Provide suspendable undo manager

richtextfx/src/integrationTest/java/org/fxmisc/richtext/api/UndoManagerTests.java

@@ -9,10 +9,12 @@
 import org.fxmisc.richtext.RichTextFXTestBase;
 import org.fxmisc.richtext.StyledTextArea;
 import org.fxmisc.richtext.model.SimpleEditableStyledDocument;
+import org.fxmisc.richtext.model.RichTextChange;
 import org.fxmisc.richtext.model.TextChange;
 import org.fxmisc.richtext.util.UndoUtils;
 import org.junit.Test;
 import org.junit.runner.RunWith;
+import org.reactfx.SuspendableYes;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
@@ -174,6 +176,20 @@ public void testForBug904() {
             interact( area::undo ); // should not throw Unexpected change received exception 
         }
 
+        @Test
+        public void suspendable_UndoManager_skips_style_check() {
+
+            SuspendableYes suspendUndo = new SuspendableYes();
+            area.setUndoManager( UndoUtils.richTextSuspendableUndoManager( area, suspendUndo ) );
+            write( "some text\n" );
+            interact( () -> suspendUndo.suspendWhile( () -> area.setStyle( 5, 9, "-fx-font-weight: bold;" ) ) );
+            write( "new line" );
+            interact( area::undo ); // should not throw Unexpected change received exception
+
+            area.setUndoManager( UndoUtils.defaultUndoManager( area ) );
+            RichTextChange.skipStyleComparison( false );
+        }
+
     }
 
     public class UsingStyledTextArea extends RichTextFXTestBase {

richtextfx/src/main/java/org/fxmisc/richtext/model/RichTextChange.java

@@ -45,4 +45,31 @@ public final PlainTextChange toPlainTextChange() {
     public final boolean isPlainTextIdentity() {
         return removed.getText().equals(inserted.getText());
     }
+
+    private static boolean skipStyleComparison = false;
+
+    public static void skipStyleComparison( boolean value )
+    {
+        skipStyleComparison = value;
+    }
+
+    /* 
+     * This gets used, by the default UndoManagers supplied by UndoUtils,
+     * to check that a submitted undo/redo matches the change reported. 
+     */
+    public boolean equals( Object other )
+    {
+        if( skipStyleComparison && other instanceof RichTextChange )
+        {
+            PlainTextChange otherChange = ((RichTextChange) other).toPlainTextChange();
+            boolean matches = toPlainTextChange().equals( otherChange );
+            if ( ! matches ) System.err.println(
+                "Plain text comparison mismatch caused by text change"
+                +" during undo manager suspension (styling ignored)."
+            );
+            return matches;
+        }
+
+        return super.equals( other );
+    }
 }

richtextfx/src/main/java/org/fxmisc/richtext/util/UndoUtils.java

@@ -7,6 +7,9 @@
 import org.fxmisc.richtext.model.TextChange;
 import org.fxmisc.undo.UndoManager;
 import org.fxmisc.undo.UndoManagerFactory;
+import org.fxmisc.undo.impl.MultiChangeUndoManagerImpl;
+import org.fxmisc.undo.impl.UnlimitedChangeQueue;
+import org.reactfx.SuspendableYes;
 import org.reactfx.value.Val;
 
 import javafx.beans.value.ObservableBooleanValue;
@@ -121,6 +124,38 @@ public static <PS, SEG, S> UndoManager<List<RichTextChange<PS, SEG, S>>> richTex
                 preventMergeDelay);
     };
 
+    /**
+     * Returns an UndoManager with an unlimited history that can undo/redo {@link RichTextChange}s. New changes
+     * emitted from the stream will not be merged with the previous change after {@link #DEFAULT_PREVENT_MERGE_DELAY}
+     * <p><b>Note</b>: that <u>only styling changes</u> may occur <u>during suspension</u> of the undo manager.
+     */
+    public static <PS, SEG, S> UndoManager<List<RichTextChange<PS, SEG, S>>> richTextSuspendableUndoManager(
+            GenericStyledArea<PS, SEG, S> area, SuspendableYes suspendUndo) {
+        return richTextSuspendableUndoManager(area, DEFAULT_PREVENT_MERGE_DELAY, suspendUndo);
+    }
+
+    /**
+     * Returns an UndoManager with an unlimited history that can undo/redo {@link RichTextChange}s. New changes
+     * emitted from the stream will not be merged with the previous change after {@code preventMergeDelay}.
+     * <p><b>Note</b>: that <u>only styling changes</u> may occur <u>during suspension</u> of the undo manager.
+     */
+    public static <PS, SEG, S> UndoManager<List<RichTextChange<PS, SEG, S>>> richTextSuspendableUndoManager(
+            GenericStyledArea<PS, SEG, S> area, Duration preventMergeDelay, SuspendableYes suspendUndo) {
+
+        RichTextChange.skipStyleComparison( true );
+
+        return new MultiChangeUndoManagerImpl<>
+        (
+            new UnlimitedChangeQueue<>(),
+            TextChange::invert,
+            applyMultiRichTextChange(area),
+            TextChange::mergeWith,
+            TextChange::isIdentity,
+            area.multiRichChanges().conditionOn(suspendUndo),
+            preventMergeDelay
+        );
+    };
+
     /**
      * Returns an UndoManager with an unlimited history that can undo/redo {@link PlainTextChange}s. New changes
      * emitted from the stream will not be merged with the previous change