Turn #ifdef LOG into a command-line option for debugging use

[u/mdw/putty] / terminal.c

#include <windows.h>

#include <stdio.h>
#include <stdlib.h>

#include "putty.h"

static unsigned long *text;            /* buffer of text on terminal screen */
static unsigned long *scrtop;          /* top of working screen */
static unsigned long *disptop;         /* top of displayed screen */
static unsigned long *sbtop;           /* top of scrollback */
static unsigned long *cpos;            /* cursor position (convenience) */
static unsigned long *disptext;        /* buffer of text on real screen */
static unsigned long *wanttext;        /* buffer of text we want on screen */
static unsigned long *alttext;         /* buffer of text on alt. screen */

static unsigned char *selspace;        /* buffer for building selections in */

#define TSIZE (sizeof(*text))
#define fix_cpos  do { cpos = scrtop + curs_y * (cols+1) + curs_x; } while(0)

static unsigned long curr_attr, save_attr;

static int curs_x, curs_y;             /* cursor */
static int save_x, save_y;             /* saved cursor position */
static int marg_t, marg_b;             /* scroll margins */
static int dec_om;                     /* DEC origin mode flag */
static int wrap, wrapnext;             /* wrap flags */
static int insert;                     /* insert-mode flag */
static int cset;                       /* 0 or 1: which char set */
static int save_cset, save_csattr;     /* saved with cursor position */
static int rvideo;                     /* global reverse video flag */

static unsigned long cset_attr[2];

/*
 * Saved settings on the alternate screen.
 */
static int alt_x, alt_y, alt_om, alt_wrap, alt_wnext, alt_ins, alt_cset;
static int alt_t, alt_b;
static int alt_which;

#define ARGS_MAX 32                    /* max # of esc sequence arguments */
#define ARG_DEFAULT -1                 /* if an arg isn't specified */
#define def(a,d) ( (a) == ARG_DEFAULT ? (d) : (a) )
static int esc_args[ARGS_MAX];
static int esc_nargs;
static int esc_query;

#define OSC_STR_MAX 2048
static int osc_strlen;
static char osc_string[OSC_STR_MAX+1];
static int osc_w;

static unsigned char *tabs;

#define MAXNL 5
static int nl_count;

static int scroll_heuristic;

static enum {
    TOPLEVEL,
    SEEN_ESC,
    SEEN_CSI,
    SEEN_OSC,
    SEEN_OSC_W,

    DO_CTRLS,

    IGNORE_NEXT,
    SET_GL, SET_GR,
    SEEN_OSC_P,
    OSC_STRING, OSC_MAYBE_ST,
    SEEN_ESCHASH
} termstate;

static enum {
    NO_SELECTION, ABOUT_TO, DRAGGING, SELECTED
} selstate;
static enum {
    SM_CHAR, SM_WORD, SM_LINE
} selmode;
static unsigned long *selstart, *selend, *selanchor;

static short wordness[256] = {
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, /* 01 */
    0,1,2,1,1,1,1,1,1,1,1,1,1,2,2,2, 2,2,2,2,2,2,2,2,2,2,1,1,1,1,1,1, /* 23 */
    1,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2, 2,2,2,2,2,2,2,2,2,2,2,1,1,1,1,2, /* 45 */
    1,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2, 2,2,2,2,2,2,2,2,2,2,2,1,1,1,1,1, /* 67 */
    1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, /* 89 */
    1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, /* AB */
    2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2, 2,2,2,2,2,2,2,1,2,2,2,2,2,2,2,2, /* CD */
    2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2, 2,2,2,2,2,2,2,1,2,2,2,2,2,2,2,2, /* EF */
};

static unsigned char sel_nl[] = SEL_NL;

/*
 * Internal prototypes.
 */
static void do_paint (Context, int);
static void erase_lots (int, int, int);
static void swap_screen (int);
static void update_sbar (void);
static void deselect (void);

/*
 * Set up power-on settings for the terminal.
 */
static void power_on(void) {
    curs_x = curs_y = alt_x = alt_y = save_x = save_y = 0;
    alt_t = marg_t = 0;
    if (rows != -1)
        alt_b = marg_b = rows - 1;
    else
        alt_b = marg_b = 0;
    if (cols != -1) {
        int i;
        for (i = 0; i < cols; i++)
            tabs[i] = (i % 8 == 0 ? TRUE : FALSE);
    }
    alt_om = dec_om = cfg.dec_om;
    alt_wnext = wrapnext = alt_ins = insert = FALSE;
    alt_wrap = wrap = cfg.wrap_mode;
    alt_cset = cset = 0;
    cset_attr[0] = cset_attr[1] = ATTR_ASCII;
    rvideo = 0;
    save_attr = curr_attr = ATTR_DEFAULT;
    app_cursor_keys = cfg.app_cursor;
    app_keypad_keys = cfg.app_keypad;
    alt_which = 0;
    {
        int i;
        for (i = 0; i < 256; i++)
            wordness[i] = cfg.wordness[i];
    }
    if (text) {
        swap_screen (1);
        erase_lots (FALSE, TRUE, TRUE);
        swap_screen (0);
        erase_lots (FALSE, TRUE, TRUE);
    }
}

/*
 * Force a screen update.
 */
void term_update(void) {
    Context ctx;
    ctx = get_ctx();
    if (ctx) {
        if ( (seen_key_event && (unscroll_event & US_KEY)) &&
             (seen_disp_event && (unscroll_event & US_DISP)) ) {
            disptop = scrtop;
            seen_disp_event = seen_key_event = 0;
        }
        do_paint (ctx, TRUE);
        free_ctx (ctx);
        nl_count = 0;
        scroll_heuristic = 0;
    }
}

