Make margins collapse handling on cells a bit more consitent

DEVSIX-1195

Author: yulian-gaponenko

layout/src/main/java/com/itextpdf/layout/margincollapse/MarginsCollapseHandler.java

@@ -243,9 +243,7 @@ public void endMarginsCollapse(Rectangle layoutBox) {
         } else {
             ownCollapseAfter = new MarginsCollapse();
         }
-        if (ownCollapseAfter != null) {
-            ownCollapseAfter.joinMargin(getModelBottomMargin(renderer));
-        }
+        ownCollapseAfter.joinMargin(getModelBottomMargin(renderer));
         collapseInfo.setOwnCollapseAfter(ownCollapseAfter);
 
         if (collapseInfo.isSelfCollapsing()) {
@@ -290,7 +288,7 @@ public void endMarginsCollapse(Rectangle layoutBox) {
     }
 
     private void updateCollapseBeforeIfPrevKidIsFirstAndSelfCollapsed(MarginsCollapse collapseAfter) {
-        if (prevChildMarginInfo.isSelfCollapsing() && prevChildMarginInfo.isIgnoreOwnMarginTop() && collapseAfter != null) {
+        if (prevChildMarginInfo.isSelfCollapsing() && prevChildMarginInfo.isIgnoreOwnMarginTop()) {
             // prevChildMarginInfo.isIgnoreOwnMarginTop() is true only if it's the first kid and is adjoined to parent margin
             collapseInfo.getCollapseBefore().joinMargin(collapseAfter);
         }
@@ -560,7 +558,8 @@ private static boolean rendererIsFloated(IRenderer renderer) {
 
     private static float getModelTopMargin(IRenderer renderer) {
         Float margin = renderer.getModelElement().<Float>getProperty(Property.MARGIN_TOP);
-        return margin != null ? (float) margin : 0;
+        // TODO Concerning "renderer instanceof CellRenderer" check: may be try to apply more general solution in future
+        return margin != null && !(renderer instanceof CellRenderer) ? (float) margin : 0;
     }
 
     private static void ignoreModelTopMargin(IRenderer renderer) {
@@ -573,7 +572,8 @@ private static void overrideModelTopMargin(IRenderer renderer, float collapsedMa
 
     private static float getModelBottomMargin(IRenderer renderer) {
         Float margin = renderer.getModelElement().<Float>getProperty(Property.MARGIN_BOTTOM);
-        return margin != null ? (float) margin : 0;
+        // TODO Concerning "renderer instanceof CellRenderer" check: may be try to apply more general solution in future
+        return margin != null && !(renderer instanceof CellRenderer) ? (float) margin : 0;
     }
 
     private static void ignoreModelBottomMargin(IRenderer renderer) {

layout/src/main/java/com/itextpdf/layout/renderer/BlockRenderer.java

@@ -122,9 +122,7 @@ public LayoutResult layout(LayoutContext layoutContext) {
 
         boolean isCellRenderer = this instanceof CellRenderer;
         if (marginsCollapsingEnabled) {
-            if (!isCellRenderer) {
-                marginsCollapseHandler.startMarginsCollapse(parentBBox);
-            }
+            marginsCollapseHandler.startMarginsCollapse(parentBBox);
         }
 
         Border[] borders = getBorders();
@@ -168,9 +166,7 @@ public LayoutResult layout(LayoutContext layoutContext) {
                     if (result.getStatus() != LayoutResult.NOTHING) {
                         marginsCollapseHandler.endChildMarginsHandling(layoutBox);
                     }
-                    if (!isCellRenderer) {
-                        marginsCollapseHandler.endMarginsCollapse(layoutBox);
-                    }
+                    marginsCollapseHandler.endMarginsCollapse(layoutBox);
                 }
                 if (Boolean.TRUE.equals(getPropertyAsBoolean(Property.FILL_AVAILABLE_AREA_ON_SPLIT))
                         || Boolean.TRUE.equals(getPropertyAsBoolean(Property.FILL_AVAILABLE_AREA))) {
@@ -365,7 +361,7 @@ public LayoutResult layout(LayoutContext layoutContext) {
             }
         }
         float overflowPartHeight = getOverflowPartHeight(overflowY, layoutBox);
-        if (marginsCollapsingEnabled && !isCellRenderer) {
+        if (marginsCollapsingEnabled) {
             marginsCollapseHandler.endMarginsCollapse(layoutBox);
         }