[wip] draw_images(): w, h, spos -> box screen_img; img_box -> pixel_box

[elinks/images.git] / src / terminal / kbd.c

/** Support for keyboard interface
 * @file
 *
 * @todo TODO: move stuff from here to itrm.{c,h} and mouse.{c,h}
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <stdlib.h>
#include <string.h>
#ifdef HAVE_TERMIOS_H
#include <termios.h>
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef __hpux__
#include <limits.h>
#define HPUX_PIPE       (len > PIPE_BUF || errno != EAGAIN)
#else
#define HPUX_PIPE       1
#endif

#include "elinks.h"

#include "config/options.h"
#include "intl/gettext/libintl.h"
#include "main/select.h"
#include "main/timer.h"
#include "osdep/ascii.h"
#include "osdep/osdep.h"
#include "osdep/image.h"
#include "terminal/hardio.h"
#include "terminal/itrm.h"
#include "terminal/kbd.h"
#include "terminal/mouse.h"
#include "terminal/terminal.h"
#include "util/error.h"
#include "util/memory.h"
#include "util/string.h"
#include "util/time.h"

struct itrm *ditrm = NULL;

static void free_itrm(struct itrm *);
static void in_kbd(struct itrm *);
static void in_sock(struct itrm *);
static int process_queue(struct itrm *);
static void handle_itrm_stdin(struct itrm *);
static void unhandle_itrm_stdin(struct itrm *);

#ifdef CONFIG_DEBUG
/** This hack makes GCC put enum term_event_special_key in the debug
 * information even though it is not otherwise used.  The const
 * prevents an unused-variable warning.  */
static const enum term_event_special_key dummy_term_event_special_key;
#endif


int
is_blocked(void)
{
        return ditrm && ditrm->blocked;
}


void
free_all_itrms(void)
{
        if (ditrm) free_itrm(ditrm);
}


/** A select_handler_T write_func for itrm_out.sock.  This is called
 * when there is data in @c itrm->out.queue and it is possible to write
 * it to @c itrm->out.sock.  When @c itrm->out.queue becomes empty, this
 * handler is temporarily removed.  */
static void
itrm_queue_write(struct itrm *itrm)
{
        int written;
        int qlen = int_min(itrm->out.queue.len, 128);

        assertm(qlen, "event queue empty");
        if_assert_failed return;

        written = safe_write(itrm->out.sock, itrm->out.queue.data, qlen);
        if (written <= 0) {
                if (written < 0) free_itrm(itrm); /* write error */
                return;
        }

        itrm->out.queue.len -= written;

        if (itrm->out.queue.len == 0) {
                set_handlers(itrm->out.sock,
                             get_handler(itrm->out.sock, SELECT_HANDLER_READ),
                             NULL,
                             get_handler(itrm->out.sock, SELECT_HANDLER_ERROR),
                             get_handler(itrm->out.sock, SELECT_HANDLER_DATA));
        } else {
                assert(itrm->out.queue.len > 0);
                memmove(itrm->out.queue.data, itrm->out.queue.data + written, itrm->out.queue.len);
        }
}


void
itrm_queue_event(struct itrm *itrm, unsigned char *data, int len)
{
        int w = 0;

        if (!len) return;

        if (!itrm->out.queue.len && can_write(itrm->out.sock)) {
                w = safe_write(itrm->out.sock, data, len);
                if (w <= 0 && HPUX_PIPE) {
                        register_bottom_half(free_itrm, itrm);
                        return;
                }
        }

        if (w < len) {
                int left = len - w;
                unsigned char *c = mem_realloc(itrm->out.queue.data,
                                               itrm->out.queue.len + left);

                if (!c) {
                        free_itrm(itrm);
                        return;
                }

                itrm->out.queue.data = c;
                memcpy(itrm->out.queue.data + itrm->out.queue.len, data + w, left);
                itrm->out.queue.len += left;
                set_handlers(itrm->out.sock,
                             get_handler(itrm->out.sock, SELECT_HANDLER_READ),
                             (select_handler_T) itrm_queue_write,
                             (select_handler_T) free_itrm, itrm);
        }
}


void
kbd_ctrl_c(void)
{
        struct interlink_event ev;

        if (!ditrm) return;
        /* This is called because of a signal, and there may be input
         * pending from the terminal, so do not reset
         * ditrm->bracketed_pasting.  */
        set_kbd_interlink_event(&ev, KBD_CTRL_C, KBD_MOD_NONE);
        itrm_queue_event(ditrm, (unsigned char *) &ev, sizeof(ev));
}

#define write_sequence(fd, seq) \
        hard_write(fd, seq, sizeof(seq) - 1)


#define INIT_TERMINAL_SEQ       "\033)0\0337"   /**< Special Character and Line Drawing Set, Save Cursor */
#define INIT_ALT_SCREEN_SEQ     "\033[?47h"     /**< Use Alternate Screen Buffer */
#define INIT_BRACKETED_PASTE_SEQ "\033[?2004h"  /**< Enable XTerm bracketed paste mode */

static void
send_init_sequence(int h, int altscreen)
{
        write_sequence(h, INIT_TERMINAL_SEQ);

        /* If alternate screen is supported switch to it. */
        if (altscreen) {
                write_sequence(h, INIT_ALT_SCREEN_SEQ);
        }
#ifdef CONFIG_MOUSE
        send_mouse_init_sequence(h);
#endif
        write_sequence(h, INIT_BRACKETED_PASTE_SEQ);
}

#define DONE_CLS_SEQ            "\033[2J"       /**< Erase in Display, Clear All */
#define DONE_TERMINAL_SEQ       "\0338\r \b"    /**< Restore Cursor (DECRC) + ??? */
#define DONE_ALT_SCREEN_SEQ     "\033[?47l"     /**< Use Normal Screen Buffer */
#define DONE_BRACKETED_PASTE_SEQ "\033[?2004l"  /**< Disable XTerm bracketed paste mode */

static void
send_done_sequence(int h, int altscreen)
{
        write_sequence(h, DONE_BRACKETED_PASTE_SEQ);
        write_sequence(h, DONE_CLS_SEQ);