/*
 * Same as power_on(), but an external function.
 */
void term_pwron(void) {
    power_on();
    fix_cpos;
    disptop = scrtop;
    deselect();
    term_update();
}

/*
 * Clear the scrollback.
 */
void term_clrsb(void) {
    disptop = sbtop = scrtop;
    update_sbar();
}

/*
 * Initialise the terminal.
 */
void term_init(void) {
    text = sbtop = scrtop = disptop = cpos = NULL;
    disptext = wanttext = NULL;
    tabs = NULL;
    selspace = NULL;
    deselect();
    rows = cols = -1;
    nl_count = 0;
    power_on();
}

/*
 * Set up the terminal for a given size.
 */
void term_size(int newrows, int newcols, int newsavelines) {
    unsigned long *newtext, *newdisp, *newwant, *newalt;
    int i, j, crows, ccols;

    if (newrows == rows && newcols == cols && newsavelines == savelines)
        return;                        /* nothing to do */

    alt_t = marg_t = 0;
    alt_b = marg_b = newrows - 1;

    newtext = smalloc ((newrows+newsavelines)*(newcols+1)*TSIZE);
    disptop = newtext + newsavelines*(newcols+1);
    for (i=0; i<(newrows+newsavelines)*(newcols+1); i++)
        newtext[i] = ERASE_CHAR;
    if (rows != -1) {
        crows = rows + (scrtop - sbtop) / (cols+1);
        if (crows > newrows+newsavelines)
            crows = newrows+newsavelines;
        ccols = (cols < newcols ? cols : newcols);
        for (i=0; i<crows; i++) {
            int oldidx = (rows + savelines - crows + i) * (cols+1);
            int newidx = (newrows + newsavelines - crows + i) * (newcols+1);
            for (j=0; j<ccols; j++)
                newtext[newidx+j] = text[oldidx+j];
            newtext[newidx+newcols] =
                (cols == newcols ? text[oldidx+cols] : 0);
        }
        sbtop = disptop - (crows - newrows) * (newcols+1);
        if (sbtop > disptop)
            sbtop = disptop;
    } else
        sbtop = disptop;
    scrtop = disptop;
    sfree (text);
    text = newtext;

    newdisp = smalloc (newrows*(newcols+1)*TSIZE);
    for (i=0; i<newrows*(newcols+1); i++)
        newdisp[i] = ATTR_INVALID;
    sfree (disptext);
    disptext = newdisp;

    newwant = smalloc (newrows*(newcols+1)*TSIZE);
    for (i=0; i<newrows*(newcols+1); i++)
        newwant[i] = ATTR_INVALID;
    sfree (wanttext);
    wanttext = newwant;

    newalt = smalloc (newrows*(newcols+1)*TSIZE);
    for (i=0; i<newrows*(newcols+1); i++)
        newalt[i] = ERASE_CHAR;
    sfree (alttext);
    alttext = newalt;

    sfree (selspace);
    selspace = smalloc ( (newrows+newsavelines) * (newcols+sizeof(sel_nl)) );

    tabs = srealloc (tabs, newcols*sizeof(*tabs));
    {
        int i;
        for (i = (cols > 0 ? cols : 0); i < newcols; i++)
            tabs[i] = (i % 8 == 0 ? TRUE : FALSE);
    }

    if (rows > 0)
        curs_y += newrows - rows;
    if (curs_y < 0)
        curs_y = 0;
    if (curs_y >= newrows)
        curs_y = newrows-1;
    if (curs_x >= newcols)
        curs_x = newcols-1;
    alt_x = alt_y = 0;
    wrapnext = alt_wnext = FALSE;

    rows = newrows;
    cols = newcols;
    savelines = newsavelines;
    fix_cpos;

    deselect();
    update_sbar();
    term_update();
}

/*
 * Swap screens.
 */
static void swap_screen (int which) {
    int t;
    unsigned long tt;

    if (which == alt_which)
        return;

    alt_which = which;

    for (t=0; t<rows*(cols+1); t++) {
        tt = scrtop[t]; scrtop[t] = alttext[t]; alttext[t] = tt;
    }

    t = curs_x; curs_x = alt_x; alt_x = t;
    t = curs_y; curs_y = alt_y; alt_y = t;
    t = marg_t; marg_t = alt_t; alt_t = t;
    t = marg_b; marg_b = alt_b; alt_b = t;
    t = dec_om; dec_om = alt_om; alt_om = t;
    t = wrap; wrap = alt_wrap; alt_wrap = t;
    t = wrapnext; wrapnext = alt_wnext; alt_wnext = t;
    t = insert; insert = alt_ins; alt_ins = t;
    t = cset; cset = alt_cset; alt_cset = t;

    fix_cpos;
}

/*
 * Retrieve a character from `inbuf'.
 */
static int inbuf_getc(void) {
    if (inbuf_head == inbuf_reap)
        return -1;                     /* EOF */
    else {
        int n = inbuf_reap;
        inbuf_reap = (inbuf_reap+1) & INBUF_MASK;
        return inbuf[n];
    }
}

/*
 * Update the scroll bar.
 */
static void update_sbar(void) {
    int min;

    min = (sbtop - text) / (cols+1);
    set_sbar ((scrtop - text) / (cols+1) + rows - min,
              (disptop - text) / (cols+1) - min,
              rows);
}

/*
 * Check whether the region bounded by the two pointers intersects
 * the scroll region, and de-select the on-screen selection if so.
 */
static void check_selection (unsigned long *from, unsigned long *to) {
    if (from < selend && selstart < to)
        deselect();
}

