Class TerminalScreen

  • All Implemented Interfaces:
    Scrollable, InputProvider, Screen, java.io.Closeable, java.lang.AutoCloseable

    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. This will place the terminal in private mode during the screen operations and leave private mode afterwards.
    • Field Detail

      • terminal

        private final Terminal terminal
      • isStarted

        private boolean isStarted
      • fullRedrawHint

        private boolean fullRedrawHint
    • Constructor Detail

      • TerminalScreen

        public TerminalScreen​(Terminal terminal)
                       throws java.io.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:
        java.io.IOException - If there was an underlying I/O error when querying the size of the terminal
      • TerminalScreen

        public TerminalScreen​(Terminal terminal,
                              TextCharacter defaultCharacter)
                       throws java.io.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:
        java.io.IOException - If there was an underlying I/O error when querying the size of the terminal
    • Method Detail

      • startScreen

        public void startScreen()
                         throws java.io.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:
        java.io.IOException - if there was an underlying IO error when exiting from private mode
      • stopScreen

        public void stopScreen()
                        throws java.io.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:
        java.io.IOException - if there was an underlying IO error when exiting from private mode
      • stopScreen

        public void stopScreen​(boolean flushInput)
                        throws java.io.IOException
        Throws:
        java.io.IOException
      • refresh

        public void refresh​(Screen.RefreshType refreshType)
                     throws java.io.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:
        java.io.IOException - If there was an underlying I/O error
        See Also:
        Screen.RefreshType
      • useScrollHint

        private void useScrollHint()
                            throws java.io.IOException
        Throws:
        java.io.IOException
      • refreshByDelta

        private void refreshByDelta()
                             throws java.io.IOException
        Throws:
        java.io.IOException
      • refreshFull

        private void refreshFull()
                          throws java.io.IOException
        Throws:
        java.io.IOException
      • 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 java.io.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:
        java.io.IOException - Propagated error if the underlying stream gave errors
      • pollInput

        public KeyStroke pollInput()
                            throws java.io.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:
        java.io.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.
      • scrollLines

        public void scrollLines​(int firstLine,
                                int lastLine,
                                int distance)
        Perform the scrolling and save scroll-range and distance in order to be able to optimize Terminal-update later.
        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.