The branch stable/14 has been updated by bapt:
URL:
https://cgit.FreeBSD.org/src/commit/?id=80cd5ab568e26f185cd2dad3a7766514cf4a6443
commit 80cd5ab568e26f185cd2dad3a7766514cf4a6443
Author: Baptiste Daroussin <b...@freebsd.org>
AuthorDate: 2024-06-20 13:33:23 +0000
Commit: Baptiste Daroussin <b...@freebsd.org>
CommitDate: 2024-06-27 09:06:23 +0000
ncurses: readd 2 html files in the doc (fix MK_HTML=yes)
Reported by: Michael Butler <i...@protected-networks.net>
(cherry picked from commit 8d9900a313593adeeaae295b4aea982cb14cb8a5)
---
contrib/ncurses/doc/html/hackguide.html | 962 ++++++++
contrib/ncurses/doc/html/ncurses-intro.html | 3390 +++++++++++++++++++++++++++
2 files changed, 4352 insertions(+)
diff --git a/contrib/ncurses/doc/html/hackguide.html
b/contrib/ncurses/doc/html/hackguide.html
new file mode 100644
index 000000000000..2b9445538dc8
--- /dev/null
+++ b/contrib/ncurses/doc/html/hackguide.html
@@ -0,0 +1,962 @@
+<!--
+ $Id: hackguide.html,v 1.36 2022/11/26 19:31:56 tom Exp $
+ ****************************************************************************
+ * Copyright 2019-2020,2022 Thomas E. Dickey *
+ * Copyright 2000-2013,2017 Free Software Foundation, Inc. *
+ * *
+ * Permission is hereby granted, free of charge, to any person obtaining a *
+ * copy of this software and associated documentation files (the *
+ * "Software"), to deal in the Software without restriction, including *
+ * without limitation the rights to use, copy, modify, merge, publish, *
+ * distribute, distribute with modifications, sublicense, and/or sell *
+ * copies of the Software, and to permit persons to whom the Software is *
+ * furnished to do so, subject to the following conditions: *
+ * *
+ * The above copyright notice and this permission notice shall be included *
+ * in all copies or substantial portions of the Software. *
+ * *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS *
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF *
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. *
+ * IN NO EVENT SHALL THE ABOVE COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, *
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR *
+ * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR *
+ * THE USE OR OTHER DEALINGS IN THE SOFTWARE. *
+ * *
+ * Except as contained in this notice, the name(s) of the above copyright *
+ * holders shall not be used in advertising or otherwise to promote the *
+ * sale, use or other dealings in this Software without prior written *
+ * authorization. *
+ ****************************************************************************
+-->
+<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN">
+<html>
+<head>
+ <meta name="generator" content=
+ "HTML Tidy for HTML5 for Linux version 5.6.0">
+ <title>A Hacker's Guide to Ncurses Internals</title>
+ <link rel="author" href="mailto:bugs-ncur...@gnu.org";>
+ <meta http-equiv="Content-Type" content=
+ "text/html; charset=us-ascii"><!--
+This document is self-contained, *except* that there is one relative link to
+the ncurses-intro.html document, expected to be in the same directory with
+this one.
+-->
+</head>
+<body>
+ <h1 class="no-header">A Hacker's Guide to NCURSES</h1>
+
+ <h2>A Hacker's Guide to NCURSES</h2>
+
+ <div class="nav">
+ <h2>Contents</h2>
+
+ <ul>
+ <li><a href="#abstract">Abstract</a></li>
+
+ <li>
+ <a href="#objective">Objective of the Package</a>
+ <ul>
+ <li><a href="#whysvr4">Why System V Curses?</a></li>
+
+ <li><a href="#extensions">How to Design Extensions</a></li>
+ </ul>
+ </li>
+
+ <li><a href="#portability">Portability and Configuration</a></li>
+
+ <li><a href="#documentation">Documentation Conventions</a></li>
+
+ <li><a href="#bugtrack">How to Report Bugs</a></li>
+
+ <li>
+ <a href="#ncurslib">A Tour of the Ncurses Library</a>
+ <ul>
+ <li><a href="#loverview">Library Overview</a></li>
+
+ <li><a href="#engine">The Engine Room</a></li>
+
+ <li><a href="#input">Keyboard Input</a></li>
+
+ <li><a href="#mouse">Mouse Events</a></li>
+
+ <li><a href="#output">Output and Screen Updating</a></li>
+ </ul>
+ </li>
+
+ <li><a href="#fmnote">The Forms and Menu Libraries</a></li>
+
+ <li>
+ <a href="#tic">A Tour of the Terminfo Compiler</a>
+ <ul>
+ <li><a href="#nonuse">Translation of
+ Non-<strong>use</strong> Capabilities</a></li>
+
+ <li><a href="#uses">Use Capability Resolution</a></li>
+
+ <li><a href="#translation">Source-Form Translation</a></li>
+ </ul>
+ </li>
+
+ <li><a href="#utils">Other Utilities</a></li>
+
+ <li><a href="#style">Style Tips for Developers</a></li>
+
+ <li><a href="#port">Porting Hints</a></li>
+ </ul>
+ </div>
+
+ <h2><a name="abstract" id="abstract">Abstract</a></h2>
+
+ <p>This document is a hacker's tour of the
+ <strong>ncurses</strong> library and utilities. It discusses
+ design philosophy, implementation methods, and the conventions
+ used for coding and documentation. It is recommended reading for
+ anyone who is interested in porting, extending or improving the
+ package.</p>
+
+ <h2><a name="objective" id="objective">Objective of the
+ Package</a></h2>
+
+ <p>The objective of the <strong>ncurses</strong> package is to
+ provide a free software API for character-cell terminals and
+ terminal emulators with the following characteristics:</p>
+
+ <ul>
+ <li>Source-compatible with historical curses implementations