/*
 * Scroll the screen. (`lines' is +ve for scrolling forward, -ve
 * for backward.) `sb' is TRUE if the scrolling is permitted to
 * affect the scrollback buffer.
 */
static void scroll (int topline, int botline, int lines, int sb) {
    unsigned long *scroll_top;
    int scroll_size, size, i;

    scroll_top = scrtop + topline*(cols+1);
    size = (lines < 0 ? -lines : lines) * (cols+1);
    scroll_size = (botline - topline + 1) * (cols+1) - size;

    if (lines > 0 && topline == 0 && alt_which == 0 && sb) {
        /*
         * Since we're going to scroll the top line and we're on the 
         * scrolling screen let's also affect the scrollback buffer.
         */
        sbtop -= lines * (cols+1);
        if (sbtop < text)
            sbtop = text;
        scroll_size += scroll_top - sbtop;
        scroll_top = sbtop;
        update_sbar();
    }

    if (scroll_size < 0) {
        size += scroll_size;
        scroll_size = 0;
    }

    if (lines > 0) {
        if (scroll_size)
            memmove (scroll_top, scroll_top + size, scroll_size*TSIZE);
        for (i = 0; i < size; i++)
            scroll_top[i+scroll_size] = ERASE_CHAR;
        if (selstart > scroll_top &&
            selstart < scroll_top + size + scroll_size) {
            selstart -= size;
            if (selstart < scroll_top)
                selstart = scroll_top;
        }
        if (selend > scroll_top &&
            selend < scroll_top + size + scroll_size) {
            selend -= size;
            if (selend < scroll_top)
                selend = scroll_top;
        }
    } else {
        if (scroll_size)
            memmove (scroll_top + size, scroll_top, scroll_size*TSIZE);
        for (i = 0; i < size; i++)
            scroll_top[i] = ERASE_CHAR;
        if (selstart > scroll_top &&
            selstart < scroll_top + size + scroll_size) {
            selstart += size;
            if (selstart > scroll_top + size + scroll_size)
                selstart = scroll_top + size + scroll_size;
        }
        if (selend > scroll_top &&
            selend < scroll_top + size + scroll_size) {
            selend += size;
            if (selend > scroll_top + size + scroll_size)
                selend = scroll_top + size + scroll_size;
        }
    }

    scroll_heuristic += lines;
}

/*
 * Move the cursor to a given position, clipping at boundaries. We
 * may or may not want to clip at the scroll margin: marg_clip is 0
 * not to, 1 to disallow _passing_ the margins, and 2 to disallow
 * even _being_ outside the margins.
 */
static void move (int x, int y, int marg_clip) {
    if (x < 0)
        x = 0;
    if (x >= cols)
        x = cols-1;
    if (marg_clip) {
        if ((curs_y >= marg_t || marg_clip == 2) && y < marg_t)
            y = marg_t;
        if ((curs_y <= marg_b || marg_clip == 2) && y > marg_b)
            y = marg_b;
    }
    if (y < 0)
        y = 0;
    if (y >= rows)
        y = rows-1;
    curs_x = x;
    curs_y = y;
    fix_cpos;
    wrapnext = FALSE;
}

/*
 * Save or restore the cursor and SGR mode.
 */
static void save_cursor(int save) {
    if (save) {
        save_x = curs_x;
        save_y = curs_y;
        save_attr = curr_attr;
        save_cset = cset;
        save_csattr = cset_attr[cset];
    } else {
        curs_x = save_x;
        curs_y = save_y;
        curr_attr = save_attr;
        cset = save_cset;
        cset_attr[cset] = save_csattr;
        fix_cpos;
    }
}

/*
 * Erase a large portion of the screen: the whole screen, or the
 * whole line, or parts thereof.
 */
static void erase_lots (int line_only, int from_begin, int to_end) {
    unsigned long *startpos, *endpos;

    if (line_only) {
        startpos = cpos - curs_x;
        endpos = startpos + cols+1;
    } else {
        startpos = scrtop;
        endpos = startpos + rows * (cols+1);
    }
    if (!from_begin)
        startpos = cpos;
    if (!to_end)
        endpos = cpos;
    check_selection (startpos, endpos);
    while (startpos < endpos)
        *startpos++ = ERASE_CHAR;
}

/*
 * Insert or delete characters within the current line. n is +ve if
 * insertion is desired, and -ve for deletion.
 */
static void insch (int n) {
    int dir = (n < 0 ? -1 : +1);
    int m;

    n = (n < 0 ? -n : n);
    if (n > cols - curs_x)
        n = cols - curs_x;
    m = cols - curs_x - n;
    check_selection (cpos, cpos+n);
    if (dir < 0) {
        memmove (cpos, cpos+n, m*TSIZE);
        while (n--)
            cpos[m++] = ERASE_CHAR;
    } else {
        memmove (cpos+n, cpos, m*TSIZE);
        while (n--)
            cpos[n] = ERASE_CHAR;
    }
}

/*
 * Toggle terminal mode `mode' to state `state'. (`query' indicates
 * whether the mode is a DEC private one or a normal one.)
 */
static void toggle_mode (int mode, int query, int state) {
    if (query) switch (mode) {
      case 1:                          /* application cursor keys */
        app_cursor_keys = state;
        break;
      case 3:                          /* 80/132 columns */
        deselect();
        request_resize (state ? 132 : 80, rows);
        break;
      case 5:                          /* reverse video */
        rvideo = state;
        seen_disp_event = TRUE;
        break;
      case 6:                          /* DEC origin mode */
        dec_om = state;
        break;
      case 7:                          /* auto wrap */
        wrap = state;
        break;
      case 47:                         /* alternate screen */
        deselect();
        swap_screen (state);
        disptop = scrtop;
        break;
    } else switch (mode) {
      case 4:                          /* set insert mode */
        insert = state;
        break;
    }
}

