Moves the mouse pointer between screens on an X11 display

moveptr.c

/**
 * @file
 * @brief Moves the mouse pointer between screens on an X11 display.
 *
 * This program might be useful to you if you wish to switch between two X11
 * screens without moving your hands from the keyboard. I configure bbkeys to
 * map the otherwise-unused windows keys and right-click key to move to the left
 * screen, move to the right screen, and toggle between screens, respectively.
 *
 * Run with zero to three arguments (additional arguments are ignored). The
 * first argument is taken as an integer specifying the screen number on which
 * to place the mouse cursor in the center of the screen under the display
 * specified by the DISPLAY environment variable. If there is no first argument
 * or if the first argument is negative, the screen number is chosen by taking
 * the screen number parsed from DISPLAY (e.g., screen 1 if DISPLAY = ":0.1")
 * and setting the new value to (current - arg1) % number_of_screens. The
 * optional second and third arguments specify the x and y coordinates of the
 * mouse cursor (defaulting to the center of the screen). Absolute coordinates
 * are used by default; relative coordinates are accepted when an argument
 * begins with '+' or '-'. Relative and absolute arguments cannot be mixed, but
 * this effect can sometimes be acheived by making multiple calls to moveptr.
 * Relative cursor movements can be made only on the current display, so the
 * screen parameter is ignored.
 *
 * As a special case, if the screen number (first argument) is negative zero
 * (-0), the current screen is used for cursor positioning.
 *
 * This code is in the public domain. Originally written by Darren Kulp in 2009.
 *
 * @return Exits with return code 1 if the display cannot be opened, with return
 * code 2 if the XTEST extension is not supported, with return code 3 if the
 * motion event failed, with return code 4 if an argument parsing error
 * occurred, with return code 5 if a miscellaneous error occurred, or with
 * return code 0 if the operation appeared to complete successfully.
 */

#include <stdlib.h>
#include <string.h>

#include <X11/Xlib.h>
#include <X11/keysym.h>
#include <X11/extensions/XTest.h>

int main(int argc, char *argv[])
{
    enum { SUCCESS, CANT_OPEN, NO_XTEST, MOTION_FAILED, BAD_ARGS, MISC_ERROR };

    Display* dpy = XOpenDisplay(NULL);
    if (!dpy)
        return CANT_OPEN;

    {
        int trash;
        int ext = XTestQueryExtension(dpy, &trash, &trash, &trash, &trash);
        if (!ext)
            return NO_XTEST;
    }

    int screen = -1;
    int screenset = 0;
    char *check;
    if (argc > 1) {
        screenset = 1;
        screen = strtol(argv[1], &check, 0);
        if (check == argv[1])
            return BAD_ARGS;
        else if (screen == 0 && argv[1][0] == '-')
            screen = -1;
    }

    if (!screenset) {
        char* curr = getenv("DISPLAY");
        if (!curr)
            return MISC_ERROR;
        curr = strrchr(curr, '.') + 1;
        screen = (strtol(curr, &check, 0) - screen) % ScreenCount(dpy);
        if (check == curr)
            return BAD_ARGS;
    }

    int width  = DisplayWidth(dpy, screen);
    int height = DisplayHeight(dpy, screen);
    int x = 0;
    int y = 0;
    int xset = 0;
    int yset = 0;

    int relative = 0;

    switch (argc) {
        default:
        case 4:
            relative |= (argv[3][0] == '-' || argv[3][0] == '+');
            y = strtol(argv[3], &check, 0);
            yset = 1;
            if (check == argv[3])
                return BAD_ARGS;
        case 3:
            relative |= (argv[2][0] == '-' || argv[2][0] == '+');
            x = strtol(argv[2], &check, 0);
            xset = 1;
            if (check == argv[2])
                return BAD_ARGS;
        case 2:
        case 1:
        case 0:
            break;
    }

    if (!relative) {
        if (!xset) x = width  >> 1;
        if (!yset) y = height >> 1;
    }

    Status rc = relative
        ? XTestFakeRelativeMotionEvent(dpy, x, y, CurrentTime)
        : XTestFakeMotionEvent(dpy, screen, x, y, CurrentTime);

    if (!rc)
        return MOTION_FAILED;

    rc = XCloseDisplay(dpy);
    if (!rc)
        return MISC_ERROR;

    return SUCCESS;
}

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