#ifdef CONFIG_MOUSE
        send_mouse_done_sequence(h);
#endif

        /* Switch from alternate screen. */
        if (altscreen) {
                write_sequence(h, DONE_ALT_SCREEN_SEQ);
        }

        write_sequence(h, DONE_TERMINAL_SEQ);
}


#undef write_sequence

void
resize_terminal(void)
{
        struct interlink_event ev;
        int width, height;
        int xres, yres;

        get_terminal_size(ditrm->out.std, &width, &height);
#ifdef CONFIG_IMAGES
        if (ditrm->image_h)
                slave_images_getres(ditrm->image_h, &xres, &yres);
#endif
        set_resize_interlink_event(&ev, width, height, xres, yres);
        itrm_queue_event(ditrm, (char *) &ev, sizeof(ev));
}

void
get_terminal_name(unsigned char name[MAX_TERM_LEN])
{
        unsigned char *term = getenv("TERM");
        int i;

        memset(name, 0, MAX_TERM_LEN);

        if (!term) return;

        for (i = 0; term[i] != 0 && i < MAX_TERM_LEN - 1; i++)
                name[i] = isident(term[i]) ? term[i] : '-';
}


static int
setraw(struct itrm *itrm, int save_orig)
{
        struct termios t;
        long vdisable = -1;

        memset(&t, 0, sizeof(t));
        if (tcgetattr(itrm->in.ctl, &t)) return -1;

        if (save_orig) copy_struct(&itrm->t, &t);

#ifdef _POSIX_VDISABLE
        vdisable = _POSIX_VDISABLE;
#elif defined(HAVE_FPATHCONF)
        vdisable = fpathconf(itrm->in.ctl, _PC_VDISABLE);
#endif

#ifdef VERASE
/* Is VERASE defined on Windows? */
        if (vdisable != -1 && t.c_cc[VERASE] == vdisable)
                itrm->verase = -1;
        else
                itrm->verase = (unsigned char) t.c_cc[VERASE];
#else
        itrm->verase = -1;
#endif

        elinks_cfmakeraw(&t);
        t.c_lflag |= ISIG;
#ifdef TOSTOP
        t.c_lflag |= TOSTOP;
#endif
        t.c_oflag |= OPOST;
        if (tcsetattr(itrm->in.ctl, TCSANOW, &t)) return -1;

        return 0;
}

/** Construct the struct itrm of this process, make ::ditrm point to it,
 * set up select() handlers, and send the initial interlink packet.
 *
 * The first five parameters are file descriptors that this function
 * saves in submembers of struct itrm, and for which this function may
 * set select() handlers.  Please see the definitions of struct
 * itrm_in and struct itrm_out for further explanations.
 *
 * @param std_in        itrm_in.std: read tty device (or pipe)
 * @param std_out       itrm_out.std: write tty device (or pipe)
 * @param sock_in       itrm_in.sock
 *                      - If master: == @a std_out (masterhood flag)
 *                      - If slave: read socket from master
 * @param sock_out      itrm_out.sock
 *                      - If master: write pipe to same process
 *                      - If slave: write socket to master
 * @param ctl_in        itrm_in.ctl: control tty device
 *
 * The remaining three parameters control the initial interlink packet.
 *
 * @param init_string   A string to be passed to the master process.  Need
 *                      not be null-terminated.  If @a remote == 0, this is
 *                      a URI.  Otherwise, this is a remote command.
 * @param init_len      The length of init_string, in bytes.
 * @param remote        = 0 if asking the master to start a new session
 *                      and display it via this process.  Otherwise,
 *                      enum ::remote_session_flags.  */
void
handle_trm(int std_in, int std_out, int sock_in, int sock_out, int ctl_in,
           void *init_string, int init_len, int remote)
{
        struct itrm *itrm;
        struct terminal_info info;
        struct interlink_event_size *size = &info.event.info.size;
        unsigned char *ts;

        memset(&info, 0, sizeof(info));

        get_terminal_size(ctl_in, &size->width, &size->height);
        info.event.ev = EVENT_INIT;
        info.system_env = get_system_env();
        info.length = init_len;

        if (remote) {
                info.session_info = remote;
                info.magic = INTERLINK_REMOTE_MAGIC;
        } else {
                info.session_info = get_cmd_opt_int("base-session");
                info.magic = INTERLINK_NORMAL_MAGIC;
        }

        itrm = mem_calloc(1, sizeof(*itrm));
        if (!itrm) return;

        itrm->in.queue.data = mem_calloc(1, ITRM_IN_QUEUE_SIZE);
        if (!itrm->in.queue.data) {
                mem_free(itrm);
                return;
        }

        ditrm = itrm;
        itrm->in.std = std_in;
        itrm->out.std = std_out;
        itrm->in.sock = sock_in;
        itrm->out.sock = sock_out;
        itrm->in.ctl = ctl_in;
        itrm->timer = TIMER_ID_UNDEF;
        itrm->remote = !!remote;

        /* If the master does not tell which charset it's using in
         * this terminal, assume it's some ISO 8859.  Because that's
         * what older versions of ELinks did.  */
        itrm->title_codepage = get_cp_index("ISO-8859-1");

        /* FIXME: Combination altscreen + xwin does not work as it should,
         * mouse clicks are reportedly partially ignored. */
        if (info.system_env & (ENV_SCREEN | ENV_XWIN))
                itrm->altscreen = 1;

        if (!remote) {
                if (ctl_in >= 0) setraw(itrm, 1);
                send_init_sequence(std_out, itrm->altscreen);
                handle_terminal_resize(ctl_in, resize_terminal);
#ifdef CONFIG_MOUSE
                enable_mouse();
#endif
#ifdef CONFIG_IMAGES
                itrm->image_h = init_images();
                if (itrm->image_h)
                        slave_images_getres(itrm->image_h, &size->xres, &size->yres);
#endif
                handle_itrm_stdin(itrm);
        } else {
                /* elinks -remote may not have a valid stdin if not run from a tty (bug 938) */
                if (std_in >= 0) handle_itrm_stdin(itrm);
        }

        if (sock_in != std_out)
                set_handlers(sock_in, (select_handler_T) in_sock,
                             NULL, (select_handler_T) free_itrm, itrm);

        get_terminal_name(info.name);

        ts = get_cwd();
        if (ts) {
                memcpy(info.cwd, ts, int_min(strlen(ts), MAX_CWD_LEN));
                mem_free(ts);
        }

        itrm_queue_event(itrm, (char *) &info, TERMINAL_INFO_SIZE);
        itrm_queue_event(itrm, (char *) init_string, init_len);
}