/*
 * Process an OSC sequence: set window title or icon name.
 */
static void do_osc(void) {
    if (osc_w) {
        while (osc_strlen--)
            wordness[(unsigned char)osc_string[osc_strlen]] = esc_args[0];
    } else {
        osc_string[osc_strlen] = '\0';
        switch (esc_args[0]) {
          case 0:
          case 1:
            set_icon (osc_string);
            if (esc_args[0] == 1)
                break;
            /* fall through: parameter 0 means set both */
          case 2:
          case 21:
            set_title (osc_string);
            break;
        }
    }
}

/*
 * Remove everything currently in `inbuf' and stick it up on the
 * in-memory display. There's a big state machine in here to
 * process escape sequences...
 */
void term_out(void) {
    int c;

    while ( (c = inbuf_getc()) != -1) {
        /*
         * Optionally log the session traffic to a file. Useful for
         * debugging and possibly also useful for actual logging.
         */
        if (logfile) {
            static FILE *fp = NULL;
            if (!fp) fp = fopen(logfile, "wb");
            if (fp) fputc (c, fp);
        }
        if( termstate < DO_CTRLS && (c&0x60) == 0 ) {
            switch (c) {
              case '\005':             /* terminal type query */
                ldisc->send ("PuTTY\r", 6);
                break;
              case '\007':
                beep();
                disptop = scrtop;
                break;
              case '\b':
                if (curs_x == 0 && curs_y > 0)
                    curs_x = cols-1, curs_y--;
                else if (wrapnext)
                    wrapnext = FALSE;
                else
                    curs_x--;
                fix_cpos;
                seen_disp_event = TRUE;
                break;
              case '\016':
                cset = 1;
                break;
              case '\017':
                cset = 0;
                break;
              case '\033':
                termstate = SEEN_ESC;
                break;
              case 0233:
                termstate = SEEN_CSI;
                esc_nargs = 1;
                esc_args[0] = ARG_DEFAULT;
                esc_query = FALSE;
                break;
              case 0235:
                termstate = SEEN_OSC;
                esc_args[0] = 0;
                break;
              case '\r':
                curs_x = 0;
                wrapnext = FALSE;
                fix_cpos;
                seen_disp_event = TRUE;
                break;
              case '\013':
              case '\014':
              case '\n':
                if (curs_y == marg_b)
                    scroll (marg_t, marg_b, 1, TRUE);
                else if (curs_y < rows-1)
                    curs_y++;
                if (cfg.lfhascr)
                    curs_x = 0;
                fix_cpos;
                wrapnext = FALSE;
                seen_disp_event = 1;
                nl_count++;
                break;
              case '\t':
                do {
                    curs_x++;
                } while (curs_x < cols-1 && !tabs[curs_x]);
                if (curs_x >= cols)
                    curs_x = cols-1;
                {
                    unsigned long *old_cpos = cpos;
                    fix_cpos;
                    check_selection (old_cpos, cpos);
                }
                seen_disp_event = TRUE;
                break;
            }
        }
        else switch (termstate) {
          case TOPLEVEL:
            if (c >= ' ' && c != 0234) {
                if (wrapnext) {
                    cpos[1] = ATTR_WRAPPED;
                    if (curs_y == marg_b)
                        scroll (marg_t, marg_b, 1, TRUE);
                    else if (curs_y < rows-1)
                        curs_y++;
                    curs_x = 0;
                    fix_cpos;
                    wrapnext = FALSE;
                    nl_count++;
                }
                if (insert)
                    insch (1);
                check_selection (cpos, cpos+1);
                *cpos++ = xlat_tty2scr((unsigned char)c) | curr_attr |
                    (c <= 0x7F ? cset_attr[cset] : ATTR_ASCII);
                curs_x++;
                if (curs_x == cols) {
                    cpos--;
                    curs_x--;
                    wrapnext = wrap;
                }
                seen_disp_event = 1;
            }
            break;

