incise.org: tinywm

incise.org: tinywm

TinyWM is a tiny window manager that I created as an exercise in minimalism. It is also maybe helpful in learning some of the very basics of creating a window manager. It is only around 50 lines of C. There is also a Python version using python-xlib.

It lets you do four basic things:

Move windows interactively with Alt+Button1 drag (left mouse button)
Resize windows interactively with Alt+Button3 drag (right mouse button)
Raise windows with Alt+F1 (not high on usability I know, but I needed a keybinding in there somewhere)
Focus windows with the mouse pointer (X does this on its own)
Download
http://incise.org/files/dev/tinywm-1.3.tgz
Github
Known to be packaged in
Debian
Ubuntu
FreeBSD
CRUX
TinyWM around the web
SkatOSWM
In Lisp
someone hacking it
Is this cool, or what?
In a car PC
This guy is doing something or another with it
Ada version
XCB version
Some Processing-related project at the Rhode Island School of Design
Chicken Scheme version
Giles Orr’s Window Manager Report
An extension for Tiny Core Linux
Possum window manaager
SmallWM
See Also
not so tiny window managers
whimsy
The source
Here is tinywm.c from the most recent release, 1.3:


/* TinyWM is written by Nick Welch <mack@incise.org>, 2005.
 *
 * This software is in the public domain
 * and is provided AS IS, with NO WARRANTY. */

#include <X11/Xlib.h>

#define MAX(a, b) ((a) > (b) ? (a) : (b))

int main()
{
    Display * dpy;
    Window root;
    XWindowAttributes attr;
    XButtonEvent start;
    XEvent ev;

    if(!(dpy = XOpenDisplay(0x0))) return 1;

    root = DefaultRootWindow(dpy);

    XGrabKey(dpy, XKeysymToKeycode(dpy, XStringToKeysym("F1")), Mod1Mask, root,
            True, GrabModeAsync, GrabModeAsync);
    XGrabButton(dpy, 1, Mod1Mask, root, True, ButtonPressMask, GrabModeAsync,
            GrabModeAsync, None, None);
    XGrabButton(dpy, 3, Mod1Mask, root, True, ButtonPressMask, GrabModeAsync,
            GrabModeAsync, None, None);

    for(;;)
    {
        XNextEvent(dpy, &ev);
        if(ev.type == KeyPress && ev.xkey.subwindow != None)
            XRaiseWindow(dpy, ev.xkey.subwindow);
        else if(ev.type == ButtonPress && ev.xbutton.subwindow != None)
        {
            XGrabPointer(dpy, ev.xbutton.subwindow, True,
                    PointerMotionMask|ButtonReleaseMask, GrabModeAsync,
                    GrabModeAsync, None, None, CurrentTime);
            XGetWindowAttributes(dpy, ev.xbutton.subwindow, &attr);
            start = ev.xbutton;
        }
        else if(ev.type == MotionNotify)
        {
            int xdiff, ydiff;
            while(XCheckTypedEvent(dpy, MotionNotify, &ev));
            xdiff = ev.xbutton.x_root - start.x_root;
            ydiff = ev.xbutton.y_root - start.y_root;
            XMoveResizeWindow(dpy, ev.xmotion.window,
                attr.x + (start.button==1 ? xdiff : 0),
                attr.y + (start.button==1 ? ydiff : 0),
                MAX(1, attr.width + (start.button==3 ? xdiff : 0)),
                MAX(1, attr.height + (start.button==3 ? ydiff : 0)));
        }
        else if(ev.type == ButtonRelease)
            XUngrabPointer(dpy, CurrentTime);
    }
}

Here is annotated.c, which is just tinywm.c with a lot of comments explaining what is going on. This should give you a reasonable idea of how everything works.

/* TinyWM is written by Nick Welch <mack@incise.org>, 2005.
 *
 * This software is in the public domain
 * and is provided AS IS, with NO WARRANTY. */

/* much of tinywm's purpose is to serve as a very basic example of how to do X
 * stuff and/or understand window managers, so i wanted to put comments in the
 * code explaining things, but i really hate wading through code that is
 * over-commented -- and for that matter, tinywm is supposed to be as concise
 * as possible, so having lots of comments just wasn't really fitting for it.
 * i want tinywm.c to be something you can just look at and go "wow, that's
 * it?  cool!"  so what i did was just copy it over to annotated.c and comment
 * the hell out of it.  ahh, but now i have to make every code change twice!
 * oh well.  i could always use some sort of script to process the comments out
 * of this and write it to tinywm.c ... nah.
 */

