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+PDCurses Implementor's Guide
+============================
+
+Version 1.3 - 200?/??/?? - notes about official ports
+Version 1.2 - 2007/07/11 - added PDC_init_pair(), PDC_pair_content(),
+ version history; removed pdc_atrtab
+Version 1.1 - 2007/06/06 - minor cosmetic change
+Version 1.0 - 2007/04/01 - initial revision
+
+This document is for those wishing to port PDCurses to a new platform,
+or just wanting to better understand how it works. Nothing here should
+be needed for application programming; for that, refer to PDCurses.txt,
+as built in doc/, or distributed as a file separate from this source
+package. This document assumes that you've read the user-level
+documentation and are very familiar with application-level curses
+programming.
+
+If you want to submit your port for possible inclusion into the main
+PDCurses distribution, please follow these guidelines:
+
+ - Don't modify anything in the pdcurses directory or in other port
+ directories. Don't modify curses.h or curspriv.h unless absolutely
+ necessary. (And prefer modifying curspriv.h over curses.h.)
+
+ - Use the same indentation style, naming and scope conventions as the
+ existing code.
+
+ - Release all your code to the public domain -- no copyright. Code
+ under GPL, BSD, etc. will not be accepted.
+
+
+DATA STRUCTURES
+---------------
+
+A port of PDCurses must provide acs_map[], a 128-element array of
+chtypes, with values laid out based on the Alternate Character Set of
+the VT100 (see curses.h). PDC_transform_line() must use this table; when
+it encounters a chtype with the A_ALTCHARSET flag set, and an A_CHARTEXT
+value in the range 0-127, it must render it using the A_CHARTEXT portion
+of the corresponding value from this table, instead of the original
+value. Also, values may be read from this table by apps, and passed
+through functions such as waddch(), which does no special processing on
+control characters (0-31 and 127) when the A_ALTCHARSET flag is set.
+Thus, any control characters used in acs_map[] should also have the
+A_ALTCHARSET flag set. Implementations should provide suitable values
+for all the ACS_ macros defined in curses.h; other values in the table
+should be filled with their own indices (e.g., acs_map['E'] == 'E'). The
+table can be either hardwired, or filled by PDC_scr_open(). Existing
+ports define it in pdcdisp.c, but this is not required.
+
+
+FUNCTIONS
+---------
+
+A port of PDCurses must implement the following functions, with extern
+scope. These functions are traditionally divided into several modules,
+as indicated below; this division is not required (only the functions
+are), but may make it easier to follow for someone familiar with the
+existing ports.
+
+Any other functions you create as part of your implementation should
+have static scope, if possible. If they can't be static, they should be
+named with the "PDC_" prefix. This minimizes the risk of collision with
+an application's choices.
+
+Current PDCurses style also uses a single leading underscore with the
+name of any static function; and modified BSD/Allman-style indentation,
+approximately equivalent to "indent -kr -i8 -bl -bli0", with adjustments
+to keep every line under 80 columns. This isn't essential, but a
+consistent style helps readability.
+
+
+pdcdisp.c:
+----------
+
+void PDC_gotoyx(int y, int x);
+
+Move the physical cursor (as opposed to the logical cursor affected by
+wmove()) to the given location. This is called mainly from doupdate().
+In general, this function need not compare the old location with the new
+one, and should just move the cursor unconditionally.
+
+void PDC_transform_line(int lineno, int x, int len, const chtype *srcp);
+
+The core output routine. It takes len chtype entities from srcp (a
+pointer into curscr) and renders them to the physical screen at line
+lineno, column x. It must also translate characters 0-127 via acs_map[],
+if they're flagged with A_ALTCHARSET in the attribute portion of the
+chtype.
+
+
+pdcgetsc.c:
+-----------
+
+int PDC_get_columns(void);
+
+Returns the size of the screen in columns. It's used in resize_term() to
+set the new value of COLS. (Some existing implementations also call it
+internally from PDC_scr_open(), but this is not required.)
