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<h1>
Debian Menu System
<br>Chapter 7 - The internals of the menu package
</h1>
<hr>
<hr>
<h2><a name="s7.1"></a>7.1 The update-menus program</h2>
<p>
On startup, update-menus checks the file <code>/var/run/update-menus.pid</code>
and the pid in it. If there's an <code>update-menus</code> process with that
pid it kills it. If <code>/var/lib/dpkg/lock</code> exists, it checks to see
if dpkg supports triggers. If so, it uses dpkg-trigger to trigger a real
update-menus run later. Otherwise, it forks to background and returns control
to dpkg. The background process checks the <code>/var/lib/dpkg/lock</code>
file approx. every two second until the file's gone.
</p>
<p>
Once it's decided to run, whether in the background after dpkg exits, or in the
foreground when used with a trigger-capable dpkg, <code>update-menus</code>
reads the menu-entry files in the following directories:
<code>/etc/menu</code>, <code>/usr/lib/menu</code>,
<code>/usr/share/menu</code>, <code>/usr/share/menu/default</code>. (if a user
runs <code>update-menus</code>, it will add <code>~/.menu</code> to the front
of that list). For every menu entry line in each file it checks if the
corresponding package is installed. The menu entries of all packages marked as
installed by dpkg are added together in one big buffer that is kept in memory
(exception: executable menu entry files are executed, and stdout is placed in
the buffer).
</p>
<p>
Once it's read all menu entry files, <code>update-menus</code> starts all
executable scripts in <code>/etc/menu-methods/</code>, hands the scripts the
previously created buffer via stdin. (If <code>update-menus</code> is run by a
user, it will first try to run the scripts in <code>~/.menu-methods</code>, and
only if that directory doesn't exist, it will run the scripts in
<code>/etc/menu-methods</code>).
</p>
<p>
Note that as an aid to debugging, one can use
</p>
<pre>
update-menus --stdout > /tmp/menu-stdin
</pre>
<p>
and then view the file <code>/tmp/menu-stdin</code> to see exactly what
<code>update-menus</code> handed the menu-methods on their stdin.
</p>
<p>
This may also be useful for people writing <code>/etc/menu-method/*</code>
scripts: Running <code>update-menus</code> every time you changed something in
the script may be quite time-consuming. So, it's much easier to run
<code>update-menus --stdout</code> once, and then run
</p>
<pre>
/etc/menu-methods/mymethod < /tmp/menu-stdin
</pre>
<p>
(and, if that also takes too long, just try editing /tmp/menu-stdin, and
removing 90% or so of all entries)
</p>
<hr>
<h2><a name="s7.2"></a>7.2 The install-menu program</h2>
<p>
The files <code>/etc/menu-methods/$wm</code> are executable config files that
start with the line
</p>
<pre>
#!/usr/bin/install-menu
</pre>
<p>
and thus start that program, handing it the configuration file for the specific
window manager in the first command line argument. This configuration consists
of:
</p>
<ol type="1" start="1" >
<li>
<p>
the compatibility mode ("menu-1" or "menu-2").
</p>
</li>
</ol>
<ol type="1" start="2" >
<li>
<p>
where the various files should be stored/read.
</p>
</li>
</ol>
<ol type="1" start="3" >
<li>
<p>
what "needs" are supported, and what wrapper files should be used for
each "type".
</p>
</li>
</ol>
<ol type="1" start="4" >
<li>
<p>
how to remove the generated menu files.
</p>
</li>
</ol>
<p>
See <code>/usr/share/doc/menu/examples/</code> of the menu package for more
comments.
</p>
<p>
Options to <code>install-menu</code>:
</p>
<pre>
--remove Remove the menu files instead of generating them.
--verbose Output outline of operations that are performed.
</pre>
<p>
Some window managers don't support an `include'-like statement in their
<code>system.*rc</code> files (like <code>m4</code> or <code>cpp</code>
preprocessing); they cannot read the <code>menudefs.hook</code> file generated
by install-menu from their <code>system.*rc</code> config file. To still be
able to use them, <code>install-menu</code> will copy the file
<code>$path/$examplercfile</code> to <code>$path/$rcfile</code> (with
<code>$examplercfile</code> and <code>$rcfile</code> defined in the
<code>install-menu</code> config file, and <code>$path</code> either the
<code>$rootprefix</code> or <code>${HOME}/$userprefix</code>, depending on
whether root or user executed the file.), and replace all occurrences of
``install-menu-defs'' with the <code>$genmenu</code> file it just generated.
