diff: extract common focus tracking logic

platform/diff-impl/src/com/intellij/diff/tools/binary/BinaryDiffViewer.java

@@ -24,10 +24,10 @@ import com.intellij.diff.contents.FileContent;
 import com.intellij.diff.requests.ContentDiffRequest;
 import com.intellij.diff.requests.DiffRequest;
 import com.intellij.diff.tools.util.DiffNotifications;
+import com.intellij.diff.tools.util.FocusTrackerSupport;
 import com.intellij.diff.tools.util.SimpleDiffPanel;
 import com.intellij.diff.tools.util.StatusPanel;
 import com.intellij.diff.tools.util.base.ListenerDiffViewerBase;
-import com.intellij.diff.util.DiffUserDataKeys;
 import com.intellij.diff.util.DiffUtil;
 import com.intellij.diff.util.Side;
 import com.intellij.openapi.Disposable;
@@ -61,8 +61,6 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 import javax.swing.*;
-import java.awt.event.FocusAdapter;
-import java.awt.event.FocusEvent;
 import java.io.IOException;
 import java.util.Arrays;
 import java.util.List;
@@ -79,10 +77,7 @@ public class BinaryDiffViewer extends ListenerDiffViewerBase {
   @Nullable private final FileEditorProvider myEditorProvider1;
   @Nullable private final FileEditorProvider myEditorProvider2;
 
-  @Nullable private final MyEditorFocusListener myEditorFocusListener1;
-  @Nullable private final MyEditorFocusListener myEditorFocusListener2;
-
-  @NotNull private Side myCurrentSide = Side.LEFT;
+  @NotNull private final FocusTrackerSupport.TwosideFocusTrackerSupport myFocusTrackerSupport;
 
   public BinaryDiffViewer(@NotNull DiffContext context, @NotNull DiffRequest request) {
     super(context, (ContentDiffRequest)request);
@@ -96,16 +91,7 @@ public class BinaryDiffViewer extends ListenerDiffViewerBase {
     myEditorProvider2 = editors.second.second;
     assert myEditor1 != null || myEditor2 != null;
 
-    if (myEditor1 != null && myEditor2 != null) {
-      myEditorFocusListener1 = new MyEditorFocusListener(Side.LEFT);
-      myEditorFocusListener2 = new MyEditorFocusListener(Side.RIGHT);
-    }
-    else {
-      myEditorFocusListener1 = null;
-      myEditorFocusListener2 = null;
-    }
-
-
+    myFocusTrackerSupport = new FocusTrackerSupport.TwosideFocusTrackerSupport(myEditor1, myEditor2);
     myContentPanel = new BinaryContentPanel(titlePanel, myEditor1, myEditor2);
 
     myPanel = new SimpleDiffPanel(myContentPanel, this, context);
@@ -113,15 +99,10 @@ public class BinaryDiffViewer extends ListenerDiffViewerBase {
     myStatusPanel = new MyStatusPanel();
 
     new MyFocusOppositePaneAction().setupAction(myPanel);
-
-
-    installEditorListeners();
   }
 
-  @Override
   @CalledInAwt
   public void onDispose() {
-    destroyEditorListeners();
     destroyEditors();
     super.onDispose();
   }
@@ -130,25 +111,14 @@ public class BinaryDiffViewer extends ListenerDiffViewerBase {
   @CalledInAwt
   protected void processContextHints() {
     super.processContextHints();
-    if (myEditor1 == null) {
-      myCurrentSide = Side.RIGHT;
-    }
-    else if (myEditor2 == null) {
-      myCurrentSide = Side.LEFT;
-    }
-    else {
-      Side side = myContext.getUserData(DiffUserDataKeys.PREFERRED_FOCUS_SIDE);
-      if (side != null) myCurrentSide = side;
-    }
+    myFocusTrackerSupport.processContextHints(myRequest, myContext);
   }
 
   @Override
   @CalledInAwt
   protected void updateContextHints() {
     super.updateContextHints();
-    if (myEditor1 != null && myEditor2 != null) {
-      myContext.putUserData(DiffUserDataKeys.PREFERRED_FOCUS_SIDE, myCurrentSide);
-    }
+    myFocusTrackerSupport.updateContextHints(myRequest, myContext);
   }
 
