[vim] Allow specifying popup width and height in absolute integer value

Fix https://github.com/junegunn/fzf.vim/issues/1116

README-VIM.md

@@ -290,8 +290,8 @@ When `window` entry is a dictionary, fzf will start in a popup window. The
 following options are allowed:
 
 - Required:
-    - `width` [float range [0 ~ 1]]
-    - `height` [float range [0 ~ 1]]
+    - `width` [float range [0 ~ 1]] or [integer range [8 ~ ]]
+    - `height` [float range [0 ~ 1]] or [integer range [4 ~ ]]
 - Optional:
     - `yoffset` [float default 0.5 range [0 ~ 1]]
     - `xoffset` [float default 0.5 range [0 ~ 1]]
@@ -386,8 +386,8 @@ The latest versions of Vim and Neovim include builtin terminal emulator
 
 ```vim
 " Required:
-" - width [float range [0 ~ 1]]
-" - height [float range [0 ~ 1]]
+" - width [float range [0 ~ 1]] or [integer range [8 ~ ]]
+" - height [float range [0 ~ 1]] or [integer range [4 ~ ]]
 "
 " Optional:
 " - xoffset [float default 0.5 range [0 ~ 1]]

doc/fzf.txt

@@ -305,8 +305,8 @@ When `window` entry is a dictionary, fzf will start in a popup window. The
 following options are allowed:
 
  - Required:
-   - `width` [float range [0 ~ 1]]
-   - `height` [float range [0 ~ 1]]
+   - `width` [float range [0 ~ 1]] or [integer range [8 ~ ]]
+   - `height` [float range [0 ~ 1]] or [integer range [4 ~ ]]
  - Optional:
    - `yoffset` [float default 0.5 range [0 ~ 1]]
    - `xoffset` [float default 0.5 range [0 ~ 1]]

plugin/fzf.vim

@@ -864,9 +864,9 @@ function! s:popup(opts) abort
   let ambidouble = &ambiwidth == 'double' ? 2 : 1
 
   " Size and position
-  let width = min([max([0, float2nr(&columns * a:opts.width)]), &columns])
+  let width = min([max([8, a:opts.width > 1 ? a:opts.width : float2nr(&columns * a:opts.width)]), &columns])
   let width += width % ambidouble
-  let height = min([max([0, float2nr(&lines * a:opts.height)]), &lines - has('nvim')])
+  let height = min([max([4, a:opts.height > 1 ? a:opts.height : float2nr(&lines * a:opts.height)]), &lines - has('nvim')])
   let row = float2nr(get(a:opts, 'yoffset', 0.5) * (&lines - height))
   let col = float2nr(get(a:opts, 'xoffset', 0.5) * (&columns - width))