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authorPhilipp Gesang <phg42.2a@gmail.com>2013-05-13 17:01:27 +0200
committerPhilipp Gesang <phg42.2a@gmail.com>2013-05-13 17:01:27 +0200
commit69e1a2d1249afc6d661e78483f74669ce7868284 (patch)
treeec8a9769a7205d08ee282b9ae8f287fed95f7f9e /luaotfload.dtx
parent6f39e53c424a7bf460f757a36ab4534ca81492ff (diff)
downloadluaotfload-69e1a2d1249afc6d661e78483f74669ce7868284.tar.gz
[doc] document auxlib
Diffstat (limited to 'luaotfload.dtx')
-rw-r--r--luaotfload.dtx194
1 files changed, 191 insertions, 3 deletions
diff --git a/luaotfload.dtx b/luaotfload.dtx
index 7ccd6e8..e576112 100644
--- a/luaotfload.dtx
+++ b/luaotfload.dtx
@@ -187,11 +187,14 @@ and the derived files
{\normalsize\rmfamily\bfseries}
{\movecountertomargin\thepart} \zeropoint {}
\titleformat \section
- {\normalsize\rmfamily\scshape}%% no \word; life is full of disappointments
+ {\normalsize\rmfamily\scshape}
{\movecountertomargin\thesection} \zeropoint {}
\titleformat \subsection
{\small\rmfamily\itshape}
{\movecountertomargin\thesubsection} \zeropoint {}
+\titleformat \subsubsection
+ {\normalsize\rmfamily\upshape}
+ {\movecountertomargin\thesubsubsection} \zeropoint {}
\usepackage{tocloft}
\renewcommand \cftpartfont {\rmfamily\upshape}
@@ -1178,6 +1181,174 @@ and the derived files
% \label{file-graph}
% \end{figure}
%
+% \section{Auxiliary Functions}
+%
+% With release version 2.2, \identifier{luaotfload} received
+% additional functions for package authors to call from outside
+% (see the file \fileent{luaotfload-auxiliary.lua} for details).
+% The purpose of this addition twofold.
+% Firstly, \identifier{luaotfload} failed to provide a stable interface
+% to internals in the past which resulted in an unmanageable situation
+% of different packages abusing the raw access to font objects by means
+% of the \luafunction{patch_font} callback.
+% When the structure of the font object changed due to an update, all
+% of these imploded and several packages had to be fixed while
+% simultaneously providing fallbacks for earlier versions.
+% Now the patching is done on the \identifier{luaotfload} side and can
+% be adapted with future modifications to font objects without touching
+% the packages that depend on it.
+% Second, some the capabilities of the font loader and the names
+% database are not immediately relevant in \identifier{luaotfload}
+% itself but might nevertheless be of great value to package authors or
+% end users.
+%
+% Note that the current interface is not yet set in stone and the
+% development team is open to suggestions for improvements or
+% additions.
+%
+% \subsection{Callback Functions}
+%
+% The \luafunction{patch_font} callback is inserted in the wrapper
+% \identifier{luaotfload} provides for the font definition callback
+% (see below, page \pageref{define-font}).
+% At this place it allows manipulating the font object immediately after
+% the font loader is done creating it.
+% For a short demonstration of its usefulness, here is a snippet that
+% writes an entire font object to the file \fileent{fontdump.lua}:
+%
+% \begin{quote}
+% \begin{verbatim}
+% \input luaotfload.sty
+% \directlua{
+% local dumpfile = "fontdump.lua"
+% local dump_font = function (tfmdata)
+% local data = table.serialize(tfmdata)
+% io.savedata(dumpfile, data)
+% end
+%
+% luatexbase.add_to_callback(
+% "luaotfload.patch_font",
+% dump_font,
+% "my_private_callbacks.dump_font"
+% )
+% }
+% \font\dumpme=name:Iwona
+% \bye
+% \end{verbatim}
+% \end{quote}
+%
+% \emphasis{Beware}: this creates a Lua file of around 150,000 lines of
+% code, taking up 3~\abbrev{mb} of disk space.
+% By inspecting the output you can get a first impression of how a font
+% is structured in \LUATEX’s memory, what elements it is composed of,
+% and in what ways it can be rearranged.
+%
+% \subsubsection{Compatibility with Earlier Versions}
+%
+% As has been touched on in the preface to this section, the structure
+% of the object as returned by the fontloader underwent rather drastic
+% changes during different stages of its development, and not all
+% packages that made use of font patching have kept up with every one
+% of it.
+% To ensure compatibility with these as well as older versions of
+% some packages, \identifier{luaotfload} sets up copies of or references
+% to data in the font table where it used to be located.
+% For instance, important parameters like the requested point size, the
+% units factor, and the font name have again been made accessible from
+% the toplevel of the table even though they were migrated to different
+% subtables in the meantime.