   //
@@ -222,20 +192,6 @@ public class BinaryDiffViewer extends ListenerDiffViewerBase {
     }
   }
 
-  private void installEditorListeners() {
-    if (myEditor1 != null && myEditor2 != null) {
-      myEditor1.getComponent().addFocusListener(myEditorFocusListener1);
-      myEditor2.getComponent().addFocusListener(myEditorFocusListener2);
-    }
-  }
-
-  private void destroyEditorListeners() {
-    if (myEditor1 != null && myEditor2 != null) {
-      myEditor1.getComponent().removeFocusListener(myEditorFocusListener1);
-      myEditor2.getComponent().removeFocusListener(myEditorFocusListener2);
-    }
-  }
-
   //
   // Diff
   //
@@ -364,8 +320,12 @@ public class BinaryDiffViewer extends ListenerDiffViewerBase {
   }
 
   @NotNull
-  Side getCurrentSide() {
-    return myCurrentSide;
+  public Side getCurrentSide() {
+    return myFocusTrackerSupport.getCurrentSide();
+  }
+
+  public void setCurrentSide(@NotNull Side side) {
+    myFocusTrackerSupport.setCurrentSide(side);
   }
 
   @Nullable
@@ -447,7 +407,7 @@ public class BinaryDiffViewer extends ListenerDiffViewerBase {
     @Override
     public void actionPerformed(@NotNull AnActionEvent e) {
       assert myEditor1 != null && myEditor2 != null;
-      myCurrentSide = myCurrentSide.other();
+      setCurrentSide(getCurrentSide().other());
       myPanel.requestFocus();
     }
 
@@ -465,7 +425,7 @@ public class BinaryDiffViewer extends ListenerDiffViewerBase {
   @Override
   public Object getData(@NonNls String dataId) {
     if (CommonDataKeys.VIRTUAL_FILE.is(dataId)) {
-      return DiffUtil.getVirtualFile(myRequest, myCurrentSide);
+      return DiffUtil.getVirtualFile(myRequest, getCurrentSide());
     }
     return super.getData(dataId);
   }
@@ -476,17 +436,4 @@ public class BinaryDiffViewer extends ListenerDiffViewerBase {
       return -1;
     }
   }
-
-  private class MyEditorFocusListener extends FocusAdapter {
-    @NotNull private final Side mySide;
-
-    private MyEditorFocusListener(@NotNull Side side) {
-      mySide = side;
-    }
-
-    public void focusGained(FocusEvent e) {
-      if (myEditor1 == null || myEditor2 == null) return;
-      myCurrentSide = mySide;
-    }
-  }
 }

