* If you want to do more complicated drawing operations, please see the class {@code DefaultScreenWriter} which has many * utility methods that works on Screens. * * @author Martin */ public interface Screen extends InputProvider, Scrollable { /** * This is the character Screen implementations should use as a filler is there are areas not set to any particular * character. */ TextCharacter DEFAULT_CHARACTER = new TextCharacter(' '); /** * 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 {@code stopScreen()}. * * @throws IOException if there was an underlying IO error when exiting from private mode */ void startScreen() throws IOException; /** * Calling this method will make the underlying terminal leave private mode, effectively going back to whatever * state the terminal was in before calling {@code startScreen()}. Once a screen has been stopped, you can start it * again with {@code startScreen()} which will restore the screens content to the terminal. * * @throws IOException if there was an underlying IO error when exiting from private mode */ void stopScreen() throws IOException; /** * 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. */ void clear(); /** * A screen implementation typically keeps a location on the screen where the cursor will be placed after drawing * and refreshing the buffers, this method returns that location. If it returns null, it means that the terminal * will attempt to hide the cursor (if supported by the terminal). * * @return Position where the cursor will be located after the screen has been refreshed or {@code null} if the * cursor is not visible */ TerminalPosition getCursorPosition(); /** * A screen implementation typically keeps a location on the screen where the cursor will be placed after drawing * and refreshing the buffers, this method controls that location. If you pass null, it means that the terminal * will attempt to hide the cursor (if supported by the terminal). * * @param position TerminalPosition of the new position where the cursor should be placed after refresh(), or if * {@code null}, hides the cursor */ void setCursorPosition(TerminalPosition position); /** * Gets the behaviour for what to do about tab characters. If a tab character is written to the Screen, it would * cause issues because we don't know how the terminal emulator would render it and we wouldn't know what state the * front-buffer is in. Because of this, we convert tabs to a determined number of spaces depending on different * rules that are available. * * @return Tab behaviour that is used currently * @see TabBehaviour */ TabBehaviour getTabBehaviour(); /** * Sets the behaviour for what to do about tab characters. If a tab character is written to the Screen, it would * cause issues because we don't know how the terminal emulator would render it and we wouldn't know what state the * front-buffer is in. Because of this, we convert tabs to a determined number of spaces depending on different * rules that are available. * * @param tabBehaviour Tab behaviour to use when converting a \t character to a spaces * @see TabBehaviour */ void setTabBehaviour(TabBehaviour tabBehaviour); /** * Returns the size of the screen. This call is not blocking but should return the size of the screen as it is * represented by the buffer at the time this method is called. * * @return Size of the screen, in columns and rows */ TerminalSize getTerminalSize(); /** * Sets a character in the back-buffer to a specified value with specified colors and modifiers. * @param column Column of the character to modify (x coordinate) * @param row Row of the character to modify (y coordinate) * @param screenCharacter New data to put at the specified position */ void setCharacter(int column, int row, TextCharacter screenCharacter); /** * Sets a character in the back-buffer to a specified value with specified colors and modifiers. * @param position Which position in the terminal to modify * @param screenCharacter New data to put at the specified position */ void setCharacter(TerminalPosition position, TextCharacter screenCharacter); /** * Creates a new TextGraphics objects that is targeting this Screen for writing to. Any operations done on this * TextGraphics will be affecting this screen. Remember to call {@code refresh()} on the screen to see your changes. * * @return New TextGraphic object targeting this Screen */ TextGraphics newTextGraphics(); /** * Reads a character and its associated meta-data from the front-buffer and returns it encapsulated as a * ScreenCharacter. * @param column Which column to get the character from * @param row Which row to get the character from * @return A {@code ScreenCharacter} representation of the character in the front-buffer at the specified location */ TextCharacter getFrontCharacter(int column, int row); /** * Reads a character and its associated meta-data from the front-buffer and returns it encapsulated as a * ScreenCharacter. * @param position What position to read the character from * @return A {@code ScreenCharacter} representation of the character in the front-buffer at the specified location */ TextCharacter getFrontCharacter(TerminalPosition position); /** * Reads a character and its associated meta-data from the back-buffer and returns it encapsulated as a * ScreenCharacter. * @param column Which column to get the character from * @param row Which row to get the character from * @return A {@code ScreenCharacter} representation of the character in the back-buffer at the specified location */ TextCharacter getBackCharacter(int column, int row); /** * Reads a character and its associated meta-data from the back-buffer and returns it encapsulated as a * ScreenCharacter. * @param position What position to read the character from * @return A {@code ScreenCharacter} representation of the character in the back-buffer at the specified location */ TextCharacter getBackCharacter(TerminalPosition position); /** * 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. * @throws java.io.IOException If there was an underlying I/O error * @see RefreshType */ void refresh() throws IOException; /** * 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 {@code refresh()} gives you a little bit more control over how the screen will * be refreshed. * @param refreshType What type of refresh to do * @throws java.io.IOException If there was an underlying I/O error * @see RefreshType */ void refresh(RefreshType refreshType) throws IOException; /** * 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. * * @return 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. */ TerminalSize doResizeIfNecessary(); /** * Scroll a range of lines of this Screen according to given distance. * * Screen implementations of this method do not throw IOException. */ @Override void scrollLines(int firstLine, int lastLine, int distance); /** * This enum represents the different ways a Screen can refresh the screen, moving the back-buffer data into the * front-buffer that is being displayed. */ enum RefreshType { /** * Using automatic mode, the Screen will make a guess at which refresh type would be the fastest and use this one. */ AUTOMATIC, /** * In {@code RefreshType.DELTA} mode, the Screen will calculate a diff between the back-buffer and the * front-buffer, then figure out the set of terminal commands that is required to make the front-buffer exactly * like the back-buffer. This normally works well when you have modified only parts of the screen, but if you * have modified almost everything it will cause a lot of overhead and you should use * {@code RefreshType.COMPLETE} instead. */ DELTA, /** * In {@code RefreshType.COMPLETE} mode, the screen will send a clear command to the terminal, then redraw the * whole back-buffer line by line. This is more expensive than {@code RefreshType.COMPLETE}, especially when you * have only touched smaller parts of the screen, but can be faster if you have modified most of the content, * as well as if you suspect the screen's internal front buffer is out-of-sync with what's really showing on the * terminal (you didn't go and call methods on the underlying Terminal while in screen mode, did you?) */ COMPLETE, ; } }