1. CS 190 Lecture Notes: My Editor Design
Position
Position(int line, int charIndex) Position(Position other) public int line; public int charIndex; boolean equals(Position other) int compareTo(Position other) void set(int line, int charIndex) void set(Position other) String toString()
CS 190 Lecture Notes: My Editor Design

2. CS 190 Lecture Notes: My Editor Design
Text
Text() Text(String fileName) throws FileNotFoundException, IOException String getFileName() void writeFile(String fileName) void adjustPosition(Position p) Position advancePosition(Position p, int numChars) void insert(Position pos, String newText) void delete(Position start, Position end) CharSequence getRange(Position start, Position end) String getAll() int getTotalLines() void addTracker(Tracker tracker) void removeTracker(Tracker tracker)
CS 190 Lecture Notes: My Editor Design

3. CS 190 Lecture Notes: My Editor Design
Text.Tracker
public interface Tracker { void afterInsertion(Position start, Position end); void beforeDeletion(Position start, Position end); }
CS 190 Lecture Notes: My Editor Design

4. CS 190 Lecture Notes: My Editor Design
TextPanel
Knows everything about displaying text
Handles scrolling, window resizes
Knows nothing about other events
TextPanel(JFrame frame, Text text, Font font)
Position getCharUnderPoint(int x, int y)
Position getInsertPosition()
void setInsertPosition(Position p)
Position getSelectionStart()
Position getSelectionEnd()
String getSelection()
void setSelection(Position start, Position end)
void makeVisible(Position position)
CS 190 Lecture Notes: My Editor Design

5. CS 190 Lecture Notes: My Editor Design
EventHandler
Defines the application’s user interface
No public methods (except event handlers called by Swing/AWT)
EventHandler(Context context, TextPanel panel, JFrame frame)
CS 190 Lecture Notes: My Editor Design

6. CS 190 Lecture Notes: My Editor Design
Context
Represents a file being edited (and all of its windows)
Top-level state shared among windows
Also, creates top-level windows
public String fileName;
public Text text;
public Undo undo;
public UndoText undoText;
public TextPanel focusPanel;
Context(String fileName)
public void newWindow()
CS 190 Lecture Notes: My Editor Design

7. CS 190 Lecture Notes: My Editor Design
TrackedPosition
Subclass of Position
Implements the Tracker interface: automatically updates when text is modified
TrackedPosition(Text text, int line, int charIndex);
CS 190 Lecture Notes: My Editor Design

8. Using Trackers for Displaying
TextPanel
insert
selStart
selEnd
Position
Position
Position
TrackedPositions
Tracker
Tracker
Tracker
Tracker
Text
CS 190 Lecture Notes: My Editor Design

9. CS 190 Lecture Notes: My Editor Design
Undo
public class Undo { public interface Action { public void redo(); public void undo(); } Undo() void addAction(Action action) void addFence() void undo() void redo()
CS 190 Lecture Notes: My Editor Design

10. CS 190 Lecture Notes: My Editor Design
UndoText
No methods, just constructor:
new UndoText(Text text, Undo undo);
insert/delete text
EventHandler
undo/redo
UndoText
Undo
Text
Tracker
UndoableDelete
UndoableInsert
CS 190 Lecture Notes: My Editor Design

11. Undoing Cursor and Selection
Before insertions and deletions: context.undo.addAction(new UndoCursorSelection(context)); ... probably should have been: new UndoCursorSelection(context); ... or, even better? UndoCursorSelection.record(context);
CS 190 Lecture Notes: My Editor Design

12. CS 190 Lecture Notes: My Editor Design
Undo Grouping
When to add fences?
When mouse clicked
Before and after insertions > 1 character
But, doesn’t handle single-character paste ops correctly...
Before and after deleting selection
Advantage: can understand each fence (pair?) in isolation
Disadvantage: may not scale well (future ops will require fences before and after?)
CS 190 Lecture Notes: My Editor Design