platform/diff-impl/src/com/intellij/diff/tools/util/FocusTrackerSupport.java

@@ -0,0 +1,188 @@
+/*
+ * Copyright 2000-2015 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.diff.tools.util;
+
+import com.intellij.diff.DiffContext;
+import com.intellij.diff.requests.DiffRequest;
+import com.intellij.diff.util.DiffUserDataKeys;
+import com.intellij.diff.util.Side;
+import com.intellij.diff.util.ThreeSide;
+import com.intellij.openapi.editor.Editor;
+import com.intellij.openapi.fileEditor.FileEditor;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import javax.swing.*;
+import java.awt.event.FocusAdapter;
+import java.awt.event.FocusEvent;
+import java.util.List;
+
+public class FocusTrackerSupport<T> {
+  public static class TwosideFocusTrackerSupport {
+    @NotNull private Side myCurrentSide;
+
+    private final boolean myDumbMode;
+    @Nullable private final MyFocusListener myListener1;
+    @Nullable private final MyFocusListener myListener2;
+
+    public TwosideFocusTrackerSupport(@Nullable Editor editor1, @Nullable Editor editor2) {
+      this(getComponent(editor1), getComponent(editor2));
+    }
+
+    public TwosideFocusTrackerSupport(@Nullable FileEditor editor1, @Nullable FileEditor editor2) {
+      this(getComponent(editor1), getComponent(editor2));
+    }
+
+    public TwosideFocusTrackerSupport(@Nullable JComponent component1, @Nullable JComponent component2) {
+      assert component1 != null || component2 != null;
+      myCurrentSide = component2 != null ? Side.RIGHT : Side.LEFT;
+
+      myDumbMode = component1 == null || component2 == null;
+      if (!myDumbMode) {
+        myListener1 = new MyFocusListener(Side.LEFT);
+        component1.addFocusListener(myListener1);
+
+        myListener2 = new MyFocusListener(Side.RIGHT);
+        component2.addFocusListener(myListener2);
+      }
+      else {
+        myListener1 = null;
+        myListener2 = null;
+      }
+    }
+
+    @NotNull
+    public Side getCurrentSide() {
+      return myCurrentSide;
+    }
+
+    public void setCurrentSide(@NotNull Side side) {
+      if (myDumbMode) return;
+      myCurrentSide = side;
+    }
+
+    public void processContextHints(@NotNull DiffRequest request, @NotNull DiffContext context) {
+      Side side = context.getUserData(DiffUserDataKeys.PREFERRED_FOCUS_SIDE);
+      if (side != null) setCurrentSide(side);
+    }
+
+    public void updateContextHints(@NotNull DiffRequest request, @NotNull DiffContext context) {
+      if (myDumbMode) return;
+      context.putUserData(DiffUserDataKeys.PREFERRED_FOCUS_SIDE, myCurrentSide);
+    }
+
+    private class MyFocusListener extends FocusAdapter {
+      @NotNull private final Side mySide;
+
+      private MyFocusListener(@NotNull Side side) {
+        mySide = side;
+      }
+
+      public void focusGained(FocusEvent e) {
+        myCurrentSide = mySide;
+      }
+    }
+  }
+
+  public static class ThreesideFocusTrackerSupport {
+    @NotNull private ThreeSide myCurrentSide;
+
+    private final boolean myDumbMode;
+    @Nullable private final MyFocusListener myListener1;
+    @Nullable private final MyFocusListener myListener2;
+    @Nullable private final MyFocusListener myListener3;
+
+    public ThreesideFocusTrackerSupport(@NotNull List<? extends Editor> editors) {
+      this(editors.get(0), editors.get(1), editors.get(2));
+    }
+
+    public ThreesideFocusTrackerSupport(@Nullable Editor editor1, @Nullable Editor editor2, @Nullable Editor editor3) {
+      this(getComponent(editor1), getComponent(editor2), getComponent(editor3));
+    }
+
+    public ThreesideFocusTrackerSupport(@Nullable FileEditor editor1, @Nullable FileEditor editor2, @Nullable FileEditor editor3) {
+      this(getComponent(editor1), getComponent(editor2), getComponent(editor3));
+    }
+
+    public ThreesideFocusTrackerSupport(@Nullable JComponent component1, @Nullable JComponent component2, @Nullable JComponent component3) {
+      assert component1 != null || component2 != null || component3 != null;
+      myCurrentSide = component2 != null ? ThreeSide.BASE : component1 != null ? ThreeSide.LEFT : ThreeSide.RIGHT;
+
+      boolean c1 = component1 != null;
+      boolean c2 = component2 != null;
+      boolean c3 = component3 != null;
+      myDumbMode = (!c1 && !c2) || (!c1 && !c3) || (!c2 && !c3); // only one not-null element
+
+      if (!myDumbMode) {
+        myListener1 = component1 != null ? new MyFocusListener(ThreeSide.LEFT) : null;
+        if (component1 != null) component1.addFocusListener(myListener1);
+
+        myListener2 = component2 != null ? new MyFocusListener(ThreeSide.BASE) : null;
+        if (component2 != null) component2.addFocusListener(myListener2);
+
+        myListener3 = component3 != null ? new MyFocusListener(ThreeSide.RIGHT) : null;
+        if (component3 != null) component3.addFocusListener(myListener3);
+      }
+      else {
+        myListener1 = null;
+        myListener2 = null;
+        myListener3 = null;
+      }
+    }
+
+    @NotNull
+    public ThreeSide getCurrentSide() {
+      return myCurrentSide;
+    }
+
+    public void setCurrentSide(@NotNull ThreeSide side) {
+      if (myDumbMode || side.select(myListener1, myListener2, myListener3) == null) return;
+      myCurrentSide = side;
+    }
+
+    public void processContextHints(@NotNull DiffRequest request, @NotNull DiffContext context) {
+      ThreeSide side = context.getUserData(DiffUserDataKeys.PREFERRED_FOCUS_THREESIDE);
+      if (side != null) setCurrentSide(side);
+    }
+
+    public void updateContextHints(@NotNull DiffRequest request, @NotNull DiffContext context) {
+      if (myDumbMode) return;
+      context.putUserData(DiffUserDataKeys.PREFERRED_FOCUS_THREESIDE, myCurrentSide);
+    }
+
+    private class MyFocusListener extends FocusAdapter {
+      @NotNull private final ThreeSide mySide;
+
+      private MyFocusListener(@NotNull ThreeSide side) {
+        mySide = side;
+      }
+
+      public void focusGained(FocusEvent e) {
+        myCurrentSide = mySide;
+      }
+    }
+  }
+
+  @Nullable
+  private static JComponent getComponent(@Nullable Editor editor) {
+    return editor != null ? editor.getContentComponent() : null;
+  }
+
+  @Nullable
+  private static JComponent getComponent(@Nullable FileEditor editor) {
+    return editor != null ? editor.getComponent() : null;
+  }
+}

