Package com.googlecode.lanterna.screen

Class VirtualScreen

java.lang.Object

com.googlecode.lanterna.screen.AbstractScreen

com.googlecode.lanterna.screen.VirtualScreen

All Implemented Interfaces:

Scrollable, InputProvider, Screen, Closeable, AutoCloseable

public class VirtualScreen
extends AbstractScreen

VirtualScreen wraps a normal screen and presents it as a screen that has a configurable minimum size; if the real screen is smaller than this size, the presented screen will add scrolling to get around it. To anyone using this class, it will appear and behave just as a normal screen. Scrolling is done by using CTRL + arrow keys.

The use case for this class is to allow you to set a minimum size that you can count on be honored, no matter how small the user makes the terminal. This should make programming GUIs easier.

Author:

Martin

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static interface	VirtualScreen.FrameRenderer	Interface for rendering the virtual screen's frame when the real terminal is too small for the virtual screen

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	Description
VirtualScreen(Screen screen)	Creates a new VirtualScreen that wraps a supplied Screen.

Method Summary

Modifier and Type	Method	Description
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).
TextCharacter	getFrontCharacter(TerminalPosition position)	Reads a character and its associated meta-data from the front-buffer and returns it encapsulated as a ScreenCharacter.
TerminalSize	getMinimumSize()	Returns the minimum size this virtual screen can have.
TerminalSize	getViewportSize()	Returns the current size of the viewport.
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	scrollLines(int firstLine, int lastLine, int distance)	Performs the scrolling on its back-buffer.
void	setCursorPosition(TerminalPosition position)	Moves the current cursor position or hides it.
void	setMinimumSize(TerminalSize minimumSize)	Sets the minimum size we want the virtual screen to have.
void	setViewportTopLeft(TerminalPosition position)
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, clear, close, getBackBuffer, getBackCharacter, getBackCharacter, getCursorPosition, getFrontBuffer, getFrontCharacter, getTabBehaviour, getTerminalSize, newTextGraphics, refresh, setCharacter, setCharacter, setTabBehaviour, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

VirtualScreen

public VirtualScreen(Screen screen)

Creates a new VirtualScreen that wraps a supplied Screen. The screen passed in here should be the real screen that is created on top of the real Terminal, it will have the correct size and content for what's actually displayed to the user, but this class will present everything as one view with a fixed minimum size, no matter what size the real terminal has.

The initial minimum size will be the current size of the screen.

Parameters:

screen - Real screen that will be used when drawing the whole or partial virtual screen

Method Detail

setMinimumSize

public void setMinimumSize(TerminalSize minimumSize)

Sets the minimum size we want the virtual screen to have. If the user resizes the real terminal to something smaller than this, the virtual screen will refuse to make it smaller and add scrollbars to the view.

Parameters:

minimumSize - Minimum size we want the screen to have

getMinimumSize

public TerminalSize getMinimumSize()

Returns the minimum size this virtual screen can have. If the real terminal is made smaller than this, the virtual screen will draw scrollbars and implement scrolling

Returns:

Minimum size configured for this virtual screen

getViewportSize

public TerminalSize getViewportSize()

Returns the current size of the viewport. This will generally match the dimensions of the underlying terminal.

Returns:

Viewport size for this VirtualScreen

setViewportTopLeft

public void setViewportTopLeft(TerminalPosition position)

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

getFrontCharacter

public TextCharacter getFrontCharacter(TerminalPosition position)

Description copied from interface: Screen

Reads a character and its associated meta-data from the front-buffer and returns it encapsulated as a ScreenCharacter.

Specified by:

getFrontCharacter in interface Screen

Overrides:

getFrontCharacter in class AbstractScreen

Parameters:

position - What position to read the character from

Returns:

A ScreenCharacter representation of the character in the front-buffer at the specified location

setCursorPosition

public void setCursorPosition(TerminalPosition position)

Description copied from class: AbstractScreen

Moves the current cursor position or hides it. If the cursor is hidden and given a new position, it will be visible after this method call.

Specified by:

setCursorPosition in interface Screen

Overrides:

setCursorPosition in class AbstractScreen

Parameters:

position - 0-indexed column and row numbers of the new position, or if null, hides the cursor

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.

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

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

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

scrollLines

public void scrollLines(int firstLine,
                        int lastLine,
                        int distance)

Description copied from class: AbstractScreen

Performs the scrolling on its back-buffer.

Specified by:

scrollLines in interface Screen

Specified by:

scrollLines in interface Scrollable

Overrides:

scrollLines in class AbstractScreen

Parameters:

firstLine - first line of the range to be scrolled (top line is 0)

lastLine - last (inclusive) line of the range to be scrolled

distance - if > 0: move lines up, else if < 0: move lines down.