strtok has a "first case" and "other case" usage. The first time you call strtok, you pass it the string. Future calls must pass NULL for this same session. This leads to this kind of code:

void foo(char *mystr) {
  char *tok;

  tok = strtok(mystr, " ");
  while (tok != NULL) {
    // Do something with tok

    tok = strtok(NULL, " ");
  }
}

Notice the above duplicate code. You can use pointers properly and achieve this same result with only one line using strtok:

void foo(char *mystr) {
  char *tok;
  char *strptr = mystr;

  while ( (tok = strtok(strptr, " ")) != NULL ) {
    if (strptr != NULL)
      strptr = NULL;
    // Do something with tok
  }
}

This method lets you still invoke both first and nonfirst cases of strtok but you only have one line of code using strtok, making your code more maintainable and readable. This way has the great benefit of being able to use 'continue' inside your loop and you still move on to the next token.

Today was a learning day. A few months ago, I released keynav, a tool to make large-area mouse navigation very quick. However, I found myself using keynav to do the same things over and over again. Select certain windows, clicking on certain UI widgets, etc; things that are annoying to do repeatedly.

What if we had a way to describe input actions? What if you could say "Focus the firefox URL bar" with a simple keystroke, without having firefox focused? This premise is fairly simple - Focus firefox, then "click" on a certain part of the window. The URL bar's location is pretty reliable (a few pixels from the top).

If you're like me, firefox is on another virtual desktop. What if firefox isn't shown right now because you're on "Desktop 1" and firefox lives on "Desktop 2"? Well we can find out if it's hidden, then send the keystrokes (via XTEST) to switch to "Desktop 2" and then do whatever we would normally do to focus on Firefox's URL bar. The basic pseudocode of the script would look like:

if firefox is not shown:
  go to desktop 2 ("fake send alt+2")

focus firefox (via fake click?)
fake send "Control+L" (Firefox's shortcut for focusing the urlbar)

Seems pretty simple. "Fake" above refers to events sent using the XTest, an extension to X11 (Xorg/XFree86) that lets you send keystrokes and mouse events as if they had been typed.

So, tonight I started work on a project that would let you script actions. Generally, I'm aiming at scripting UI interaction to make common tasks such as "take me to firefox" simpler.

I revisited some man pages for Xlib I hadn't seen in many months, and now I can traverse the list of all open windows in X and show their status. Here's what this tool outputs; notice how I can tell if the window is visible ("shown" by the window manager):

+ 8388621 (1x16@424,324) [Visible]
  teabag(.../home/jls/projects/navmacro)
  "xterm" "XTerm" 
+ 44040205 (1x16@424,324) [Hidden]
  snack(~) % @ snack
  "xterm" "XTerm" 
+ 29360192 (1x15@1278,1008) [Hidden]
  HMUG: man XWindowAttributes (3) - Mozilla Firefox
  "firefox-bin" "Firefox-bin"

The other piece of learning I did tonight was to learn GTK2. Enough fiddling around and I was able to get a input field that pops up over everything and is as wide as the screen to input your macros in. GTK's not that bad. Its API design is fairly intuitive and I didn't have much trouble getting things working. I even figured out how to ask GTK what it's X window ID is. Most of this knowledge comes from the GDK X Windows Interaction documentation.

#include <gtk/gtk.h>
#include <gdk/gdkx.h>

static void activate(GtkWidget *widget, gpointer data) {
  // widget->window is the GdkWindow containing this widget.
  g_print("Display handle: %x\n", GDK_WINDOW_XDISPLAY(widget->window));
  g_print("Window id: %d\n", GDK_WINDOW_XID(widget->window));
}

int main(int argc, char **argv) {
  GtkWidget *window;

  gtk_init (&argc, &argv);
  window = gtk_window_new (GTK_WINDOW_TOPLEVEL);

  g_signal_connect(G_OBJECT(window), "realize",
                   G_CALLBACK(activate), NULL);

  gtk_widget_show_all(window);
  gtk_main();
  return 0;
}

Compiled with: gcc `pkg-config --cflags --libs x11` test.c

The little bit of GTK I wrote tonight can be found here. It's not much, but it does example how to use GTK and Xlib at the same time, on the same windows.

Oops... it's getting light outside. Naptime ;)