/** A select_handler_T read_func and error_func for the pipe (long) @a h.
 * This is called when the subprocess started on the terminal of this
 * ELinks process exits.  ELinks then resumes using the terminal.  */
static void
unblock_itrm_x(void *h)
{
        close_handle(h);
        if (!ditrm) return;
        unblock_itrm();

        /* Note: External editor support depends on this resize event. */
        resize_terminal();
}


int
unblock_itrm(void)
{
        if (!ditrm) return -1;

        if (ditrm->in.ctl >= 0 && setraw(ditrm, 0)) return -1;
        ditrm->blocked = 0;
        send_init_sequence(ditrm->out.std, ditrm->altscreen);

        handle_itrm_stdin(ditrm);
        resume_mouse(ditrm->mouse_h);

        handle_terminal_resize(ditrm->in.ctl, resize_terminal);
        unblock_stdin();

        return 0;
}


void
block_itrm(void)
{
        if (!ditrm) return;

        ditrm->blocked = 1;
        block_stdin();
        kill_timer(&ditrm->timer);
        ditrm->in.queue.len = 0;
        unhandle_terminal_resize(ditrm->in.ctl);
        send_done_sequence(ditrm->out.std, ditrm->altscreen);
        tcsetattr(ditrm->in.ctl, TCSANOW, &ditrm->t);
        unhandle_itrm_stdin(ditrm);
        suspend_mouse(ditrm->mouse_h);
}


static void
free_itrm(struct itrm *itrm)
{
        if (!itrm) return;

        if (!itrm->remote) {
                if (itrm->orig_title && *itrm->orig_title) {
                        set_window_title(itrm->orig_title, itrm->title_codepage);

                } else if (itrm->touched_title) {
                        /* Set the window title to the value of $TERM if X11
                         * wasn't compiled in. Should hopefully make at least
                         * half the users happy. (debian bug #312955) */
                        unsigned char title[MAX_TERM_LEN];

                        get_terminal_name(title);
                        if (*title)
                                set_window_title(title,
                                                 get_cp_index("US-ASCII"));
                }


                unhandle_terminal_resize(itrm->in.ctl);
#ifdef CONFIG_MOUSE
                disable_mouse();
#endif
                send_done_sequence(itrm->out.std, itrm->altscreen);
                tcsetattr(itrm->in.ctl, TCSANOW, &itrm->t);
        }

        mem_free_set(&itrm->orig_title, NULL);

        /* elinks -remote may not have a valid stdin if not run from a tty (bug 938) */
        if (!itrm->remote || itrm->in.std >= 0) clear_handlers(itrm->in.std);
        clear_handlers(itrm->in.sock);
        clear_handlers(itrm->out.std);
        clear_handlers(itrm->out.sock);

        kill_timer(&itrm->timer);

        if (itrm == ditrm) ditrm = NULL;
        mem_free_if(itrm->out.queue.data);
        mem_free_if(itrm->in.queue.data);
        mem_free(itrm);
}

/** Resize terminal to dimensions specified by @a text string.
 * @a text should look like "width,height,old-width,old-height"
 * where width and height are integers. */
static inline void
resize_terminal_from_str(unsigned char *text)
{
        enum { NEW_WIDTH = 0, NEW_HEIGHT, OLD_WIDTH, OLD_HEIGHT, NUMBERS } i;
        int numbers[NUMBERS];

        assert(text && *text);
        if_assert_failed return;

        for (i = 0; i < NUMBERS; i++) {
                unsigned char *p = strchr(text, ',');

                if (p) {
                        *p++ = '\0';

                } else if (i < OLD_HEIGHT) {
                        return;
                }

                numbers[i] = atoi(text);

                if (p) text = p;
        }

        resize_window(numbers[NEW_WIDTH], numbers[NEW_HEIGHT],
                      numbers[OLD_WIDTH], numbers[OLD_HEIGHT]);
        resize_terminal();
}

void
dispatch_special(unsigned char *text)
{
        switch (text[0]) {
                case TERM_FN_TITLE:
                        if (ditrm) {
                                if (ditrm->remote)
                                        break;

                                if (!ditrm->orig_title)
                                        ditrm->orig_title = get_window_title(
                                                ditrm->title_codepage);
                                ditrm->touched_title = 1;
                        }
                        /* TODO: Is it really possible to get here with
                         * ditrm == NULL, and which charset would then
                         * be most appropriate?  */
                        set_window_title(text + 1,
                                         ditrm ? ditrm->title_codepage
                                         : get_cp_index("US-ASCII"));
                        break;
                case TERM_FN_RESIZE:
                        if (ditrm && ditrm->remote)
                                break;

                        resize_terminal_from_str(text + 1);
                        break;
                case TERM_FN_TITLE_CODEPAGE:
                        if (ditrm) {
                                int cp = get_cp_index(text + 1);

                                /* If the master sends the name of an
                                 * unrecognized charset, assume only
                                 * that it's ASCII compatible.  */
                                if (cp == -1)
                                        cp = get_cp_index("US-ASCII");
                                ditrm->title_codepage = cp;
                        }
                        break;

#ifdef CONFIG_IMAGES
                case TERM_FN_IMG_DRAW:
                        if (ditrm && ditrm->image_h) {
                                int imgid;
                                struct box b;
                                unsigned char file[4096];

