diff --git a/platform/platform-impl/src/com/intellij/openapi/editor/impl/EditorImpl.java b/platform/platform-impl/src/com/intellij/openapi/editor/impl/EditorImpl.java
index d1505e61a566..b69e92258937 100644
--- a/platform/platform-impl/src/com/intellij/openapi/editor/impl/EditorImpl.java
+++ b/platform/platform-impl/src/com/intellij/openapi/editor/impl/EditorImpl.java
@@ -270,6 +270,8 @@ public final class EditorImpl extends UserDataHolderBase implements EditorEx, Hi
   private boolean myStickySelection;
   private int myStickySelectionStart;
   private boolean myScrollToCaret = true;
+  
+  private final EditorSizeAdjustmentStrategy mySizeAdjustmentStrategy = new EditorSizeAdjustmentStrategy();
 
   static {
     ourCaretBlinkingCommand = new RepaintCursorCommand();
@@ -1497,6 +1499,10 @@ public final class EditorImpl extends UserDataHolderBase implements EditorEx, Hi
     Dimension dim = getPreferredSize();
 
     if (!dim.equals(myPreferredSize) && !myDocument.isInBulkUpdate()) {
+      dim = mySizeAdjustmentStrategy.adjust(dim, myPreferredSize, this);
+      if (dim == null) {
+        return;
+      } 
       myPreferredSize = dim;
 
       stopOptimizedScrolling();
diff --git a/platform/platform-impl/src/com/intellij/openapi/editor/impl/EditorSizeAdjustmentStrategy.java b/platform/platform-impl/src/com/intellij/openapi/editor/impl/EditorSizeAdjustmentStrategy.java
new file mode 100644
index 000000000000..dd22bc3ac766
--- /dev/null
+++ b/platform/platform-impl/src/com/intellij/openapi/editor/impl/EditorSizeAdjustmentStrategy.java
@@ -0,0 +1,141 @@
+/*
+ * Copyright 2000-2011 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.editor.impl;
+
+import com.intellij.openapi.editor.ex.util.EditorUtil;
+import com.intellij.util.Alarm;
+import gnu.trove.TLongArrayList;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import javax.swing.*;
+import java.awt.*;
+
+/**
+ * This class is aimed to help {@link EditorImpl the editor} when user extensively modifies the longest line 
+ * at the document (e.g. is typing at its end).
+ * <p/>
+ * The problem is that the longest line's width is a {@link JComponent#getPreferredSize() preferred size's width} as well.
+ * So, every time width of the longest line is changed, editor's preferred size is changed too and that triggers the whole
+ * component repaint.
+ * <p/>
+ * This component comes into the play here - it's assumed that editor notifies it every time preferred size is changed and
+ * receives instructions for the further actions. For example, we can reserve additional space if we see that preferred size
+ * is permanently increasing (the user is typing at the end of the longest line) etc. See method javadocs for more details.
+ * <p/>
+ * Not thread-safe.
+ * 
+ * @author Denis Zhdanov
+ * @since 6/17/11 2:45 PM
+ */
+public class EditorSizeAdjustmentStrategy {
+
+  /** Amount of time (in milliseconds) to keep information about preferred size change. */
+  private static final long TIMING_TTL_MILLIS = 10000L;
+  
+  /** Constant that indicates minimum number of preferred size changes per target amount of time that is considered to be frequent. */
+  private static final int FREQUENT_SIZE_CHANGES_NUMBER = 10;
+  
+  /** Default number of columns to reserve during frequent typing at the end of the longest document line. */
+  private static final int DEFAULT_RESERVE_COLUMNS_NUMBER = 4;
+
+  private final Alarm          myAlarm   = new Alarm();
+  private final TLongArrayList myTimings = new TLongArrayList();
+
+  private int myReserveColumns = DEFAULT_RESERVE_COLUMNS_NUMBER;
+  private boolean mySkip;
+  
+  /**
+   * Asks to adjust new preferred size appliance if necessary.
+   * 
+   * @param newPreferredSize  newly calculated preferred size that differs from the old preferred size
+   * @param oldPreferredSize  old preferred size (if any)
+   * @param editor            target editor
+   * @return                  preferred size to use (given 'new preferred size' may be adjusted); <code>null</code> if given
+   *                          new preferred size should not be applied
+   */
+  @Nullable
+  public Dimension adjust(@NotNull Dimension newPreferredSize, @Nullable Dimension oldPreferredSize, @NotNull EditorImpl editor) {
+    if (oldPreferredSize == null || mySkip) {
+      return newPreferredSize;
+    }
+    // Process only width change.
+    if (newPreferredSize.height != oldPreferredSize.height) {
+      return newPreferredSize;
+    }
+
+    stripTimings();
+    myTimings.add(System.currentTimeMillis());
+    if (myTimings.size() < FREQUENT_SIZE_CHANGES_NUMBER) {
+      return newPreferredSize;
+    }
+
+    boolean increaseWidth = newPreferredSize.width > oldPreferredSize.width;
+    if (increaseWidth) {
+      final int spaceWidth = EditorUtil.getSpaceWidth(Font.PLAIN, editor);
+      newPreferredSize.width += myReserveColumns * spaceWidth;
+      myReserveColumns += 3;
+      
+    } 
+    // Don't reduce preferred size on frequent reduce of the longest document line.
+
+    scheduleSizeUpdate(editor);
+    return newPreferredSize;
+  }
+
+  /**
+   * Removes old timings.
+   */
+  private void stripTimings() {
+    long limit = System.currentTimeMillis() - TIMING_TTL_MILLIS;
+    int endIndex = 0;
+    for (; endIndex < myTimings.size(); endIndex++) {
+      if (myTimings.get(endIndex) > limit) {
+        break;
+      }
+    }
+    if (endIndex > 0) {
+      myTimings.remove(0, endIndex);
+    } 
+  }
+
+  private void scheduleSizeUpdate(@NotNull EditorImpl editor) {
+    myAlarm.cancelAllRequests();
+    myAlarm.addRequest(new UpdateSizeTask(editor), 1000);
+  }
+  
+  private class UpdateSizeTask implements Runnable {
+    
+    private final EditorImpl myEditor;
+
+    UpdateSizeTask(@NotNull EditorImpl editor) {
+      myEditor = editor;
+    }
+
+    @Override
+    public void run() {
+      mySkip = true;
+      myReserveColumns = DEFAULT_RESERVE_COLUMNS_NUMBER;
+      myTimings.clear();
+      try {
+        myEditor.validateSize();
+      }
+      finally {
+        mySkip = false;
+      }
+    }
+  }
+}