+ (including the original BSD curses and System V curses.</li>
+
+ <li>Conformant with the XSI Curses standard issued as part of
+ XPG4 by X/Open.</li>
+
+ <li>High-quality — stable and reliable code, wide
+ portability, good packaging, superior documentation.</li>
+
+ <li>Featureful — should eliminate as much of the drudgery
+ of C interface programming as possible, freeing programmers to
+ think at a higher level of design.</li>
+ </ul>
+
+ <p>These objectives are in priority order. So, for example,
+ source compatibility with older version must trump featurefulness
+ — we cannot add features if it means breaking the portion
+ of the API corresponding to historical curses versions.</p>
+
+ <h3><a name="whysvr4" id="whysvr4">Why System V Curses?</a></h3>
+
+ <p>We used System V curses as a model, reverse-engineering their
+ API, in order to fulfill the first two objectives.</p>
+
+ <p>System V curses implementations can support BSD curses
+ programs with just a recompilation, so by capturing the System V
+ API we also capture BSD's.</p>
+
+ <p>More importantly for the future, the XSI Curses standard
+ issued by X/Open is explicitly and closely modeled on System V.
+ So conformance with System V took us most of the way to
+ base-level XSI conformance.</p>
+
+ <h3><a name="extensions" id="extensions">How to Design
+ Extensions</a></h3>
+
+ <p>The third objective (standards conformance) requires that it
+ be easy to condition source code using <strong>ncurses</strong>
+ so that the absence of nonstandard extensions does not break the
+ code.</p>
+
+ <p>Accordingly, we have a policy of associating with each
+ nonstandard extension a feature macro, so that ncurses client
+ code can use this macro to condition in or out the code that
+ requires the <strong>ncurses</strong> extension.</p>
+
+ <p>For example, there is a macro
+ <code>NCURSES_MOUSE_VERSION</code> which XSI Curses does not
+ define, but which is defined in the <strong>ncurses</strong>
+ library header. You can use this to condition the calls to the
+ mouse API calls.</p>
+
+ <h2><a name="portability" id="portability">Portability and
+ Configuration</a></h2>
+
+ <p>Code written for <strong>ncurses</strong> may assume an
+ ANSI-standard C compiler and POSIX-compatible OS interface. It
+ may also assume the presence of a System-V-compatible
+ <em>select(2)</em> call.</p>
+
+ <p>We encourage (but do not require) developers to make the code
+ friendly to less-capable UNIX environments wherever possible.</p>
+
+ <p>We encourage developers to support OS-specific optimizations
+ and methods not available under POSIX/ANSI, provided only
+ that:</p>
+
+ <ul>
+ <li>All such code is properly conditioned so the build process
+ does not attempt to compile it under a plain ANSI/POSIX
+ environment.</li>
+
+ <li>Adding such implementation methods does not introduce
+ incompatibilities in the <strong>ncurses</strong> API between
+ platforms.</li>
+ </ul>
+
+ <p>We use GNU <code>autoconf(1)</code> as a tool to deal with
+ portability issues. The right way to leverage an OS-specific
+ feature is to modify the autoconf specification files
+ (configure.in and aclocal.m4) to set up a new feature macro,
+ which you then use to condition your code.</p>
+
+ <h2><a name="documentation" id="documentation">Documentation
+ Conventions</a></h2>
+
+ <p>There are three kinds of documentation associated with this
+ package. Each has a different preferred format:</p>
+
+ <ul>
+ <li>Package-internal files (README, INSTALL, TO-DO etc.)</li>
+
+ <li>Manual pages.</li>
+
+ <li>Everything else (i.e., narrative documentation).</li>
+ </ul>
+
+ <p>Our conventions are simple:</p>
+
+ <ol>
+ <li><strong>Maintain package-internal files in plain
+ text.</strong> The expected viewer for them is <em>more(1)</em> or
+ an editor window; there is no point in elaborate mark-up.</li>
+
+ <li><strong>Mark up manual pages in the man macros.</strong>
+ These have to be viewable through traditional <em>man(1)</em>
+ programs.</li>
+
+ <li><strong>Write everything else in HTML.</strong>
+ </li>
+ </ol>
+
+ <p>When in doubt, HTMLize a master and use <em>lynx(1)</em> to
+ generate plain ASCII (as we do for the announcement
+ document).</p>
+
+ <p>The reason for choosing HTML is that it is (a) well-adapted
+ for on-line browsing through viewers that are everywhere; (b)
+ more easily readable as plain text than most other mark-ups, if
+ you do not have a viewer; and (c) carries enough information that
+ you can generate a nice-looking printed version from it. Also, of
+ course, it make exporting things like the announcement document
+ to WWW pretty trivial.</p>
+
+ <h2><a name="bugtrack" id="bugtrack">How to Report Bugs</a></h2>
+
+ <p>The <a name="bugreport" id="bugreport">reporting address for
+ bugs</a> is <a href=
+ "mailto:bug-ncur...@gnu.org";>bug-ncur...@gnu.org</a>. This is a
+ majordomo list; to join, write to
+ <code>bug-ncurses-requ...@gnu.org</code> with a message
+ containing the line:</p>
+
+ <pre class="code-block">
+ subscribe <name>@<host.domain>
+</pre>
+ <p>The <code>ncurses</code> code is maintained by a small group
+ of volunteers. While we try our best to fix bugs promptly, we
+ simply do not have a lot of hours to spend on elementary
+ hand-holding. We rely on intelligent cooperation from our users.
