Java Text User Interface
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README.md

Jexer - Java Text User Interface library

This library implements a text-based windowing system reminiscient of Borland's Turbo Vision system. (For those wishing to use the actual C++ Turbo Vision library, see Sergio Sigala's C++ version based on the sources released by Borland, or consider Free Pascal's Free Vision library.)

Jexer currently supports three backends:

  • System.in/out to a command-line ECMA-48 / ANSI X3.64 type terminal (tested on Linux + xterm). I/O is handled through terminal escape sequences generated by the library itself: ncurses is not required or linked to. xterm mouse tracking using UTF8 and SGR coordinates are supported. For the demo application, this is the default backend on non-Windows/non-Mac platforms.

  • The same command-line ECMA-48 / ANSI X3.64 type terminal as above, but to any general InputStream/OutputStream or Reader/Writer. See the file jexer.demos.Demo2 for an example of running the demo over a TCP socket. jexer.demos.Demo3 demonstrates how one might use a character encoding than the default UTF-8.

  • Java Swing UI. The default window size for Swing is 80x25 and 20 point font; this can be changed in the TApplication(BackendType) constructor. For the demo applications, this is the default backend on Windows and Mac platforms. This backend can be explicitly selected for the demo applications by setting jexer.Swing=true.

Additional backends can be created by subclassing jexer.backend.Backend and passing it into the TApplication constructor. See Demo5 and Demo6 for examples of other backends.

The Jexer homepage, which includes additional information and binary release downloads, is at: https://jexer.sourceforge.io . The Jexer source code is hosted at: https://github.com/klamonte/jexer .

License

This project is licensed under the MIT License. See the file LICENSE for the full license text.

Acknowledgements

Jexer makes use of the Terminus TrueType font made available here .

Usage

Simply subclass TApplication and then run it in a new thread:

import jexer.*;

class MyApplication extends TApplication {

    public MyApplication() throws Exception {
        super(BackendType.SWING); // Could also use BackendType.XTERM

        // Create standard menus for File and Window
        addFileMenu();
        addWindowMenu();

        // Add a custom window, see below for its code.  The TWindow
        // constructor will add it to this application.
        new MyWindow(this);
    }

    public static void main(String [] args) {
        try {
            MyApplication app = new MyApplication();
            (new Thread(app)).start();
        } catch (Throwable t) {
            t.printStackTrace();
        }
    }
}

Similarly, subclass TWindow and add some widgets:

class MyWindow extends TWindow {

    public MyWindow(TApplication application) {
        // See TWindow's API for several constructors.  This one uses the
        // application, title, width, and height.  Note that the window width
        // and height include the borders.  The widgets inside the window
        // will see (0, 0) as the top-left corner inside the borders,
        // i.e. what the window would see as (1, 1).
        super(application, "My Window", 30, 20);

        // See TWidget's API for convenience methods to add various kinds of
        // widgets.  Note that ANY widget can be a container for other
        // widgets: TRadioGroup for example has TRadioButtons as child
        // widgets.

        // We will add a basic label, text entry field, and button.
        addLabel("This is a label", 5, 3);
        addField(5, 5, 20, false, "enter text here");
        // For the button, we will pop up a message box if the user presses
        // it.
        addButton("Press &Me!", 5, 8, new TAction() {
            public void DO() {
                MyWindow.this.messageBox("Box Title", "You pressed me, yay!");
            }
        } );
    }
}

Put these into a file, compile it with jexer.jar in the classpath, run it and you'll see an application like this:

The Example Code Above

See the files in jexer.demos for many more detailed examples showing all of the existing UI controls. The available demos can be run as follows:

  • 'java -jar jexer.jar' . This will use System.in/out with xterm-like sequences on non-Windows non-Mac platforms. On Windows and Mac it will use a Swing JFrame.

  • 'java -Djexer.Swing=true -jar jexer.jar' . This will always use Swing on any platform.

