feat: support preview from floating window (#403)

* implement floating window

* reset width on closing window

* use gap from new config parameter

* use minimal style for preview in floating

* lower z-index

* add configuration of preview position in floating window

* fix in verions earlier than nvim 0.10

* close preview on opening floating window

Close the any existing preview because otherwise strange errors happen when the preview is open and the floating window is opened at the same time.

* reset formatting changes

* remove empty line

* change z-index of preview window to floating window z-index

* add configurations to oil.txt

* formatting

* add auto configuration

* update oil doc

* refactor: move logic into layout.lua and eliminate flicker

* fix: floating preview window title is file name

* doc: clarify default_file_explorer

* refactor: don't need a preview_gap option

* refactor: only find preview win in current tabpage

---------

Co-authored-by: Steven Arcangeli <stevearc@stevearc.com>

lua/oil/init.lua

@@ -244,6 +244,7 @@ M.open_float = function(dir)
   local layout = require("oil.layout")
   local util = require("oil.util")
   local view = require("oil.view")
+
   local parent_url, basename = M.get_url_for_path(dir)
   if not parent_url then
     return
@@ -254,31 +255,7 @@ M.open_float = function(dir)
 
   local bufnr = vim.api.nvim_create_buf(false, true)
   vim.bo[bufnr].bufhidden = "wipe"
-  local total_width = vim.o.columns
-  local total_height = layout.get_editor_height()
-  local width = total_width - 2 * config.float.padding
-  if config.float.border ~= "none" then
-    width = width - 2 -- The border consumes 1 col on each side
-  end
-  if config.float.max_width > 0 then
-    width = math.min(width, config.float.max_width)
-  end
-  local height = total_height - 2 * config.float.padding
-  if config.float.max_height > 0 then
-    height = math.min(height, config.float.max_height)
-  end
-  local row = math.floor((total_height - height) / 2)
-  local col = math.floor((total_width - width) / 2) - 1 -- adjust for border width
-  local win_opts = {
-    relative = "editor",
-    width = width,
-    height = height,
-    row = row,
-    col = col,
-    border = config.float.border,
-    zindex = 45,
-  }
-  win_opts = config.float.override(win_opts) or win_opts
+  local win_opts = layout.get_fullscreen_win_opts()
 
   local original_winid = vim.api.nvim_get_current_win()
   local winid = vim.api.nvim_open_win(bufnr, true, win_opts)
@@ -332,12 +309,13 @@ M.open_float = function(dir)
           if not vim.api.nvim_win_is_valid(winid) or vim.api.nvim_win_get_buf(winid) ~= winbuf then
             return
           end
+          local cur_win_opts = vim.api.nvim_win_get_config(winid)
           vim.api.nvim_win_set_config(winid, {
             relative = "editor",
-            row = win_opts.row,
-            col = win_opts.col,
-            width = win_opts.width,
-            height = win_opts.height,
+            row = cur_win_opts.row,
+            col = cur_win_opts.col,
+            width = cur_win_opts.width,
+            height = cur_win_opts.height,
             title = get_title(),
           })
         end,
@@ -444,6 +422,8 @@ end
 ---    split "aboveleft"|"belowright"|"topleft"|"botright" Split modifier
 M.open_preview = function(opts, callback)
   opts = opts or {}
+  local config = require("oil.config")
+  local layout = require("oil.layout")
   local util = require("oil.util")
 
   local function finish(err)
@@ -465,18 +445,59 @@ M.open_preview = function(opts, callback)
       opts.split = vim.o.splitright and "belowright" or "aboveleft"
     end
   end
-  if util.is_floating_win() then
-    return finish("oil preview doesn't work in a floating window")
-  end
+
+  local preview_win = util.get_preview_win()
+  local prev_win = vim.api.nvim_get_current_win()
+  local bufnr = vim.api.nvim_get_current_buf()
 
   local entry = M.get_cursor_entry()
   if not entry then
     return finish("Could not find entry under cursor")
   end
+  local entry_title = entry.name
+  if entry.type == "directory" then
+    entry_title = entry_title .. "/"
+  end
 
-  local preview_win = util.get_preview_win()
-  local prev_win = vim.api.nvim_get_current_win()
-  local bufnr = vim.api.nvim_get_current_buf()
+  if util.is_floating_win() then
+    if preview_win == nil then
+      local root_win_opts, preview_win_opts =
+        layout.split_window(0, config.float.preview_split, config.float.padding)
+
+      local win_opts_oil = {
+        relative = "editor",
+        width = root_win_opts.width,
+        height = root_win_opts.height,
+        row = root_win_opts.row,
+        col = root_win_opts.col,
+        border = config.float.border,
+        zindex = 45,
+      }
+      vim.api.nvim_win_set_config(0, win_opts_oil)
+      local win_opts = {
+        relative = "editor",
+        width = preview_win_opts.width,
+        height = preview_win_opts.height,
+        row = preview_win_opts.row,
+        col = preview_win_opts.col,
+        border = config.float.border,
+        zindex = 45,
+        focusable = false,
+        noautocmd = true,
+        style = "minimal",
+      }
+
+      if vim.fn.has("nvim-0.9") == 1 then
+        win_opts.title = entry_title
+      end
+
+      preview_win = vim.api.nvim_open_win(bufnr, true, win_opts)
+      vim.api.nvim_set_option_value("previewwindow", true, { scope = "local", win = preview_win })
+      vim.api.nvim_set_current_win(prev_win)
+    elseif vim.fn.has("nvim-0.9") == 1 then
+      vim.api.nvim_win_set_config(preview_win, { title = entry_title })
+    end
+  end
 
   local cmd = preview_win and "buffer" or "sbuffer"
   local mods = {
@@ -485,7 +506,6 @@ M.open_preview = function(opts, callback)
     split = opts.split,
   }
 
-  local is_visual_mode = util.is_visual_mode()
   -- HACK Switching windows takes us out of visual mode.
   -- Switching with nvim_set_current_win causes the previous visual selection (as used by `gv`) to
   -- not get set properly. So we have to switch windows this way instead.
@@ -494,15 +514,16 @@ M.open_preview = function(opts, callback)
     vim.cmd.wincmd({ args = { "w" }, count = winnr })
   end
 
-  if preview_win then
-    if is_visual_mode then
-      hack_set_win(preview_win)
-    else
-      vim.api.nvim_set_current_win(preview_win)
-    end
-  end
-
   util.get_edit_path(bufnr, entry, function(normalized_url)
+    local is_visual_mode = util.is_visual_mode()
+    if preview_win then
+      if is_visual_mode then
+        hack_set_win(preview_win)
+      else
+        vim.api.nvim_set_current_win(preview_win)
+      end
+    end
+
     local filebufnr = vim.fn.bufadd(normalized_url)
     local entry_is_file = not vim.endswith(normalized_url, "/")