                                sscanf(text + 1, "%d %d %d %s %d %d", &imgid, &b.x, &b.y, file, &b.width, &b.height);
                                slave_render_image(ditrm->image_h, imgid, &b, file);
                        }
                        break;
                case TERM_FN_IMG_HIDE_REG:
                        if (ditrm && ditrm->image_h) {
                                struct box b;

                                sscanf(text + 1, "%d %d %d %d", &b.x, &b.y, &b.width, &b.height);
                                slave_hide_image_region(ditrm->image_h, &b);
                        }
                        break;
                case TERM_FN_IMG_SYNC:
                        if (ditrm && ditrm->image_h) {
                                slave_sync_images(ditrm->image_h);
                        }
                        break;
#endif
        }
}

static void inline
safe_hard_write(int fd, unsigned char *buf, int len)
{
        if (is_blocked()) return;

        want_draw();
        hard_write(fd, buf, len);
        done_draw();
}

/** A select_handler_T read_func for itrm_in.sock.  A slave process
 * calls this when the master sends it data to be displayed.  The
 * master process never calls this.  */
static void
in_sock(struct itrm *itrm)
{
        struct string path;
        struct string delete;
        char ch;
        int fg; /* enum term_exec */
        ssize_t bytes_read, i, p;
        unsigned char buf[ITRM_OUT_QUEUE_SIZE];

        bytes_read = safe_read(itrm->in.sock, buf, ITRM_OUT_QUEUE_SIZE);
        if (bytes_read <= 0) goto free_and_return;

qwerty:
        for (i = 0; i < bytes_read; i++)
                if (!buf[i])
                        goto has_nul_byte;

        safe_hard_write(itrm->out.std, buf, bytes_read);
        return;

has_nul_byte:
        if (i) safe_hard_write(itrm->out.std, buf, i);

        i++;
        assert(ITRM_OUT_QUEUE_SIZE - i > 0);
        memmove(buf, buf + i, ITRM_OUT_QUEUE_SIZE - i);
        bytes_read -= i;
        p = 0;

#define RD(xx) {                                                        \
                unsigned char cc;                                       \
                                                                        \
                if (p < bytes_read)                                     \
                        cc = buf[p++];                                  \
                else if ((hard_read(itrm->in.sock, &cc, 1)) <= 0)       \
                        goto free_and_return;                           \
                xx = cc;                                                \
        }

        RD(fg);

        if (!init_string(&path)) goto free_and_return;

        while (1) {
                RD(ch);
                if (!ch) break;
                add_char_to_string(&path, ch);
        }

        if (!init_string(&delete)) {
                done_string(&path);
                goto free_and_return;
        }

        while (1) {
                RD(ch);
                if (!ch) break;
                add_char_to_string(&delete, ch);
        }

#undef RD

        if (!*path.source) {
                dispatch_special(delete.source);

        } else {
                int blockh;
                unsigned char *param;
                int path_len, del_len, param_len;

                /* TODO: Should this be changed to allow TERM_EXEC_NEWWIN
                 * in a blocked terminal?  There is similar code in
                 * exec_on_terminal().  --KON, 2007 */
                if (is_blocked() && fg != TERM_EXEC_BG) {
                        if (*delete.source) unlink(delete.source);
                        goto nasty_thing;
                }

                path_len = path.length;
                del_len = delete.length;
                param_len = path_len + del_len + 3;

                param = mem_alloc(param_len);
                if (!param) goto nasty_thing;

                param[0] = fg;
                memcpy(param + 1, path.source, path_len + 1);
                memcpy(param + 1 + path_len + 1, delete.source, del_len + 1);

                if (fg == TERM_EXEC_FG) block_itrm();

                blockh = start_thread((void (*)(void *, int)) exec_thread,
                                      param, param_len);
                mem_free(param);

                if (blockh == -1) {
                        if (fg == TERM_EXEC_FG)
                                unblock_itrm();

                        goto nasty_thing;
                }

                if (fg == TERM_EXEC_FG) {
                        set_handlers(blockh, (select_handler_T) unblock_itrm_x,
                                     NULL, (select_handler_T) unblock_itrm_x,
                                     (void *) (long) blockh);

                } else {
                        set_handlers(blockh, close_handle, NULL, close_handle,
                                     (void *) (long) blockh);
                }
        }

nasty_thing:
        done_string(&path);
        done_string(&delete);
        assert(ITRM_OUT_QUEUE_SIZE - p > 0);
        memmove(buf, buf + p, ITRM_OUT_QUEUE_SIZE - p);
        bytes_read -= p;

        goto qwerty;

free_and_return:
        free_itrm(itrm);
}


/** Parse an ECMA-48 control sequence that was received from a
 * terminal.  Extract the Final Byte (if there are no Intermediate
 * Bytes) and the value of the first parameter (if it is an integer).
 *
 * This function assumes the control sequence begins with a CSI -
 * CONTROL SEQUENCE INTRODUCER encoded as ESC [.  (ECMA-48 also allows
 * 0x9B as a single-byte CSI, but we don't support that here.)
 *
 * @returns one of:
 * - -1 if the control sequence is not yet complete; the caller sets a timer.
 * - 0 if the control sequence does not comply with ECMA-48.
 * - The length of the control sequence otherwise.  */
static inline int
get_esc_code(unsigned char *str, int len, unsigned char *final_byte,
             int *first_param_value)
{
        const int parameter_pos = 2;
        int intermediate_pos;
        int final_pos;
        int pos;

        *final_byte = '\0';
        *first_param_value = 0;

        /* Parameter Bytes */
        pos = parameter_pos;
        while (pos < len && str[pos] >= 0x30 && str[pos] <= 0x3F)
                ++pos;

        /* Intermediate Bytes */
        intermediate_pos = pos;
        while (pos < len && str[pos] >= 0x20 && str[pos] <= 0x2F)
                ++pos;

        /* Final Byte */
        final_pos = pos;
        if (pos >= len)
                return -1;
        if (!(str[pos] >= 0x40 && str[pos] <= 0x7E))
                return 0;

