patch.c

#define _GNU_SOURCE
#include <sys/ioctl.h>
#include <stdint.h>
#include <stdbool.h>
#include <stdio.h>
#include <signal.h>
#include <unistd.h>
#include <time.h>
#include <errno.h>

#include "wptypes.h"
#include "wpfuncs.h"
#include "wpvars.h"
#include "hook.h"

// WordPerfect expects 4 decimal characters on mouse press, XXYY. I don't know
// what terminal generates this sequence, certainly no mouse tracking
// mode that XTerm supports looks like that.
//
// https://www.xfree86.org/current/ctlseqs.html#Mouse%20Tracking
//
// The closest is DEC Locator mode, which sends CSI M C b C x C y, but those are
// not decimal coordinates -- they're binary. It's also 3 bytes of parameters, not
// 4. The solution is to patch the callback table and decode the parameters
// ourselves.
static void xy_xterm_mouse()
{
    // The button is currently ignored, but we could examine it.
    uint16_t button = msqot() - 0x20;
    *mouse_x = msqot() - 0x21;
    *mouse_y = msqot() - 0x21;
}

// The wp implementation of dodelay() busy waits, which means macros waiting
// for responses or using {WAIT} keep a whole core busy. Let's use sleep
// instead.
static void delay_millis(int delay)
{
    struct timespec req = {
        .tv_sec = delay / 100,
        .tv_nsec = (delay % 100) * 10000000,
    };

    do {
        if (nanosleep(&req, &req) == 0)
            return;
    } while (errno == EINTR);
}

// Fake a resize event by setting up a SIGWINCH handler.
static void win_resize_event(int signum)
{
    struct winsize w = {0};

    // Fetch the new size.
    if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &w) != 0) {
        return;
    }

    // Make sure this looks sane.
    if (w.ws_col < 24)
        w.ws_col = 24;
    if (w.ws_row < 80)
        w.ws_row = 80;

    // Okay, send this to wordperfect.
    win_resize(w.ws_col, w.ws_row);

    // Rewrite screen.
    frewrt();
}

static struct sigaction winchact = {
    .sa_handler = win_resize_event,
};

uint16_t zero_ext_mapkey(uint16_t code);

void _init()
{
    // This code is called on startup, we can hook or replace wp internals.

    // Patch the mouse event callback to use an XTerm compatible version.
    ms_tbl[0].nbytes     = 3;
    ms_tbl[0].mscallback = xy_xterm_mouse;

    // Insert hooks and redirects.
    insert_function_redirect(dodelay, delay_millis, HOOK_REPLACE_FUNCTION);
    insert_function_redirect(mapkey, zero_ext_mapkey, HOOK_REPLACE_FUNCTION);

    // WordPerfect expects the terminal to send an escape sequence on resize.
    // This isn't how things work on Linux, but we can fake it by setting up a
    // SIGWINCH handler.
    sigaction(SIGWINCH, &winchact, NULL);
}