com.googlecode.lanterna.screen

Class TerminalScreen

java.lang.Object

com.googlecode.lanterna.screen.AbstractScreen

com.googlecode.lanterna.screen.TerminalScreen

All Implemented Interfaces:

InputProvider, Screen

public class TerminalScreen
extends AbstractScreen

This is the default concrete implementation of the Screen interface, a buffered layer sitting on top of a Terminal. If you want to get started with the Screen layer, this is probably the class you want to use. Remember to start the screen before you can use it and stop it when you are done with it.

Author:

martin

Nested Class Summary

Nested classes/interfaces inherited from interface com.googlecode.lanterna.screen.Screen

Screen.RefreshType

Field Summary

Fields inherited from interface com.googlecode.lanterna.screen.Screen

DEFAULT_CHARACTER

Constructor Summary

Constructors

Constructor and Description
TerminalScreen(Terminal terminal) Creates a new Screen on top of a supplied terminal, will query the terminal for its size.
TerminalScreen(Terminal terminal, TextCharacter defaultCharacter) Creates a new Screen on top of a supplied terminal, will query the terminal for its size.

Method Summary

Methods

Modifier and Type	Method and Description
void	clear() Erases all the characters on the screen, effectively giving you a blank area.
TerminalSize	doResizeIfNecessary() One problem working with Screens is that whenever the terminal is resized, the front and back buffers needs to be adjusted accordingly and the program should have a chance to figure out what to do with this extra space (or less space).
Terminal	getTerminal() Returns the underlying Terminal interface that this Screen is using.
KeyStroke	pollInput() Returns the next Key off the input queue or null if there is no more input events available.
KeyStroke	readInput() Returns the next Key off the input queue or blocks until one is available.
void	refresh(Screen.RefreshType refreshType) This method will take the content from the back-buffer and move it into the front-buffer, making the changes visible to the terminal in the process.
void	startScreen() Before you can use a Screen, you need to start it.
void	stopScreen() Calling this method will make the underlying terminal leave private mode, effectively going back to whatever state the terminal was in before calling startScreen().

Methods inherited from class com.googlecode.lanterna.screen.AbstractScreen

addResizeRequest, getBackBuffer, getBackCharacter, getBackCharacter, getCursorPosition, getFrontBuffer, getFrontCharacter, getFrontCharacter, getTabBehaviour, getTerminalSize, newTextGraphics, refresh, setCharacter, setCharacter, setCursorPosition, setTabBehaviour

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

TerminalScreen

public TerminalScreen(Terminal terminal)
               throws IOException

Creates a new Screen on top of a supplied terminal, will query the terminal for its size. The screen is initially blank. The default character used for unused space (the newly initialized state of the screen and new areas after expanding the terminal size) will be a blank space in 'default' ANSI front- and background color.

Before you can display the content of this buffered screen to the real underlying terminal, you must call the startScreen() method. This will ask the terminal to enter private mode (which is required for Screens to work properly). Similarly, when you are done, you should call stopScreen() which will exit private mode.

Parameters:

terminal - Terminal object to create the DefaultScreen on top of

Throws:

IOException - If there was an underlying I/O error when querying the size of the terminal

TerminalScreen

public TerminalScreen(Terminal terminal,
              TextCharacter defaultCharacter)
               throws IOException

Creates a new Screen on top of a supplied terminal, will query the terminal for its size. The screen is initially blank. The default character used for unused space (the newly initialized state of the screen and new areas after expanding the terminal size) will be a blank space in 'default' ANSI front- and background color.

Before you can display the content of this buffered screen to the real underlying terminal, you must call the startScreen() method. This will ask the terminal to enter private mode (which is required for Screens to work properly). Similarly, when you are done, you should call stopScreen() which will exit private mode.

