feat: config.view.entries.vertical_positioning = 'above'|'below'

Works best with vim.opt.scrolloff = 999

Fixes: #495
Suggested-by: Thanatermesis <thanatermesis@gmail.com>

Author: llllvvuu

lua/cmp/config/default.lua

@@ -94,6 +94,7 @@ return function()
       entries = {
         name = 'custom',
         selection_order = 'top_down',
+        vertical_positioning = 'below',
       },
       docs = {
         auto_open = true,

lua/cmp/types/cmp.lua

@@ -176,6 +176,7 @@ cmp.ItemField = {
 ---@class cmp.CustomEntriesViewConfig
 ---@field name 'custom'
 ---@field selection_order 'top_down'|'near_cursor'
+---@field vertical_positioning 'above'|'below'
 
 ---@class cmp.NativeEntriesViewConfig
 ---@field name 'native'

lua/cmp/view/custom_entries_view.lua

@@ -117,7 +117,8 @@ custom_entries_view.is_direction_top_down = function(self)
 end
 
 custom_entries_view.open = function(self, offset, entries)
-  local completion = config.get().window.completion
+  local c = config.get()
+  local completion = c.window.completion
   self.offset = offset
   self.entries = {}
   self.column_width = { abbr = 0, kind = 0, menu = 0 }
@@ -161,12 +162,20 @@ custom_entries_view.open = function(self, offset, entries)
   local border_info = window.get_border_info({ style = completion })
   local border_offset_row = border_info.top + border_info.bottom
   local border_offset_col = border_info.left + border_info.right
-  if math.floor(vim.o.lines * 0.5) <= row + border_offset_row and vim.o.lines - row - border_offset_row <= math.min(DEFAULT_HEIGHT, height) then
+
+  local prefers_above = c.view.entries.vertical_positioning == 'above'
+  local cant_fit_at_bottom = vim.o.lines - row - border_offset_row <= math.min(DEFAULT_HEIGHT, height)
+  local cant_fit_at_top = row - border_offset_row <= math.min(DEFAULT_HEIGHT, height)
+  local should_position_above = cant_fit_at_bottom or (prefers_above and not cant_fit_at_top)
+  if should_position_above then
+    self.bottom_up = true
     height = math.min(height, row - 1)
     row = row - height - border_offset_row - 1
     if row < 0 then
       height = height + row
     end
+  else
+    self.bottom_up = false
   end
   if math.floor(vim.o.columns * 0.5) <= col + border_offset_col and vim.o.columns - col - border_offset_col <= width then
     width = math.min(width, vim.o.columns - 1)
@@ -176,12 +185,6 @@ custom_entries_view.open = function(self, offset, entries)
     end
   end
 
-  if pos[1] > row then
-    self.bottom_up = true
-  else
-    self.bottom_up = false
-  end
-
   if not self:is_direction_top_down() then
     local n = #self.entries
     for i = 1, math.floor(n / 2) do
@@ -208,9 +211,9 @@ custom_entries_view.open = function(self, offset, entries)
   })
   -- always set cursor when starting. It will be adjusted on the call to _select
   vim.api.nvim_win_set_cursor(self.entries_win.win, { 1, 0 })
-  if preselect_index > 0 and config.get().preselect == types.cmp.PreselectMode.Item then
+  if preselect_index > 0 and c.preselect == types.cmp.PreselectMode.Item then
     self:_select(preselect_index, { behavior = types.cmp.SelectBehavior.Select, active = false })
-  elseif not string.match(config.get().completion.completeopt, 'noselect') then
+  elseif not string.match(c.completion.completeopt, 'noselect') then
     if self:is_direction_top_down() then
       self:_select(1, { behavior = types.cmp.SelectBehavior.Select, active = false })
     else