Package com.googlecode.lanterna.terminal

Interface Terminal

All Superinterfaces:

AutoCloseable, Closeable, InputProvider

All Known Subinterfaces:

ExtendedTerminal, IOSafeExtendedTerminal, IOSafeTerminal, VirtualTerminal

All Known Implementing Classes:

AbstractTerminal, ANSITerminal, AWTTerminal, AWTTerminalFrame, CygwinTerminal, DefaultVirtualTerminal, IOSafeTerminalAdapter, IOSafeTerminalAdapter.Extended, ScrollingAWTTerminal, ScrollingSwingTerminal, StreamBasedTerminal, SwingTerminal, SwingTerminalFrame, TelnetTerminal, UnixLikeTerminal, UnixLikeTTYTerminal, UnixTerminal

public interface Terminal
extends InputProvider, Closeable

This is the main terminal interface, at the lowest level supported by Lanterna. You can write your own implementation of this if you want to target an exotic text terminal specification or another graphical environment (like SWT), but you should probably extend AbstractTerminal instead of implementing this interface directly.

The normal way you interact in Java with a terminal is through the standard output (System.out) and standard error (System.err) and it's usually through printing text only. This interface abstracts a terminal at a more fundamental level, expressing methods for not only printing text but also changing colors, moving the cursor new positions, enable special modifiers and get notified when the terminal's size has changed.

If you want to write an application that has a very precise control of the terminal, this is the interface you should be programming against.

Author:

Martin

Method Summary

Modifier and Type	Method	Description
void	addResizeListener(TerminalResizeListener listener)	Adds a TerminalResizeListener to be called when the terminal has changed size.
void	bell()	Prints 0x7 to the terminal, which will make the terminal (emulator) ring a bell (or more likely beep).
void	clearScreen()	Removes all the characters, colors and graphics from the screen and leaves you with a big empty space.
void	close()	Closes the terminal, if applicable.
void	disableSGR(SGR sgr)	Deactivates an SGR (Selected Graphic Rendition) code which has previously been activated through enableSGR(..).
void	enableSGR(SGR sgr)	Activates an SGR (Selected Graphic Rendition) code.
byte[]	enquireTerminal(int timeout, TimeUnit timeoutUnit)	Retrieves optional information from the terminal by printing the ENQ (\u005) character.
void	enterPrivateMode()	Calling this method will, where supported, give your terminal a private area to use, separate from what was there before.
void	exitPrivateMode()	If you have previously entered private mode, this method will exit this and, depending on implementation, maybe restore what the terminal looked like before private mode was entered.
void	flush()	Calls flush() on the underlying OutputStream object, or whatever other implementation this terminal is built around.
TerminalPosition	getCursorPosition()	Returns the position of the cursor, as reported by the terminal.
TerminalSize	getTerminalSize()	Returns the size of the terminal, expressed as a TerminalSize object.
TextGraphics	newTextGraphics()	Creates a new TextGraphics object that uses this Terminal directly when outputting.
void	putCharacter(char c)	Prints one character to the terminal at the current cursor location.
void	removeResizeListener(TerminalResizeListener listener)	Removes a TerminalResizeListener from the list of listeners to be notified when the terminal has changed size
void	resetColorAndSGR()	Removes all currently active SGR codes and sets foreground and background colors back to default.
void	setBackgroundColor(TextColor color)	Changes the background color for all the following characters put to the terminal.
void	setCursorPosition(int x, int y)	Moves the text cursor to a new location on the terminal.
void	setCursorPosition(TerminalPosition position)	Same as calling setCursorPosition(position.getColumn(), position.getRow())
void	setCursorVisible(boolean visible)	Hides or shows the text cursor, but not all terminal (-emulators) supports this.
void	setForegroundColor(TextColor color)	Changes the foreground color for all the following characters put to the terminal.

Methods inherited from interface com.googlecode.lanterna.input.InputProvider

pollInput, readInput

Method Detail

enterPrivateMode

void enterPrivateMode()
               throws IOException

Calling this method will, where supported, give your terminal a private area to use, separate from what was there before. Some terminal emulators will preserve the terminal history and restore it when you exit private mode. Some terminals will just clear the screen and put the cursor in the top-left corner. Typically, if you terminal supports scrolling, going into private mode will disable the scrolling and leave you with a fixed screen, which can be useful if you don't want to deal with what the terminal buffer will look like if the user scrolls up.