        /* The control sequence seems OK.  If the first Parameter
         * Byte indicates that the parameter string is formatted
         * as specified in clause 5.4.2 of ECMA-48, and the first
         * parameter is an integer, then compute its value.
         * (We need not check @len here because the loop cannot get
         * past the Final Byte.)  */
        for (pos = parameter_pos; str[pos] >= 0x30 && str[pos] <= 0x39; ++pos)
                *first_param_value = *first_param_value * 10 + str[pos] - 0x30;
        /* If the first parameter contains an embedded separator, then
         * the value is not an integer, so discard what we computed.  */
        if (str[pos] == 0x3A)
                *first_param_value = 0;

        /* The meaning of the Final Byte depends on the Intermediate
         * Bytes.  Because we don't currently need to recognize any
         * control sequences that use Intermediate Bytes, we just
         * discard the Final Byte if there are any Intermediate
         * Bytes.  */
        if (intermediate_pos == final_pos)
                *final_byte = str[final_pos];

        return final_pos + 1;
}

/* Define it to dump queue content in a readable form,
 * it may help to determine terminal sequences, and see what goes on. --Zas */
/* #define DEBUG_ITRM_QUEUE */

#ifdef DEBUG_ITRM_QUEUE
#include <stdio.h>
#include <ctype.h>      /* isprint() isspace() */
#endif

/** Decode a control sequence that begins with CSI (CONTROL SEQUENCE
 * INTRODUCER) encoded as ESC [, and set @a *ev accordingly.
 * (ECMA-48 also allows 0x9B as a single-byte CSI, but we don't
 * support that here.)
 *
 * @returns one of:
 * - -1 if the control sequence is not yet complete; the caller sets a timer.
 * - 0 if the control sequence should be parsed by some other function.
 * - The length of the control sequence otherwise.
 * Returning >0 does not imply this function has altered @a *ev.  */
static int
decode_terminal_escape_sequence(struct itrm *itrm, struct interlink_event *ev)
{
        struct term_event_keyboard kbd = { KBD_UNDEF, KBD_MOD_NONE };
        unsigned char c;
        int v;
        int el;

        if (itrm->in.queue.len < 3) return -1;

        if (itrm->in.queue.data[2] == '[') {
                /* The terminfo entry for linux has "kf1=\E[[A", etc.
                 * These are not control sequences compliant with
                 * clause 5.4 of ECMA-48.  (According to ECMA-48,
                 * "\E[[" is SRS - START REVERSED STRING.)  */
                if (itrm->in.queue.len >= 4
                    && itrm->in.queue.data[3] >= 'A'
                    && itrm->in.queue.data[3] <= 'L') {
                        kbd.key = number_to_kbd_fkey(itrm->in.queue.data[3] - 'A' + 1);
                        set_kbd_interlink_event(ev, kbd.key, kbd.modifier);
                        return 4;
                }

                return -1;
        }

        el = get_esc_code(itrm->in.queue.data, itrm->in.queue.len, &c, &v);
        if (el == -1) {
                /* If the control sequence is incomplete but itrm->in.queue
                 * is already full, then we must not wait for more input:
                 * kbd_timeout might call in_kbd and thus process_input
                 * and come right back here.  Better just reject the whole
                 * thing and let the initial CSI be handled as Alt-[.  */
                if (itrm->in.queue.len == ITRM_IN_QUEUE_SIZE)
                        return 0;
                else
                        return -1;
        }
#ifdef DEBUG_ITRM_QUEUE
        fprintf(stderr, "esc code: %c v=%d c=%c el=%d\n", itrm->in.queue.data[1], v, c, el);
        fflush(stderr);
#endif

        /* The following information should be listed for each escape
         * sequence recognized here:
         *
         * 1. Which control function ECMA-48 assigns to the sequence.
         *    Put parentheses around this if the control function
         *    seems unrelated to how ELinks actually treats the
         *    sequence.  Write "private" if it is a control sequence
         *    reserved for private or experimental use in ECMA-48.
         *    (Those have a Final Byte in the range 0x70 to 0x7F,
         *    optionally preceded by a single Intermediate Byte 0x20.)
         *
         * 2. The capname used by Terminfo, if any.  These should help
         *    when ELinks is eventually changed to read escape
         *    sequences from Terminfo (bug 96).
         *
         * 3. The $TERM identifier of some terminal that generates
         *    this escape sequence with the meaning expected by
         *    ELinks.  Escape sequences with no known terminal may end
         *    up being removed from ELinks when bug 96 is fixed.
         */                                     /* ECMA-48 Terminfo $TERM */
        switch (c) {                            /* ------- -------- ----- */
        case 'A': kbd.key = KBD_UP; break;      /*    CUU  kcuu1    vt200 */
        case 'B': kbd.key = KBD_DOWN; break;    /*    CUD  kcud1    vt200 */
        case 'C': kbd.key = KBD_RIGHT; break;   /*    CUF  kcuf1    vt200 */
        case 'D': kbd.key = KBD_LEFT; break;    /*    CUB  kcub1    vt200 */
        case 'F':                               /*   (CPL) kend     cons25 */
        case 'e': kbd.key = KBD_END; break;     /*   (VPR) kend */
        case 'H': kbd.key = KBD_HOME; break;    /*    CUP  khome    cons25 */
        case 'I': kbd.key = KBD_PAGE_UP; break; /*   (CHT) kpp      cons25 */
        case 'G': kbd.key = KBD_PAGE_DOWN; break; /* (CHA) knp      cons25 */
        case 'L': kbd.key = KBD_INS; break;     /*   (IL)  kich1    cons25 */
/* Free BSD (TERM=cons25 etc.) */
/*      case 'M': kbd.key = KBD_F1; break;*/    /*   (DL)  kf1      cons25 */
        case 'N': kbd.key = KBD_F2; break;      /*   (EF)  kf2      cons25 */
        case 'O': kbd.key = KBD_F3; break;      /*   (EA)  kf3      cons25 */
        case 'P': kbd.key = KBD_F4; break;      /*   (DCH) kf4      cons25 */
        case 'Q': kbd.key = KBD_F5; break;      /*   (SEE) kf5      cons25 */
/*      case 'R': kbd.key = KBD_F6; break;*/    /*   (CPR) kf6      cons25 */
        case 'S': kbd.key = KBD_F7; break;      /*   (SU)  kf7      cons25 */
        case 'T': kbd.key = KBD_F8; break;      /*   (SD)  kf8      cons25 */
        case 'U': kbd.key = KBD_F9; break;      /*   (NP)  kf9      cons25 */
        case 'V': kbd.key = KBD_F10; break;     /*   (PP)  kf10     cons25 */
        case 'W': kbd.key = KBD_F11; break;     /*   (CTC) kf11     cons25 */
        case 'X': kbd.key = KBD_F12; break;     /*   (ECH) kf12     cons25 */

