### LuaTeX Example: Create Fontsampler

Source: https://wiki.luatex.org/index.php?diff=next&oldid=3577&title=Main_Page

Provides an example of creating a font sampler using plain LuaTeX and the `luaotfload` module.

```tex
Create a fontsampler using plain LuaTeX and `luaotfload`.
```

--------------------------------

### Lua Debug Traceback Example

Source: https://wiki.luatex.org/index.php?diff=cur&oldid=57&title=Writing_Lua_in_TeX

This example demonstrates how to use `debug.traceback(1)` in Lua within a \directlua command to get the current call stack. Be cautious if passing the output to TeX, as it might be interpreted as TeX code.

```tex
\directlua{
print(debug.traceback(1))
}
```

--------------------------------

### Create and Shipout a Node List

Source: https://wiki.luatex.org/index.php?action=edit&title=TeX_without_TeX&undo=122&undoafter=121

Demonstrates creating a whatsit node, packing it into an hbox with a rule, and shipping it to the PDF.

```lua
start_link.action = node.new("whatsit","pdf_action") start_link.action.action_type = 1 start_link.action.action_id = dest local rule = mkrule(tenpt) local hbox = hpack(start_link, rule, end_link) add_to_page(hbox) -- This pagelist consists of an hbox whose contents is "start_link", -- the 10pt x 10pt rule and the "end_link" node. shipout() --------------------------- -- Just to show you that you can get some memory usage statistics: print(string.format("\nnode_mem_usage=%s",status.node_mem_usage))
```

--------------------------------

### Visual Debugging with LuaLaTeX

Source: https://wiki.luatex.org/index.php?direction=prev&oldid=163&printable=yes&title=Main_Page

Example of using the `lua-visual-debug` package for visual debugging within LuaLaTeX. Requires the package to be installed.

```lua
\usepackage{lua-visual-debug}
% Your Lua code here
```

--------------------------------

### Create a PDF Link Node

Source: https://wiki.luatex.org/index.php?diff=10845&oldid=117&title=TeX_without_TeX

Demonstrates creating a PDF link using whatsit nodes and packing them into an hbox.

```lua
local start_link = node.new("whatsit","pdf_start_link")
local end_link = node.new("whatsit","pdf_end_link")
  
start_link.width = tenpt
start_link.height = tenpt / 2
start_link.depth = tenpt / 2
start_link.link_attr = "/C [0.9 1 0] /Border [0 0 2]"
  
--start_link.action = node.new("action")
--there has been an update of the luatex
start_link.action = node.new("whatsit","pdf_action")
start_link.action.action_type = 1
start_link.action.action_id = dest
  
local rule = mkrule(tenpt)
local hbox = hpack(start_link, rule, end_link)
add_to_page(hbox)
  
-- This pagelist consists of an hbox whose contents is "start_link",
-- the 10pt x 10pt rule and the "end_link" node. 
  
shipout()
```

--------------------------------

### luaindex Package Example

Source: https://wiki.luatex.org/index.php?action=edit&title=Main_Page&undo=163&undoafter=162

Demonstrates the use of the \`luaindex\` package to create an index in LuaLaTeX. This requires the \`luaindex\` package to be installed.

```tex
\documentclass{article}
\usepackage{luaindex}
\begin{document}
\index{example}
This is an example document.
\printindex
\end{document}
```

--------------------------------

### Create and Shipout a Node List

Source: https://wiki.luatex.org/index.php?action=edit&title=TeX_without_TeX&undo=140&undoafter=139

Demonstrates creating a node list containing an action, a rule, and an hbox, then shipping it to the PDF.

```lua
[0 0 2]" --start_link.action = node.new("action") --there has been an update of the luatex start_link.action = node.new("whatsit","pdf_action") start_link.action.action_type = 1 start_link.action.action_id = dest local rule = mkrule(tenpt) local hbox = hpack(start_link, rule, end_link) add_to_page(hbox) -- This pagelist consists of an hbox whose contents is "start_link", -- the 10pt x 10pt rule and the "end_link" node. shipout() --------------------------- -- Just to show you that you can get some memory usage statistics: print(string.format("\nnode_mem_usage=%s",status.node_mem_usage))
```