Throws:

IOException - If there was an underlying I/O error

IllegalStateException - If you are already in private mode

exitPrivateMode

void exitPrivateMode()
              throws IOException

If you have previously entered private mode, this method will exit this and, depending on implementation, maybe restore what the terminal looked like before private mode was entered. If the terminal doesn't support a secondary buffer for private mode, it will probably make a new line below the private mode and place the cursor there.

Throws:

IOException - If there was an underlying I/O error

IllegalStateException - If you are not in private mode

clearScreen

void clearScreen()
          throws IOException

Removes all the characters, colors and graphics from the screen and leaves you with a big empty space. Text cursor position is undefined after this call (depends on platform and terminal) so you should always call moveCursor next. Some terminal implementations doesn't reset color and modifier state so it's also good practise to call resetColorAndSGR() after this.

Throws:

IOException - If there was an underlying I/O error

setCursorPosition

void setCursorPosition(int x,
                       int y)
                throws IOException

Moves the text cursor to a new location on the terminal. The top-left corner has coordinates 0 x 0 and the bottom- right corner has coordinates terminal_width-1 x terminal_height-1. You can retrieve the size of the terminal by calling getTerminalSize().

Parameters:

x - The 0-indexed column to place the cursor at

y - The 0-indexed row to place the cursor at

Throws:

IOException - If there was an underlying I/O error

setCursorPosition

void setCursorPosition(TerminalPosition position)
                throws IOException

Same as calling setCursorPosition(position.getColumn(), position.getRow())

Parameters:

position - Position to place the cursor at

Throws:

IOException - If there was an underlying I/O error

getCursorPosition

TerminalPosition getCursorPosition()
                            throws IOException

Returns the position of the cursor, as reported by the terminal. The top-left corner has coordinates 0 x 0 and the bottom-right corner has coordinates terminal_width-1 x terminal_height-1.

Returns:

Position of the cursor

Throws:

IOException - In there was an underlying I/O error

setCursorVisible

void setCursorVisible(boolean visible)
               throws IOException

Hides or shows the text cursor, but not all terminal (-emulators) supports this. The text cursor is normally a text block or an underscore, sometimes blinking, which shows the user where keyboard-entered text is supposed to show up.

Parameters:

visible - Hides the text cursor if false and shows it if true

Throws:

IOException - If there was an underlying I/O error

putCharacter

void putCharacter(char c)
           throws IOException

Prints one character to the terminal at the current cursor location. Please note that the cursor will then move one column to the right, so multiple calls to putCharacter will print out a text string without the need to reposition the text cursor. If you reach the end of the line while putting characters using this method, you can expect the text cursor to move to the beginning of the next line.

You can output CJK (Chinese, Japanese, Korean) characters (as well as other regional scripts) but remember that the terminal that the user is using might not have the required font to render it. Also worth noticing is that CJK (and some others) characters tend to take up 2 columns per character, simply because they are a square in their construction as opposed to the somewhat rectangular shape we fit latin characters in. As it's very difficult to create a monospace font for CJK with a 2:1 height-width proportion, it seems like the implementers back in the days simply gave up and made each character take 2 column. It causes issues for the random terminal programmer because you can't really trust 1 character = 1 column, but I suppose it's "しょうがない". If you try to print non-printable control characters, the terminal is likely to ignore them (all Terminal implementations bundled with Lanterna will).

Parameters:

c - Character to place on the terminal

Throws:

IOException - If there was an underlying I/O error

newTextGraphics

TextGraphics newTextGraphics()
                      throws IOException

Creates a new TextGraphics object that uses this Terminal directly when outputting. Keep in mind that you are probably better off to switch to a Screen to make advanced text graphics more efficient. Also, this TextGraphics implementation will not call .flush() after any operation, so you'll need to do that on your own.

Returns:

TextGraphics implementation that draws directly using this Terminal interface

Throws:

IOException - If there was an I/O error when setting up the TextGraphics object

enableSGR

void enableSGR(SGR sgr)
        throws IOException

Activates an SGR (Selected Graphic Rendition) code. This code modifies a state inside the terminal that will apply to all characters written afterwards, such as bold, italic, blinking code and so on.

Parameters:

sgr - SGR code to apply

Throws:

IOException - If there was an underlying I/O error

See Also:

SGR, http://www.vt100.net/docs/vt510-rm/SGR

disableSGR

void disableSGR(SGR sgr)
         throws IOException

Deactivates an SGR (Selected Graphic Rendition) code which has previously been activated through enableSGR(..).

Parameters:

sgr - SGR code to apply

Throws:

IOException - If there was an underlying I/O error

See Also:

SGR, http://www.vt100.net/docs/vt510-rm/SGR

resetColorAndSGR

void resetColorAndSGR()
               throws IOException

Removes all currently active SGR codes and sets foreground and background colors back to default.