  • 'java -cp jexer.jar jexer.demos.Demo2 PORT' (where PORT is a number to run the TCP daemon on). This will use the telnet protocol to establish an 8-bit clean channel and be aware of screen size changes.

  • 'java -cp jexer.jar jexer.demos.Demo3' . This will use System.in/out with xterm-like sequences. One can see in the code how to pass a different InputReader and OutputReader to TApplication, permitting a different encoding than UTF-8.

  • 'java -cp jexer.jar jexer.demos.Demo4' . This demonstrates hidden windows and a custom TDesktop.

  • 'java -cp jexer.jar jexer.demos.Demo5' . This demonstrates two demo applications using different fonts in the same Swing frame.

  • 'java -cp jexer.jar jexer.demos.Demo6' . This demonstrates one application performing I/O to two screens: an xterm screen and a Swing screen.

More Screenshots

Several Windows Open Including A Terminal

Yo Dawg...

System Properties

The following properties control features of Jexer:

jexer.Swing

Used only by jexer.demos.Demo1 and jexer.demos.Demo4. If true, use the Swing interface for the demo application. Default: true on Windows (os.name starts with "Windows") and Mac (os.name starts with "Mac"), false on non-Windows and non-Mac platforms.

jexer.Swing.cursorStyle

Used by jexer.backend.SwingTerminal. Selects the cursor style to draw. Valid values are: underline, block, outline. Default: underline.

jexer.Swing.tripleBuffer

Used by jexer.backend.SwingTerminal. If true, use triple-buffering which reduces screen tearing but may also be slower to draw on slower systems. If false, use naive Swing thread drawing, which may be faster on slower systems but also more likely to have screen tearing. Default: true.

jexer.TTerminal.ptypipe

Used by jexer.TTerminalWindow. If true, spawn shell using the 'ptypipe' utility rather than 'script'. This permits terminals to resize with the window. ptypipe is a separate C language utility, available at https://github.com/klamonte/ptypipe. Default: false.

Known Issues / Arbitrary Decisions

Some arbitrary design decisions had to be made when either the obviously expected behavior did not happen or when a specification was ambiguous. This section describes such issues.

  • See jexer.tterminal.ECMA48 for more specifics of terminal emulation limitations.

  • TTerminalWindow uses cmd.exe on Windows. Output will not be seen until enter is pressed, due to cmd.exe's use of line-oriented input (see the ENABLE_LINE_INPUT flag for GetConsoleMode() and SetConsoleMode()).

  • TTerminalWindow by default launches 'script -fqe /dev/null' or 'script -q -F /dev/null' on non-Windows platforms. This is a workaround for the C library behavior of checking for a tty: script launches $SHELL in a pseudo-tty. This works on Linux and Mac but might not on other Posix-y platforms.

  • Closing a TTerminalWindow without exiting the process inside it may result in a zombie 'script' process.

  • TTerminalWindow can only notify the child process of changes in window size if using the 'ptypipe' utility, due to Java's lack of support for forkpty() and similar. ptypipe is available at https://github.com/klamonte/ptypipe.

  • Java's InputStreamReader as used by the ECMA48 backend requires a valid UTF-8 stream. The default X10 encoding for mouse coordinates outside (160,94) can corrupt that stream, at best putting garbage keyboard events in the input queue but at worst causing the backend reader thread to throw an Exception and exit and make the entire UI unusable. Mouse support therefore requires a terminal that can deliver either UTF-8 coordinates (1005 mode) or SGR coordinates (1006 mode). Most modern terminals can do this.

  • jexer.session.TTYSession calls 'stty size' once every second to check the current window size, performing the same function as ioctl(TIOCGWINSZ) but without requiring a native library.

  • jexer.backend.ECMA48Terminal calls 'stty' to perform the equivalent of cfmakeraw() when using System.in/out. System.out is also (blindly!) put in 'stty sane cooked' mode when exiting.

Roadmap

Many tasks remain before calling this version 1.0. See docs/TODO.md for the complete list of tasks.