fix(ui): ensure screen update before waiting for input #30576

Ensure the screen is fully updated before blocking for input. This did
not always happen before, for example when setting `cursorline
scrolloff=9999`, which lead to jerky movement when using some GUI
applications.

Because of the duality of redraw_later, this can't be done in
command-line or when waiting for "Press ENTER". In many of those cases
the redraw is expected AFTER the key press, while normally it should
update the screen immediately. So, those special cases are excluded.

1 files changed, 253 insertions, 0 deletions

diff --git a/test/functional/ui/multigrid_spec.lua b/test/functional/ui/multigrid_spec.lua
index 63ae38d3c3..e009ed0a29 100644
--- a/test/functional/ui/multigrid_spec.lua
+++ b/test/functional/ui/multigrid_spec.lua
@@ -2599,4 +2599,257 @@ describe('ext_multigrid', function()
     ]])
     eq(1, api.nvim_get_option_value('cmdheight', {}))
   end)
+
+  describe('centered cursorline', function()
+    before_each(function()
+      -- Force a centered cursorline, this caused some redrawing problems described in #30576.
+      -- Most importantly, win_viewport was not received in time, and sum_scroll_delta did not refresh.
+      command('set cursorline scrolloff=9999')
+    end)
+    it('insert line scrolls correctly', function()
+      for i = 1, 11 do
+        insert('line' .. i .. '\n')
+      end
+      screen:expect({
+        grid = [[
+        ## grid 1
+          [2:-----------------------------------------------------]|*12
+          {11:[No Name] [+]                                        }|
+          [3:-----------------------------------------------------]|
+        ## grid 2
+          line1                                                |
+          line2                                                |
+          line3                                                |
+          line4                                                |
+          line5                                                |
+          line6                                                |
+          line7                                                |
+          line8                                                |
+          line9                                                |
+          line10                                               |
+          line11                                               |
+          {23:^                                                     }|
+        ## grid 3
+                                                               |
+        ]], win_viewport={
+        [2] = {win = 1000, topline = 0, botline = 12, curline = 11, curcol = 0, linecount = 12, sum_scroll_delta = 0};
+      }, win_viewport_margins={
+        [2] = {
+          bottom = 0,
+          left = 0,
+          right = 0,
+          top = 0,
+          win = 1000
+        }
+      }})
+      insert('line12\n')
+      screen:expect({
+        grid = [[
+        ## grid 1
+          [2:-----------------------------------------------------]|*12
+          {11:[No Name] [+]                                        }|
+          [3:-----------------------------------------------------]|
+        ## grid 2
+          line2                                                |
+          line3                                                |
+          line4                                                |
+          line5                                                |
+          line6                                                |
+          line7                                                |
+          line8                                                |
+          line9                                                |
+          line10                                               |
+          line11                                               |
+          line12                                               |
+          {23:^                                                     }|
+        ## grid 3
+                                                               |
+        ]], win_viewport={
+        [2] = {win = 1000, topline = 1, botline = 13, curline = 12, curcol = 0, linecount = 13, sum_scroll_delta = 1};
+      }, win_viewport_margins={
+        [2] = {
+          bottom = 0,
+          left = 0,
+          right = 0,
+          top = 0,
+          win = 1000
+        }
+      }})
+    end)
+
+    it('got to top scrolls correctly', function()
+      for i = 1, 20 do
+        insert('line' .. i .. '\n')
+      end
+      screen:expect({
+        grid = [[
+        ## grid 1
+          [2:-----------------------------------------------------]|*12
+          {11:[No Name] [+]                                        }|
+          [3:-----------------------------------------------------]|
+        ## grid 2
+          line10                                               |
+          line11                                               |
+          line12                                               |
+          line13                                               |
+          line14                                               |
+          line15                                               |
+          line16                                               |
+          line17                                               |
+          line18                                               |
+          line19                                               |
+          line20                                               |
+          {23:^                                                     }|
+        ## grid 3
+                                                               |
+        ]], win_viewport={
+        [2] = {win = 1000, topline = 9, botline = 21, curline = 20, curcol = 0, linecount = 21, sum_scroll_delta = 9};
+      }, win_viewport_margins={
+        [2] = {
+          bottom = 0,
+          left = 0,
+          right = 0,
+          top = 0,
+          win = 1000
+        }
+      }})
+      feed('gg')
+      screen:expect({
+        grid = [[
+        ## grid 1