          case IGNORE_NEXT:
            termstate = TOPLEVEL;
            break;
          case OSC_MAYBE_ST:
            /*
             * This state is virtually identical to SEEN_ESC, with the
             * exception that we have an OSC sequence in the pipeline,
             * and _if_ we see a backslash, we process it.
             */
            if (c == '\\') {
                do_osc();
                termstate = TOPLEVEL;
                break;
            }
            /* else fall through */
          case SEEN_ESC:
            termstate = TOPLEVEL;
            switch (c) {
              case ' ':                /* some weird sequence? */
                termstate = IGNORE_NEXT;
                break;
              case '[':                /* enter CSI mode */
                termstate = SEEN_CSI;
                esc_nargs = 1;
                esc_args[0] = ARG_DEFAULT;
                esc_query = FALSE;
                break;
              case ']':                /* xterm escape sequences */
                termstate = SEEN_OSC;
                esc_args[0] = 0;
                break;
              case '(':                /* should set GL */
                termstate = SET_GL;
                break;
              case ')':                /* should set GR */
                termstate = SET_GR;
                break;
              case '7':                /* save cursor */
                save_cursor (TRUE);
                break;
              case '8':                /* restore cursor */
                save_cursor (FALSE);
                seen_disp_event = TRUE;
                break;
              case '=':
                app_keypad_keys = TRUE;
                break;
              case '>':
                app_keypad_keys = FALSE;
                break;
              case 'D':                /* exactly equivalent to LF */
                if (curs_y == marg_b)
                    scroll (marg_t, marg_b, 1, TRUE);
                else if (curs_y < rows-1)
                    curs_y++;
                fix_cpos;
                wrapnext = FALSE;
                seen_disp_event = TRUE;
                nl_count++;
                break;
              case 'E':                /* exactly equivalent to CR-LF */
                curs_x = 0;
                wrapnext = FALSE;
                if (curs_y == marg_b)
                    scroll (marg_t, marg_b, 1, TRUE);
                else if (curs_y < rows-1)
                    curs_y++;
                fix_cpos;
                wrapnext = FALSE;
                nl_count++;
                seen_disp_event = TRUE;
                break;
              case 'M':                /* reverse index - backwards LF */
                if (curs_y == marg_t)
                    scroll (marg_t, marg_b, -1, TRUE);
                else if (curs_y > 0)
                    curs_y--;
                fix_cpos;
                wrapnext = FALSE;
                seen_disp_event = TRUE;
                break;
              case 'Z':                /* terminal type query */
                ldisc->send ("\033[?6c", 5);
                break;
              case 'c':                /* restore power-on settings */
                power_on();
                fix_cpos;
                disptop = scrtop;
                seen_disp_event = TRUE;
                break;
              case '#':                /* ESC # 8 fills screen with Es :-) */
                termstate = SEEN_ESCHASH;
                break;
              case 'H':                /* set a tab */
                tabs[curs_x] = TRUE;
                break;
            }
            break;
          case SEEN_CSI:
            termstate = TOPLEVEL;      /* default */
            switch (c) {
              case '0': case '1': case '2': case '3': case '4':
              case '5': case '6': case '7': case '8': case '9':
                if (esc_nargs <= ARGS_MAX) {
                    if (esc_args[esc_nargs-1] == ARG_DEFAULT)
                        esc_args[esc_nargs-1] = 0;
                    esc_args[esc_nargs-1] =
                        10 * esc_args[esc_nargs-1] + c - '0';
                }
                termstate = SEEN_CSI;
                break;
              case ';':
                if (++esc_nargs <= ARGS_MAX)
                    esc_args[esc_nargs-1] = ARG_DEFAULT;
                termstate = SEEN_CSI;
                break;
              case '?':
                esc_query = TRUE;
                termstate = SEEN_CSI;
                break;
              case 'A':                /* move up N lines */
                move (curs_x, curs_y - def(esc_args[0], 1), 1);
                seen_disp_event = TRUE;
                break;
              case 'B': case 'e':      /* move down N lines */
                move (curs_x, curs_y + def(esc_args[0], 1), 1);
                seen_disp_event = TRUE;
                break;
              case 'C': case 'a':      /* move right N cols */
                move (curs_x + def(esc_args[0], 1), curs_y, 1);
                seen_disp_event = TRUE;
                break;
              case 'D':                /* move left N cols */
                move (curs_x - def(esc_args[0], 1), curs_y, 1);
                seen_disp_event = TRUE;
                break;
              case 'E':                /* move down N lines and CR */
                move (0, curs_y + def(esc_args[0], 1), 1);
                seen_disp_event = TRUE;
                break;
              case 'F':                /* move up N lines and CR */
                move (0, curs_y - def(esc_args[0], 1), 1);
                seen_disp_event = TRUE;
                break;
              case 'G': case '`':      /* set horizontal posn */
                move (def(esc_args[0], 1) - 1, curs_y, 0);
                seen_disp_event = TRUE;
                break;
              case 'd':                /* set vertical posn */
                move (curs_x, (dec_om ? marg_t : 0) + def(esc_args[0], 1) - 1,
                      (dec_om ? 2 : 0));
                seen_disp_event = TRUE;
                break;
              case 'H': case 'f':      /* set horz and vert posns at once */
                if (esc_nargs < 2)
                    esc_args[1] = ARG_DEFAULT;
                move (def(esc_args[1], 1) - 1,
                      (dec_om ? marg_t : 0) + def(esc_args[0], 1) - 1,
                      (dec_om ? 2 : 0));
                seen_disp_event = TRUE;
                break;
              case 'J':                /* erase screen or parts of it */
                {
                    unsigned int i = def(esc_args[0], 0) + 1;
                    if (i > 3)
                        i = 0;
                    erase_lots(FALSE, !!(i & 2), !!(i & 1));
                }
                disptop = scrtop;
                seen_disp_event = TRUE;
                break;
              case 'K':                /* erase line or parts of it */
                {
                    unsigned int i = def(esc_args[0], 0) + 1;
                    if (i > 3)
                        i = 0;
                    erase_lots(TRUE, !!(i & 2), !!(i & 1));
                }
                seen_disp_event = TRUE;
                break;
              case 'L':                /* insert lines */
                if (curs_y <= marg_b)
                    scroll (curs_y, marg_b, -def(esc_args[0], 1), FALSE);
                seen_disp_event = TRUE;
                break;
              case 'M':                /* delete lines */
                if (curs_y <= marg_b)
                    scroll (curs_y, marg_b, def(esc_args[0], 1), TRUE);
                seen_disp_event = TRUE;
                break;
              case '@':                /* insert chars */
                insch (def(esc_args[0], 1));
                seen_disp_event = TRUE;
                break;
              case 'P':                /* delete chars */
                insch (-def(esc_args[0], 1));
                seen_disp_event = TRUE;
                break;
              case 'c':                /* terminal type query */
                ldisc->send ("\033[?6c", 5);
                break;
              case 'n':                /* cursor position query */
                if (esc_args[0] == 6) {
                    char buf[32];
                    sprintf (buf, "\033[%d;%dR", curs_y + 1, curs_x + 1);
                    ldisc->send (buf, strlen(buf));
                }
                break;
              case 'h':                /* toggle a mode to high */
                toggle_mode (esc_args[0], esc_query, TRUE);
                break;
              case 'l':                /* toggle a mode to low */
                toggle_mode (esc_args[0], esc_query, FALSE);
                break;
              case 'g':                /* clear tabs */
                if (esc_nargs == 1) {
                    if (esc_args[0] == 0) {
                        tabs[curs_x] = FALSE;
                    } else if (esc_args[0] == 3) {
                        int i;
                        for (i = 0; i < cols; i++)
                            tabs[i] = FALSE;
                    }
                }