</p>
<p>
As an example, consider the following:
<samp>examplercfile=system.foo-wm-example</samp>,
<samp>rcfile=system.foo-wm</samp>, <samp>genmenu=menudefs.hook</samp> and
<samp>rootprefix=/var/lib/foo-wm/menu</samp>. Now, if
<code>install-menu</code> gets run, it will first generate the file
<code>/var/lib/foo-wm/menu/menudefs.hook</code>. Next, it will line-by-line
read the file <code>/var/lib/foo-wm/menu/system.foo-wm-example</code> and copy
its contents to <code>/var/lib/foo-wm/menu/system.foo-wm</code>, replacing
every occurrence of the string <samp>install-menu-defs</samp> with the contents
of the file <code>/var/lib/foo-wm/menu/menudefs.hook</code>.
</p>
<p>
To activate the file copying in this way, simply define the
<samp>$examplercfile</samp> and <samp>$rcfile</samp> variables in the
<code>install-menu</code> configuration file (for example, see
<code>/etc/menu-methods/fvwm</code>), and make sure there is a
<code>$path/$examplercfile</code> (<samp>$path</samp> being either
<samp>$rootprefix</samp>, or <code>$userprefix</code>.)
</p>
<p>
If you are writing a menu method, you can use the following to make debugging
it somewhat more easily:
</p>
<ol type="1" start="1" >
<li>
<p>
use <samp>update-menus --stdout > /tmp/menu-stdin</samp> to create a list of
menu entries in <code>/tmp/menu-stdin</code> and then
</p>
</li>
</ol>
<ol type="1" start="2" >
<li>
<p>
you can run just your menu-method with (if it's called wm):
</p>
<pre>
./wm -v < /tmp/menu-stdin
</pre>
</li>
</ol>
<hr>
<h2><a name="s7.3"></a>7.3 The install-menu config script definitions</h2>
<p>
The menu-methods in <code>/etc/menu-methods/*</code> are basically made up of a
lot of ``tag=string'' definitions, telling <code>install-menu</code> how to
generate a <code>system.${wm}rc</code> script. This way you can tune the look
of generated <code>system.${wm}rc</code> to your needs.
</p>
<p>
In the following, something like
</p>
<pre>
treewalk="c(m)"
</pre>
<p>
means that the treewalk variable by default has the value "c(m)".
</p>
<p>
For examples of what these scripts can look like, see
<code>/usr/share/doc/menu/examples/*</code>.
</p>
<dl>
<dt><samp>compat="menu-1"</samp></dt>
<dd>
<p>
Two mode are defined:
</p>
<dl>
<dt><samp>"menu-1"</samp></dt>
<dd>
<p>
menu directives are terminated by an end-of-line character.
</p>
</dd>
</dl>
<dl>
<dt><samp>"menu-2"</samp></dt>
<dd>
<p>
menu directives are terminated by a semicolon character.
</p>
</dd>
</dl>
<p>
This must be just after the <samp>!include "menu.h"</samp> directive
so that <code>menu.h</code> can use its own compat mode.
</p>
</dd>
</dl>
<dl>
<dt><samp>outputencoding="UTF-8"</samp></dt>
<dd>
<p>
Set the encoding used for output files. Use <samp>iconv --list</samp> to get
the list of supported encoding. Useful values include "UTF-8" and
"ISO-8859-1". The special value "LOCALE" means that the
current locale encoding will be used. If set to an empty string, no
translations are performed. This is the default.
</p>
</dd>
</dl>
<dl>
<dt><samp>outputlanguage=""</samp></dt>
<dd>
<p>
If set to "C" automatic translations will be disabled. Note that you
can still use translate() to perform explicit translation.
</p>
</dd>
</dl>
<dl>
<dt><samp>supported</samp></dt>
<dt><samp>endsupported</samp></dt>
<dd>
<p>
Between the <samp>supported</samp> and <samp>endsupported</samp> keywords you
define what "needs" are supported by this window manager. So, the
following is an example for a wm that supports both needs=x11 and needs=text:
</p>
<pre>
function q($s) = "\"" esc($s,"\\\"") "\""
supported
x11 =" ShowEntry(" q(title()) ", " q($command) ")"
text=" ShowEntry(" q(title()) ", " q(term()) ")"
endsupported
</pre>
<p>
For the variable substitution (and functions, not shown above), see the next
paragraph. In the above example, you'll notice that for the menu entries that
"need=text", the term() function is used. This is a user-supplied
function that will run $command in a X terminal emulator. Also, as X11 is
higher up in the supported list above than text, a package that supplies both a
"needs=X11" and a "needs=text" entry will have the
needs=X11 entry installed, in favour of the needs=text entry. You can continue
lines on the next line with a backslash ("\"), but make sure you
don't add any spaces after the backslash.
