fix(auto): swap render → source on auto_off so toggle is symmetric (#18)

`:MdRender auto` is `auto_toggle` in disguise, so calling it twice
should return to the pre-toggle state. Previously `auto_off` only tore
down the autocmd / keymaps / b: marker but left the render buffer on
screen, so two `:MdRender auto` invocations ended up with auto OFF
plus render still displayed — surprising for a toggle.

Make `auto_off` also call `MdPreview.toggle()` when the current window
is showing this buffer's render view. `auto_toggle` inherits the fix
without further change. Update :help and tests accordingly.

Author: delphinus

doc/md-render.txt

@@ -218,9 +218,12 @@ still registered as deprecated aliases — see |md-render-deprecated-commands|.
 	  immediately, and registers `InsertEnter` / `InsertLeave` autocmds
 	  that swap to source on entry and back to render on leave.
 	- `:MdRender auto off` removes the autocmds and the buffer marker.
-	  The displayed mode is left unchanged.
+	  If the current window is showing the render view of this buffer,
+	  it also swaps back to source so the buffer ends up in the same
+	  state it had before `:MdRender auto on`.
 	- `:MdRender auto toggle`, or `:MdRender auto` with no second arg,
-	  toggles between on and off.
+	  toggles between on and off.  Calling it twice returns the buffer
+	  to its original (auto-off, source displayed) state.
 
 	The plugin does not register a |FileType| autocmd of its own.  To
 	enable auto mode for every Markdown buffer, add one yourself: >vim
@@ -531,8 +534,10 @@ MdPreview.auto_on({opts}) ~
 
 							   *MdPreview.auto_off()*
 MdPreview.auto_off() ~
-	[EXPERIMENTAL] Disable auto-toggle for the current buffer.  The
-	displayed mode is left as-is.  See |:MdRender-auto|.
+	[EXPERIMENTAL] Disable auto-toggle for the current buffer.  If the
+	current window is showing this buffer's render view, it also swaps
+	back to source so the post-`auto_off` state matches what existed
+	before |MdPreview.auto_on()|.  See |:MdRender-auto|.
 
 							*MdPreview.auto_toggle()*
 MdPreview.auto_toggle({opts}) ~

lua/md-render/preview.lua

@@ -1954,7 +1954,9 @@ function MdPreview.auto_on(opts)
   end
 end
 
---- Disable auto-toggle for the current buffer; leave the displayed mode untouched.
+--- Disable auto-toggle for the current buffer and, if the current window is
+--- showing this buffer's render view, swap back to source so a single
+--- `auto_off` (or a second `auto_toggle`) returns to the pre-`auto_on` state.
 function MdPreview.auto_off()
   local bufnr = get_auto_target_buf()
   if not vim.b[bufnr].md_render_auto then return end
@@ -1970,6 +1972,12 @@ function MdPreview.auto_off()
 
   local session = _toggle_sessions[bufnr]
   if session then uninstall_auto_insert_keymaps(session.buf) end
+
+  local win = vim.api.nvim_get_current_win()
+  local win_state = get_win_state(win)
+  if win_state and win_state.mode == "render" and win_state.source_buf == bufnr then
+    MdPreview.toggle()
+  end
 end
 
 --- Flip auto-toggle state for the current buffer.

tests/toggle_test.lua

@@ -607,14 +607,14 @@ test("auto-transition to render swaps source → render after 50ms", function()
 end)
 
 -- ----------------------------------------------------------------------
--- Test 18: auto_off clears autocmds and leaves displayed mode untouched
+-- Test 18: auto_off clears autocmds and restores source display
 -- ----------------------------------------------------------------------
-test("auto_off clears autocmds and preserves displayed mode", function()
+test("auto_off clears autocmds and swaps render back to source", function()
   local source = setup_md_buffer({ "# Hello" })
   local win = vim.api.nvim_get_current_win()
 
   preview.auto_on()
-  local before_buf = vim.api.nvim_win_get_buf(win)
+  assert_false(vim.api.nvim_win_get_buf(win) == source, "precondition: render after auto_on")
 
   preview.auto_off()
 
@@ -629,7 +629,48 @@ test("auto_off clears autocmds and preserves displayed mode", function()
   })
   assert_true(not ok or #autocmds == 0, "no auto autocmds should remain")
 
-  assert_eq(vim.api.nvim_win_get_buf(win), before_buf, "displayed mode should be unchanged")
+  assert_eq(vim.api.nvim_win_get_buf(win), source, "should be back on source after auto_off")
+
+  cleanup_buffer(source)
+end)
+
+-- ----------------------------------------------------------------------
+-- Test 18b: auto_toggle twice returns to the original (source, auto-off) state
+-- ----------------------------------------------------------------------
+test("auto_toggle twice returns to original source/auto-off state", function()
+  local source = setup_md_buffer({ "# Hello" })
+  local win = vim.api.nvim_get_current_win()
+
+  assert_eq(vim.api.nvim_win_get_buf(win), source, "precondition: source")
+  assert_eq(vim.b[source].md_render_auto, nil, "precondition: auto off")
+
+  preview.auto_toggle()
+  assert_eq(vim.b[source].md_render_auto, true, "after 1st toggle: auto on")
+  assert_false(vim.api.nvim_win_get_buf(win) == source, "after 1st toggle: render displayed")
+
+  preview.auto_toggle()
+  assert_eq(vim.b[source].md_render_auto, nil, "after 2nd toggle: auto off")
+  assert_eq(vim.api.nvim_win_get_buf(win), source, "after 2nd toggle: source displayed")
+
+  cleanup_buffer(source)
+end)
+
+-- ----------------------------------------------------------------------
+-- Test 18c: auto_off leaves displayed mode unchanged when not showing render
+-- ----------------------------------------------------------------------
+test("auto_off does not swap when current window is not showing render", function()
+  local source = setup_md_buffer({ "# Hello" })
+  local win = vim.api.nvim_get_current_win()
+
+  preview.auto_on()
+  -- Manually swap back to source so auto_off has nothing to swap.
+  preview.toggle()
+  assert_eq(vim.api.nvim_win_get_buf(win), source, "precondition: source displayed")
+
+  preview.auto_off()
+
+  assert_eq(vim.b[source].md_render_auto, nil, "b:md_render_auto should be cleared")
+  assert_eq(vim.api.nvim_win_get_buf(win), source, "should still be on source after auto_off")
 
   cleanup_buffer(source)
 end)