+
+int PDC_get_cursor_mode(void);
+
+Returns the size/shape of the cursor. The format of the result is
+unspecified, except that it must be returned as an int. This function is
+called from initscr(), and the result is stored in SP->orig_cursor,
+which is used by PDC_curs_set() to determine the size/shape of the
+cursor in normal visibility mode (curs_set(1)).
+
+int PDC_get_rows(void);
+
+Returns the size of the screen in rows. It's used in resize_term() to
+set the new value of LINES. (Some existing implementations also call it
+internally from PDC_scr_open(), but this is not required.)
+
+
+pdckbd.c:
+---------
+
+bool PDC_check_key(void);
+
+Keyboard/mouse event check, called from wgetch(). Returns TRUE if
+there's an event ready to process. This function must be non-blocking.
+
+void PDC_flushinp(void);
+
+This is the core of flushinp(). It discards any pending key or mouse
+events, removing them from any internal queue and from the OS queue, if
+applicable.
+
+int PDC_get_key(void);
+
+Get the next available key, or mouse event (indicated by a return of
+KEY_MOUSE), and remove it from the OS' input queue, if applicable. This
+function is called from wgetch(). This function may be blocking, and
+traditionally is; but it need not be. If a valid key or mouse event
+cannot be returned, for any reason, this function returns -1. Valid keys
+are those that fall within the appropriate character set, or are in the
+list of special keys found in curses.h (KEY_MIN through KEY_MAX). When
+returning a special key code, this routine must also set SP->key_code to
+TRUE; otherwise it must set it to FALSE. If SP->return_key_modifiers is
+TRUE, this function may return modifier keys (shift, control, alt),
+pressed alone, as special key codes; if SP->return_key_modifiers is
+FALSE, it must not. If modifier keys are returned, it should only happen
+if no other keys were pressed in the meantime; i.e., the return should
+happen on key up. But if this is not possible, it may return the
+modifier keys on key down (if and only if SP->return_key_modifiers is
+TRUE).
+
+int PDC_modifiers_set(void);
+
+Called from PDC_return_key_modifiers(). If your platform needs to do
+anything in response to a change in SP->return_key_modifiers, do it
+here. Returns OK or ERR, which is passed on by the caller.
+
+int PDC_mouse_set(void);
+
+Called by mouse_set(), mouse_on(), and mouse_off() -- all the functions
+that modify SP->_trap_mbe. If your platform needs to do anything in
+response to a change in SP->_trap_mbe (for example, turning the mouse
+cursor on or off), do it here. Returns OK or ERR, which is passed on by
+the caller.
+
+void PDC_set_keyboard_binary(bool on);
+
+Set keyboard input to "binary" mode. If you need to do something to keep
+the OS from processing ^C, etc. on your platform, do it here. TRUE turns
+the mode on; FALSE reverts it. This function is called from raw() and
+noraw().
+
+
+pdcscrn.c:
+----------
+
+bool PDC_can_change_color(void);
+
+Returns TRUE if init_color() and color_content() give meaningful
+results, FALSE otherwise. Called from can_change_color().
+
+int PDC_color_content(short color, short *red, short *green, short *blue);
+
+The core of color_content(). This does all the work of that function,
+except checking for values out of range and null pointers.
+
+int PDC_init_color(short color, short red, short green, short blue);
+
+The core of init_color(). This does all the work of that function,
+except checking for values out of range.
+
+void PDC_init_pair(short pair, short fg, short bg);
+
+The core of init_pair(). This does all the work of that function, except
+checking for values out of range. The values passed to this function
+should be returned by a call to PDC_pair_content() with the same pair
+number. PDC_transform_line() should use the specified colors when
+rendering a chtype with the given pair number.
+
+int PDC_pair_content(short pair, short *fg, short *bg);
+
+The core of pair_content(). This does all the work of that function,
+except checking for values out of range and null pointers.
+
+void PDC_reset_prog_mode(void);
+
+The non-portable functionality of reset_prog_mode() is handled here --
+whatever's not done in _restore_mode(). In current ports: In OS/2, this
+sets the keyboard to binary mode; in Win32, it enables or disables the
+mouse pointer to match the saved mode; in others it does nothing.
