Subject: [PATCH 12/20] Add support for lazy object number assignment

---
 src/java/org/apache/fop/pdf/PDFDocument.java |   34 +++++++++++++++++++++++++-
 src/java/org/apache/fop/pdf/PDFObject.java   |   14 ++++++++++-
 2 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/src/java/org/apache/fop/pdf/PDFDocument.java b/src/java/org/apache/fop/pdf/PDFDocument.java
index e97e649..697af11 100644
--- a/src/java/org/apache/fop/pdf/PDFDocument.java
+++ b/src/java/org/apache/fop/pdf/PDFDocument.java
@@ -404,7 +404,7 @@ public class PDFDocument {
         if (obj == null) {
             throw new NullPointerException("obj must not be null");
         }
-        if (obj.hasObjectNumber()) {
+        if (!obj.hasLazyObjectNumber() && obj.hasObjectNumber()) {
             throw new IllegalStateException(
                 "Error registering a PDFObject: "
                     + "PDFObject already has an object number");
@@ -424,6 +424,35 @@ public class PDFDocument {
     }
 
     /**
+     * Assigns the {@link PDFObject} an object number when it is first used,
+     * and sets the parent of the {@link PDFObject} to this document.
+     *
+     * @param obj {@link PDFObject} to assign a number to
+     */
+    public void lazyAssignObjectNumber(PDFObject obj) {
+        if (obj == null) {
+            throw new NullPointerException("obj must not be null");
+        }
+        if (obj.hasObjectNumber()) {
+            throw new IllegalStateException(
+                "Error registering a PDFObject: "
+                    + "PDFObject already has an object number");
+        }
+        PDFDocument currentParent = obj.getDocument();
+        if (currentParent != null && currentParent != this) {
+            throw new IllegalStateException(
+                "Error registering a PDFObject: "
+                    + "PDFObject already has a parent PDFDocument");
+        }
+
+        obj.setObjectNumber(-1);
+
+        if (currentParent == null) {
+            obj.setDocument(this);
+        }
+    }
+
+    /**
      * Adds a {@link PDFObject} to this document.
      * The object <em>MUST</em> have an object number assigned.
      *
@@ -1107,6 +1136,9 @@ public class PDFDocument {
                 throw new IOException("PDF file too large. PDF cannot grow beyond approx. 9.3GB.");
             }
 
+            if (s.equals("0"))
+                throw new IOException("PDF object "+(count+1)+" with position 0");
+
             /* contruct xref entry for object */
             loc = padding.substring(s.length()) + s;
 
diff --git a/src/java/org/apache/fop/pdf/PDFObject.java b/src/java/org/apache/fop/pdf/PDFObject.java
index 897c2f8..ef2f3e1 100644
--- a/src/java/org/apache/fop/pdf/PDFObject.java
+++ b/src/java/org/apache/fop/pdf/PDFObject.java
@@ -69,6 +69,9 @@ public abstract class PDFObject implements PDFWritable {
         if (this.objnum == 0) {
             throw new IllegalStateException("Object has no number assigned: " + this.toString());
         }
+        if (this.objnum == -1) {
+            document.assignObjectNumber(this);
+        }
         return this.objnum;
     }
 
@@ -93,7 +96,16 @@ public abstract class PDFObject implements PDFWritable {
      * @return True if it has an object number
      */
     public boolean hasObjectNumber() {
-        return this.objnum > 0;
+        return this.objnum > 0 || this.objnum == -1;
+    }
+
+    /**
+     * Indicates whether this PDFObject will be assigned an
+     * object number.
+     * @return True if it has an object number
+     */
+    public boolean hasLazyObjectNumber() {
+        return this.objnum == -1;
     }
 
     /**
-- 
1.6.4.2