        case 'Z':                               /*    CBT  kcbt     cons25 */
                kbd.key = KBD_TAB; kbd.modifier = KBD_MOD_SHIFT; break;

        case 'z': switch (v) {                  /* private */
                case 247: kbd.key = KBD_INS; break;     /* kich1 */
                case 214: kbd.key = KBD_HOME; break;    /* khome    sun */
                case 220: kbd.key = KBD_END; break;     /* kend     sun */
                case 216: kbd.key = KBD_PAGE_UP; break; /* kpp      sun */
                case 222: kbd.key = KBD_PAGE_DOWN; break; /* knp    sun */
                case 249: kbd.key = KBD_DEL; break;     /* kdch1 */
                } break;

        case '~': switch (v) {                  /* private */
                case 1: kbd.key = KBD_HOME; break;      /* khome    linux */
                case 2: kbd.key = KBD_INS; break;       /* kich1    linux */
                case 3: kbd.key = KBD_DEL; break;       /* kdch1    linux */
                case 4: kbd.key = KBD_END; break;       /* kend     linux */
                case 5: kbd.key = KBD_PAGE_UP; break;   /* kpp      linux */
                case 6: kbd.key = KBD_PAGE_DOWN; break; /* knp      linux */
                case 7: kbd.key = KBD_HOME; break;      /* khome    rxvt */
                case 8: kbd.key = KBD_END; break;       /* kend     rxvt */

                case 11: kbd.key = KBD_F1; break;       /* kf1      rxvt */
                case 12: kbd.key = KBD_F2; break;       /* kf2      rxvt */
                case 13: kbd.key = KBD_F3; break;       /* kf3      rxvt */
                case 14: kbd.key = KBD_F4; break;       /* kf4      rxvt */
                case 15: kbd.key = KBD_F5; break;       /* kf5      rxvt */

                case 17: kbd.key = KBD_F6; break;       /* kf6      vt200 */
                case 18: kbd.key = KBD_F7; break;       /* kf7      vt200 */
                case 19: kbd.key = KBD_F8; break;       /* kf8      vt200 */
                case 20: kbd.key = KBD_F9; break;       /* kf9      vt200 */
                case 21: kbd.key = KBD_F10; break;      /* kf10     vt200 */

                case 23: kbd.key = KBD_F11; break;      /* kf11     vt200 */
                case 24: kbd.key = KBD_F12; break;      /* kf12     vt200 */

                /* Give preference to F11 and F12 over shifted F1 and F2. */
                /*
                case 23: kbd.key = KBD_F1; kbd.modifier = KBD_MOD_SHIFT; break;
                case 24: kbd.key = KBD_F2; kbd.modifier = KBD_MOD_SHIFT; break;
                */

                case 25: kbd.key = KBD_F3; kbd.modifier = KBD_MOD_SHIFT; break;
                case 26: kbd.key = KBD_F4; kbd.modifier = KBD_MOD_SHIFT; break;

                case 28: kbd.key = KBD_F5; kbd.modifier = KBD_MOD_SHIFT; break;
                case 29: kbd.key = KBD_F6; kbd.modifier = KBD_MOD_SHIFT; break;

                case 31: kbd.key = KBD_F7; kbd.modifier = KBD_MOD_SHIFT; break;
                case 32: kbd.key = KBD_F8; kbd.modifier = KBD_MOD_SHIFT; break;
                case 33: kbd.key = KBD_F9; kbd.modifier = KBD_MOD_SHIFT; break;
                case 34: kbd.key = KBD_F10; kbd.modifier = KBD_MOD_SHIFT; break;

                case 200: itrm->bracketed_pasting = 1; break;    /* xterm */
                case 201: itrm->bracketed_pasting = 0; break;    /* xterm */

                } break;

        case 'R': resize_terminal(); break;     /*    CPR  u6 */
        case 'M':                               /*   (DL)  kmous    xterm */
#ifdef CONFIG_MOUSE
                el = decode_terminal_mouse_escape_sequence(itrm, ev, el, v);
#endif /* CONFIG_MOUSE */
                break;
        }

        /* KBD_UNDEF here means it was unrecognized or a mouse event.  */
        if (kbd.key != KBD_UNDEF)
                set_kbd_interlink_event(ev, kbd.key, kbd.modifier);

        return el;
}

/** Decode an escape sequence that begins with SS3 (SINGLE SHIFT 3).
 * These are used for application cursor keys and the application keypad.
 * @returns one of:
 * - -1 if the escape sequence is not yet complete; the caller sets a timer.
 * - 0 if the escape sequence should be parsed by some other function.
 * - The length of the escape sequence otherwise.
 * Returning >0 does not imply this function has altered @a *ev.  */
static int
decode_terminal_application_key(struct itrm *itrm, struct interlink_event *ev)
{
        unsigned char c;
        struct interlink_event_keyboard kbd = { KBD_UNDEF, KBD_MOD_NONE };

        assert(itrm->in.queue.len >= 2);
        assert(itrm->in.queue.data[0] == ASCII_ESC);
        assert(itrm->in.queue.data[1] == 0x4F); /* == 'O', incidentally */
        if_assert_failed return 0;

        if (itrm->in.queue.len < 3) return -1;
        /* According to ECMA-35 section 8.4, a single (possibly multibyte)
         * character follows the SS3.  We now assume the code identifies
         * GL as the single-shift area and the designated set has 94
         * characters.  */
        c = itrm->in.queue.data[2];
        if (c < 0x21 || c > 0x7E) return 0;

