sixel in README

[fanfix.git] / README.md

Jexer - Java Text User Interface library
========================================

This library implements a text-based windowing system loosely
reminiscient of Borland's [Turbo
Vision](http://en.wikipedia.org/wiki/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,](http://tvision.sourceforge.net/) or consider Free Pascal's
[Free Vision library.](http://wiki.freepascal.org/Free_Vision))

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 is supported using both UTF8 and
  SGR coordinates.  Images are optionally rendered via sixel graphics
  (see jexer.ECMA48.sixel).  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 (telnet) 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://gitlab.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](http://files.ax86.net/terminus-ttf/) .



Usage
-----

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

```Java
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:

```Java
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](/screenshots/readme_application.png?raw=true "The application in the text of README.md")

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](/screenshots/screenshot1.png?raw=true "Several Windows Open Including A Terminal")

![Yo Dawg...](/screenshots/yodawg.png?raw=true "Yo Dawg, I heard you like text windowing systems, so I ran a text windowing system inside your text windowing system so you can have a terminal in your terminal.")

![Sixel Pictures Of Cliffs Of Moher And Buoy](/screenshots/sixel_images.png?raw=true "Sixel Pictures Of Cliffs Of Moher And Buoy")

![Sixel Color Wheel](/screenshots/sixel_color_wheel.png?raw=true "Sixel Color Wheel")



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://gitlab.com/klamonte/ptypipe.  Default: false.

  jexer.TTerminal.closeOnExit
  ---------------------------

  Used by jexer.TTerminalWindow.  If true, close the window when the
  spawned shell exits.  Default: false.

  jexer.ECMA48.rgbColor
  ---------------------

  Used by jexer.backend.ECMA48Terminal.  If true, emit T.416-style RGB
  colors for normal system colors.  This is expensive in bandwidth,
  and potentially terrible looking for non-xterms.  Default: false.

  jexer.ECMA48.sixel
  ------------------

  Used by jexer.backend.ECMA48Terminal.  If true, emit image data
  using sixel, otherwise show blank cells where images could be.  This
  is expensive in bandwidth, very expensive in CPU (especially for
  large images), and will leave artifacts on the screen if the
  terminal does not support sixel.  Default: true.



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.

  - When using the Swing backend, and not using 'ptypipe', closing a
    TTerminalWindow without exiting the process inside it may result
    in a SIGTERM to the JVM causing it to crash.  The root cause is
    currently unknown, but is potentially a bug in more recent
    releases of the 'script' utility from the util-linux package.

  - 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://gitlab.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.

  - jexer.backend.ECMA48Terminal uses a single palette containing
    MAX_COLOR_REGISTERS colors for all sixel images.  These colors are
    generated in the SixelPalette.makePalette() method with bits for
    hue, saturation, and luminance, and the two extremes set to pure
    black and pure white.  This provides a reasonable general-purpose
    palette light on CPU, but at a cost that individual images do not
    look as good as the terminal is actually capable of.



See Also
--------

[Tranquil Java IDE](https://tjide.sourceforge.io) is a TUI-based
integrated development environment for the Java language that was
built using a very lightly modified GPL version of Jexer.  TJ provided
a real-world use case to shake out numerous bugs and limitations of
Jexer.