feat: Allow customizing preview window background

Closes #64

README.md

@@ -36,6 +36,7 @@ vim.g.symbols_outline = {
     show_numbers = false,
     show_relative_numbers = false,
     show_symbol_details = true,
+    preview_bg_highlight = 'Pmenu',
     keymaps = { -- These keymaps can be a string or a table for multiple keys
         close = {"<Esc>", "q"},
         goto_location = "<Cr>",
@@ -88,6 +89,7 @@ vim.g.symbols_outline = {
 | show_numbers           | Shows numbers with the outline                                                 | boolean            | false                    |
 | show_relative_numbers  | Shows relative numbers with the outline                                        | boolean            | false                    |
 | show_symbol_details    | Shows extra details with the symbols (lsp dependent)                           | boolean            | true                     |
+| preview_bg_highlight   | Background color of the preview window                                         | string             | Pmenu                    |
 | keymaps                | Which keys do what                                                             | table (dictionary) | [here](#default-keymaps) |
 | symbols                | Icon and highlight config for symbol icons                                     | table (dictionary) | scroll up                |
 | lsp_blacklist          | Which lsp clients to ignore                                                    | table (array)      | {}                       |

doc/symbols-outline.txt

@@ -52,6 +52,7 @@ or skip this section entirely if you want to roll with the defaults.
         show_numbers = false,
         show_relative_numbers = false,
         show_symbol_details = true,
+        preview_bg_highlight = 'Pmenu',
         -- These keymaps can be a string or a table for multiple keys
         keymaps = {
             close = {"<Esc>", "q"},
@@ -167,6 +168,15 @@ show_symbol_details
 
     Type: boolean
 
+-----------------------------------------------------------------------------
+preview_bg_highlight
+
+    Background color of the preview window
+
+    Default: Pmenu
+
+    Type: string
+
 -----------------------------------------------------------------------------
 keymaps
 

lua/symbols-outline/config.lua

@@ -11,6 +11,7 @@ M.defaults = {
     show_numbers = false,
     show_relative_numbers = false,
     show_symbol_details = true,
+    preview_bg_highlight = 'Pmenu',
     keymaps = { -- These keymaps can be a string or a table for multiple keys
         close = {"<Esc>", "q"},
         goto_location = "<Cr>",

lua/symbols-outline/preview.lua

@@ -136,6 +136,12 @@ local function setup_hover_buf()
     update_hover()
 end
 
+local function set_bg_hl()
+    local winhi = "Normal:" .. config.options.preview_bg_highlight
+    vim.api.nvim_win_set_option(state.preview_win, "winhighlight", winhi)
+    vim.api.nvim_win_set_option(state.hover_win, "winhighlight", winhi)
+end
+
 local function show_preview()
     if state.preview_win == nil and state.preview_buf == nil then
         state.preview_buf = vim.api.nvim_create_buf(false, true)
@@ -195,6 +201,7 @@ function M.show()
 
     show_preview()
     show_hover()
+    set_bg_hl()
 end
 
 function M.close()