--------------------------------

### External Q&A Site Link

Source: https://wiki.luatex.org/index.php?action=edit&oldid=81&title=Main_Page

Example of linking to an external question and answer site. Use to guide users to relevant community support platforms.

```WikiText
* [http://tex.stackexchange.com/ tex.stackexchange.com] is a q&a site for questions related to TeX, and you can ask (and answer) LuaTeX related questions there.
```

--------------------------------

### Create PDF Pages with Lua

Source: https://wiki.luatex.org/index.php?action=edit&title=TeX_without_TeX&undo=137&undoafter=136

A complete example demonstrating node manipulation, box creation, and PDF shipout using Lua.

```Lua
do -- this will hold the items that go onto the page local pagelist -- Call tex.shipout() with the contents of the pagelist function shipout() local vbox,b = node.vpack(pagelist) -- we ignore the badness 'b' tex.box[666] = vbox tex.shipout(666) pagelist = nil -- Not strictly necessary. TeX holds the current page number in counter 0. -- TeX displays the contents of this counter when it puts a page into -- the pdf (tex.shipout()). If we don't change the counter, TeX will -- display [1] [1], instead of [1] [2] for our two page document. tex.count[0] = tex.count[0] + 1 end function add_to_page( list ) -- We attach the nodelist 'list' to the end of the pagelist -- if pagelist doesn't exist, 'list' is our new pagelist -- if it exists, we go to the end with node.tail() and adjust -- the prev and next pointers, so list becomes part -- of pagelist. if not pagelist then pagelist = list else local tail = node.tail(pagelist) tail.next = list list.prev = tail end end end -- This creates a new square rule and returns the pointer to it. function mkrule( size ) local r = node.new("rule") r.width = size r.height = size / 2 r.depth = size / 2 return r end do local destcounter = 0 -- Create a pdf anchor (dest object). It returns a whatsit node and the -- number of the anchor, so it can be used in a pdf link or an outline. function mkdest() destcounter = destcounter + 1 local d = node.new("whatsit","pdf_dest") d.named_id = 0 d.dest_id = destcounter d.dest_type = 3 return d, destcounter end end -- Take a list of nodes and put them into an hbox. The prev and next fields -- of the nodes will be set automatically. Return a pointer to the hbox. function hpack( ... ) local start, tmp, cur start = select(1,...) tmp = start for i=2,select("#",...) do cur = select(i,...) tmp.next = cur cur.prev = tmp tmp = cur end local h,b = node.hpack(start) -- ignore badness return h end local tenpt = 10 * 2^16 --------------------------- -- page 1 --------------------------- local n,dest = mkdest() -- dest is needed for the link to this anchor add_to_page(n) add_to_page(mkrule(2 * tenpt)) -- The pagelist contains a pdf dest node (a link destination) and a rule of size 20pt x 20pt. shipout() --------------------------- -- page 2 --------------------------- -- This is the page with the link to the anchor (dest) on page one. A -- link consists of three nodes: a pdf_start_link, a pdf_end_link and and -- action node that specifies the action to perform when the user clicks on -- the link. -- The pdf link must be inside a horizontal box, that's why we hpack() it. -- The link_attr (link attributes) is optional, here it draws a yellowish border -- around the link. local start_link = node.new("whatsit","pdf_start_link") local end_link = node.new("whatsit","pdf_end_link") start_link.width = tenpt start_link.height = tenpt / 2 start_link.depth = tenpt / 2 start_link.link_attr = "/C [0.9 1 0] /Border [0 0 2]" --start_link.action = node.new("action") --there has been an update of the luatex start_link.action = node.new("whatsit","pdf_action") start_link.action.action_type = 1 start_link.action.action_id = dest local rule = mkrule(tenpt) local hbox = hpack(start_link, rule, end_link) add_to_page(hbox) -- This p
```

--------------------------------

### Create and Output a Simple Hbox with a Rule

Source: https://wiki.luatex.org/index.php?action=edit&title=TeX_without_TeX&undo=118&undoafter=117