+ If you think you have found a bug in <code>ncurses</code>, there
+ are some steps you can take before contacting us that will help
+ get the bug fixed quickly.</p>
+
+ <p>In order to use our bug-fixing time efficiently, we put people
+ who show us they have taken these steps at the head of our queue.
+ This means that if you do not, you will probably end up at the
+ tail end and have to wait a while.</p>
+
+ <ol>
+ <li><p>Develop a recipe to reproduce the bug.
+ <p>Bugs we can reproduce are likely to be fixed very quickly,
+ often within days. The most effective single thing you can do
+ to get a quick fix is develop a way we can duplicate the bad
+ behavior — ideally, by giving us source for a small,
+ portable test program that breaks the library. (Even better
+ is a keystroke recipe using one of the test programs provided
+ with the distribution.)</p>
+ </li>
+
+ <li><p>Try to reproduce the bug on a different terminal type.
+ <p>In our experience, most of the behaviors people report as
+ library bugs are actually due to subtle problems in terminal
+ descriptions. This is especially likely to be true if you are
+ using a traditional asynchronous terminal or PC-based
+ terminal emulator, rather than xterm or a UNIX console
+ entry.</p>
+
+ <p>It is therefore extremely helpful if you can tell us
+ whether or not your problem reproduces on other terminal
+ types. Usually you will have both a console type and xterm
+ available; please tell us whether or not your bug reproduces
+ on both.</p>
+
+ <p>If you have xterm available, it is also good to collect
+ xterm reports for different window sizes. This is especially
+ true if you normally use an unusual xterm window size —
+ a surprising number of the bugs we have seen are either
+ triggered or masked by these.</p>
+ </li>
+
+ <li><p>Generate and examine a trace file for the broken behavior.
+ <p>Recompile your program with the debugging versions of the
+ libraries. Insert a <code>trace()</code> call with the
+ argument set to <code>TRACE_UPDATE</code>. (See <a href=
+ "ncurses-intro.html#debugging">"Writing Programs with
+ NCURSES"</a> for details on trace levels.) Reproduce your
+ bug, then look at the trace file to see what the library was
+ actually doing.</p>
+
+ <p>Another frequent cause of apparent bugs is application
+ coding errors that cause the wrong things to be put on the
+ virtual screen. Looking at the virtual-screen dumps in the
+ trace file will tell you immediately if this is happening,
+ and save you from the possible embarrassment of being told
+ that the bug is in your code and is your problem rather than
+ ours.</p>
+
+ <p>If the virtual-screen dumps look correct but the bug
+ persists, it is possible to crank up the trace level to give
+ more and more information about the library's update actions
+ and the control sequences it issues to perform them. The test
+ directory of the distribution contains a tool for digesting
+ these logs to make them less tedious to wade through.</p>
+
+ <p>Often you will find terminfo problems at this stage by
+ noticing that the escape sequences put out for various
+ capabilities are wrong. If not, you are likely to learn
+ enough to be able to characterize any bug in the
+ screen-update logic quite exactly.</p>
+ </li>
+
+ <li><p>Report details and symptoms, not just interpretations.
+ <p>If you do the preceding two steps, it is very likely that
+ you will discover the nature of the problem yourself and be
+ able to send us a fix. This will create happy feelings all
+ around and earn you good karma for the first time you run
+ into a bug you really cannot characterize and fix
+ yourself.</p>
+
+ <p>If you are still stuck, at least you will know what to
+ tell us. Remember, we need details. If you guess about what
+ is safe to leave out, you are too likely to be wrong.</p>
+
+ <p>If your bug produces a bad update, include a trace file.
+ Try to make the trace at the <em>least</em> voluminous level
+ that pins down the bug. Logs that have been through
+ tracemunch are OK, it does not throw away any information
+ (actually they are better than un-munched ones because they
+ are easier to read).</p>
+
+ <p>If your bug produces a core-dump, please include a
+ symbolic stack trace generated by gdb(1) or your local
+ equivalent.</p>
+
+ <p>Tell us about every terminal on which you have reproduced
+ the bug — and every terminal on which you cannot.