                break;
              case 'r':                /* set scroll margins */
                if (!esc_query && esc_nargs <= 2) {
                    int top, bot;
                    top = def(esc_args[0], 1) - 1;
                    if (top < 0)
                        top = 0;
                    bot = (esc_nargs <= 1 || esc_args[1] == 0 ? rows :
                           def(esc_args[1], rows)) - 1;
                    if (bot >= rows)
                        bot = rows-1;
                    if (top <= bot) {
                        marg_t = top;
                        marg_b = bot;
                        curs_x = 0;
                        /*
                         * I used to think the cursor should be
                         * placed at the top of the newly marginned
                         * area. Apparently not: VMS TPU falls over
                         * if so.
                         */
                        curs_y = 0;
                        fix_cpos;
                        seen_disp_event = TRUE;
                    }
                }
                break;
              case 'm':                /* set graphics rendition */
                {
                    int i;
                    for (i=0; i<esc_nargs; i++) {
                        switch (def(esc_args[i], 0)) {
                          case 0:      /* restore defaults */
                            curr_attr = ATTR_DEFAULT; break;
                          case 1:      /* enable bold */
                            curr_attr |= ATTR_BOLD; break;
                          case 4:      /* enable underline */
                          case 21:     /* (enable double underline) */
                            curr_attr |= ATTR_UNDER; break;
                          case 7:      /* enable reverse video */
                            curr_attr |= ATTR_REVERSE; break;
                          case 22:     /* disable bold */
                            curr_attr &= ~ATTR_BOLD; break;
                          case 24:     /* disable underline */
                            curr_attr &= ~ATTR_UNDER; break;
                          case 27:     /* disable reverse video */
                            curr_attr &= ~ATTR_REVERSE; break;
                          case 30: case 31: case 32: case 33:
                          case 34: case 35: case 36: case 37:
                            /* foreground */
                            curr_attr &= ~ATTR_FGMASK;
                            curr_attr |= (esc_args[i] - 30) << ATTR_FGSHIFT;
                            break;
                          case 39:     /* default-foreground */
                            curr_attr &= ~ATTR_FGMASK;
                            curr_attr |= ATTR_DEFFG;
                            break;
                          case 40: case 41: case 42: case 43:
                          case 44: case 45: case 46: case 47:
                            /* background */
                            curr_attr &= ~ATTR_BGMASK;
                            curr_attr |= (esc_args[i] - 40) << ATTR_BGSHIFT;
                            break;
                          case 49:     /* default-background */
                            curr_attr &= ~ATTR_BGMASK;
                            curr_attr |= ATTR_DEFBG;
                            break;
                        }
                    }
                }
                break;
              case 's':                /* save cursor */
                save_cursor (TRUE);
                break;
              case 'u':                /* restore cursor */
                save_cursor (FALSE);
                seen_disp_event = TRUE;
                break;
              case 't':                /* set page size - ie window height */
                request_resize (cols, def(esc_args[0], 24));
                deselect();
                break;
              case 'X':                /* write N spaces w/o moving cursor */
                {
                    int n = def(esc_args[0], 1);
                    unsigned long *p = cpos;
                    if (n > cols - curs_x)
                        n = cols - curs_x;
                    check_selection (cpos, cpos+n);
                    while (n--)
                        *p++ = ERASE_CHAR;
                    seen_disp_event = TRUE;
                }
                break;
              case 'x':                /* report terminal characteristics */
                {
                    char buf[32];
                    int i = def(esc_args[0], 0);
                    if (i == 0 || i == 1) {
                        strcpy (buf, "\033[2;1;1;112;112;1;0x");
                        buf[2] += i;
                        ldisc->send (buf, 20);
                    }
                }
                break;
            }
            break;
          case SET_GL:
          case SET_GR:
            switch (c) {
              case 'A':
                cset_attr[termstate == SET_GL ? 0 : 1] = ATTR_GBCHR;
                break;
              case '0':
                cset_attr[termstate == SET_GL ? 0 : 1] = ATTR_LINEDRW;
                break;
              default:                 /* specifically, 'B' */
                cset_attr[termstate == SET_GL ? 0 : 1] = ATTR_ASCII;
                break;
            }
            termstate = TOPLEVEL;
            break;
          case SEEN_OSC:
            osc_w = FALSE;
            switch (c) {
              case 'P':                /* Linux palette sequence */
                termstate = SEEN_OSC_P;
                osc_strlen = 0;
                break;
              case 'R':                /* Linux palette reset */
                palette_reset();
                term_invalidate();
                termstate = TOPLEVEL;
                break;
              case 'W':                /* word-set */
                termstate = SEEN_OSC_W;
                osc_w = TRUE;
                break;
              case '0': case '1': case '2': case '3': case '4':
              case '5': case '6': case '7': case '8': case '9':
                esc_args[0] = 10 * esc_args[0] + c - '0';
                break;
              case 'L':
                /*
                 * Grotty hack to support xterm and DECterm title
                 * sequences concurrently.
                 */
                if (esc_args[0] == 2) {
                    esc_args[0] = 1;
                    break;
                }
                /* else fall through */
              default:
                termstate = OSC_STRING;
                osc_strlen = 0;
            }
            break;
          case OSC_STRING:
            if (c == 0234 || c == '\007') {
                /*
                 * These characters terminate the string; ST and BEL
                 * terminate the sequence and trigger instant
                 * processing of it, whereas ESC goes back to SEEN_ESC
                 * mode unless it is followed by \, in which case it is
                 * synonymous with ST in the first place.
                 */
                do_osc();
                termstate = TOPLEVEL;
            } else if (c == '\033')
                    termstate = OSC_MAYBE_ST;
            else if (osc_strlen < OSC_STR_MAX)
                osc_string[osc_strlen++] = c;
            break;
          case SEEN_OSC_P:
            {
                int max = (osc_strlen == 0 ? 21 : 16);
                int val;
                if (c >= '0' && c <= '9')
                    val = c - '0';
                else if (c >= 'A' && c <= 'A'+max-10)
                    val = c - 'A' + 10;
                else if (c >= 'a' && c <= 'a'+max-10)
                    val = c - 'a' + 10;
                else
                    termstate = TOPLEVEL;
                osc_string[osc_strlen++] = val;
                if (osc_strlen >= 7) {
                    palette_set (osc_string[0],
                                 osc_string[1] * 16 + osc_string[2],
                                 osc_string[3] * 16 + osc_string[4],
                                 osc_string[5] * 16 + osc_string[6]);
                    term_invalidate();
                    termstate = TOPLEVEL;
                }
            }
            break;
          case SEEN_OSC_W:
            switch (c) {
              case '0': case '1': case '2': case '3': case '4':
              case '5': case '6': case '7': case '8': case '9':
                esc_args[0] = 10 * esc_args[0] + c - '0';
                break;
              default:
                termstate = OSC_STRING;
                osc_strlen = 0;
            }
            break;
          case SEEN_ESCHASH:
            if (c == '8') {
                unsigned long *p = scrtop;
                int n = rows * (cols+1);
                while (n--)
                    *p++ = ATTR_DEFAULT | 'E';
                disptop = scrtop;
                seen_disp_event = TRUE;
                check_selection (scrtop, scrtop + rows * (cols+1));
            }
            termstate = TOPLEVEL;
            break;
        }
        check_selection (cpos, cpos+1);
    }
        