        switch (c) {                                    /* Terminfo $TERM */
        case ' ': kbd.key = ' '; break;                 /*          xterm */
        case 'A': kbd.key = KBD_UP; break;              /* kcuu1    vt100 */
        case 'B': kbd.key = KBD_DOWN; break;            /* kcud1    vt100 */
        case 'C': kbd.key = KBD_RIGHT; break;           /* kcuf1    vt100 */
        case 'D': kbd.key = KBD_LEFT; break;            /* kcub1    vt100 */
        case 'F': kbd.key = KBD_END; break;             /* kend     xterm */
        case 'H': kbd.key = KBD_HOME; break;            /* khome    xterm */
        case 'I': kbd.key = KBD_TAB; break;             /*          xterm */
        case 'M': kbd.key = KBD_ENTER; break;           /* kent     vt100 */
                /* FIXME: xterm generates ESC O 2 P for Shift-PF1 */
        case 'P': kbd.key = KBD_F1; break;              /* kf1      vt100 */
        case 'Q': kbd.key = KBD_F2; break;              /* kf2      vt100 */
        case 'R': kbd.key = KBD_F3; break;              /* kf3      vt100 */
        case 'S': kbd.key = KBD_F4; break;              /* kf4      vt100 */
        case 'X': kbd.key = '='; break;                 /*          xterm */

        case 'j': case 'k': case 'l': case 'm': /* *+,-             xterm */
        case 'n': case 'o': case 'p': case 'q': /* ./01             xterm */
        case 'r': case 's': case 't': case 'u': /* 2345             xterm */
        case 'v': case 'w': case 'x': case 'y': /* 6789             xterm */
                kbd.key = c - 'p' + '0'; break;
        }
        if (kbd.key != KBD_UNDEF)
                copy_struct(&ev->info.keyboard, &kbd);

        return 3;               /* even if we didn't recognize it */
}


/** Initialize @a *ev to match the byte @a key received from the terminal.
 * @a key must not be a value from enum term_event_special_key.  */
static void
set_kbd_event(const struct itrm *itrm, struct interlink_event *ev,
              int key, term_event_modifier_T modifier)
{
        if (key == itrm->verase)
                key = KBD_BS;
        else switch (key) {
        case ASCII_TAB:
                key = KBD_TAB;
                break;
        case ASCII_DEL: /* often overridden by itrm->verase above */
                key = KBD_DEL;
                break;
        case ASCII_LF:
        case ASCII_CR:
                key = KBD_ENTER;
                break;

        case ASCII_ESC:
                key = KBD_ESC;
                break;

        case ASCII_BS:  /* often overridden by itrm->verase above */
        default:
                if (key < ' ') {
                        key += 'A' - 1;
                        modifier |= KBD_MOD_CTRL;
                }
        }

        set_kbd_interlink_event(ev, key, modifier);
}

/** Timer callback for itrm.timer.  As explained in install_timer(),
 * this function must erase the expired timer ID from all variables.  */
static void
kbd_timeout(struct itrm *itrm)
{
        struct interlink_event ev;
        int el;

        itrm->timer = TIMER_ID_UNDEF;
        /* The expired timer ID has now been erased.  */

        assertm(itrm->in.queue.len, "timeout on empty queue");
        assert(!itrm->blocked); /* block_itrm should have killed itrm->timer */
        if_assert_failed return;

        if (can_read(itrm->in.std)) {
                in_kbd(itrm);
                return;
        }

        if (itrm->in.queue.len >= 2 && itrm->in.queue.data[0] == ASCII_ESC) {
                /* This is used for ESC [ and ESC O.  */
                set_kbd_event(itrm, &ev, itrm->in.queue.data[1], KBD_MOD_ALT);
                el = 2;
        } else {
                set_kbd_event(itrm, &ev, itrm->in.queue.data[0], KBD_MOD_NONE);
                el = 1;
        }
        itrm->bracketed_pasting = 0;
        itrm_queue_event(itrm, (char *) &ev, sizeof(ev));

        itrm->in.queue.len -= el;
        if (itrm->in.queue.len)
                memmove(itrm->in.queue.data, itrm->in.queue.data + el, itrm->in.queue.len);

        while (process_queue(itrm));
}

/** Parse one event from itrm_in.queue and append to itrm_out.queue.
 * @pre On entry, @a *itrm must not be blocked.
 * @returns the number of bytes removed from itrm->in.queue; at least 0.
 * @post If this function leaves the queue not full, it also reenables
 * reading from itrm->in.std.  (Because it does not add to the queue,
 * it never need disable reading.)  */
static int
process_queue(struct itrm *itrm)
{
        struct interlink_event ev;
        int el = 0;

        if (!itrm->in.queue.len) goto return_without_event;
        assert(!itrm->blocked);
        if_assert_failed return 0; /* unlike goto, don't enable reading */

        set_kbd_interlink_event(&ev, KBD_UNDEF, KBD_MOD_NONE);

#ifdef DEBUG_ITRM_QUEUE
        {
                int i;

                /* Dump current queue in a readable form to stderr. */
                for (i = 0; i < itrm->in.queue.len; i++)
                        if (itrm->in.queue.data[i] == ASCII_ESC)
                                fprintf(stderr, "ESC ");
                        else if (isprint(itrm->in.queue.data[i]) && !isspace(itrm->in.queue.data[i]))
                                fprintf(stderr, "%c ", itrm->in.queue.data[i]);
                        else
                                fprintf(stderr, "0x%02x ", itrm->in.queue.data[i]);

                fprintf(stderr, "\n");
                fflush(stderr);
        }
#endif /* DEBUG_ITRM_QUEUE */

        /* el == -1 means itrm->in.queue appears to be the beginning of an
         *          escape sequence but it is not yet complete.  Set a timer;
         *          if it times out, then assume it wasn't an escape sequence
         *          after all.
         * el == 0 means this function has not yet figured out what the data
         *         in itrm->in.queue is, but some possibilities remain.
         *         One of them will be chosen before returning.
         * el > 0 means some bytes were successfully parsed from the beginning
         *        of itrm->in.queue and should now be removed from there.
         *        However, this does not always imply an event will be queued.
         */