+ Ideally, send us terminfo sources for all of these (yours
+ might differ from ours).</p>
+
+ <p>Include your ncurses version and your OS/machine type, of
+ course! You can find your ncurses version in the
+ <code>curses.h</code> file.</p>
+ </li>
+ </ol>
+
+ <p>If your problem smells like a logic error or in cursor
+ movement or scrolling or a bad capability, there are a couple of
+ tiny test frames for the library algorithms in the progs
+ directory that may help you isolate it. These are not part of the
+ normal build, but do have their own make productions.</p>
+
+ <p>The most important of these is <code>mvcur</code>, a test
+ frame for the cursor-movement optimization code. With this
+ program, you can see directly what control sequences will be
+ emitted for any given cursor movement or scroll/insert/delete
+ operations. If you think you have got a bad capability
+ identified, you can disable it and test again. The program is
+ command-driven and has on-line help.</p>
+
+ <p>If you think the vertical-scroll optimization is broken, or
+ just want to understand how it works better, build
+ <code>hashmap</code> and read the header comments of
+ <code>hardscroll.c</code> and <code>hashmap.c</code>; then try it
+ out. You can also test the hardware-scrolling optimization
+ separately with <code>hardscroll</code>.</p>
+
+ <h2><a name="ncurslib" id="ncurslib">A Tour of the Ncurses
+ Library</a></h2>
+
+ <h3><a name="loverview" id="loverview">Library Overview</a></h3>
+
+ <p>Most of the library is superstructure — fairly trivial
+ convenience interfaces to a small set of basic functions and data
+ structures used to manipulate the virtual screen (in particular,
+ none of this code does any I/O except through calls to more
+ fundamental modules described below). The files</p>
+
+ <blockquote>
+ <code>lib_addch.c lib_bkgd.c lib_box.c lib_chgat.c lib_clear.c
+ lib_clearok.c lib_clrbot.c lib_clreol.c lib_colorset.c
+ lib_data.c lib_delch.c lib_delwin.c lib_echo.c lib_erase.c
+ lib_gen.c lib_getstr.c lib_hline.c lib_immedok.c lib_inchstr.c
+ lib_insch.c lib_insdel.c lib_insstr.c lib_instr.c
+ lib_isendwin.c lib_keyname.c lib_leaveok.c lib_move.c
+ lib_mvwin.c lib_overlay.c lib_pad.c lib_printw.c lib_redrawln.c
+ lib_scanw.c lib_screen.c lib_scroll.c lib_scrollok.c
+ lib_scrreg.c lib_set_term.c lib_slk.c lib_slkatr_set.c
+ lib_slkatrof.c lib_slkatron.c lib_slkatrset.c lib_slkattr.c
+ lib_slkclear.c lib_slkcolor.c lib_slkinit.c lib_slklab.c
+ lib_slkrefr.c lib_slkset.c lib_slktouch.c lib_touch.c
+ lib_unctrl.c lib_vline.c lib_wattroff.c lib_wattron.c
+ lib_window.c</code>
+ </blockquote>
+
+ <p>are all in this category. They are very unlikely to need
+ change, barring bugs or some fundamental reorganization in the
+ underlying data structures.</p>
+
+ <p>These files are used only for debugging support:</p>
+
+ <blockquote>
+ <code>lib_trace.c lib_traceatr.c lib_tracebits.c lib_tracechr.c
+ lib_tracedmp.c lib_tracemse.c trace_buf.c</code>
+ </blockquote>
+
+ <p>It is rather unlikely you will ever need to change these,
+ unless you want to introduce a new debug trace level for some
+ reason.</p>
+
+ <p>There is another group of files that do direct I/O via
+ <em>tputs()</em>, computations on the terminal capabilities, or
+ queries to the OS environment, but nevertheless have only fairly
+ low complexity. These include:</p>
+
+ <blockquote>
+ <code>lib_acs.c lib_beep.c lib_color.c lib_endwin.c
+ lib_initscr.c lib_longname.c lib_newterm.c lib_options.c
+ lib_termcap.c lib_ti.c lib_tparm.c lib_tputs.c lib_vidattr.c
+ read_entry.c.</code>
+ </blockquote>
+
+ <p>They are likely to need revision only if ncurses is being
+ ported to an environment without an underlying terminfo
+ capability representation.</p>
+
+ <p>These files have serious hooks into the tty driver and signal
+ facilities:</p>
+
+ <blockquote>
+ <code>lib_kernel.c lib_baudrate.c lib_raw.c lib_tstp.c
+ lib_twait.c</code>
+ </blockquote>
+
+ <p>If you run into porting snafus moving the package to another
+ UNIX, the problem is likely to be in one of these files. The file
+ <code>lib_print.c</code> uses sleep(2) and also falls in this
+ category.</p>
+
+ <p>Almost all of the real work is done in the files</p>
+
+ <blockquote>
+ <code>hardscroll.c hashmap.c lib_addch.c lib_doupdate.c
+ lib_getch.c lib_mouse.c lib_mvcur.c lib_refresh.c lib_setup.c
+ lib_vidattr.c</code>
+ </blockquote>
+
+ <p>Most of the algorithmic complexity in the library lives in
+ these files. If there is a real bug in <strong>ncurses</strong>
+ itself, it is probably here. We will tour some of these files in
+ detail below (see <a href="#engine">The Engine Room</a>).</p>
+
+ <p>Finally, there is a group of files that is actually most of
+ the terminfo compiler. The reason this code lives in the
+ <strong>ncurses</strong> library is to support fallback to
+ /etc/termcap. These files include</p>
+
+ <blockquote>
+ <code>alloc_entry.c captoinfo.c comp_captab.c comp_error.c
+ comp_hash.c comp_parse.c comp_scan.c parse_entry.c
+ read_termcap.c write_entry.c</code>
+ </blockquote>
+
+ <p>We will discuss these in the compiler tour.</p>
+
+ <h3><a name="engine" id="engine">The Engine Room</a></h3>
+