platform/diff-impl/src/com/intellij/diff/tools/util/threeside/ThreesideTextDiffViewer.java

@@ -24,12 +24,12 @@ import com.intellij.diff.requests.ContentDiffRequest;
 import com.intellij.diff.requests.DiffRequest;
 import com.intellij.diff.requests.SimpleDiffRequest;
 import com.intellij.diff.tools.util.DiffDataKeys;
+import com.intellij.diff.tools.util.FocusTrackerSupport.ThreesideFocusTrackerSupport;
 import com.intellij.diff.tools.util.SimpleDiffPanel;
 import com.intellij.diff.tools.util.SyncScrollSupport;
 import com.intellij.diff.tools.util.SyncScrollSupport.ThreesideSyncScrollSupport;
 import com.intellij.diff.tools.util.base.InitialScrollPositionSupport;
 import com.intellij.diff.tools.util.base.TextDiffViewerBase;
-import com.intellij.diff.util.DiffUserDataKeys;
 import com.intellij.diff.util.DiffUtil;
 import com.intellij.diff.util.Side;
 import com.intellij.diff.util.ThreeSide;
@@ -55,8 +55,6 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 import javax.swing.*;
-import java.awt.event.FocusAdapter;
-import java.awt.event.FocusEvent;
 import java.util.ArrayList;
 import java.util.List;
 
@@ -72,18 +70,14 @@ public abstract class ThreesideTextDiffViewer extends TextDiffViewerBase {
 
   @NotNull protected final List<DocumentContent> myActualContents;
 
-  @NotNull private final List<MyEditorFocusListener> myEditorFocusListeners =
-    ContainerUtil.newArrayList(new MyEditorFocusListener(ThreeSide.LEFT),
-                               new MyEditorFocusListener(ThreeSide.BASE),
-                               new MyEditorFocusListener(ThreeSide.RIGHT));
   @NotNull private final MyVisibleAreaListener myVisibleAreaListener1 = new MyVisibleAreaListener(Side.LEFT);
   @NotNull private final MyVisibleAreaListener myVisibleAreaListener2 = new MyVisibleAreaListener(Side.RIGHT);
 
   @NotNull protected final MySetEditorSettingsAction myEditorSettingsAction;
 
-  @Nullable private ThreesideSyncScrollSupport mySyncScrollListener;
+  @NotNull private final ThreesideFocusTrackerSupport myFocusTrackerSupport;
 
-  @NotNull private ThreeSide myCurrentSide;
+  @Nullable private ThreesideSyncScrollSupport mySyncScrollListener;
 
   public ThreesideTextDiffViewer(@NotNull DiffContext context, @NotNull ContentDiffRequest request) {
     super(context, request);
@@ -97,8 +91,7 @@ public abstract class ThreesideTextDiffViewer extends TextDiffViewerBase {
     myEditors = createEditors();
     List<JComponent> titlePanel = DiffUtil.createTextTitles(myRequest, myEditors);
 