    if (nl_count > MAXNL)
        term_update();
}

/*
 * Compare two lines to determine whether they are sufficiently
 * alike to scroll-optimise one to the other. Return the degree of
 * similarity.
 */
static int linecmp (unsigned long *a, unsigned long *b) {
    int i, n;

    for (i=n=0; i < cols; i++)
        n += (*a++ == *b++);
    return n;
}

/*
 * Given a context, update the window. Out of paranoia, we don't
 * allow WM_PAINT responses to do scrolling optimisations.
 */
static void do_paint (Context ctx, int may_optimise){ 
    int i, j, start, our_curs_y;
    unsigned long attr, rv, cursor;
    char ch[1024];

    cursor = (has_focus ? ATTR_ACTCURS : ATTR_PASCURS);
    rv = (rvideo ? ATTR_REVERSE : 0);
    our_curs_y = curs_y + (scrtop - disptop) / (cols+1);

    for (i=0; i<rows; i++) {
        int idx = i*(cols+1);
        for (j=0; j<=cols; j++,idx++) {
            unsigned long *d = disptop+idx;
            wanttext[idx] = ((*d ^ rv
                              ^ (selstart <= d && d < selend ?
                                 ATTR_REVERSE : 0)) |
                             (i==our_curs_y && j==curs_x ? cursor : 0));
        }
    }

    /*
     * We would perform scrolling optimisations in here, if they
     * didn't have a nasty tendency to cause the whole sodding
     * program to hang for a second at speed-critical moments.
     * We'll leave it well alone...
     */

    for (i=0; i<rows; i++) {
        int idx = i*(cols+1);
        start = -1;
        for (j=0; j<=cols; j++,idx++) {
            unsigned long t = wanttext[idx];
            int needs_update = (j < cols && t != disptext[idx]);
            int keep_going = (start != -1 && needs_update &&
                              (t & ATTR_MASK) == attr &&
                              j-start < sizeof(ch));
            if (start != -1 && !keep_going) {
                do_text (ctx, start, i, ch, j-start, attr);
                start = -1;
            }
            if (needs_update) {
                if (start == -1) {
                    start = j;
                    attr = t & ATTR_MASK;
                }
                ch[j-start] = (char) (t & CHAR_MASK);
            }
            disptext[idx] = t;
        }
    }
}

/*
 * Invalidate the whole screen so it will be repainted in full.
 */
void term_invalidate(void) {
    int i;

    for (i=0; i<rows*(cols+1); i++)
        disptext[i] = ATTR_INVALID;
}

/*
 * Paint the window in response to a WM_PAINT message.
 */
void term_paint (Context ctx, int l, int t, int r, int b) {
    int i, j, left, top, right, bottom;

    left = l / font_width;
    right = (r - 1) / font_width;
    top = t / font_height;
    bottom = (b - 1) / font_height;
    for (i = top; i <= bottom && i < rows ; i++)
      for (j = left; j <= right && j < cols ; j++)
            disptext[i*(cols+1)+j] = ATTR_INVALID;

    do_paint (ctx, FALSE);
}

/*
 * Attempt to scroll the scrollback. The second parameter gives the
 * position we want to scroll to; the first is +1 to denote that
 * this position is relative to the beginning of the scrollback, -1
 * to denote it is relative to the end, and 0 to denote that it is
 * relative to the current position.
 */
void term_scroll (int rel, int where) {
    int n = where * (cols+1);

    disptop = (rel < 0 ? scrtop :
               rel > 0 ? sbtop : disptop) + n;
    if (disptop < sbtop)
        disptop = sbtop;
    if (disptop > scrtop)
        disptop = scrtop;
    update_sbar();
    term_update();
}

