git: 80cd5ab568e2 - stable/14 - ncurses: readd 2 html files in the doc (fix MK_HTML=yes)
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Date: Thu, 27 Jun 2024 09:08:24 UTC
The branch stable/14 has been updated by bapt: URL: https://cgit.FreeBSD.org/src/commit/?id=80cd5ab568e26f185cd2dad3a7766514cf4a6443 commit 80cd5ab568e26f185cd2dad3a7766514cf4a6443 Author: Baptiste Daroussin <bapt@FreeBSD.org> AuthorDate: 2024-06-20 13:33:23 +0000 Commit: Baptiste Daroussin <bapt@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 <imb@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-ncurses@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-ncurses@gnu.org">bug-ncurses@gnu.org</a>. This is a + majordomo list; to join, write to + <code>bug-ncurses-request@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 <esr@snark.thyrsus.com> + </address> + (Note: This is <em>not</em> the <a href="#bugtrack">bug + address</a>!) *** 3398 LINES SKIPPED ***