-    myCurrentSide = ThreeSide.BASE;
-
+    myFocusTrackerSupport = new ThreesideFocusTrackerSupport(myEditors);
     myContentPanel = new ThreesideTextContentPanel(myEditors, titlePanel);
 
     myPanel = new SimpleDiffPanel(myContentPanel, this, context);
@@ -121,15 +114,14 @@ public abstract class ThreesideTextDiffViewer extends TextDiffViewerBase {
   @CalledInAwt
   protected void processContextHints() {
     super.processContextHints();
-    ThreeSide side = myContext.getUserData(DiffUserDataKeys.PREFERRED_FOCUS_THREESIDE);
-    if (side != null) myCurrentSide = side;
+    myFocusTrackerSupport.processContextHints(myRequest, myContext);
   }
 
   @Override
   @CalledInAwt
   protected void updateContextHints() {
     super.updateContextHints();
-    myContext.putUserData(DiffUserDataKeys.PREFERRED_FOCUS_THREESIDE, myCurrentSide);
+    myFocusTrackerSupport.updateContextHints(myRequest, myContext);
   }
 
   @NotNull
@@ -168,9 +160,6 @@ public abstract class ThreesideTextDiffViewer extends TextDiffViewerBase {
   @Override
   protected void installEditorListeners() {
     super.installEditorListeners();
-    for (int i = 0; i < 3; i++) {
-      myEditors.get(i).getContentComponent().addFocusListener(myEditorFocusListeners.get(i));
-    }
 
     myEditors.get(0).getScrollingModel().addVisibleAreaListener(myVisibleAreaListener1);
     myEditors.get(1).getScrollingModel().addVisibleAreaListener(myVisibleAreaListener1);
@@ -190,10 +179,6 @@ public abstract class ThreesideTextDiffViewer extends TextDiffViewerBase {
   public void destroyEditorListeners() {
     super.destroyEditorListeners();
 
-    for (int i = 0; i < 3; i++) {
-      myEditors.get(i).getContentComponent().removeFocusListener(myEditorFocusListeners.get(i));
-    }
-
     myEditors.get(0).getScrollingModel().removeVisibleAreaListener(myVisibleAreaListener1);
     myEditors.get(1).getScrollingModel().removeVisibleAreaListener(myVisibleAreaListener1);
 
@@ -238,12 +223,12 @@ public abstract class ThreesideTextDiffViewer extends TextDiffViewerBase {
 
   @NotNull
   public EditorEx getCurrentEditor() {
-    return myCurrentSide.select(myEditors);
+    return getCurrentSide().select(myEditors);
   }
 
   @NotNull
   public DocumentContent getCurrentContent() {
-    return myCurrentSide.select(myActualContents);
+    return getCurrentSide().select(myActualContents);
   }
 
   @NotNull
@@ -254,7 +239,11 @@ public abstract class ThreesideTextDiffViewer extends TextDiffViewerBase {
 
   @NotNull
   public ThreeSide getCurrentSide() {
-    return myCurrentSide;
+    return myFocusTrackerSupport.getCurrentSide();
+  }
+
+  public void setCurrentSide(@NotNull ThreeSide side) {
+    myFocusTrackerSupport.setCurrentSide(side);
   }
 
   //
@@ -265,7 +254,7 @@ public abstract class ThreesideTextDiffViewer extends TextDiffViewerBase {
   protected void scrollToLine(@NotNull ThreeSide side, int line) {
     Editor editor = side.select(myEditors);
     DiffUtil.scrollEditor(editor, line, false);
-    myCurrentSide = side;
+    setCurrentSide(side);
   }
 
   @Nullable
@@ -365,26 +354,14 @@ public abstract class ThreesideTextDiffViewer extends TextDiffViewerBase {
       return getCurrentEditor();
     }
     else if (CommonDataKeys.VIRTUAL_FILE.is(dataId)) {
-      return DiffUtil.getVirtualFile(myRequest, myCurrentSide);
+      return DiffUtil.getVirtualFile(myRequest, getCurrentSide());
     }
     else if (DiffDataKeys.CURRENT_CONTENT.is(dataId)) {
       return getCurrentContent();
     }
     return super.getData(dataId);
   }
-
-  private class MyEditorFocusListener extends FocusAdapter {
-    @NotNull private final ThreeSide mySide;
-
-    private MyEditorFocusListener(@NotNull ThreeSide side) {
-      mySide = side;
-    }
-
-    public void focusGained(FocusEvent e) {
-      myCurrentSide = mySide;
-    }
-  }
-
+  
   private class MyVisibleAreaListener implements VisibleAreaListener {
     @NotNull Side mySide;
 

platform/diff-impl/src/com/intellij/diff/tools/util/twoside/TwosideTextDiffViewer.java

