The interaction between 'winblend' and doublewidth chars in the background
does not look very good. But check no chars get incorrectly placed
at least.
Also check that hidden EndOfBuffer region (from style="minimal") blends
correctly.
- Allow floating windows of width 1. #9846
- For a new floating window the size must be specified. Later on we
might try to calculate a reasonable size by buffer contents
- Remember the configured size of a window, just like its position.
- Make get_config and set_config more consistent. Handle relative='' properly in set_config.
get_config doesn't return keys that don't make sense for a non-floating window.
- Don't use width=0 for non-changed width, just omit the key.
Using `:wincmd j` and friends doesn't make much sense to a floating window. For
convenience though, any direction will simply change to the previous window.
Make sure the previous window is valid, not the current window, and not another
floating window. Change to the first window (which is never a floating window)
otherwise.
validate_cursor() is called regularly, but only for the current window.
When changing the buffer for a non-current window, we need to invoke it
in the context of that window.
