Issue a warning, when non-restartable content is flowing to a narrower page, that part of it may be clipped

git-svn-id: https://svn.apache.org/repos/asf/xmlgraphics/fop/trunk@827621 13f79535-47bb-0310-9956-ffa450edef68

4 files changed, 24 insertions, 19 deletions

diff --git a/src/java/org/apache/fop/layoutmgr/AbstractBreaker.java b/src/java/org/apache/fop/layoutmgr/AbstractBreaker.java
index 2ee4a8a3a..53a52597b 100644
--- a/src/java/org/apache/fop/layoutmgr/AbstractBreaker.java
+++ b/src/java/org/apache/fop/layoutmgr/AbstractBreaker.java
@@ -367,7 +367,7 @@ public abstract class AbstractBreaker {
                 alg.setConstantLineWidth(flowBPD);
                 int optimalPageCount = alg.findBreakingPoints(effectiveList, 1, true,
                         BreakingAlgorithm.ALL_BREAKS);
-                if (alg.ipdChanged()) {
+                if (alg.getIPDdifference() != 0) {
                     KnuthNode optimalBreak = alg.getBestNodeBeforeIPDChange();
                     int positionIndex = optimalBreak.position;
                     KnuthElement elementAtBreak = alg.getElement(positionIndex);
@@ -381,6 +381,11 @@ public abstract class AbstractBreaker {
                     LayoutManager restartAtLM = null;
                     List firstElements = Collections.EMPTY_LIST;
                     if (containsNonRestartableLM(positionAtBreak)) {
+                        if (alg.getIPDdifference() > 0) {
+                            log.warn("Content that cannot handle IPD changes is flowing to a"
+                                    + " narrower page. Part of it may be clipped"
+                                    + " by the page border.");
+                        }
                         firstElements = new LinkedList();
                         boolean boxFound = false;
                         Iterator iter = effectiveList.listIterator(positionIndex + 1);
diff --git a/src/java/org/apache/fop/layoutmgr/BreakingAlgorithm.java b/src/java/org/apache/fop/layoutmgr/BreakingAlgorithm.java
index cad047508..4516c8d97 100644
--- a/src/java/org/apache/fop/layoutmgr/BreakingAlgorithm.java
+++ b/src/java/org/apache/fop/layoutmgr/BreakingAlgorithm.java
@@ -491,7 +491,7 @@ public abstract class BreakingAlgorithm {
                     elementIndex, previousIsBox, allowedBreaks).isBox();
 
             if (activeNodeCount == 0) {
-                if (ipdChanged()) {
+                if (getIPDdifference() != 0) {
                     return handleIpdChange();
                 }
                 if (!force) {
@@ -538,8 +538,8 @@ public abstract class BreakingAlgorithm {
         return line;
     }
 
-    protected boolean ipdChanged() {
-        return false;
+    protected int getIPDdifference() {
+        return 0;
     }
 
     protected int handleIpdChange() {
diff --git a/src/java/org/apache/fop/layoutmgr/PageBreakingAlgorithm.java b/src/java/org/apache/fop/layoutmgr/PageBreakingAlgorithm.java
index c238f3c27..83dea01bf 100644
--- a/src/java/org/apache/fop/layoutmgr/PageBreakingAlgorithm.java
+++ b/src/java/org/apache/fop/layoutmgr/PageBreakingAlgorithm.java
@@ -96,7 +96,7 @@ class PageBreakingAlgorithm extends BreakingAlgorithm {
     //Controls whether a single part should be forced if possible (ex. block-container)
     private boolean favorSinglePart = false;
 
-    private boolean ipdChange;
+    private int ipdDifference;
     private KnuthNode bestNodeForIPDChange;
 
     //Used to keep track of switches in keep-context
@@ -1077,8 +1077,8 @@ class PageBreakingAlgorithm extends BreakingAlgorithm {
     }
 
     /** {@inheritDoc} */
-    protected boolean ipdChanged() {
-        return ipdChange;
+    protected int getIPDdifference() {
+        return ipdDifference;
     }
 
     /** {@inheritDoc} */
@@ -1104,9 +1104,9 @@ class PageBreakingAlgorithm extends BreakingAlgorithm {
      * @param node the active node to add
      */
     protected void addNode(int line, KnuthNode node) {
-        if (node.position < par.size() - 1 && line > 0 && ipdChange(line - 1)) {
+        if (node.position < par.size() - 1 && line > 0
+                && (ipdDifference = compareIPDs(line - 1)) != 0) {
             log.trace("IPD changes at page " + line);
-            ipdChange = true;
             if (bestNodeForIPDChange == null
                     || node.totalDemerits < bestNodeForIPDChange.totalDemerits) {
                 bestNodeForIPDChange = node;
@@ -1117,7 +1117,7 @@ class PageBreakingAlgorithm extends BreakingAlgorithm {
                  * The whole sequence could actually fit on the last page before
                  * the IPD change. No need to do any special handling.
                  */
-                ipdChange = false;
+                ipdDifference = 0;
             }
             super.addNode(line, node);
         }
@@ -1127,12 +1127,11 @@ class PageBreakingAlgorithm extends BreakingAlgorithm {
         return bestNodeForIPDChange;
     }
 
-    /** {@inheritDoc} */
-    protected boolean ipdChange(int line) {
+    private int compareIPDs(int line) {
         if (pageProvider == null) {
-            return false;
+            return 0;
         }
-        return pageProvider.ipdChange(line);
+        return pageProvider.compareIPDs(line);
     }
 
 }
diff --git a/src/java/org/apache/fop/layoutmgr/PageProvider.java b/src/java/org/apache/fop/layoutmgr/PageProvider.java
index bd556366a..2e531a8d8 100644
--- a/src/java/org/apache/fop/layoutmgr/PageProvider.java
+++ b/src/java/org/apache/fop/layoutmgr/PageProvider.java
@@ -161,12 +161,13 @@ public class PageProvider implements Constants {
     }
 
     /**
-     * Returns true if the part following the given one has a different IPD.
+     * Compares the IPD of the given part with the following one.
      *
      * @param index index of the current part
-     * @return true if the following part has a different IPD, false otherwise
+     * @return a negative integer, zero or a positive integer as the current IPD is less
+     * than, equal to or greater than the IPD of the following part
      */
-    public boolean ipdChange(int index) {
+    public int compareIPDs(int index) {
         int columnCount = 0;
         int colIndex = startColumnOfCurrentElementList + index;
         int pageIndex = -1;
@@ -179,11 +180,11 @@ public class PageProvider implements Constants {
         } while (colIndex >= columnCount);
         if (colIndex + 1 < columnCount) {
             // Next part is a column on same page => same IPD
-            return false;
+            return 0;
         } else {
             Page nextPage = getPage(false, pageIndex + 1, RELTO_CURRENT_ELEMENT_LIST);
             return page.getPageViewport().getBodyRegion().getIPD()
-                    != nextPage.getPageViewport().getBodyRegion().getIPD();
+                    - nextPage.getPageViewport().getBodyRegion().getIPD();
         }
     }