perf(ui-ext): approximate scroll_delta when scrolling too much (#24234)

runtime/doc/ui.txt

@@ -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.
 
 ["win_extmark", grid, win, ns_id, mark_id, row, col] ~
 	Updates the position of an extmark which is currently visible in a

src/nvim/buffer_defs.h

@@ -1226,6 +1226,7 @@ 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
 

src/nvim/window.c

@@ -1030,15 +1030,13 @@ void ui_ext_win_position(win_T *wp, bool validate)
 void ui_ext_win_viewport(win_T *wp)
 {
   if ((wp == curwin || ui_has(kUIMultigrid)) && wp->w_viewport_invalid) {
-    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);
-      // TODO(bfredl): The might be more cases to consider, like how does this
+    const linenr_T cur_botline = MIN(wp->w_botline, line_count);
-      // interact with incomplete final line? Diff filler lines?
-      botline = wp->w_buffer->b_ml.ml_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) {
@@ -1047,19 +1045,39 @@ void ui_ext_win_viewport(win_T *wp)
       last_topfill = 0;
       last_skipcol = MAXCOL;
     }
-    if (wp->w_topline < last_topline
+    last_botline = MIN(last_botline, line_count);
-        || (wp->w_topline == last_topline && wp->w_skipcol < last_skipcol)) {
+    if (cur_topline < last_topline
-      delta -= win_get_text_height(wp, wp->w_topline, last_topline, wp->w_skipcol, last_skipcol);
+        || (cur_topline == last_topline && wp->w_skipcol < last_skipcol)) {
-    } else if ((wp->w_topline > last_topline && wp->w_topline <= line_count)
+      if (last_topline > 0 && cur_botline < last_topline) {
-               || (wp->w_topline == last_topline && wp->w_skipcol > last_skipcol)) {
+        // Scrolling too many lines: only give an approximate "scroll_delta".
-      delta += win_get_text_height(wp, last_topline, wp->w_topline, last_skipcol, wp->w_skipcol);
+        delta -= win_get_text_height(wp, cur_topline, cur_botline, wp->w_skipcol, 0);
+        delta -= last_topline - cur_botline;
+      } else {
+        delta -= win_get_text_height(wp, cur_topline, last_topline, wp->w_skipcol, last_skipcol);
+      }
+    } 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_get_text_height(wp, last_topline, last_botline, last_skipcol, 0);
+        delta += cur_topline - last_botline;
+      } else {
+        delta += win_get_text_height(wp, last_topline, cur_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,
+    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?
+      ev_botline = line_count;
+    }
+    ui_call_win_viewport(wp->w_grid_alloc.handle, wp->handle, wp->w_topline - 1, ev_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_botline = wp->w_botline;
     wp->w_viewport_last_topfill = wp->w_topfill;
     wp->w_viewport_last_skipcol = wp->w_skipcol;
   }

test/functional/ui/multigrid_spec.lua

@@ -3631,6 +3631,221 @@ 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};
+    }}
+    command('autocmd CursorMoved * ++once call line("w$")')  -- FIXME: this should not be needed
+    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=[[