Demonstrates creating a pagelist with a start link, a rule, and an end link, then packing them into an hbox and outputting it to the page.

```lua
node.new("whatsit","pdf_action")
start_link.action.action_type = 1
start_link.action.action_id = dest
local rule = mkrule(tenpt)
local hbox = hpack(start_link, rule, end_link)
add_to_page(hbox)
-- This pagelist consists of an hbox whose contents is "start_link",
-- the 10pt x 10pt rule and the "end_link" node.
shipout()
```

--------------------------------

### Example Output of Node Traversal

Source: https://wiki.luatex.org/index.php?action=edit&oldid=56&title=Traversing_TeX_nodes

This is an example of the output generated by the LuaTeX node traversal code when processing the example document.

```text
This is luaTeX, Version 3.141592-snapshot-2007062922 (Web2C 7.5.6) ( NODE type=whatsit subtype=6 NODE type=hlist subtype=0 NODE type=glyph subtype=0 font=51 char=98 NODE type=glyph subtype=0 font=51 char=108 NODE type=glyph subtype=0 font=51 char=941 NODE type=glue subtype=0 NODE type=glyph subtype=0 font=51 char=98 NODE type=glyph subtype=0 font=51 char=108 NODE type=glyph subtype=0 font=51 char=97 NODE type=glue subtype=0 NODE type=glyph subtype=0 font=51 char=98 NODE type=glyph subtype=0 font=51 char=108 NODE type=glyph subtype=0 font=51 char=97 NODE type=glue subtype=0 NODE type=glyph subtype=0 font=51 char=98 NODE type=glyph subtype=0 font=51 char=108 NODE type=glyph subtype=0 font=51 char=97 NODE type=glue subtype=0 Underfull \hbox (badness 10000) in paragraph at lines 14--15 [1] )
```

--------------------------------

### Callback Examples

Source: https://wiki.luatex.org/index.php?diff=cur&oldid=97&title=Callbacks

Examples of specific callbacks and their usage.

```APIDOC
## Callback Examples

### Description
Illustrates the usage and purpose of various callbacks within LuaTeX.

### Callbacks

#### `process_output_buffer`

##### Description
Called for each line TeX writes to an external file, excluding the log file, terminal, and `\write18` calls.

##### Parameters
- **line** (string) - The line being written to the output file.
- **modified_line** (string) - The modified line (can be altered by the callback).

##### Response
- The callback can modify the `modified_line`.

#### `process_jobname`

##### Description
Processes the jobname when queried with `\jobname` or `tex.jobname`. The internal job name used for output and log files remains untouched. This callback appeared in v.0.71.

##### Parameters
- **modified_string** (string) - The jobname string.

##### Response
- The callback can modify the `modified_string`.

#### `token_filter`

##### Description
Called when TeX needs a token. No argument is passed to the callback. The next token must be fetched with `token.get_next()`. What is returned is immediately processed by TeX.

##### Parameters
None

##### Response
- The callback must return the next token to be processed by TeX.
```

--------------------------------

### Create and Shipout a Node List

Source: https://wiki.luatex.org/index.php?action=edit&title=TeX_without_TeX&undo=147&undoafter=141

Demonstrates creating a link node, a rule, and packing them into an hbox for PDF output.

```lua
_link.width = tenpt start_link.height = tenpt / 2 start_link.depth = tenpt / 2 start_link.link_attr = "/C [0.9 1 0] /Border [0 0 2]" --start_link.action = node.new("action") --there has been an update of the luatex start_link.action = node.new("whatsit","pdf_action") start_link.action.action_type = 1 start_link.action.action_id = dest local rule = mkrule(tenpt) local hbox = hpack(start_link, rule, end_link) add_to_page(hbox) -- This pagelist consists of an hbox whose contents is "start_link", -- the 10pt x 10pt rule and the "end_link" node. shipout() --------------------------- -- Just to show you that you can get some memory usage statistics: print(string.format("\nnode_mem_usage=%s",status.node_mem_usage))
```