/* most X stuff will be included with Xlib.h, but a few things require other
 * headers, like Xmd.h, keysym.h, etc.
 */
#include <X11/Xlib.h>

#define MAX(a, b) ((a) > (b) ? (a) : (b))

int main()
{
    Display * dpy;
    Window root;
    XWindowAttributes attr;

    /* we use this to save the pointer's state at the beginning of the
     * move/resize.
     */
    XButtonEvent start;

    XEvent ev;


    /* return failure status if we can't connect */
    if(!(dpy = XOpenDisplay(0x0))) return 1;

    /* you'll usually be referencing the root window a lot.  this is a somewhat
     * naive approach that will only work on the default screen.  most people
     * only have one screen, but not everyone.  if you run multi-head without
     * xinerama then you quite possibly have multiple screens. (i'm not sure
     * about vendor-specific implementations, like nvidia's)
     *
     * many, probably most window managers only handle one screen, so in
     * reality this isn't really *that* naive.
     *
     * if you wanted to get the root window of a specific screen you'd use
     * RootWindow(), but the user can also control which screen is our default:
     * if they set $DISPLAY to ":0.foo", then our default screen number is
     * whatever they specify "foo" as.
     */
    root = DefaultRootWindow(dpy);

    /* you could also include keysym.h and use the XK_F1 constant instead of
     * the call to XStringToKeysym, but this method is more "dynamic."  imagine
     * you have config files which specify key bindings.  instead of parsing
     * the key names and having a huge table or whatever to map strings to XK_*
     * constants, you can just take the user-specified string and hand it off
     * to XStringToKeysym.  XStringToKeysym will give you back the appropriate
     * keysym or tell you if it's an invalid key name.
     *
     * a keysym is basically a platform-independent numeric representation of a
     * key, like "F1", "a", "b", "L", "5", "Shift", etc.  a keycode is a
     * numeric representation of a key on the keyboard sent by the keyboard
     * driver (or something along those lines -- i'm no hardware/driver expert)
     * to X.  so we never want to hard-code keycodes, because they can and will
     * differ between systems.
     */
    XGrabKey(dpy, XKeysymToKeycode(dpy, XStringToKeysym("F1")), Mod1Mask, root,
            True, GrabModeAsync, GrabModeAsync);

    /* XGrabKey and XGrabButton are basically ways of saying "when this
     * combination of modifiers and key/button is pressed, send me the events."
     * so we can safely assume that we'll receive Alt+F1 events, Alt+Button1
     * events, and Alt+Button3 events, but no others.  You can either do
     * individual grabs like these for key/mouse combinations, or you can use
     * XSelectInput with KeyPressMask/ButtonPressMask/etc to catch all events
     * of those types and filter them as you receive them.
     */
    XGrabButton(dpy, 1, Mod1Mask, root, True, ButtonPressMask, GrabModeAsync,
            GrabModeAsync, None, None);
    XGrabButton(dpy, 3, Mod1Mask, root, True, ButtonPressMask, GrabModeAsync,
            GrabModeAsync, None, None);

    for(;;)
    {
        /* this is the most basic way of looping through X events; you can be
         * more flexible by using XPending(), or ConnectionNumber() along with
         * select() (or poll() or whatever floats your boat).
         */
        XNextEvent(dpy, &ev);

        /* this is our keybinding for raising windows.  as i saw someone
         * mention on the ratpoison wiki, it is pretty stupid; however, i
         * wanted to fit some sort of keyboard binding in here somewhere, and
         * this was the best fit for it.
         *
         * i was a little confused about .window vs. .subwindow for a while,
         * but a little RTFMing took care of that.  our passive grabs above
         * grabbed on the root window, so since we're only interested in events
         * for its child windows, we look at .subwindow.  when subwindow
         * None, that means that the window the event happened in was the same
         * window that was grabbed on -- in this case, the root window.
         */
        if(ev.type == KeyPress && ev.xkey.subwindow != None)
            XRaiseWindow(dpy, ev.xkey.subwindow);
        else if(ev.type == ButtonPress && ev.xbutton.subwindow != None)
        {
            /* now we take command of the pointer, looking for motion and
             * button release events.
             */
            XGrabPointer(dpy, ev.xbutton.subwindow, True,
                    PointerMotionMask|ButtonReleaseMask, GrabModeAsync,
                    GrabModeAsync, None, None, CurrentTime);

