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FTWL has been completely removed starting from freeciv 2.4, and it had been non-functional for many releases before that.

Freeciv Theme and Widget LayerEdit

Freeciv Theme and Widget Layer (FTWL) is a low-level library for manipulating the graphics and input systems on your computer, and displaying screens with widgets based on themes loaded from configuration files.

A few naming conventions:

be_* backend functions
te_* theme engine functions
sw_* widget related functions
osda off-screen drawing area buffer

Programming in FTWL is quite simple. Here is an annotated example:

#include <config.h>
Always remember this one, folks, otherwise you end up with bugs that are horribly difficult to figure out. I speak from experience...
#include <assert.h>
#include <stdio.h>

#include "shared.h"
#include "support.h"
These are utility files.
#include "back_end.h"
#include "widget.h"
These two contain the public API of FTWL.
struct sw_widget *root;
A variable to point to the root window.
void nullfunc(int socket); /* prototype */

static bool my_key_handler(struct sw_widget *widget,
                           const struct be_key *key, void *data)
  if (key->type == BE_KEY_NORMAL && key->key == 'q') {
    return TRUE;
  return FALSE;
The above function is a callback that handles all keypresses that are received on the root window. We use this to add a convenient way to exit our example application.
void nullfunc(int socket)
The main loop expects a function pointer that can give it input from outside devices, eg the network. We just use an empty function here.
int main(int argc, char **argv)
  struct ct_size res;
  struct ct_size size;

  res.width = 640;
  res.height = 480;
  be_init(&res, FALSE);
Now we have set up the main window at 640x480.
  /* Error checking */
  if (size.width != res.width || size.height != res.height) {
    die("Instead of the desired screen resolution (%dx%d) "
        "got (%dx%d). This may be a problem with the window-manager.",
        res.width, res.height, size.width, size.height);
Error checking is always nice.
  root = sw_create_root_window();
Set up the root window.
  sw_window_set_key_notify(root, my_key_handler, NULL);
Register our key handler from above. You need to register key handlers for any widget that is supposed to receive key presses.
Start the main loop. Unlike more primitive libraries, FTWL has a built-in main loop, and your program must be callback-driven.
  return 0;
That's it.


  • Add more documentation!
  • Support UNICODE
  • Support more depth on the existing backend
  • Create a backend with palette mode (no transparency, no AA)
  • OpenGL, Quartz and DirectX backends

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