--------------------------------

### Create a fontsampler example

Source: https://wiki.luatex.org/index.php?action=edit&title=Main_Page&undo=10858&undoafter=10141

Provides an example of creating a font sampler using plain LuaTeX and the \`luaotfload\` package. This demonstrates practical application of LuaTeX.

```TeX
[[fontsampler|Create a fontsampler]] using plain LuaTeX and <tt>luaotfload</tt>.
```

--------------------------------

### Lua Traceback Example

Source: https://wiki.luatex.org/index.php?diff=10870&oldid=47&printable=yes&title=Writing_Lua_in_TeX

An example of a Lua stack traceback output.

```text
| +| 1  
| +| stack traceback:  
| +|  <\directlua >:1: in main chunk
```

--------------------------------

### Create a Font Sampler with LuaTeX

Source: https://wiki.luatex.org/index.php?action=edit&title=Main_Page&undo=10858&undoafter=161

Guide on creating a font sampler utility using plain LuaTeX and the `luaotfload` package. Useful for previewing font characteristics.

```lua
require "luaotfload"
-- code to generate font sampler
```

--------------------------------

### Define Footnote Command Start and Stop

Source: https://wiki.luatex.org/index.php?printable=yes&title=T_wo_T_r%3Acommands.lua

Defines the start and stop functions for the 'Footnote' command. The start function is a no-op, while the stop function handles the actual footnote processing.

```lua
local do_command_start = function()
                         end
  State.do_command_start = do_command_start
  local do_command_stop = do_footnote
  push_do_command_stop(do_command_stop)
```

--------------------------------

### luatexbase Package Example

Source: https://wiki.luatex.org/index.php?action=edit&title=Main_Page&undo=163&undoafter=162

Illustrates the use of \`luatexbase\`, providing basic resource management for LuaTeX code. This example shows how to register a callback.

```tex
\documentclass{article}
\usepackage{luatexbase}
\begin{document}
\begin{luacode}
function my_callback(arg)
  tex.print('Callback executed with: ' .. arg)
end
luatexbase.add_callback('my_callback', my_callback)
\end{luacode}
\directlua{my_callback('test')}
\end{document}
```

--------------------------------

### Markup Examples

Source: https://wiki.luatex.org/index.php?action=edit&section=6&title=Process_input_buffer

Examples of input text strings used for markup processing.

```text
This is in /italic/ and this is in *bold*.
```

```text
This is in \italic{italic} and this is in \bold{bold}.
```

```text
This will /not be/ in italic.
```

```text
# A section
## A subsection
### A subsubsection
```

```text
... the file should be contained in user/directory/myfiles...
```

--------------------------------

### Create a font sampler with LuaTeX and luaotfload

Source: https://wiki.luatex.org/index.php/Special%3AExport/Main_Page

This example demonstrates how to create a font sampler using plain LuaTeX and the <tt>luaotfload</tt> package. It is useful for previewing and selecting OpenType fonts.

```tex
\documentclass{article}
\usepackage{luaotfload}
\begin{document}
\fontspec{Times New Roman}
This is a sample text in Times New Roman.
\end{document}
```

--------------------------------

### DirectLua Commands and Output Examples

Source: https://wiki.luatex.org/index.php?diff=next&oldid=77&title=Writing_Lua_in_TeX

Examples of using `\directlua` commands within a .tex file to interact with Lua and capture output, including examples of printing table contents and debug tracebacks.

```APIDOC
## DirectLua Commands and Output Examples

### Description
Demonstrates how to use `\directlua` commands in a .tex file to execute Lua code and print its output to stdout. Includes examples for inspecting Lua tables and obtaining debug tracebacks.

### Method
N/A (These are TeX commands using Lua integration)

### Endpoint
N/A (Executed within a .tex file)

### Parameters
N/A

### Request Example
```latex
\typeout{==\directlua{for k,v in pairs(tex) do print(k,v) end}==}
\typeout{==\directlua{for k,v in pairs(lua) do print(k,v) end}==}
\typeout{==\directlua{print(debug.traceback(1))}==}
```

### Response
#### Success Response (200)
Output from Lua's `print` function will be sent to stdout, delimited by `==`.

#### Response Example
```
tprint	function: 0x89086e8
box	table: 0x895a0a0
...
====
setluaname	function: 0x895efb8
...
====
1
stack traceback:
	<\directlua >:1: in main chunk
====
```

### Error Handling
Using `tex.print(debug.traceback())` directly can lead to errors in LaTeX due to special characters like '>'. Use `\directlua{print(debug.traceback())}` instead.
```

