What is the ideal way of applying shadows to windows made floating manually (or on startup)?

[maxigaz]

I would like to apply shadows for windows that are not tiled because I have gaps inner set to its default value (0), and casting shadows over adjacent tiled windows would be distracting.

I've tried putting the following line in my config:

for_window [floating] decoration shadow true shadow_dynamic false shadow_size 10 shadow_blur 30 shadow_offset 40 40 shadow_color #00000070

This seems to work for dialogue windows (e.g. the About window in virt-manager), but not for windows that were originally spawned as tiled and made floating by me with floating toggle.

Also, I have this in my config, which runs a dedicated instance of Alacritty and makes it floating and hidden on startup (so that it could be shown/hidden on demand later):

# (Re)start a terminal instance in floating mode
# (in case the floating terminal has been killed)
bindsym $mod+Shift+Return exec $term --class alacritty_float

# Toggle visibility of the floating terminal
bindsym $mod+eacute [app_id="alacritty_float"] scratchpad show, resize set 1492 872, move position center

# Scratchpad window rules
for_window [app_id="alacritty_float"] floating enable
for_window [app_id="alacritty_float"] resize set 1292 772
for_window [app_id="alacritty_float"] move position center
for_window [app_id="alacritty_float"] move scratchpad

# Run the terminal on startup
exec alacritty --class alacritty_float -e tmux

When I make the floating window appear, it doesn't have any shadows.

[dawsers]

Like you discovered, for_window only works at window creation.

The easiest and most powerful way is to use a Lua script referenced in your config:

set $lua_scripts /home/xxxx/.config/scroll/scripts
lua $lua_scripts/floating.lua

In floating.lua you can set anything you like for floating windows, for example, in this one I add a title bar and simple shadows:

local function on_float(cbview, _)
  local container = scroll.view_get_container(cbview)
  if scroll.container_get_floating(container) then
    scroll.command(container, "decoration shadow true; border normal")
  else
    scroll.command(container, "decoration shadow false; border pixel")
  end
end

scroll.add_callback("view_float", on_float, nil)