feat(ui): add scroll_delta to win_viewport event #19270

scroll_delta contains how much the top line of a window moved since the
last time win_viewport was emitted. It is expected to be used to
implement smooth scrolling. For this purpose it only counts "virtual" or
"displayed" so folds should count as one line. Because of this it
adds extra information that cannot be computed from the topline
parameter.

Fixes #19227

1 files changed, 6 insertions, 3 deletions

diff --git a/test/functional/ui/screen.lua b/test/functional/ui/screen.lua
index e5a449fa66..f5ae9c8e89 100644
--- a/test/functional/ui/screen.lua
+++ b/test/functional/ui/screen.lua
@@ -803,14 +803,17 @@ function Screen:_handle_win_pos(grid, win, startrow, startcol, width, height)
   self.float_pos[grid] = nil
 end
 
-function Screen:_handle_win_viewport(grid, win, topline, botline, curline, curcol, linecount)
+function Screen:_handle_win_viewport(grid, win, topline, botline, curline, curcol, linecount, scroll_delta)
+  -- accumulate scroll delta
+  local last_scroll_delta = self.win_viewport[grid] and self.win_viewport[grid].sum_scroll_delta or 0
   self.win_viewport[grid] = {
     win = win,
     topline = topline,
     botline = botline,
     curline = curline,
     curcol = curcol,
-    linecount = linecount
+    linecount = linecount,
+    sum_scroll_delta = scroll_delta + last_scroll_delta
   }
 end
 
@@ -1348,7 +1351,7 @@ local function fmt_ext_state(name, state)
     for k,v in pairs(state) do
       str = (str.."  ["..k.."] = {win = {id = "..v.win.id.."}, topline = "
              ..v.topline..", botline = "..v.botline..", curline = "..v.curline
-             ..", curcol = "..v.curcol..", linecount = "..v.linecount.."};\n")
+             ..", curcol = "..v.curcol..", linecount = "..v.linecount..", scroll_delta = "..v.scroll_delta.."};\n")
     end
     return str .. "}"
   elseif name == "float_pos" then