+
+void PDC_reset_shell_mode(void);
+
+The same thing, for reset_shell_mode(). In OS/2 and Win32, it restores
+the default console mode; in others it does nothing.
+
+int PDC_resize_screen(int nlines, int ncols);
+
+This does the main work of resize_term(). It may respond to non-zero
+parameters, by setting the screen to the specified size; to zero
+parameters, by setting the screen to a size chosen by the user at
+runtime, in an unspecified way (e.g., by dragging the edges of the
+window); or both. It may also do nothing, if there's no appropriate
+action for the platform.
+
+void PDC_restore_screen_mode(int i);
+
+Called from _restore_mode() in kernel.c, this function does the actual
+mode changing, if applicable. Currently used only in DOS and OS/2.
+
+void PDC_save_screen_mode(int i);
+
+Called from _save_mode() in kernel.c, this function saves the actual
+screen mode, if applicable. Currently used only in DOS and OS/2.
+
+void PDC_scr_close(void);
+
+The platform-specific part of endwin(). It may restore the image of the
+original screen saved by PDC_scr_open(), if the PDC_RESTORE_SCREEN
+environment variable is set; either way, if using an existing terminal,
+this function should restore it to the mode it had at startup, and move
+the cursor to the lower left corner. (The X11 port does nothing.)
+
+void PDC_scr_free(void);
+
+Frees the memory for SP allocated by PDC_scr_open(). Called by
+delscreen().
+
+int PDC_scr_open(int argc, char **argv);
+
+The platform-specific part of initscr(). It's actually called from
+Xinitscr(); the arguments, if present, correspond to those used with
+main(), and may be used to set the title of the terminal window, or for
+other, platform-specific purposes. (The arguments are currently used
+only in X11.) PDC_scr_open() must allocate memory for SP, and must
+initialize acs_map[] (unless it's preset) and several members of SP,
+including lines, cols, mouse_wait, orig_attr (and if orig_attr is TRUE,
+orig_fore and orig_back), mono, _restore and _preserve. (Although SP is
+used the same way in all ports, it's allocated here in order to allow
+the X11 port to map it to a block of shared memory.) If using an
+existing terminal, and the environment variable PDC_RESTORE_SCREEN is
+set, this function may also store the existing screen image for later
+restoration by PDC_scr_close().
+
+
+pdcsetsc.c:
+-----------
+
+int PDC_curs_set(int visibility);
+
+Called from curs_set(). Changes the appearance of the cursor -- 0 turns
+it off, 1 is normal (the terminal's default, if applicable, as
+determined by SP->orig_cursor), and 2 is high visibility. The exact
+appearance of these modes is not specified.
+
+
+pdcutil.c:
+----------
+
+void PDC_beep(void);
+
+Emits a short audible beep. If this is not possible on your platform,
+you must set SP->audible to FALSE during initialization (i.e., from
+PDC_scr_open() -- not here); otherwise, set it to TRUE. This function is
+called from beep().
+
+void PDC_napms(int ms);
+
+This is the core delay routine, called by napms(). It pauses for about
+(the X/Open spec says "at least") ms milliseconds, then returns. High
+degrees of accuracy and precision are not expected (though desirable, if
+you can achieve them). More important is that this function gives back
+the process' time slice to the OS, so that PDCurses idles at low CPU
+usage.
+
+const char *PDC_sysname(void);
+
+Returns a short string describing the platform, such as "DOS" or "X11".
+This is used by longname(). It must be no more than 100 characters; it
+should be much, much shorter (existing platforms use no more than 5).
+
+--------------------------------------------------------------------------
+
+The following functions are implemented in the platform directories, but
+are accessed directly by apps. Refer to the user documentation for their
+descriptions:
+
+
+pdcclip.c:
+----------
+
+int PDC_clearclipboard(void);
+int PDC_freeclipboard(char *contents);
+int PDC_getclipboard(char **contents, long *length);
+int PDC_setclipboard(const char *contents, long length);
+
+
+pdckbd.c:
+---------
+
+unsigned long PDC_get_input_fd(void);
+
+
+pdcsetsc.c:
+-----------
+
+int PDC_set_blink(bool blinkon);
+void PDC_set_title(const char *title);