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.

  • Field Details

  • Constructor Details

    • 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 Details

    • 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.
    • calculateViewport

      private TerminalSize calculateViewport(TerminalSize realTerminalSize)
    • 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:
    • 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
    • filter

      private KeyStroke filter(KeyStroke keyStroke) throws IOException
      Throws:
      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.