--------------------------------

### Glyph substitution example

Source: https://wiki.luatex.org/index.php?direction=next&oldid=15&title=Explore_the_table_obtained_from_a_TrueType_font

Example of a glyph entry containing OpenType substitution data.

```text
......12 -> {
.........boundingbox -> {
............1 -> 41
............2 -> -315
............3 -> 530
............4 -> 1600
.........}
.........name -> parenright
.........unicodeenc -> 41
.........possub -> {
............1 -> {
...............flags -> 0
...............type -> substitution
...............subs -> {
..................variant -> parenleft
...............}
...............script_lang_index -> 1
...............tag -> rtla
............}
.........}
.........width -> 649
......}
......13 -> {
.........boundingbox -> {
............1 -> 70
............2 -> 709
............3 -> 846
```

--------------------------------

### LuaTeX Show Hyphenation Points Example

Source: https://wiki.luatex.org/index.php?action=edit&title=Main_Page&undo=153&undoafter=143

Demonstrates how to show hyphenation points using a LuaTeX callback. Useful for linguistic analysis.

```text
Show the hyphenation points
```

--------------------------------

### LuaTeX Example: Splitting comma-separated lists

Source: https://wiki.luatex.org/index.php?diff=next&oldid=112&printable=yes&title=Main_Page

Code example for splitting a comma-separated list.

```lua
you want to split a comma separated list;
```

--------------------------------

### Create and Shipout a PDF Link

Source: https://wiki.luatex.org/index.php?action=edit&title=TeX_without_TeX&undo=123&undoafter=122

Demonstrates creating a whatsit node for a PDF link and shipping it out to the page.

```lua
t_link") local end_link = node.new("whatsit","pdf_end_link") start_link.width = tenpt start_link.height = tenpt / 2 start_link.depth = tenpt / 2 start_link.link_attr = "/C [0.9 1 0] /Border [0 0 2]" --start_link.action = node.new("action") --there has been an update of the luatex start_link.action = node.new("whatsit","pdf_action") start_link.action.action_type = 1 start_link.action.action_id = dest local rule = mkrule(tenpt) local hbox = hpack(start_link, rule, end_link) add_to_page(hbox) -- This pagelist consists of an hbox whose contents is "start_link", -- the 10pt x 10pt rule and the "end_link" node. shipout() --------------------------- -- Just to show you that you can get some memory usage statistics: print(string.format("\nnode_mem_usage=%s",status.node_mem_usage))
```

--------------------------------

### Markup Syntax Example

Source: https://wiki.luatex.org/index.php?action=edit&oldid=168&title=Process_input_buffer

Example of lightweight markup syntax for italic and bold text.

```text
This is in /italic/ and this is in *bold*.
```

--------------------------------

### luamplib Package Example

Source: https://wiki.luatex.org/index.php?action=edit&title=Main_Page&undo=163&undoafter=162

Shows how to use LuaTeX's built-in MetaPost interpreter via the \`luamplib\` package. This example includes a simple MetaPost drawing.

```tex
\documentclass{article}
\usepackage{luamplib}
\begin{document}
\mplibsetfile{standalone}
\begin{mplibcode}
  draw (0,0) -- (100,100);
\end{mplibcode}
\end{document}
```

--------------------------------

### Lua debug output example

Source: https://wiki.luatex.org/index.php?diff=prev&oldid=148&title=Writing_Lua_in_TeX

