Class VirtualScreen

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

    • 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 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
      • 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 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
      • 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
      • 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
      • filter

        private KeyStroke filter​(KeyStroke keyStroke)
                          throws java.io.IOException
        Throws:
        java.io.IOException
      • 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.