@@ -24,12 +24,12 @@ import com.intellij.diff.contents.EmptyContent;
 import com.intellij.diff.requests.ContentDiffRequest;
 import com.intellij.diff.requests.DiffRequest;
 import com.intellij.diff.tools.util.DiffDataKeys;
+import com.intellij.diff.tools.util.FocusTrackerSupport.TwosideFocusTrackerSupport;
 import com.intellij.diff.tools.util.SimpleDiffPanel;
 import com.intellij.diff.tools.util.SyncScrollSupport;
 import com.intellij.diff.tools.util.SyncScrollSupport.TwosideSyncScrollSupport;
 import com.intellij.diff.tools.util.base.InitialScrollPositionSupport;
 import com.intellij.diff.tools.util.base.TextDiffViewerBase;
-import com.intellij.diff.util.DiffUserDataKeys;
 import com.intellij.diff.util.DiffUtil;
 import com.intellij.diff.util.Side;
 import com.intellij.openapi.actionSystem.AnActionEvent;
@@ -52,8 +52,6 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 import javax.swing.*;
-import java.awt.event.FocusAdapter;
-import java.awt.event.FocusEvent;
 import java.util.Collections;
 import java.util.List;
 
@@ -73,13 +71,11 @@ public abstract class TwosideTextDiffViewer extends TextDiffViewerBase {
 
   @NotNull protected final MySetEditorSettingsAction myEditorSettingsAction;
 
-  @NotNull private final MyEditorFocusListener myEditorFocusListener1 = new MyEditorFocusListener(Side.LEFT);
-  @NotNull private final MyEditorFocusListener myEditorFocusListener2 = new MyEditorFocusListener(Side.RIGHT);
   @NotNull private final MyVisibleAreaListener myVisibleAreaListener = new MyVisibleAreaListener();
 
-  @Nullable protected TwosideSyncScrollSupport mySyncScrollSupport;
+  @NotNull private final TwosideFocusTrackerSupport myFocusTrackerSupport;
 
-  @NotNull private Side myCurrentSide;
+  @Nullable protected TwosideSyncScrollSupport mySyncScrollSupport;
 
   public TwosideTextDiffViewer(@NotNull DiffContext context, @NotNull ContentDiffRequest request) {
     super(context, request);
@@ -97,8 +93,7 @@ public abstract class TwosideTextDiffViewer extends TextDiffViewerBase {
     myEditor2 = editors.get(1);
     assert myEditor1 != null || myEditor2 != null;
 
-    myCurrentSide = myEditor1 == null ? Side.RIGHT : Side.LEFT;
-
+    myFocusTrackerSupport = new TwosideFocusTrackerSupport(myEditor1, myEditor2);
     myContentPanel = new TwosideTextContentPanel(titlePanel, myEditor1, myEditor2);
 
     myPanel = new SimpleDiffPanel(myContentPanel, this, context);
@@ -124,25 +119,14 @@ public abstract class TwosideTextDiffViewer extends TextDiffViewerBase {
   @CalledInAwt
   protected void processContextHints() {
     super.processContextHints();
-    if (myEditor1 == null) {
-      myCurrentSide = Side.RIGHT;
-    }
-    else if (myEditor2 == null) {
-      myCurrentSide = Side.LEFT;
-    }
-    else {
-      Side side = myContext.getUserData(DiffUserDataKeys.PREFERRED_FOCUS_SIDE);
-      if (side != null) myCurrentSide = side;
-    }
+    myFocusTrackerSupport.processContextHints(myRequest, myContext);
   }
 
   @Override
   @CalledInAwt
   protected void updateContextHints() {
     super.updateContextHints();
-    if (myEditor1 != null && myEditor2 != null) {
-      myContext.putUserData(DiffUserDataKeys.PREFERRED_FOCUS_SIDE, myCurrentSide);
-    }
+    myFocusTrackerSupport.updateContextHints(myRequest, myContext);
   }
 
