render all the non-floating windows, then render
	in the `compindex` order, overwriting any floating window cells.
	Finally, blend the floating window cells against the non-floating
	background. To add more blending, you can group the windows by zindex,
	and blend between the layers. But note that windows inside the same
	zindex should still overwrite previous cells inside the same layer
	without blending. This ensures that plugins that render multiple
	windows, to add borders for example, work as expected.

["win_external_pos", grid, win] ~
	Display or reconfigure external window `win`. The window should be
	displayed as a separate top-level window in the desktop environment,
	or something similar.

["win_hide", grid] ~
	Stop displaying the window. The window can be shown again later.

["win_close", grid] ~
	Close the window.

["msg_set_pos", grid, row, scrolled, sep_char, zindex, compindex] ~
	Display messages on `grid`.  The grid will be displayed at `row` on
	the default grid (grid=1), covering the full column width. `scrolled`
	indicates whether the message area has been scrolled to cover other
	grids. It can be useful to draw a separator then |msgsep|. The Builtin
	TUI draws a full line filled with `sep_char` ('fillchars' msgsep
	field) and |hl-MsgSeparator| highlight.

	When |ui-messages| is active, no message grid is used, and this event
	will not be sent.

	`zindex` and `compindex` have the same meaning as for `win_float_pos`.
	The `zindex` always has a fixed value of 200 and included for
	completeness.

["win_viewport", grid, win, topline, botline, curline, curcol, line_count, scroll_delta] ~
	Indicates the range of buffer text displayed in the window, as well
	as the cursor position in the buffer. All positions are zero-based.
	`botline` is set to one more than the line count of the buffer, if
	there are filler lines past the end. `scroll_delta` contains how much
	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. 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.
	Applications implementing, for example, smooth scrolling should take
	this into account and keep the grid separated from what's displayed on
	the screen and copy it to the viewport destination once `win_viewport`
	is received.

["win_viewport_margins", grid, win, top, bottom, left, right] ~
	Indicates the margins of a window grid which are _not_ part of the
	viewport as indicated by the `win_viewport` event. This happens
	e.g. in the presence of 'winbar' and floating window borders.

["win_extmark", grid, win, ns_id, mark_id, row, col] ~
	Updates the position of an extmark which is currently visible in a
	window. Only emitted if the mark has the `ui_watched` attribute.

==============================================================================
Popupmenu Events						 *ui-popupmenu*

Activated by the `ext_popupmenu` |ui-option|.

This UI extension delegates presentation of the |popupmenu-completion| and
command-line 'wildmenu'.

The UI decides how to present the menu. For example, depending on the last
`mode_change` event, command-line wildmenu may be presented horizontally,
while insert-mode completion would show a vertical popupmenu.

["popupmenu_show", items, selected, row, col, grid] ~
	Show |popupmenu-completion|. `items` is an array of completion items
	to show; each item is an array of the form [word, kind, menu, info] as
	defined at |complete-items|, except that `word` is replaced by `abbr`
	if present.  `selected` is the initially-selected item, a zero-based
	index into the array of items (-1 if no item is selected). `row` and
	`col` give the anchor position, where the first character of the
	completed word will be.