Throws:

IOException - If there was an underlying I/O error

See Also:

SGR, http://www.vt100.net/docs/vt510-rm/SGR

setForegroundColor

void setForegroundColor(TextColor color)
                 throws IOException

Changes the foreground color for all the following characters put to the terminal. The foreground color is what color to draw the text in, as opposed to the background color which is the color surrounding the characters.

This overload is using the TextColor class to define a color, which is a layer of abstraction above the three different color formats supported (ANSI, indexed and RGB). The other setForegroundColor(..) overloads gives you direct access to set one of those three.

Note to implementers of this interface, just make this method call color.applyAsForeground(this);

Parameters:

color - Color to use for foreground

Throws:

IOException - If there was an underlying I/O error

setBackgroundColor

void setBackgroundColor(TextColor color)
                 throws IOException

Changes the background color for all the following characters put to the terminal. The background color is the color surrounding the text being printed.

This overload is using the TextColor class to define a color, which is a layer of abstraction above the three different color formats supported (ANSI, indexed and RGB). The other setBackgroundColor(..) overloads gives you direct access to set one of those three.

Note to implementers of this interface, just make this method call color.applyAsBackground(this);

Parameters:

color - Color to use for the background

Throws:

IOException - If there was an underlying I/O error

addResizeListener

void addResizeListener(TerminalResizeListener listener)

Adds a TerminalResizeListener to be called when the terminal has changed size. There is no guarantee that this listener will really be invoked when the terminal has changed size, at all depends on the terminal emulator implementation. Normally on Unix systems the WINCH signal will be sent to the process and lanterna can intercept this.

There are no guarantees on what thread the call will be made on, so please be careful with what kind of operation you perform in this callback. You should probably not take too long to return.

Parameters:

listener - Listener object to be called when the terminal has been changed

See Also:

TerminalResizeListener

removeResizeListener

void removeResizeListener(TerminalResizeListener listener)

Removes a TerminalResizeListener from the list of listeners to be notified when the terminal has changed size

Parameters:

listener - Listener object to remove

See Also:

TerminalResizeListener

getTerminalSize

TerminalSize getTerminalSize()
                      throws IOException

Returns the size of the terminal, expressed as a TerminalSize object. Please bear in mind that depending on the Terminal implementation, this may or may not be accurate. See the implementing classes for more information. Most commonly, calling getTerminalSize() will involve some kind of hack to retrieve the size of the terminal, like moving the cursor to position 5000x5000 and then read back the location, unless the terminal implementation has a more smooth way of getting this data. Keep this in mind and see if you can avoid calling this method too often. There is a helper class, SimpleTerminalResizeListener, that you can use to cache the size and update it only when resize events are received (which depends on if a resize is detectable, which they are not on all platforms).

Returns:

Size of the terminal

Throws:

IOException - if there was an I/O error trying to retrieve the size of the terminal

enquireTerminal

byte[] enquireTerminal(int timeout,
                       TimeUnit timeoutUnit)
                throws IOException

Retrieves optional information from the terminal by printing the ENQ (\u005) character. Terminals and terminal emulators may or may not respond to this command, sometimes it's configurable.

Parameters:

timeout - How long to wait for the talk-back message, if there's nothing immediately available on the input stream, you should probably set this to a somewhat small value to prevent unnecessary blockage on the input stream but large enough to accommodate a round-trip to the user's terminal (~300 ms if you are connection across the globe).

timeoutUnit - What unit to use when interpreting the timeout parameter

Returns:

Answer-back message from the terminal or empty if there was nothing

Throws:

IOException - If there was an I/O error while trying to read the enquiry reply

bell

void bell()
   throws IOException

Prints 0x7 to the terminal, which will make the terminal (emulator) ring a bell (or more likely beep). Not all terminals implements this. Wikipedia has more details.

Throws:

IOException - If there was an underlying I/O error

flush

void flush()
    throws IOException

Calls flush() on the underlying OutputStream object, or whatever other implementation this terminal is built around. Some implementing classes of this interface (like SwingTerminal) doesn't do anything as it doesn't really apply to them.

Throws:

IOException - If there was an underlying I/O error

close

void close()
    throws IOException

Closes the terminal, if applicable. If the implementation doesn't support closing the terminal, this will do nothing. The Swing/AWT emulator implementations will translate this into a dispose() call on the UI resources, the telnet implementation will hang out the connection.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Throws:

IOException - If there was an underlying I/O error