Example output generated by the Lua debug inspection commands.

```text
tprint	function: 0x89086e8
box	table: 0x895a0a0
getsfcode	function: 0x895ae10
pdffontsize	function: 0x895b048
shipout	function: 0x895b2d8
getmath	function: 0x895b380
setuccode	function: 0x895ae48
getskip	function: 0x8908860
pdfxformname	function: 0x895b170
setlist	function: 0x895ab38
setattribute	function: 0x8908898
count	table: 0x895b600
getuccode	function: 0x895ae80
getbox	function: 0x895ab00
uniformdeviate	function: 0x895b080
fontname	function: 0x895af58
primitives	function: 0x895b220
badness	function: 0x895b310
setmath	function: 0x895b348
setskip	function: 0x8908828
getmathcode	function: 0x895ada0
getcount	function: 0x8908950
toks	table: 0x895b6b0
setsfcode	function: 0x895add8
run	function: 0x8908638
sfcode	table: 0x895a130
pdfpageref	function: 0x895b138
setcount	function: 0x8908918
setdimen	function: 0x89087b8
print	function: 0x89086d0
setlccode	function: 0x895acf8
fontidentifier	function: 0x895af90
getlccode	function: 0x895ad30
setmathcode	function: 0x895ad68
round	function: 0x895aeb8
getdimen	function: 0x89087f0
write	function: 0x89086b8
set	function: 0x8908770
definefont	function: 0x895b1b0
dimen	table: 0x895b550
get	function: 0x89087a0
number	function: 0x895b0c0
nest	table: 0x895a600
lists	table: 0x895a550
setcatcode	function: 0x895ac18
delcode	table: 0x895a4a0
setnest	function: 0x895aba8
mathcode	table: 0x895a3f0
getdelcode	function: 0x895acc0
catcode	table: 0x895a340
pdffontname	function: 0x895afd0
uccode	table: 0x895a290
setdelcode	function: 0x895ac88
lccode	table: 0x895a1e0
sp	function: 0x895af28
attribute	table: 0x895b410
getcatcode	function: 0x895ac50
extraprimitives	function: 0x895b258
linebreak	function: 0x895b3b8
setbox	function: 0x895aac8
skip	table: 0x895b4c0
pdffontobjnum	function: 0x895b008
settoks	function: 0x8908988
gettoks	function: 0x895aa90
enableprimitives	function: 0x895b298
getlist	function: 0x895ab70
getnest	function: 0x895abe0
getattribute	function: 0x89088d8
romannumeral	function: 0x895b0f8
scale	function: 0x895aef0
hashtokens	function: 0x895b1e8
error	function: 0x8908720
finish	function: 0x8908668

====
setluaname	function: 0x895efb8
setbytecode	function: 0x895f028
name	table: 0x895ef50
getluaname	function: 0x895ef80
getbytecode	function: 0x895eff0
version	Lua 5.1
bytecode	table: 0x895f080
====
1
stack traceback:
	<\directlua >:1: in main chunk
====
```

--------------------------------

### Metapost with LuaTeX example

Source: https://wiki.luatex.org/index.php?action=edit&title=Main_Page&undo=10858&undoafter=10141

Shows how to use Metapost with LuaTeX. This is from the old bluwiki.com.

```TeX
using mplib to write [[metapost with LuaTeX]]
```

--------------------------------

### Sort a token list example

Source: https://wiki.luatex.org/index.php?action=edit&title=Main_Page&undo=10858&undoafter=10141

Provides an example of how to sort a token list. This is from the old bluwiki.com.

```TeX
you want to [[sort a token list]];
```

--------------------------------

### Create a fontsampler using LuaTeX and luaotfload

Source: https://wiki.luatex.org/index.php?action=edit&title=Main_Page&undo=10858&undoafter=154

Provides an example of creating a font sampler utility using plain LuaTeX and the `luaotfload` library. Useful for previewing font features.

```lua
require 'luaotfload'
-- code to generate font sampler
```

--------------------------------

### Markup Failure Example

Source: https://wiki.luatex.org/index.php?action=edit&oldid=168&title=Process_input_buffer

Example demonstrating that markup processing is line-based and does not span across lines.

```text
This will /not be/ in italic.
```