IDEA-58070 Soft wrap: Improve soft wraps performance

Corrected situation with invalid recalculation range during incremental soft wraps cache update on removal at the last document line

platform/platform-impl/src/com/intellij/openapi/editor/impl/softwrap/SoftWrapImpl.java

@@ -76,6 +76,22 @@ public class SoftWrapImpl implements SoftWrap {
     myChange.advance(diff);
   }
 
+  @Override
+  public int hashCode() {
+    int result = myChange.hashCode();
+    result = 31 * result + myIndentInColumns;
+    return 31 * result + myIndentInPixels;
+  }
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) return true;
+    if (o == null || getClass() != o.getClass()) return false;
+    
+    SoftWrapImpl that = (SoftWrapImpl)o;
+    return myIndentInColumns == that.myIndentInColumns && myIndentInPixels == that.myIndentInPixels && myChange.equals(that.myChange);
+  }
+
   @Override
   public String toString() {
     return myChange.toString();

platform/platform-impl/src/com/intellij/openapi/editor/impl/softwrap/mapping/IncrementalCacheUpdateEvent.java

@@ -172,7 +172,7 @@ class IncrementalCacheUpdateEvent {
   }
 
   private static int getLineStartOffset(int offset, Document document) {
-    if (offset >= document.getTextLength()) {
+    if (offset > document.getTextLength()) {
       return offset;
     }
     int lineNumber = document.getLineNumber(offset);

platform/platform-impl/testSrc/com/intellij/openapi/editor/impl/softwrap/mapping/SoftWrapApplianceOnDocumentModificationTest.java

@@ -24,6 +24,8 @@ import gnu.trove.TIntProcedure;
 
 import java.awt.*;
 import java.io.IOException;
+import java.util.*;
+import java.util.List;
 
 /**
  * @author Denis Zhdanov
@@ -240,6 +242,19 @@ public class SoftWrapApplianceOnDocumentModificationTest extends AbstractEditorP
     assertEquals(offset, caretModel.getOffset());
   }
   
+  public void testBackspaceAtTheEndOfSoftWrappedLine() throws IOException {
+    // There was a problem that removing text from the last document line that was soft-wrapped removed soft wraps as well.
+    String text = 
+      "This a long string that is expected to be wrapped in more than one visual line<caret>";
+    init(150, text);
+
+    List<? extends SoftWrap> softWrapsBeforeModification = new ArrayList<SoftWrap>(getSoftWrapModel().getRegisteredSoftWraps());
+    assertTrue(softWrapsBeforeModification.size() > 0);
+    
+    backspace();
+    assertEquals(softWrapsBeforeModification, getSoftWrapModel().getRegisteredSoftWraps());
+  }
+  
   private static TIntHashSet collectSoftWrapStartOffsets(int documentLine) {
     TIntHashSet result = new TIntHashSet();
     for (SoftWrap softWrap : myEditor.getSoftWrapModel().getSoftWrapsForLine(documentLine)) {