        /* ELinks should also recognize U+009B CONTROL SEQUENCE INTRODUCER
         * as meaning the same as ESC 0x5B, and U+008F SINGLE SHIFT THREE as
         * meaning the same as ESC 0x4F, but those cannot yet be implemented
         * because of bug 777: the UTF-8 decoder is run too late.  */
        if (itrm->in.queue.data[0] == ASCII_ESC) {
                if (itrm->in.queue.len < 2) {
                        el = -1;
                } else if (itrm->in.queue.data[1] == 0x5B /* CSI */) {
                        el = decode_terminal_escape_sequence(itrm, &ev);
                } else if (itrm->in.queue.data[1] == 0x4F /* SS3 */) {
                        el = decode_terminal_application_key(itrm, &ev);
                } else if (itrm->in.queue.data[1] == ASCII_ESC) {
                        /* ESC ESC can be either Alt-Esc or the
                         * beginning of e.g. ESC ESC 0x5B 0x41,
                         * which we should parse as Esc Up.  */
                        if (itrm->in.queue.len < 3) {
                                /* Need more data to figure it out.  */
                                el = -1;
                        } else if (itrm->in.queue.data[2] == 0x5B
                                   || itrm->in.queue.data[2] == 0x4F) {
                                /* The first ESC appears to be followed
                                 * by an escape sequence.  Treat it as
                                 * a standalone Esc.  */
                                el = 1;
                                set_kbd_event(itrm, &ev,
                                              itrm->in.queue.data[0],
                                              KBD_MOD_NONE);
                        } else {
                                /* The second ESC of ESC ESC is not the
                                 * beginning of any known escape sequence.
                                 * This must be Alt-Esc, then.  */
                                el = 2;
                                set_kbd_event(itrm, &ev,
                                              itrm->in.queue.data[1],
                                              KBD_MOD_ALT);
                        }
                }
                if (el == 0) {  /* Begins with ESC, but none of the above */
                        el = 2;
                        set_kbd_event(itrm, &ev, itrm->in.queue.data[1],
                                      KBD_MOD_ALT);
                }

        } else if (itrm->in.queue.data[0] == 0) {
                static const struct term_event_keyboard os2xtd[256] = {
#include "terminal/key.inc"
                };

                if (itrm->in.queue.len < 2)
                        el = -1;
                else {
                        el = 2;
                        set_kbd_interlink_event(&ev,
                                                os2xtd[itrm->in.queue.data[1]].key,
                                                os2xtd[itrm->in.queue.data[1]].modifier);
                }
        }

        if (el == 0) {
                el = 1;
                set_kbd_event(itrm, &ev, itrm->in.queue.data[0],
                              itrm->bracketed_pasting ? KBD_MOD_PASTE : KBD_MOD_NONE);
        }

        /* The call to decode_terminal_escape_sequence() might have changed the
         * keyboard event to a mouse event. */
        if (ev.ev == EVENT_MOUSE || ev.info.keyboard.key != KBD_UNDEF) {
                itrm_queue_event(itrm, (char *) &ev, sizeof(ev));
                itrm->bracketed_pasting = 
                        (ev.ev == EVENT_KBD
                         && (ev.info.keyboard.modifier & KBD_MOD_PASTE));
        }

return_without_event:
        if (el == -1) {
                install_timer(&itrm->timer, ESC_TIMEOUT, (void (*)(void *)) kbd_timeout,
                              itrm);
                return 0;
        } else {
                assertm(itrm->in.queue.len >= el, "event queue underflow");
                if_assert_failed { itrm->in.queue.len = el; }

                itrm->in.queue.len -= el;
                if (itrm->in.queue.len)
                        memmove(itrm->in.queue.data, itrm->in.queue.data + el, itrm->in.queue.len);

                if (itrm->in.queue.len < ITRM_IN_QUEUE_SIZE)
                        handle_itrm_stdin(itrm);

                return el;
        }
}


/** A select_handler_T read_func for itrm_in.std.  This is called when
 * characters typed by the user arrive from the terminal. */
static void
in_kbd(struct itrm *itrm)
{
        int r;

        if (!can_read(itrm->in.std)) return;

        kill_timer(&itrm->timer);

        if (itrm->in.queue.len >= ITRM_IN_QUEUE_SIZE) {
                unhandle_itrm_stdin(itrm);
                while (process_queue(itrm));
                return;
        }

        r = safe_read(itrm->in.std, itrm->in.queue.data + itrm->in.queue.len,
                      ITRM_IN_QUEUE_SIZE - itrm->in.queue.len);
        if (r <= 0) {
                free_itrm(itrm);
                return;
        }

        itrm->in.queue.len += r;
        if (itrm->in.queue.len > ITRM_IN_QUEUE_SIZE) {
                ERROR(gettext("Too many bytes read from the itrm!"));
                itrm->in.queue.len = ITRM_IN_QUEUE_SIZE;
        }

        while (process_queue(itrm));
}

/** Enable reading from itrm_in.std.  ELinks will read any available
 * bytes from the tty into itrm->in.queue and then parse them.
 * Reading should be enabled whenever itrm->in.queue is not full and
 * itrm->blocked is 0.  */
static void
handle_itrm_stdin(struct itrm *itrm)
{
        assert(itrm->in.std >= 0);
        if_assert_failed return;

        set_handlers(itrm->in.std, (select_handler_T) in_kbd, NULL,
                     (select_handler_T) free_itrm, itrm);
}

/** Disable reading from itrm_in.std.  Reading should be disabled
 * whenever itrm->in.queue is full (there is no room for the data)
 * or itrm->blocked is 1 (other processes may read the data).  */
static void
unhandle_itrm_stdin(struct itrm *itrm)
{
        assert(itrm->in.std >= 0);
        if_assert_failed return;

        set_handlers(itrm->in.std, (select_handler_T) NULL, NULL,
                     (select_handler_T) free_itrm, itrm);
}