+          [2:-----------------------------------------------------]|*12
+          {11:[No Name] [+]                                        }|
+          [3:-----------------------------------------------------]|
+        ## grid 2
+          {23:^line1                                                }|
+          line2                                                |
+          line3                                                |
+          line4                                                |
+          line5                                                |
+          line6                                                |
+          line7                                                |
+          line8                                                |
+          line9                                                |
+          line10                                               |
+          line11                                               |
+          line12                                               |
+        ## grid 3
+                                                               |
+        ]], win_viewport={
+        [2] = {win = 1000, topline = 0, botline = 13, curline = 0, curcol = 0, linecount = 21, sum_scroll_delta = 0};
+      }, win_viewport_margins={
+        [2] = {
+          bottom = 0,
+          left = 0,
+          right = 0,
+          top = 0,
+          win = 1000
+        }
+      }})
+    end)
+
+    it('scrolls in the middle', function()
+      for i = 1, 20 do
+        insert('line' .. i .. '\n')
+      end
+      screen:expect({
+        grid = [[
+        ## grid 1
+          [2:-----------------------------------------------------]|*12
+          {11:[No Name] [+]                                        }|
+          [3:-----------------------------------------------------]|
+        ## grid 2
+          line10                                               |
+          line11                                               |
+          line12                                               |
+          line13                                               |
+          line14                                               |
+          line15                                               |
+          line16                                               |
+          line17                                               |
+          line18                                               |
+          line19                                               |
+          line20                                               |
+          {23:^                                                     }|
+        ## grid 3
+                                                               |
+        ]], win_viewport={
+        [2] = {win = 1000, topline = 9, botline = 21, curline = 20, curcol = 0, linecount = 21, sum_scroll_delta = 9};
+      }, win_viewport_margins={
+        [2] = {
+          bottom = 0,
+          left = 0,
+          right = 0,
+          top = 0,
+          win = 1000
+        }
+      }})
+      feed('M')
+      screen:expect({
+        grid = [[
+        ## grid 1
+          [2:-----------------------------------------------------]|*12
+          {11:[No Name] [+]                                        }|
+          [3:-----------------------------------------------------]|
+        ## grid 2
+          line10                                               |
+          line11                                               |
+          line12                                               |
+          line13                                               |
+          line14                                               |
+          {23:^line15                                               }|
+          line16                                               |
+          line17                                               |
+          line18                                               |
+          line19                                               |
+          line20                                               |
+                                                               |
+        ## grid 3
+                                                               |
+        ]], win_viewport={
+        [2] = {win = 1000, topline = 9, botline = 21, curline = 14, curcol = 0, linecount = 21, sum_scroll_delta = 9};
+      }, win_viewport_margins={
+        [2] = {
+          bottom = 0,
+          left = 0,
+          right = 0,
+          top = 0,
+          win = 1000
+        }
+      }})
+      feed('k')
+      screen:expect({
+        grid = [[
+        ## grid 1
+          [2:-----------------------------------------------------]|*12
+          {11:[No Name] [+]                                        }|
+          [3:-----------------------------------------------------]|
+        ## grid 2
+          line9                                                |
+          line10                                               |
+          line11                                               |
+          line12                                               |
+          line13                                               |
+          {23:^line14                                               }|
+          line15                                               |
+          line16                                               |
+          line17                                               |
+          line18                                               |
+          line19                                               |
+          line20                                               |
+        ## grid 3
+                                                               |
+        ]], win_viewport={
+        [2] = {win = 1000, topline = 8, botline = 21, curline = 13, curcol = 0, linecount = 21, sum_scroll_delta = 8};
+      }, win_viewport_margins={
+        [2] = {
+          bottom = 0,
+          left = 0,
+          right = 0,
+          top = 0,
+          win = 1000
+        }
+      }})
+    end)
+  end)
 end)