;Mn;0;NSM;;;;;N;;;;|
+      {19:30589 }F0000;<Plane 15 Private Use, First>;Co;0;L;;;;;|
+      {19:30590 }FFFFD;<Plane 15 Private Use, Last>;Co;0;L;;;;;N|
+      {19:30591 }100000;<Plane 16 Private Use, First>;Co;0;L;;;;|
+      {19:30592 }^10FFFD;<Plane 16 Private Use, Last>;Co;0;L;;;;;|
+    ## grid 3
+                                                           |
+    ]], win_viewport={
+      [2] = {win = {id = 1000}, topline = 30580, botline = 30592, curline = 30591, curcol = 0, linecount = 30592, sum_scroll_delta = 30580};
+    }}
+    feed('gg')
+    screen:expect{grid=[[
+    ## grid 1
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      {11:test/functional/fixtures/bigfile.txt                 }|
+      [3:-----------------------------------------------------]|
+    ## grid 2
+      {19:    1 }^0000;<control>;Cc;0;BN;;;;;N;NULL;;;;          |
+      {19:    2 }0001;<control>;Cc;0;BN;;;;;N;START OF HEADING;;|
+      {19:    3 }0002;<control>;Cc;0;BN;;;;;N;START OF TEXT;;;; |
+      {19:    4 }0003;<control>;Cc;0;BN;;;;;N;END OF TEXT;;;;   |
+      {19:    5 }0004;<control>;Cc;0;BN;;;;;N;END OF TRANSMISSIO|
+      {19:    6 }0005;<control>;Cc;0;BN;;;;;N;ENQUIRY;;;;       |
+      {19:    7 }0006;<control>;Cc;0;BN;;;;;N;ACKNOWLEDGE;;;;   |
+      {19:    8 }0007;<control>;Cc;0;BN;;;;;N;BELL;;;;          |
+      {19:    9 }0008;<control>;Cc;0;BN;;;;;N;BACKSPACE;;;;     |
+      {19:   10 }0009;<control>;Cc;0;S;;;;;N;CHARACTER TABULATIO|
+      {19:   11 }000A;<control>;Cc;0;B;;;;;N;LINE FEED (LF);;;; |
+      {19:   12 }000B;<control>;Cc;0;S;;;;;N;LINE TABULATION;;;;|
+    ## grid 3
+                                                           |
+    ]], win_viewport={
+      [2] = {win = {id = 1000}, topline = 0, botline = 13, curline = 0, curcol = 0, linecount = 30592, sum_scroll_delta = 0};
+    }}
+    command('setlocal wrap')
+    screen:expect{grid=[[
+    ## grid 1
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      {11:test/functional/fixtures/bigfile.txt                 }|
+      [3:-----------------------------------------------------]|
+    ## grid 2
+      {19:    1 }^0000;<control>;Cc;0;BN;;;;;N;NULL;;;;          |
+      {19:    2 }0001;<control>;Cc;0;BN;;;;;N;START OF HEADING;;|
+      {19:      };;                                             |
+      {19:    3 }0002;<control>;Cc;0;BN;;;;;N;START OF TEXT;;;; |
+      {19:    4 }0003;<control>;Cc;0;BN;;;;;N;END OF TEXT;;;;   |
+      {19:    5 }0004;<control>;Cc;0;BN;;;;;N;END OF TRANSMISSIO|
+      {19:      }N;;;;                                          |
+      {19:    6 }0005;<control>;Cc;0;BN;;;;;N;ENQUIRY;;;;       |
+      {19:    7 }0006;<control>;Cc;0;BN;;;;;N;ACKNOWLEDGE;;;;   |
+      {19:    8 }0007;<control>;Cc;0;BN;;;;;N;BELL;;;;          |
+      {19:    9 }0008;<control>;Cc;0;BN;;;;;N;BACKSPACE;;;;     |
+      {19:   10 }0009;<control>;Cc;0;S;;;;;N;CHARACTER TABULA{1:@@@}|
+    ## grid 3
+                                                           |
+    ]], win_viewport={
+      [2] = {win = {id = 1000}, topline = 0, botline = 10, curline = 0, curcol = 0, linecount = 30592, sum_scroll_delta = 0};
+    }}
+    feed('G')
+    screen:expect{grid=[[
+    ## grid 1
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      {11:test/functional/fixtures/bigfile.txt                 }|
+      [3:-----------------------------------------------------]|
+    ## grid 2
+      {19:30587 }E01EE;VARIATION SELECTOR-255;Mn;0;NSM;;;;;N;;;;|
+      {19:      };                                              |
+      {19:30588 }E01EF;VARIATION SELECTOR-256;Mn;0;NSM;;;;;N;;;;|
+      {19:      };                                              |
+      {19:30589 }F0000;<Plane 15 Private Use, First>;Co;0;L;;;;;|
+      {19:      }N;;;;;                                         |
+      {19:30590 }FFFFD;<Plane 15 Private Use, Last>;Co;0;L;;;;;N|
+      {19:      };;;;;                                          |
+      {19:30591 }100000;<Plane 16 Private Use, First>;Co;0;L;;;;|
+      {19:      };N;;;;;                                        |
+      {19:30592 }^10FFFD;<Plane 16 Private Use, Last>;Co;0;L;;;;;|
+      {19:      }N;;;;;                                         |
+    ## grid 3
+                                                           |
+    ]], win_viewport={
+      [2] = {win = {id = 1000}, topline = 30586, botline = 30592, curline = 30591, curcol = 0, linecount = 30592, sum_scroll_delta = 30588};
+    }}
+    feed('gg')
+    screen:expect{grid=[[
+    ## grid 1
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      [2:-----------------------------------------------------]|
+      {11:test/functional/fixtures/bigfile.txt                 }|
+      [3:-----------------------------------------------------]|
+    ## grid 2
+      {19:    1 }^0000;<control>;Cc;0;BN;;;;;N;NULL;;;;          |
+      {19:    2 }0001;<control>;Cc;0;BN;;;;;N;START OF HEADING;;|
+      {19:      };;                                             |
+      {19:    3 }0002;<control>;Cc;0;BN;;;;;N;START OF TEXT;;;; |
+      {19:    4 }0003;<control>;Cc;0;BN;;;;;N;END OF TEXT;;;;   |
+      {19:    5 }0004;<control>;Cc;0;BN;;;;;N;END OF TRANSMISSIO|
+      {19:      }N;;;;                                          |
+      {19:    6 }0005;<control>;Cc;0;BN;;;;;N;ENQUIRY;;;;       |
+      {19:    7 }0006;<control>;Cc;0;BN;;;;;N;ACKNOWLEDGE;;;;   |
+      {19:    8 }0007;<control>;Cc;0;BN;;;;;N;BELL;;;;          |
+      {19:    9 }0008;<control>;Cc;0;BN;;;;;N;BACKSPACE;;;;     |
+      {19:   10 }0009;<control>;Cc;0;S;;;;;N;CHARACTER TABULA{1:@@@}|
+    ## grid 3
+                                                           |
+    ]], win_viewport={
+      [2] = {win = {id = 1000}, topline = 0, botline = 10, curline = 0, curcol = 0, linecount = 30592, sum_scroll_delta = 0};
+    }}
+  end)
+
   it('does not crash when dragging mouse across grid boundary', function()
     screen:try_resize(48, 8)
     screen:expect{grid=[[