feat: new preserve_win_context option to preserve parent window con…

…text

README.md

@@ -52,8 +52,12 @@ glance.setup({
   height = 18, -- Height of the window
   zindex = 45,
 
-  -- By default glance will open preview "embedded" within your active window
-  -- when `detached` is enabled, glance will render above all existing windows
+  -- Preserve the parent window context by appending virtual lines underneath the preview window.
+  -- requires Neovim >= 0.10.0 uses experimental nvim api that may change in the future.
+  preserve_win_context = true,
+
+  -- By default glance will open preview window "embedded" within your active window.
+  -- When `detached` is enabled glance preview will be rendered above all existing windows
   -- and won't be restiricted by the width of your active window
   detached = true,
 

lua/glance/config.lua

@@ -51,13 +51,15 @@ config.hl_ns = 'Glance'
 ---@field folds GlanceFoldsOpts
 ---@field indent_lines GlanceIndentLinesOpts
 ---@field winbar GlanceWinbarOpts
+---@field preserve_win_context boolean
 
 ---@param user_config GlanceOpts | nil
 ---@param actions GlanceActions
 function config.setup(user_config, actions)
   local defaults = {
     height = 18,
     zindex = 45,
+    preserve_win_context = true,
     detached = function(winid)
       return vim.api.nvim_win_get_width(winid) < 100
     end,
@@ -132,6 +134,7 @@ function config.setup(user_config, actions)
 
   vim.validate({
     height = { opts.height, 'n', false },
+    preserve_win_context = { opts.preserve_win_context, 'b', false },
     list = { opts.list, 't', false },
     position = utils.valid_enum(opts.list.position, { 'left', 'right' }, false),
     width = { opts.list.width, 'n', false },
@@ -143,6 +146,10 @@ function config.setup(user_config, actions)
     ),
   })
 
+  if opts.preserve_win_context and vim.fn.has('nvim-0.10.0') == 0 then
+    config.options.preserve_win_context = false
+  end
+
   -- Filter disabled mappings
   for _, mappings in pairs(opts.mappings) do
     for key, action in pairs(mappings) do

lua/glance/init.lua

@@ -8,6 +8,7 @@ local glance = {}
 Glance.__index = Glance
 local initialized = false
 local last_session = nil
+local layout_ns = vim.api.nvim_create_namespace('GlanceLayout')
 
 ---@param opts? GlanceOpts
 function Glance.setup(opts)
@@ -51,10 +52,15 @@ local function is_open()
   return list_is_valid and preview_is_valid
 end
 
-local function get_preview_win_height(winnr)
+local function get_preview_content_height(winnr)
   return math.min(vim.fn.winheight(winnr), config.options.height)
 end
 
+local function get_preview_layout_height(winnr)
+  local border_height = config.options.border.enable and 2 or 0
+  return get_preview_content_height(winnr) + border_height
+end
+
 local function is_detached(winnr)
   local detached = config.options.detached
   if type(detached) == 'function' then
@@ -85,7 +91,7 @@ local function get_win_opts(winnr, line)
   local list_width =
     utils.round(win_width * math.min(0.5, math.max(0.1, opts.list.width)))
   local preview_width = win_width - list_width
-  local height = get_preview_win_height(winnr)
+  local height = get_preview_content_height(winnr)
   local list_pos = opts.list.position
   local row = line
 
@@ -129,6 +135,31 @@ local function get_win_opts(winnr, line)
   return list_win_opts, preview_win_opts
 end
 
+-- Creates virtual lines in the parent window to reserve space for the float preview.
+-- Uses experimental neovim API that may change in the future `nvim__win_add_ns`
+-- to set window-local extmarks
+local function append_virtual_lines(winnr, start_row)
+  if not vim.api.nvim__win_add_ns then
+    return
+  end
+
+  local bufnr = vim.api.nvim_win_get_buf(winnr)
+  local height = get_preview_layout_height(winnr)
+
+  local virt_lines = {}
+  for _ = 1, height do
+    table.insert(virt_lines, { { '', 'NonText' } })
+  end
+
+  vim.api.nvim__win_add_ns(winnr, layout_ns)
+
+  vim.api.nvim_buf_set_extmark(bufnr, layout_ns, start_row, 0, {
+    virt_lines = virt_lines,
+    virt_lines_above = false,
+    scoped = true,
+  })
+end
+
 local function create(
   results,
   parent_bufnr,
@@ -403,6 +434,10 @@ function Glance:create(opts)
   local push_tagstack = utils.create_push_tagstack(opts.winnr)
   local list_win_opts, preview_win_opts = get_win_opts(opts.winnr, row)
 
+  if config.options.preserve_win_context then
+    append_virtual_lines(opts.winnr, opts.params.position.line)
+  end
+
   local list = require('glance.list').create({
     results = opts.results,
     parent_winnr = opts.winnr,
@@ -454,10 +489,7 @@ function Glance:scroll_into_view(winnr, position)
   local win_height = vim.fn.winheight(winnr)
   local row = vim.fn.winline()
   local bottom_offset = 2
-  local border_height = config.options.border.enable and 2 or 0
-  local preview_height = get_preview_win_height(winnr)
-    + border_height
-    + bottom_offset
+  local preview_height = get_preview_layout_height(winnr) + bottom_offset
 
   if preview_height >= win_height then
     return 0
@@ -569,6 +601,7 @@ function Glance:close()
 end
 
 function Glance:destroy()
+  vim.api.nvim_buf_clear_namespace(self.parent_bufnr, layout_ns, 0, -1)
   self.list:destroy()
   self.preview:destroy()
   glance = {}

lua/glance/utils.lua

@@ -125,7 +125,8 @@ function utils.get_line_byte_from_position(line, position, offset_encoding)
     if ok then
       return result
     end
-    ok, result = pcall(vim.str_byteindex, line, col, offset_encoding == 'utf-16')
+    ok, result =
+      pcall(vim.str_byteindex, line, col, offset_encoding == 'utf-16')
     if ok then
       return result
     end