platform/platform-impl/src/com/intellij/openapi/diff/impl/CurrentLineMarker.java

/*
 * Copyright 2000-2014 JetBrains s.r.o.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.intellij.openapi.diff.impl;

import com.intellij.openapi.Disposable;
import com.intellij.openapi.diagnostic.Logger;
import com.intellij.openapi.editor.CaretModel;
import com.intellij.openapi.editor.Editor;
import com.intellij.openapi.editor.event.CaretEvent;
import com.intellij.openapi.editor.event.CaretListener;
import com.intellij.openapi.editor.markup.HighlighterLayer;
import com.intellij.openapi.editor.markup.RangeHighlighter;

public class CurrentLineMarker implements CaretListener {
  private static final Logger LOG = Logger.getInstance("#com.intellij.openapi.diff.impl.CurrentLineMarker");
  private Editor myEditor;
  private RangeHighlighter myHighlighter = null;
  public static final int LAYER = HighlighterLayer.CARET_ROW + 1;

  public void attach(EditorSource editorSource) {
    if (myEditor != null) hide();
    myEditor = editorSource.getEditor();
    if (myEditor == null) return;
    final CaretModel caretModel = myEditor.getCaretModel();
    caretModel.addCaretListener(this);
    editorSource.addDisposable(new Disposable() {
      public void dispose() {
        caretModel.removeCaretListener(CurrentLineMarker.this);
      }
    });
  }

  public void set() {
    if (myEditor == null) return;
    hide();
    final int line = myEditor.getCaretModel().getLogicalPosition().line;
    myHighlighter = line < myEditor.getDocument().getLineCount() ? myEditor.getMarkupModel().addLineHighlighter(line, LAYER, null) : null;
  }

  private boolean isHiden() { return myHighlighter == null; }

  void hide() {
    if (myHighlighter != null) {
      LOG.assertTrue(myEditor != null);
      myHighlighter.dispose();
      myHighlighter = null;
    }
  }

  public void caretPositionChanged(CaretEvent e) {
    if (isHiden()) return;
    set();
  }

  @Override
  public void caretAdded(CaretEvent e) {

  }

  @Override
  public void caretRemoved(CaretEvent e) {

  }
}