+ <h4><a name="input" id="input">Keyboard Input</a></h4>
+
+ <p>All <code>ncurses</code> input funnels through the function
+ <code>wgetch()</code>, defined in <code>lib_getch.c</code>. This
+ function is tricky; it has to poll for keyboard and mouse events
+ and do a running match of incoming input against the set of
+ defined special keys.</p>
+
+ <p>The central data structure in this module is a FIFO queue,
+ used to match multiple-character input sequences against
+ special-key capabilities; also to implement pushback via
+ <code>ungetch()</code>.</p>
+
+ <p>The <code>wgetch()</code> code distinguishes between function
+ key sequences and the same sequences typed manually by doing a
+ timed wait after each input character that could lead a function
+ key sequence. If the entire sequence takes less than 1 second, it
+ is assumed to have been generated by a function key press.</p>
+
+ <p>Hackers bruised by previous encounters with variant
+ <code>select(2)</code> calls may find the code in
+ <code>lib_twait.c</code> interesting. It deals with the problem
+ that some BSD selects do not return a reliable time-left value.
+ The function <code>timed_wait()</code> effectively simulates a
+ System V select.</p>
+
+ <h4><a name="mouse" id="mouse">Mouse Events</a></h4>
+
+ <p>If the mouse interface is active, <code>wgetch()</code> polls
+ for mouse events each call, before it goes to the keyboard for
+ input. It is up to <code>lib_mouse.c</code> how the polling is
+ accomplished; it may vary for different devices.</p>
+
+ <p>Under xterm, however, mouse event notifications come in via
+ the keyboard input stream. They are recognized by having the
+ <strong>kmous</strong> capability as a prefix. This is kind of
+ klugey, but trying to wire in recognition of a mouse key prefix
+ without going through the function-key machinery would be just
+ too painful, and this turns out to imply having the prefix
+ somewhere in the function-key capabilities at terminal-type
+ initialization.</p>
+
+ <p>This kluge only works because <strong>kmous</strong> is not
+ actually used by any historic terminal type or curses
+ implementation we know of. Best guess is it is a relic of some
+ forgotten experiment in-house at Bell Labs that did not leave any
+ traces in the publicly-distributed System V terminfo files. If
+ System V or XPG4 ever gets serious about using it again, this
+ kluge may have to change.</p>
+
+ <p>Here are some more details about mouse event handling:</p>
+
+ <p>The <code>lib_mouse()</code> code is logically split into a
+ lower level that accepts event reports in a device-dependent
+ format and an upper level that parses mouse gestures and filters
+ events. The mediating data structure is a circular queue of event
+ structures.</p>
+
+ <p>Functionally, the lower level's job is to pick up primitive
+ events and put them on the circular queue. This can happen in one
+ of two ways: either (a) <code>_nc_mouse_event()</code> detects a
+ series of incoming mouse reports and queues them, or (b) code in
+ <code>lib_getch.c</code> detects the <strong>kmous</strong>
+ prefix in the keyboard input stream and calls _nc_mouse_inline to
+ queue up a series of adjacent mouse reports.</p>
+
+ <p>In either case, <code>_nc_mouse_parse()</code> should be
+ called after the series is accepted to parse the digested mouse
+ reports (low-level events) into a gesture (a high-level or
+ composite event).</p>
+
+ <h4><a name="output" id="output">Output and Screen Updating</a></h4>
+
+ <p>With the single exception of character echoes during a
+ <code>wgetnstr()</code> call (which simulates cooked-mode line
+ editing in an ncurses window), the library normally does all its
+ output at refresh time.</p>
+
+ <p>The main job is to go from the current state of the screen (as
+ represented in the <code>curscr</code> window structure) to the
+ desired new state (as represented in the <code>newscr</code>
+ window structure), while doing as little I/O as possible.</p>
+
+ <p>The brains of this operation are the modules
+ <code>hashmap.c</code>, <code>hardscroll.c</code> and
+ <code>lib_doupdate.c</code>; the latter two use
+ <code>lib_mvcur.c</code>. Essentially, what happens looks like
+ this:</p>
+
+ <ul>
+ <li>
+ <p>The <code>hashmap.c</code> module tries to detect vertical
+ motion changes between the real and virtual screens. This
+ information is represented by the oldindex members in the
+ newscr structure. These are modified by vertical-motion and
+ clear operations, and both are re-initialized after each
+ update. To this change-journalling information, the hashmap
+ code adds deductions made using a modified Heckel algorithm
+ on hash values generated from the line contents.</p>
+ </li>
+
+ <li>
+ <p>The <code>hardscroll.c</code> module computes an optimum
+ set of scroll, insertion, and deletion operations to make the
+ indices match. It calls <code>_nc_mvcur_scrolln()</code> in
+ <code>lib_mvcur.c</code> to do those motions.</p>
+ </li>
+
+ <li>
+ <p>Then <code>lib_doupdate.c</code> goes to work. Its job is
+ to do line-by-line transformations of <code>curscr</code>
+ lines to <code>newscr</code> lines. Its main tool is the
+ routine <code>mvcur()</code> in <code>lib_mvcur.c</code>.