</p>
</dd>
</dl>
<dl>
<dt><samp>startmenu=""</samp></dt>
<dt><samp>endmenu=""</samp></dt>
<dt><samp>submenutitle=""</samp></dt>
<dd>
<p>
These define what to print for the beginning/end of a menu, and how to the
print a menu entry that pops up another menu. They are substituted the same
way as the "supported" stuff is; see next paragraph.
</p>
</dd>
</dl>
<dl>
<dt><samp>treewalk="c(m)"</samp></dt>
<dd>
<p>
This string defines in what order to dump the <samp>$startmenu</samp>,
<samp>$endmenu</samp>, and <samp>$submenutitle</samp> (and its children). Each
char in the string refers to:
</p>
<pre>
c : dump children of menu.
m : dump this menu's $submenutitles
( : dump $startmenu
) : dump $endmenu
M : dump all $submenutitles of this menu and this menu's children.
</pre>
<p>
The default is "c(m)". For olvwm, one needs: "(M)"
</p>
</dd>
</dl>
<dl>
<dt><samp>genmenu=""</samp></dt>
<dd>
<p>
The menu file to generate (usually something like
<samp>system."$wm"rc</samp>). The file itself may depend on the
level or title that is currently being worked on, like
</p>
<pre>
genmenu="/subdir/" replacewith($section," ","_") "/rc.menu"
</pre>
<p>
(Substitution works just like in the supported stuff, see above). Note that
the files made this way are truncated upon opening, so if you have a genmenu
like the example above, then your <samp>endmenu=</samp> will override the
startmenu stuff (but you probably only need one of the two anyway).
</p>
</dd>
</dl>
<dl>
<dt><samp>rootsection="/Debian"</samp></dt>
<dd>
<p>
the prefix every <samp>$section</samp> variable gets.
</p>
</dd>
</dl>
<dl>
<dt><samp>prerun=""</samp></dt>
<dt><samp>postrun=""</samp></dt>
<dd>
<p>
The commands to run before and after, respectively, the actual generation of
the <code>menudefs.hook</code> (genmenu) file. Commands will be executed by
<code>sh</code>. Example:
</p>
<pre>
prerun="rm -rf " prefix() "/*"
postrun="killall -USR1 fvwm2"
</pre>
<p>
(Substitution works just like the supported stuff, see below).
</p>
</dd>
</dl>
<dl>
<dt><samp>preruntest=""</samp></dt>
<dd>
<p>
Just like prerun, but if the return value of the command is non-zero, menu will
quit.
</p>
</dd>
</dl>
<dl>
<dt><samp>also_run=""</samp></dt>
<dd>
<p>
If non-zero, install-menus will, after generating the output files, also load
the file also_run, and use the new assignments to treewalk, genmenu, etc. to
generate more output. This second time, variables like <samp>prerun</samp> and
all of the hint stuff are ignored.
</p>
</dd>
</dl>
<dl>
<dt><samp>removemenu=""</samp></dt>
<dd>
<p>
The command to run when the menu-method is invoked with the option
<samp>--remove</samp>. This should remove all the autogenerated menu files.
If this option is not present, then install menu will remove
<samp>genmenu</samp> if it is a constant string and <samp>rcfile</samp> if it
is defined, and try to remove <samp>prefix()</samp> if it is empty.
</p>
</dd>
</dl>
<dl>
<dt><samp>onlyrunasroot=false</samp></dt>
<dt><samp>onlyrunasuser=false</samp></dt>
<dd>
<p>
If <samp>onlyrunasroot</samp> is set to true, <code>install-menu</code> will
quit silently when run as a user. Similarly for <samp>onlyrunasuser</samp>.
<var><samp>onlyrunasroot</samp> is deprecated since it is simpler to just not
define <samp>userprefix</samp>.</var> On the other hand,
<samp>onlyrunasuser</samp> might be needed if you use <samp>rcfile</samp> since
<samp>rootprefix</samp> is used as a fallback location for the template.