   @NotNull
@@ -195,11 +179,9 @@ public abstract class TwosideTextDiffViewer extends TextDiffViewerBase {
   protected void installEditorListeners() {
     super.installEditorListeners();
     if (myEditor1 != null) {
-      myEditor1.getContentComponent().addFocusListener(myEditorFocusListener1);
       myEditor1.getScrollingModel().addVisibleAreaListener(myVisibleAreaListener);
     }
     if (myEditor2 != null) {
-      myEditor2.getContentComponent().addFocusListener(myEditorFocusListener2);
       myEditor2.getScrollingModel().addVisibleAreaListener(myVisibleAreaListener);
     }
     if (myEditor1 != null && myEditor2 != null) {
@@ -215,11 +197,9 @@ public abstract class TwosideTextDiffViewer extends TextDiffViewerBase {
   protected void destroyEditorListeners() {
     super.destroyEditorListeners();
     if (myEditor1 != null) {
-      myEditor1.getContentComponent().removeFocusListener(myEditorFocusListener1);
       myEditor1.getScrollingModel().removeVisibleAreaListener(myVisibleAreaListener);
     }
     if (myEditor2 != null) {
-      myEditor2.getContentComponent().removeFocusListener(myEditorFocusListener2);
       myEditor2.getScrollingModel().removeVisibleAreaListener(myVisibleAreaListener);
     }
     mySyncScrollSupport = null;
@@ -264,7 +244,11 @@ public abstract class TwosideTextDiffViewer extends TextDiffViewerBase {
 
   @NotNull
   public Side getCurrentSide() {
-    return myCurrentSide;
+    return myFocusTrackerSupport.getCurrentSide();
+  }
+
+  public void setCurrentSide(@NotNull Side side) {
+    myFocusTrackerSupport.setCurrentSide(side);
   }
 
   @NotNull
@@ -306,7 +290,7 @@ public abstract class TwosideTextDiffViewer extends TextDiffViewerBase {
     Editor editor = side.select(myEditor1, myEditor2);
     if (editor == null) return;
     DiffUtil.scrollEditor(editor, line, false);
-    myCurrentSide = side;
+    setCurrentSide(side);
   }
 
   @Nullable
@@ -365,13 +349,13 @@ public abstract class TwosideTextDiffViewer extends TextDiffViewerBase {
       if (myEditor1 == null || myEditor2 == null) return;
 
       if (myScrollToPosition) {
-        EditorEx currentEditor = myCurrentSide.select(myEditor1, myEditor2);
-        EditorEx targetEditor = myCurrentSide.other().select(myEditor1, myEditor2);
-        LogicalPosition position = transferPosition(myCurrentSide, currentEditor.getCaretModel().getLogicalPosition());
+        EditorEx currentEditor = getCurrentSide().select(myEditor1, myEditor2);
+        EditorEx targetEditor = getCurrentSide().other().select(myEditor1, myEditor2);
+        LogicalPosition position = transferPosition(getCurrentSide(), currentEditor.getCaretModel().getLogicalPosition());
         targetEditor.getCaretModel().moveToLogicalPosition(position);
       }
 
-      myCurrentSide = myCurrentSide.other();
+      setCurrentSide(getCurrentSide().other());
       myPanel.requestFocus();
       getCurrentEditor().getScrollingModel().scrollToCaret(ScrollType.MAKE_VISIBLE);
     }
@@ -406,25 +390,12 @@ public abstract class TwosideTextDiffViewer extends TextDiffViewerBase {
       return getCurrentContent();
     }
     else if (CommonDataKeys.VIRTUAL_FILE.is(dataId)) {
-      return DiffUtil.getVirtualFile(myRequest, myCurrentSide);
+      return DiffUtil.getVirtualFile(myRequest, getCurrentSide());
     }
 
     return super.getData(dataId);
   }
 
-  private class MyEditorFocusListener extends FocusAdapter {
-    @NotNull private final Side mySide;
-
-    private MyEditorFocusListener(@NotNull Side side) {
-      mySide = side;
-    }
-
-    public void focusGained(FocusEvent e) {
-      if (myEditor1 == null || myEditor2 == null) return;
-      myCurrentSide = mySide;
-    }
-  }
-
   private class MyVisibleAreaListener implements VisibleAreaListener {
     @Override
     public void visibleAreaChanged(VisibleAreaEvent e) {