+ This routine does cursor-movement optimization, attempting to
+ get from given screen location A to given location B in the
+ fewest output characters possible.</p>
+ </li>
+ </ul>
+
+ <p>If you want to work on screen optimizations, you should use
+ the fact that (in the trace-enabled version of the library)
+ enabling the <code>TRACE_TIMES</code> trace level causes a report
+ to be emitted after each screen update giving the elapsed time
+ and a count of characters emitted during the update. You can use
+ this to tell when an update optimization improves efficiency.</p>
+
+ <p>In the trace-enabled version of the library, it is also
+ possible to disable and re-enable various optimizations at
+ runtime by tweaking the variable
+ <code>_nc_optimize_enable</code>. See the file
+ <code>include/curses.h.in</code> for mask values, near the
+ end.</p>
+
+ <h2><a name="fmnote" id="fmnote">The Forms and Menu Libraries</a></h2>
+
+ <p>The forms and menu libraries should work reliably in any
+ environment you can port ncurses to. The only portability issue
+ anywhere in them is what flavor of regular expressions the
+ built-in form field type TYPE_REGEXP will recognize.</p>
+
+ <p>The configuration code prefers the POSIX regex facility,
+ modeled on System V's, but will settle for BSD regexps if the
+ former is not available.</p>
+
+ <p>Historical note: the panels code was written primarily to
+ assist in porting u386mon 2.0 (comp.sources.misc v14i001-4) to
+ systems lacking panels support; u386mon 2.10 and beyond use it.
+ This version has been slightly cleaned up for
+ <code>ncurses</code>.</p>
+
+ <h2><a name="tic" id="tic">A Tour of the Terminfo Compiler</a></h2>
+
+ <p>The <strong>ncurses</strong> implementation of
+ <strong>tic</strong> is rather complex internally; it has to do a
+ trying combination of missions. This starts with the fact that,
+ in addition to its normal duty of compiling terminfo sources into
+ loadable terminfo binaries, it has to be able to handle termcap
+ syntax and compile that too into terminfo entries.</p>
+
+ <p>The implementation therefore starts with a table-driven,
+ dual-mode lexical analyzer (in <code>comp_scan.c</code>). The
+ lexer chooses its mode (termcap or terminfo) based on the first
+ “,” or “:” it finds in each entry. The
+ lexer does all the work of recognizing capability names and
+ values; the grammar above it is trivial, just "parse entries till
+ you run out of file".</p>
+
+ <h3><a name="nonuse" id="nonuse">Translation of
+ Non-<strong>use</strong> Capabilities</a></h3>
+
+ <p>Translation of most things besides <strong>use</strong>
+ capabilities is pretty straightforward. The lexical analyzer's
+ tokenizer hands each capability name to a hash function, which
+ drives a table lookup. The table entry yields an index which is
+ used to look up the token type in another table, and controls
+ interpretation of the value.</p>
+
+ <p>One possibly interesting aspect of the implementation is the
+ way the compiler tables are initialized. All the tables are
+ generated by various awk/sed/sh scripts from a master table
+ <code>include/Caps</code>; these scripts actually write C
+ initializers which are linked to the compiler. Furthermore, the
+ hash table is generated in the same way, so it doesn't have to be
+ generated at compiler startup time (another benefit of this
+ organization is that the hash table can be in shareable text
+ space).</p>
+
+ <p>Thus, adding a new capability is usually pretty trivial, just
+ a matter of adding one line to the <code>include/Caps</code>
+ file. We will have more to say about this in the section on
+ <a href="#translation">Source-Form Translation</a>.</p>
+
+ <h3><a name="uses" id="uses">Use Capability Resolution</a></h3>
+
+ <p>The background problem that makes <strong>tic</strong> tricky
+ is not the capability translation itself, it is the resolution of
+ <strong>use</strong> capabilities. Older versions would not
+ handle forward <strong>use</strong> references for this reason
+ (that is, a using terminal always had to follow its use target in
+ the source file). By doing this, they got away with a simple
+ implementation tactic; compile everything as it blows by, then
+ resolve uses from compiled entries.</p>
+
+ <p>This will not do for <strong>ncurses</strong>. The problem is
+ that that the whole compilation process has to be embeddable in
+ the <strong>ncurses</strong> library so that it can be called by
+ the startup code to translate termcap entries on the fly. The
+ embedded version cannot go promiscuously writing everything it
+ translates out to disk — for one thing, it will typically
+ be running with non-root permissions.</p>
+
+ <p>So our <strong>tic</strong> is designed to parse an entire
+ terminfo file into a doubly-linked circular list of entry