</p>
</dd>
</dl>
<dl>
<dt><samp>preoutput="#Automatically generated file. Do not edit (see /usr/share/doc/menu/html)\n\n"</samp></dt>
<dt><samp>postoutput=""</samp></dt>
<dd>
<p>
Text to put at the beginning resp. end of the generated file ($genmenu).
</p>
</dd>
</dl>
<dl>
<dt><samp>command=""</samp></dt>
<dd>
<p>
A command to run instead of <code>install-menus</code>. This command used to
be needed to get around limitations due to compatibility stuff. But that
compatibility with pre menu-1 stuff has been dropped, and isn't needed any
more.
</p>
<p>
Example:
</p>
<pre>
command="cat > /tmp/menu-stdin"
</pre>
</dd>
</dl>
<dl>
<dt><samp>hotkeyexclude=""</samp></dt>
<dd>
<p>
Keys not to use for hotkey generation. You can use the same variables and
functions here as in for example the startmenu sections.
</p>
<p>
Example:
</p>
<pre>
hotkeyexclude="q" $section
</pre>
</dd>
</dl>
<dl>
<dt><samp>hotkeycase="insensitive"</samp></dt>
<dd>
<p>
can be either "insensitive" or "sensitive". Determines
whether the hotkeys can be of mixed case (<samp>fvwm2</samp> reads the hotkeys
case-insensitive, <samp>pdmenu</samp> case-sensitive). In case of the titles
"Xa" and "xb", hotkey case-insensitive will generate
"X" and "b", whereas case-sensitive would generate
"X" and "x".
</p>
</dd>
</dl>
<dl>
<dt><samp>sort=$sort ":" $title</samp></dt>
<dd>
<p>
Entries within one menu will be alphabetically sorted by whatever sort returns.
So, if you do <samp>sort=ifelse($command, "1",
"0"):$title</samp>, then all submenus will appear above the commands
in a submenu. (A submenu always has <samp>$command=""</samp>). Or,
as Joey Hess writes:
</p>
<pre>
You can add another field to the menu items, with whatever name you like,
let's say it's called priority. Then add this line to
/etc/menu-methods/*:
sort=ifelse($priority, $priority, "9")
This has the result of sorting things so items with a low priority sort to the
top, and items with no priority default to priority 9 and sort to the bottom.
(Note that it compares the strings alphabetically, not numerically.)
</pre>
</dd>
</dl>
<dl>
<dt><samp>rcfile=""</samp></dt>
<dd>
<p>
If the window manager doesn't support an "include filename" or
"read(filename)" statement in it's config file, you can rename the
wm's config file to <samp>system."$wm"rc-menu</samp>, and insert a
"install-menu-defs" line (without the quotes, or whitespace around
it, and "install-menu-defs" must be the only thing on the line) in
the <samp>system."$wm"rc-menu</samp> file. This will then get
replaced by the <samp>$genmenu</samp> file that was just created (see also
<samp>$examplercfile</samp>).
</p>
</dd>
</dl>
<dl>
<dt><samp>examplercfile=""</samp></dt>
<dd>
<p>
if needed (see <samp>rcfile</samp>), this is the
<samp>system.rc"$wm"-menu</samp> file. In that case, make
<samp>rcfile=system.rc"$wm"</samp>.
</p>
</dd>
</dl>
<dl>
<dt><samp>rootprefix=""</samp></dt>
<dd>
<p>
The prefix to use when running as root (applies to $genmenu, $rcfile,
$examplercfile and other old cache files). If it is not defined, the
menu-method will be skipped when run as root.
</p>
</dd>
</dl>
<dl>
<dt><samp>userprefix=""</samp></dt>
<dd>
<p>
As <samp>rootprefix</samp>, but when running as user. userprefix is relative
to the user home directory, unless it start with 2 slashes, in which case it is
treated as an absolute path. If it is not defined, the menu-method will be
skipped when run as a user.
</p>
</dd>
</dl>
<dl>
<dt><samp>hint_optimize=false</samp></dt>
<dd>
<p>
If set to true, menu will try to generate an `optimal' tree, using the
variables below. If set to false, menu will keep the sections as they are
specified in the menu entry files (and ignore any hint stuff).
</p>
</dd>
</dl>
<dl>
<dt><samp>hint_nentry=6</samp></dt>
<dd>
<p>
Optimal number of entries in a submenu. It's a float, so you can set it to 5.5
if you cannot decide between 5 and 6. Also, values less than 3 probably don't
work very well at the moment.