Parameters:

terminal - Terminal object to create the DefaultScreen on top of.

defaultCharacter - What character to use for the initial state of the screen and expanded areas

Throws:

IOException - If there was an underlying I/O error when querying the size of the terminal

Method Detail

startScreen

public void startScreen()
                 throws IOException

Description copied from interface: Screen

Before you can use a Screen, you need to start it. By starting the screen, Lanterna will make sure the terminal is in private mode (Screen only supports private mode), clears it (so that is can set the front and back buffers to a known value) and places the cursor in the top left corner. After calling startScreen(), you can begin using the other methods on this interface. When you want to exit from the screen and return to what you had before, you can call stopScreen().

Throws:

IOException - if there was an underlying IO error when exiting from private mode

stopScreen

public void stopScreen()
                throws IOException

Description copied from interface: Screen

Calling this method will make the underlying terminal leave private mode, effectively going back to whatever state the terminal was in before calling startScreen(). Once a screen has been stopped, you can start it again with startScreen() which will restore the screens content to the terminal.

Throws:

IOException - if there was an underlying IO error when exiting from private mode

refresh

public void refresh(Screen.RefreshType refreshType)
             throws IOException

Description copied from interface: Screen

This method will take the content from the back-buffer and move it into the front-buffer, making the changes visible to the terminal in the process. The graphics workflow with Screen would involve drawing text and text-like graphics on the back buffer and then finally calling refresh(..) to make it visible to the user.

Using this method call instead of refresh() gives you a little bit more control over how the screen will be refreshed.

Parameters:

refreshType - What type of refresh to do

Throws:

IOException - If there was an underlying I/O error

See Also:

Screen.RefreshType

getTerminal

public Terminal getTerminal()

Returns the underlying Terminal interface that this Screen is using.

Be aware: directly modifying the underlying terminal will most likely result in unexpected behaviour if you then go on and try to interact with the Screen. The Screen's back-buffer/front-buffer will not know about the operations you are going on the Terminal and won't be able to properly generate a refresh unless you enforce a Screen.RefreshType.COMPLETE, at which the entire terminal area will be repainted according to the back-buffer of the Screen.

Returns:

Underlying terminal used by the screen

readInput

public KeyStroke readInput()
                    throws IOException

Description copied from interface: InputProvider

Returns the next Key off the input queue or blocks until one is available. NOTE: In previous versions of Lanterna, this method was not blocking. From lanterna 3, it is blocking and you can call pollInput() for the non-blocking version.

Returns:

Key object which represents a keystroke coming in through the input stream

Throws:

IOException - Propagated error if the underlying stream gave errors

pollInput

public KeyStroke pollInput()
                    throws IOException

Description copied from interface: InputProvider

Returns the next Key off the input queue or null if there is no more input events available. Note, this method call is not blocking, it returns null immediately if there is nothing on the input stream.

Returns:

Key object which represents a keystroke coming in through the input stream

Throws:

IOException - Propagated error if the underlying stream gave errors

clear

public void clear()

Description copied from interface: Screen

Erases all the characters on the screen, effectively giving you a blank area. The default background color will be used. This is effectively the same as calling

fill(TerminalPosition.TOP_LEFT_CORNER, getSize(), TextColor.ANSI.Default)

.

Please note that calling this method will only affect the back buffer, you need to call refresh to make the change visible.

Specified by:

clear in interface Screen

Overrides:

clear in class AbstractScreen

doResizeIfNecessary

public TerminalSize doResizeIfNecessary()

Description copied from interface: Screen

One problem working with Screens is that whenever the terminal is resized, the front and back buffers needs to be adjusted accordingly and the program should have a chance to figure out what to do with this extra space (or less space). The solution is to call, at the start of your rendering code, this method, which will check if the terminal has been resized and in that case update the internals of the Screen. After this call finishes, the screen's internal buffers will match the most recent size report from the underlying terminal.

Specified by:

doResizeIfNecessary in interface Screen

Overrides:

doResizeIfNecessary in class AbstractScreen

Returns:

If the terminal has been resized since this method was last called, it will return the new size of the terminal. If not, it will return null.