+ structures in-core, and then do <strong>use</strong> resolution
+ in-memory before writing everything out. This design has other
+ advantages: it makes forward and back use-references equally easy
+ (so we get the latter for free), and it makes checking for name
+ collisions before they are written out easy to do.</p>
+
+ <p>And this is exactly how the embedded version works. But the
+ stand-alone user-accessible version of <strong>tic</strong>
+ partly reverts to the historical strategy; it writes to disk (not
+ keeping in core) any entry with no <strong>use</strong>
+ references.</p>
+
+ <p>This is strictly a core-economy kluge, implemented because the
+ terminfo master file is large enough that some core-poor systems
+ swap like crazy when you compile it all in memory...there have
+ been reports of this process taking <strong>three hours</strong>,
+ rather than the twenty seconds or less typical on the author's
+ development box.</p>
+
+ <p>So. The executable <strong>tic</strong> passes the
+ entry-parser a hook that <em>immediately</em> writes out the
+ referenced entry if it has no use capabilities. The compiler main
+ loop refrains from adding the entry to the in-core list when this
+ hook fires. If some other entry later needs to reference an entry
+ that got written immediately, that is OK; the resolution code
+ will fetch it off disk when it cannot find it in core.</p>
+
+ <p>Name collisions will still be detected, just not as cleanly.
+ The <code>write_entry()</code> code complains before overwriting
+ an entry that postdates the time of <strong>tic</strong>'s first
+ call to <code>write_entry()</code>, Thus it will complain about
+ overwriting entries newly made during the <strong>tic</strong>
+ run, but not about overwriting ones that predate it.</p>
+
+ <h3><a name="translation" id="translation">Source-Form
+ Translation</a></h3>
+
+ <p>Another use of <strong>tic</strong> is to do source
+ translation between various termcap and terminfo formats. There
+ are more variants out there than you might think; the ones we
+ know about are described in the <strong>captoinfo(1)</strong>
+ manual page.</p>
+
+ <p>The translation output code (<code>dump_entry()</code> in
+ <code>ncurses/dump_entry.c</code>) is shared with the
+ <strong>infocmp(1)</strong> utility. It takes the same internal
+ representation used to generate the binary form and dumps it to
+ standard output in a specified format.</p>
+
+ <p>The <code>include/Caps</code> file has a header comment
+ describing ways you can specify source translations for
+ nonstandard capabilities just by altering the master table. It is
+ possible to set up capability aliasing or tell the compiler to
+ plain ignore a given capability without writing any C code at
+ all.</p>
+
+ <p>For circumstances where you need to do algorithmic
+ translation, there are functions in <code>parse_entry.c</code>
+ called after the parse of each entry that are specifically
+ intended to encapsulate such translations. This, for example, is
+ where the AIX <strong>box1</strong> capability get translated to
+ an <strong>acsc</strong> string.</p>
+
+ <h2><a name="utils" id="utils">Other Utilities</a></h2>
+
+ <p>The <strong>infocmp</strong> utility is just a wrapper around
+ the same entry-dumping code used by <strong>tic</strong> for
+ source translation. Perhaps the one interesting aspect of the
+ code is the use of a predicate function passed in to
+ <code>dump_entry()</code> to control which capabilities are
+ dumped. This is necessary in order to handle both the ordinary
+ De-compilation case and entry difference reporting.</p>
+
+ <p>The <strong>tput</strong> and <strong>clear</strong> utilities
+ just do an entry load followed by a <code>tputs()</code> of a
+ selected capability.</p>
+
+ <h2><a name="style" id="style">Style Tips for Developers</a></h2>
+
+ <p>See the TO-DO file in the top-level directory of the source
+ distribution for additions that would be particularly useful.</p>
+
+ <p>The prefix <code>_nc_</code> should be used on library public
+ functions that are not part of the curses API in order to prevent
+ pollution of the application namespace. If you have to add to or
+ modify the function prototypes in curses.h.in, read
+ ncurses/MKlib_gen.sh first so you can avoid breaking XSI
+ conformance. Please join the ncurses mailing list. See the
+ INSTALL file in the top level of the distribution for details on
+ the list.</p>
+
+ <p>Look for the string <code>FIXME</code> in source files to tag
+ minor bugs and potential problems that could use fixing.</p>
+
+ <p>Do not try to auto-detect OS features in the main body of the
+ C code. That is the job of the configuration system.</p>
+
+ <p>To hold down complexity, do make your code data-driven.