</p>
</dd>
</dl>
<dl>
<dt><samp>hint_topnentry=5</samp></dt>
<dd>
<p>
Same as hint_nentry, but for the top level menu. Often here are other entries,
added by the window-manager itself (like Exit, Xterm, whatever) that menu
doesn't know about, so that you may want to instruct menu to put less entries
in the top level menu.
</p>
</dd>
</dl>
<dl>
<dt><samp>hint_mixedpenalty=15.0</samp></dt>
<dd>
<p>
Penalty for `mixed' menus. Mixed menus are those with both submenus and direct
commands in them.
</p>
</dd>
</dl>
<dl>
<dt><samp>hint_minhintfreq=0.1</samp></dt>
<dd>
<p>
Minimal relative frequency for the hints before they are considered. Internal
variable to speed up the tree generation. If you find menu slow, increase this
value (to, say 0.2 or 0.3).
</p>
</dd>
</dl>
<dl>
<dt><samp>hint_mlpenalty=2000</samp></dt>
<dd>
<p>
`max local penalty', while evaluating the possible trees, menu gives
`penalties' for submenus that don't contain the desired number of submenus.
The penalty is sqrt(n_entry_opt-n_entry), and eventually will be calculated as
a sum of all nodes. But to speed things up, menu will discard possibilities in
which any node has a `local' penalty of more than hint_mlpenalty. Increase
this value if you think menu is overlooking your favorite tree (also decrease
minhintfreq), decrease this value if you think menu is wasting too much time.
Because of hint_max_ntry, the influence of this variable is nearly zero
nowadays.
</p>
</dd>
</dl>
<dl>
<dt><samp>hint_max_ntry=4</samp></dt>
<dd>
<p>
menu will recursively, for each node, try the hint_max_ntry best local
menu-divisions.
</p>
</dd>
</dl>
<dl>
<dt><samp>hints_max_iter_hint=5</samp></dt>
<dd>
<p>
The search for what hints to use in one menu is rather expensive. But due to
the way things are sorted, menu seems to always find the `best' match in the
first 2% of iterations. Thus, a way to speed things up is simply to cut of
menu searching after `some' iterations are done. This value controls this, and
limits the number of iterations to
5+hint_max_iter_hint*number_of_possible_hints. Set this value to negative to
disable this.
</p>
</dd>
</dl>
<dl>
<dt><samp>hint_debug=false</samp></dt>
<dd>
<p>
Set to true if you want to see loads and loads of debug output.
</p>
</dd>
</dl>
<hr>
<h2><a name="s7.4"></a>7.4 Hints, tree optimization</h2>
<p>
The hints actually work in a rather strange way: when
<samp>hint_optimize=true</samp> then all <samp>$section</samp> elements are
added to the specified <samp>$hints</samp> variable, and the order
(<samp>/Applications/Editors</samp> or <samp>/Editors/Applications</samp>) of
the resulting hints is completely ignored. Then, the hints for each menu entry
are handed to the optimization routine, which will calculate a reasonable tree
for those hints. That tree must comply with the following:
</p>
<p>
When a user looks for a program "Program" with, say, hints
"Good,Bulky,Heaven", then, while walking through the tree, it should
at every node visited be clear for the user what submenu to select (or the menu
should have "Program" directly in it). So, the top-level menu may
look like
</p>
<pre>
Good
Hell
Microsoft
</pre>
<p>
because then a searcher for a menu entry with hints
"Good,Bulky,Heaven" will know to select the submenu "Good".
The toplevel menu may not look like
</p>
<pre>
Good
Hell
Heaven
</pre>
<p>
as now it isn't clear whether to visit the Good or the Heaven submenu.
</p>
<p>
That rule allows usually for many different trees, and the task of the
optimization procedure is to select, in a finite amount of time, the tree that
best matches the user's desire about the optimum number of menu entries.
</p>
<hr>
<p>
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</p>
<hr>
<p>
Debian Menu System
</p>
<address>
version 1.4, 10 November 2011<br>
<br>
Joost Witteveen <code><a href="mailto:joostje@debian.org">joostje@debian.org</a></code><br>
Joey Hess <code><a href="mailto:joeyh@debian.org">joeyh@debian.org</a></code><br>
Christian Schwarz <code><a href="mailto:schwarz@debian.org">schwarz@debian.org</a></code><br>
Bill Allombert <code><a href="mailto:ballombe@debian.org">ballombe@debian.org</a></code><br>
<br>
</address>
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