/*
 * Spread the selection outwards according to the selection mode.
 */
static unsigned long *sel_spread_half (unsigned long *p, int dir) {
    unsigned long *linestart, *lineend;
    int x;
    short wvalue;

    x = (p - text) % (cols+1);
    linestart = p - x;
    lineend = linestart + cols;

    switch (selmode) {
      case SM_CHAR:
        /*
         * In this mode, every character is a separate unit, except
         * for runs of spaces at the end of a non-wrapping line.
         */
        if (!(linestart[cols] & ATTR_WRAPPED)) {
            unsigned long *q = lineend;
            while (q > linestart && (q[-1] & CHAR_MASK) == 0x20)
                q--;
            if (q == lineend)
                q--;
            if (p >= q)
                p = (dir == -1 ? q : lineend - 1);
        }
        break;
      case SM_WORD:
        /*
         * In this mode, the units are maximal runs of characters
         * whose `wordness' has the same value.
         */
        wvalue = wordness[*p & CHAR_MASK];
        if (dir == +1) {
            while (p < lineend && wordness[p[1] & CHAR_MASK] == wvalue)
                p++;
        } else {
            while (p > linestart && wordness[p[-1] & CHAR_MASK] == wvalue)
                p--;
        }
        break;
      case SM_LINE:
        /*
         * In this mode, every line is a unit.
         */
        p = (dir == -1 ? linestart : lineend - 1);
        break;
    }
    return p;
}

static void sel_spread (void) {
    selstart = sel_spread_half (selstart, -1);
    selend = sel_spread_half (selend - 1, +1) + 1;
}

void term_mouse (Mouse_Button b, Mouse_Action a, int x, int y) {
    unsigned long *selpoint;
    
    if (y<0) y = 0;
    if (y>=rows) y = rows-1;
    if (x<0) {
        if (y > 0) {
            x = cols-1;
            y--;
        } else
            x = 0;
    }
    if (x>=cols) x = cols-1;

    selpoint = disptop + y * (cols+1) + x;

    if (b == MB_SELECT && a == MA_CLICK) {
        deselect();
        selstate = ABOUT_TO;
        selanchor = selpoint;
        selmode = SM_CHAR;
    } else if (b == MB_SELECT && (a == MA_2CLK || a == MA_3CLK)) {
        deselect();
        selmode = (a == MA_2CLK ? SM_WORD : SM_LINE);
        selstate = DRAGGING;
        selstart = selanchor = selpoint;
        selend = selstart + 1;
        sel_spread();
    } else if ((b == MB_SELECT && a == MA_DRAG) ||
               (b == MB_EXTEND && a != MA_RELEASE)) {
        if (selstate == ABOUT_TO && selanchor == selpoint)
            return;
        if (b == MB_EXTEND && a != MA_DRAG && selstate == SELECTED) {
            if (selpoint-selstart < (selend-selstart)/2)
                selanchor = selend - 1;
            else
                selanchor = selstart;
            selstate = DRAGGING;
        }
        if (selstate != ABOUT_TO && selstate != DRAGGING)
            selanchor = selpoint;
        selstate = DRAGGING;
        if (selpoint < selanchor) {
            selstart = selpoint;
            selend = selanchor + 1;
        } else {
            selstart = selanchor;
            selend = selpoint + 1;
        }
        sel_spread();
    } else if ((b == MB_SELECT || b == MB_EXTEND) && a == MA_RELEASE) {
        if (selstate == DRAGGING) {
            /*
             * We've completed a selection. We now transfer the
             * data to the clipboard.
             */
            unsigned char *p = selspace;
            unsigned long *q = selstart;

            while (q < selend) {
                int nl = FALSE;
                unsigned long *lineend = q - (q-text) % (cols+1) + cols;
                unsigned long *nlpos = lineend;

                if (!(*nlpos & ATTR_WRAPPED)) {
                    while ((nlpos[-1] & CHAR_MASK) == 0x20 && nlpos > q)
                        nlpos--;
                    if (nlpos < selend)
                        nl = TRUE;
                }
                while (q < nlpos && q < selend)
                    *p++ = (unsigned char) (*q++ & CHAR_MASK);
                if (nl) {
                    int i;
                    for (i=0; i<sizeof(sel_nl); i++)
                        *p++ = sel_nl[i];
                }
                q = lineend + 1;       /* start of next line */
            }
            write_clip (selspace, p - selspace);
            selstate = SELECTED;
        } else
            selstate = NO_SELECTION;
    } else if (b == MB_PASTE && (a==MA_CLICK || a==MA_2CLK || a==MA_3CLK)) {
        char *data;
        int len;

        get_clip((void **) &data, &len);
        if (data) {
            char *p, *q;
            p = q = data;
            while (p < data+len) {
                while (p < data+len &&
                       !(p <= data+len-sizeof(sel_nl) &&
                         !memcmp(p, sel_nl, sizeof(sel_nl))))
                    p++;

                {
                    int i;
                    unsigned char c;
                    for(i=0;i<p-q;i++)
                    {
                        c=xlat_kbd2tty(q[i]);
                        ldisc->send(&c,1);
                    }
                }

                if (p <= data+len-sizeof(sel_nl) &&
                    !memcmp(p, sel_nl, sizeof(sel_nl))) {
                    ldisc->send ("\r", 1);
                    p += sizeof(sel_nl);
                }
                q = p;
            }
        }
        get_clip(NULL, NULL);
    }

    term_update();
}

static void deselect (void) {
    selstate = NO_SELECTION;
    selstart = selend = scrtop;
}

void term_deselect (void) {
    deselect();
    term_update();
}