+ Especially, if you can drive logic from a table filtered out of
+ <code>include/Caps</code>, do it. If you find you need to augment
+ the data in that file in order to generate the proper table, that
+ is still preferable to ad-hoc code — that is why the fifth
+ field (flags) is there.</p>
+
+ <p>Have fun!</p>
+
+ <h2><a name="port" id="port">Porting Hints</a></h2>
+
+ <p>The following notes are intended to be a first step towards
+ DOS and Macintosh ports of the ncurses libraries.</p>
+
+ <p>The following library modules are “pure curses”;
+ they operate only on the curses internal structures, do all
+ output through other curses calls (not including
+ <code>tputs()</code> and <code>putp()</code>) and do not call any
+ other UNIX routines such as signal(2) or the stdio library. Thus,
+ they should not need to be modified for single-terminal
+ ports.</p>
+
+ <blockquote>
+ <code>lib_addch.c lib_addstr.c lib_bkgd.c lib_box.c lib_clear.c
+ lib_clrbot.c lib_clreol.c lib_delch.c lib_delwin.c lib_erase.c
+ lib_inchstr.c lib_insch.c lib_insdel.c lib_insstr.c
+ lib_keyname.c lib_move.c lib_mvwin.c lib_newwin.c lib_overlay.c
+ lib_pad.c lib_printw.c lib_refresh.c lib_scanw.c lib_scroll.c
+ lib_scrreg.c lib_set_term.c lib_touch.c lib_tparm.c lib_tputs.c
+ lib_unctrl.c lib_window.c panel.c</code>
+ </blockquote>
+
+ <p>This module is pure curses, but calls outstr():</p>
+
+ <blockquote>
+ <code>lib_getstr.c</code>
+ </blockquote>
+
+ <p>These modules are pure curses, except that they use
+ <code>tputs()</code> and <code>putp()</code>:</p>
+
+ <blockquote>
+ <code>lib_beep.c lib_color.c lib_endwin.c lib_options.c
+ lib_slk.c lib_vidattr.c</code>
+ </blockquote>
+
+ <p>This modules assist in POSIX emulation on non-POSIX
+ systems:</p>
+
+ <dl>
+ <dt>sigaction.c</dt>
+
+ <dd>signal calls</dd>
+ </dl>
+
+ <p>The following source files will not be needed for a
+ single-terminal-type port.</p>
+
+ <blockquote>
+ <code>alloc_entry.c captoinfo.c clear.c comp_captab.c
+ comp_error.c comp_hash.c comp_main.c comp_parse.c comp_scan.c
+ dump_entry.c infocmp.c parse_entry.c read_entry.c tput.c
+ write_entry.c</code>
+ </blockquote>
+
+ <p>The following modules will use
+ open()/read()/write()/close()/lseek() on files, but no other OS
+ calls.</p>
+
+ <dl>
+ <dt>lib_screen.c</dt>
+
+ <dd>used to read/write screen dumps</dd>
+
+ <dt>lib_trace.c</dt>
+
+ <dd>used to write trace data to the logfile</dd>
+ </dl>
+
+ <p>Modules that would have to be modified for a port start
+ here:</p>
+
+ <p>The following modules are “pure curses” but
+ contain assumptions inappropriate for a memory-mapped port.</p>
+
+ <dl>
+ <dt>lib_longname.c</dt>
+
+ <dd>assumes there may be multiple terminals</dd>
+
+ <dt>lib_acs.c</dt>
+
+ <dd>assumes acs_map as a double indirection</dd>
+
+ <dt>lib_mvcur.c</dt>
+
+ <dd>assumes cursor moves have variable cost</dd>
+
+ <dt>lib_termcap.c</dt>
+
+ <dd>assumes there may be multiple terminals</dd>
+
+ <dt>lib_ti.c</dt>
+
+ <dd>assumes there may be multiple terminals</dd>
+ </dl>
+
+ <p>The following modules use UNIX-specific calls:</p>
+
+ <dl>
+ <dt>lib_doupdate.c</dt>
+
+ <dd>input checking</dd>
+
+ <dt>lib_getch.c</dt>
+
+ <dd>read()</dd>
+
+ <dt>lib_initscr.c</dt>
+
+ <dd>getenv()</dd>
+
+ <dt>lib_newterm.c</dt>
+
+ <dt>lib_baudrate.c</dt>
+
+ <dt>lib_kernel.c</dt>
+
+ <dd>various tty-manipulation and system calls</dd>
+
+ <dt>lib_raw.c</dt>
+
+ <dd>various tty-manipulation calls</dd>
+
+ <dt>lib_setup.c</dt>
+
+ <dd>various tty-manipulation calls</dd>
+
+ <dt>lib_restart.c</dt>
+
+ <dd>various tty-manipulation calls</dd>
+
+ <dt>lib_tstp.c</dt>
+
+ <dd>signal-manipulation calls</dd>
+
+ <dt>lib_twait.c</dt>
+
+ <dd>gettimeofday(), select().</dd>
+ </dl>
+
+ <hr>
+
+ <address>
+ Eric S. Raymond <e...@snark.thyrsus.com>
+ </address>
+ (Note: This is <em>not</em> the <a href="#bugtrack">bug
+ address</a>!)
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