+%
+% \subsubsection{Patches}
+%
+% These are mostly concerned with establishing compatibility with
+% \XETEX.
+%
+% \begin{itemize}
+% \let\normalitem=\item
+% \def\ouritem#1{%
+% \normalitem{\luafunction{#1}}%
+% \hfill\break
+% }
+%
+% \ouritem {set_sscale_dimens}
+% Calculate \texmacro{fontdimen}s 10 and 11 to emulate \XETEX.
+%
+% \ouritem {set_capheight}
+% Calculates \texmacro{fontdimen} 8 like \XETEX.
+%
+% \ouritem {patch_cambria_domh}
+% Correct some values of the font \emphasis{Cambria Math}.
+%
+% \end{itemize}
+%
+% \subsection{Package Author’s Interface}
+%
+% As \LUATEX release 1.0 is nearing, the demand for a reliable interface
+% for package authors increases.
+%
+% \subsubsection{Font Properties}
+%
+% Below functions mostly concern querying the different components of a
+% font like for instance the glyphs it contains, or what font features
+% are defined for which scripts.
+%
+% \begin{itemize}
+% \let\normalitem=\item
+% \def\ouritem#1{%
+% \normalitem{\luafunction{#1}}%
+% \hfill\break
+% }
+%
+% \ouritem {aux.font_has_glyph (id : int, index : int)}
+% Predicate that returns true if the font \luafunction{id}
+% has glyph \luafunction{index}.
+%
+% \ouritem {aux.slot_of_name(name : string)}
+% Translates an Adobe Glyph name to the corresponding glyph
+% slot.
+%
+% \ouritem {aux.name_of_slot(slot : int)}
+% The inverse of \luafunction{slot_of_name}; note that this
+% might be incomplete as multiple glyph names may map to the
+% same codepoint, only one of which is returned by
+% \luafunction{name_of_slot}.
+%
+% \ouritem {aux.provides_script(id : int, script : string)}
+% Test if a font supports \luafunction{script}.
+%
+% \ouritem {aux.provides_language(id : int, script : string, language : string)}
+% Test if a font defines \luafunction{language} for a given
+% \luafunction{script}.
+%
+% \ouritem {aux.provides_feature(id : int, script : string,
+% language : string, feature : string)}
+% Test if a font defines \luafunction{feature} for
+% \luafunction{language} for a given \luafunction{script}.
+%
+% \ouritem {aux.get_math_dimension(id : int, dimension : string)}
+% Get the dimension \luafunction{dimension} of font \luafunction{id}.
+%
+% \ouritem {aux.sprint_math_dimension(id : int, dimension : string)}
+% Same as \luafunction{get_math_dimension()}, but output the value
+% in scaled points at the \TEX end.
+%
+% \end{itemize}
+%
+% \subsubsection{Database}
+%
+% \begin{itemize}
+% \let\normalitem=\item
+% \def\ouritem#1{%
+% \normalitem{\luafunction{#1}}%
+% \hfill\break
+% }
+%
+% \ouritem {aux.scan_external_dir(dir : string)}
+% Include fonts in directory \luafunction{dir} in font lookups without
+% adding them to the database.
+%
+% \end{itemize}
+%
% \section{Troubleshooting}
%
% If you encounter problems with some fonts, please first update to the latest
@@ -1215,6 +1386,22 @@ and the derived files
% \font\test=file:MyFont.otf:script=latn;+liga;
% \end{verbatim}
%
+% Another strategy that helps avoiding problems is to not access raw \LUATEX
+% internals directly.
+% Some of them, even though they are dangerous to access, have not been
+% overridden or disabled.
+% Thus, whenever possible prefer the functions in the
+% \luafunction{aux} namespace over direct manipulation of font objects.
+% For example, raw access to the \luafunction{font.fonts} table like:
+%
+% \begin{verbatim}
+% local somefont = font.fonts[2]
+% \end{verbatim}
+%
+% can render already defined fonts unusable.
+% Instead, the function \luafunction{font.getfont()} should be used because
+% it has been replaced by a safe variant.
+%
% \part{Implementation}
%
% \section{\fileent{luaotfload.lua}}
@@ -1592,8 +1779,8 @@ add_to_callback("hpack_filter",
add_to_callback("find_vf_file",
find_vf_file, "luaotfload.find_vf_file")
-loadmodule"lib-dir.lua" --- required by luaofload-database.lua
-loadmodule"override.lua" --- “luat-ovr”
+loadmodule"lib-dir.lua" --- required by luaofload-database.lua
+loadmodule"override.lua" --- “luat-ovr”
logs.set_loglevel(config.luaotfload.loglevel)
@@ -1723,6 +1910,7 @@ create_callback("luaotfload.patch_font", "simple", dummy_function)
% \end{macrocode}
% \subsection{\CONTEXT override}
+% \label{define-font}
% We provide a simplified version of the original font definition
% callback.
%