* The normal way you interact in Java with a terminal is through the standard output (System.out) and standard error * (System.err) and it's usually through printing text only. This interface abstracts a terminal at a more fundamental * level, expressing methods for not only printing text but also changing colors, moving the cursor new positions, * enable special modifiers and get notified when the terminal's size has changed. *
* If you want to write an application that has a very precise control of the terminal, this is the * interface you should be programming against. * * @author Martin */ public interface Terminal extends InputProvider { /** * Calling this method will, where supported, give your terminal a private area to use, separate from what was there * before. Some terminal emulators will preserve the terminal history and restore it when you exit private mode. * Some terminals will just clear the screen and put the cursor in the top-left corner. Typically, if you terminal * supports scrolling, going into private mode will disable the scrolling and leave you with a fixed screen, which * can be useful if you don't want to deal with what the terminal buffer will look like if the user scrolls up. * * @throws java.io.IOException If there was an underlying I/O error * @throws IllegalStateException If you are already in private mode */ void enterPrivateMode() throws IOException; /** * If you have previously entered private mode, this method will exit this and, depending on implementation, maybe * restore what the terminal looked like before private mode was entered. If the terminal doesn't support a * secondary buffer for private mode, it will probably make a new line below the private mode and place the cursor * there. * * @throws java.io.IOException If there was an underlying I/O error * @throws IllegalStateException If you are not in private mode */ void exitPrivateMode() throws IOException; /** * Removes all the characters, colors and graphics from the screen and leaves you with a big empty space. Text * cursor position is undefined after this call (depends on platform and terminal) so you should always call * {@code moveCursor} next. Some terminal implementations doesn't reset color and modifier state so it's also good * practise to call {@code resetColorAndSGR()} after this. * @throws java.io.IOException If there was an underlying I/O error */ void clearScreen() throws IOException; /** * Moves the text cursor to a new location on the terminal. The top-left corner has coordinates 0 x 0 and the bottom- * right corner has coordinates terminal_width-1 x terminal_height-1. You can retrieve the size of the terminal by * calling getTerminalSize(). * * @param x The 0-indexed column to place the cursor at * @param y The 0-indexed row to place the cursor at * @throws java.io.IOException If there was an underlying I/O error */ void setCursorPosition(int x, int y) throws IOException; /** * Hides or shows the text cursor, but not all terminal (-emulators) supports this. The text cursor is normally a * text block or an underscore, sometimes blinking, which shows the user where keyboard-entered text is supposed to * show up. * * @param visible Hides the text cursor if {@code false} and shows it if {@code true} * @throws java.io.IOException If there was an underlying I/O error */ void setCursorVisible(boolean visible) throws IOException; /** * Prints one character to the terminal at the current cursor location. Please note that the cursor will then move * one column to the right, so multiple calls to {@code putCharacter} will print out a text string without the need * to reposition the text cursor. If you reach the end of the line while putting characters using this method, you * can expect the text cursor to move to the beginning of the next line. *
* You can output CJK (Chinese, Japanese, Korean) characters (as well as other regional scripts) but remember that * the terminal that the user is using might not have the required font to render it. Also worth noticing is that * CJK (and some others) characters tend to take up 2 columns per character, simply because they are a square in * their construction as opposed to the somewhat rectangular shape we fit latin characters in. As it's very * difficult to create a monospace font for CJK with a 2:1 height-width proportion, it seems like the implementers * back in the days simply gave up and made each character take 2 column. It causes issues for the random terminal * programmer because you can't really trust 1 character = 1 column, but I suppose it's "しょうがない". * * @param c Character to place on the terminal * @throws java.io.IOException If there was an underlying I/O error */ void putCharacter(char c) throws IOException; /** * Creates a new TextGraphics object that uses this Terminal directly when outputting. Keep in mind that you are * probably better off to switch to a Screen to make advanced text graphics more efficient. Also, this TextGraphics * implementation will not call {@code .flush()} after any operation, so you'll need to do that on your own. * @return TextGraphics implementation that draws directly using this Terminal interface */ TextGraphics newTextGraphics() throws IOException; /** * Activates an {@code SGR} (Selected Graphic Rendition) code. This code modifies a state inside the terminal * that will apply to all characters written afterwards, such as bold, italic, blinking code and so on. * * @param sgr SGR code to apply * @throws java.io.IOException If there was an underlying I/O error * @see SGR * @see http://www.vt100.net/docs/vt510-rm/SGR */ void enableSGR(SGR sgr) throws IOException; /** * Deactivates an {@code SGR} (Selected Graphic Rendition) code which has previously been activated through {@code * enableSGR(..)