            /* we "remember" the position of the pointer at the beginning of
             * our move/resize, and the size/position of the window.  that way,
             * when the pointer moves, we can compare it to our initial data
             * and move/resize accordingly.
             */
            XGetWindowAttributes(dpy, ev.xbutton.subwindow, &attr);
            start = ev.xbutton;
        }
        /* the only way we'd receive a motion notify event is if we already did
         * a pointer grab and we're in move/resize mode, so we assume that. */
        else if(ev.type == MotionNotify)
        {
            int xdiff, ydiff;

            /* here we "compress" motion notify events.  if there are 10 of
             * them waiting, it makes no sense to look at any of them but the
             * most recent.  in some cases -- if the window is really big or
             * things are just acting slowly in general -- failing to do this
             * can result in a lot of "drag lag."
             *
             * for window managers with things like desktop switching, it can
             * also be useful to compress EnterNotify events, so that you don't
             * get "focus flicker" as windows shuffle around underneath the
             * pointer.
             */
            while(XCheckTypedEvent(dpy, MotionNotify, &ev));

            /* now we use the stuff we saved at the beginning of the
             * move/resize and compare it to the pointer's current position to
             * determine what the window's new size or position should be.
             *
             * if the initial button press was button 1, then we're moving.
             * otherwise it was 3 and we're resizing.
             *
             * we also make sure not to go negative with the window's
             * dimensions, resulting in "wrapping" which will make our window
             * something ridiculous like 65000 pixels wide (often accompanied
             * by lots of swapping and slowdown).
             *
             * even worse is if we get "lucky" and hit a width or height of
             * exactly zero, triggering an X error.  so we specify a minimum
             * width/height of 1 pixel.
             */
            xdiff = ev.xbutton.x_root - start.x_root;
            ydiff = ev.xbutton.y_root - start.y_root;
            XMoveResizeWindow(dpy, ev.xmotion.window,
                attr.x + (start.button==1 ? xdiff : 0),
                attr.y + (start.button==1 ? ydiff : 0),
                MAX(1, attr.width + (start.button==3 ? xdiff : 0)),
                MAX(1, attr.height + (start.button==3 ? ydiff : 0)));
        }
        /* like motion notifies, the only way we'll receive a button release is
         * during a move/resize, due to our pointer grab.  this ends the
         * move/resize.
         */
        else if(ev.type == ButtonRelease)
            XUngrabPointer(dpy, CurrentTime);
    }
}

And here’s tinywm.py. XCheckTypedEvent has no equivalent in python-xlib, so it is commented out. It doesn’t affect functionality, except that responsiveness is worse when you are moving/resizing (especially resizing a large window).

# TinyWM is written by Nick Welch <mack@incise.org>, 2005.
#
# This software is in the public domain
# and is provided AS IS, with NO WARRANTY.

from Xlib.display import Display
from Xlib import X, XK

dpy = Display()
root = dpy.screen().root

root.grab_key(XK.string_to_keysym("F1"), X.Mod1Mask, 1,
        X.GrabModeAsync, X.GrabModeAsync)
root.grab_button(1, X.Mod1Mask, 1, X.ButtonPressMask,
        X.GrabModeAsync, X.GrabModeAsync, X.NONE, X.NONE)
root.grab_button(3, X.Mod1Mask, 1, X.ButtonPressMask,
        X.GrabModeAsync, X.GrabModeAsync, X.NONE, X.NONE)

while 1:
    ev = root.display.next_event()

    if ev.type == X.KeyPress and ev.child != X.NONE:
        ev.window.circulate(X.RaiseLowest)
    elif ev.type == X.ButtonPress and ev.child != X.NONE:
        ev.child.grab_pointer(1, X.PointerMotionMask|X.ButtonReleaseMask,
                X.GrabModeAsync, X.GrabModeAsync, X.NONE, X.NONE, X.CurrentTime)
        attr = ev.child.get_geometry()
        start = ev
    elif ev.type == X.MotionNotify:
        #while(XCheckTypedEvent(dpy, MotionNotify, &ev));
        xdiff = ev.root_x - start.root_x
        ydiff = ev.root_y - start.root_y
        ev.window.configure(
            x = attr.x + (start.detail == 1 and xdiff or 0),
            y = attr.y + (start.detail == 1 and ydiff or 0),
            width = max(1, attr.width + (start.detail == 3 and xdiff or 0)),
            height = max(1, attr.height + (start.detail == 3 and ydiff or 0)))
    elif ev.type == X.ButtonRelease:
        dpy.ungrab_pointer(X.CurrentTime)

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