}. * * @param sgr SGR code to apply * @throws java.io.IOException If there was an underlying I/O error * @see SGR * @see http://www.vt100.net/docs/vt510-rm/SGR */ void disableSGR(SGR sgr) throws IOException; /** * Removes all currently active SGR codes and sets foreground and background colors back to default. * * @throws java.io.IOException If there was an underlying I/O error * @see SGR * @see http://www.vt100.net/docs/vt510-rm/SGR */ void resetColorAndSGR() throws IOException; /** * Changes the foreground color for all the following characters put to the terminal. The foreground color is what * color to draw the text in, as opposed to the background color which is the color surrounding the characters. *
* This overload is using the TextColor class to define a color, which is a layer of abstraction above the three * different color formats supported (ANSI, indexed and RGB). The other setForegroundColor(..) overloads gives * you direct access to set one of those three. *
* Note to implementers of this interface, just make this method call color.applyAsForeground(this); * * @param color Color to use for foreground * @throws java.io.IOException If there was an underlying I/O error */ void setForegroundColor(TextColor color) throws IOException; /** * Changes the background color for all the following characters put to the terminal. The background color is the * color surrounding the text being printed. *
* This overload is using the TextColor class to define a color, which is a layer of abstraction above the three * different color formats supported (ANSI, indexed and RGB). The other setBackgroundColor(..) overloads gives * you direct access to set one of those three. *
* Note to implementers of this interface, just make this method call color.applyAsBackground(this); * * @param color Color to use for the background * @throws java.io.IOException If there was an underlying I/O error */ void setBackgroundColor(TextColor color) throws IOException; /** * Adds a {@code ResizeListener} to be called when the terminal has changed size. There is no guarantee that this * listener will really be invoked when the terminal has changed size, at all depends on the terminal emulator * implementation. Normally on Unix systems the WINCH signal will be sent to the process and lanterna can intercept * this. *
* There are no guarantees on what thread the call will be made on, so please be careful with what kind of operation * you perform in this callback. You should probably not take too long to return. * * @see ResizeListener * @param listener Listener object to be called when the terminal has been changed */ void addResizeListener(ResizeListener listener); /** * Removes a {@code ResizeListener} from the list of listeners to be notified when the terminal has changed size * * @see ResizeListener * @param listener Listener object to remove */ void removeResizeListener(ResizeListener listener); /** * Returns the size of the terminal, expressed as a {@code TerminalSize} object. Please bear in mind that depending * on the {@code Terminal} implementation, this may or may not be accurate. See the implementing classes for more * information. Most commonly, calling getTerminalSize() will involve some kind of hack to retrieve the size of the * terminal, like moving the cursor to position 5000x5000 and then read back the location, unless the terminal * implementation has a more smooth way of getting this data. Keep this in mind and see if you can avoid calling * this method too often. There is a helper class, SimpleTerminalResizeListener, that you can use to cache the size * and update it only when resize events are received (which depends on if a resize is detectable, which they are not * on all platforms). * * @return Size of the terminal * @throws java.io.IOException if there was an I/O error trying to retrieve the size of the terminal */ TerminalSize getTerminalSize() throws IOException; /** * Retrieves optional information from the terminal by printing the ENQ ({@literal \}u005) character. Terminals and terminal * emulators may or may not respond to this command, sometimes it's configurable. * * @param timeout How long to wait for the talk-back message, if there's nothing immediately available on the input * stream, you should probably set this to a somewhat small value to prevent unnecessary blockage on the input stream * but large enough to accommodate a round-trip to the user's terminal (~300 ms if you are connection across the globe). * @param timeoutUnit What unit to use when interpreting the {@code timeout} parameter * @return Answer-back message from the terminal or empty if there was nothing * @throws java.io.IOException If there was an I/O error while trying to read the enquiry reply */ byte[] enquireTerminal(int timeout, TimeUnit timeoutUnit) throws IOException; /** * Calls {@code flush()} on the underlying {@code OutputStream} object, or whatever other implementation this * terminal is built around. Some implementing classes of this interface (like SwingTerminal) doesn't do anything * as it doesn't really apply to them. * @throws java.io.IOException If there was an underlying I/O error */ void flush() throws IOException; }