Support collapsing margins for flex container

DEVSIX-5137

Autoported commit.
Original commit hash: [1bae5b73b]

Author: Eugene Bochilo

itext.tests/itext.layout.tests/itext/layout/element/FlexContainerTest.cs

@@ -769,6 +769,32 @@ public virtual void LinesMaxHeightShouldBeRespectedTest() {
                 , "diff"));
         }
 
+        [NUnit.Framework.Test]
+        public virtual void CollapsingMarginsFlexContainerTest() {
+            String outFileName = destinationFolder + "collapsingMarginsFlexContainerTest" + testNumber + ".pdf";
+            String cmpFileName = sourceFolder + "cmp_collapsingMarginsFlexContainerTest" + testNumber + ".pdf";
+            PdfDocument pdfDocument = new PdfDocument(new PdfWriter(outFileName));
+            Document document = new Document(pdfDocument);
+            document.SetProperty(Property.COLLAPSING_MARGINS, true);
+            Div flexContainer = CreateFlexContainer();
+            flexContainer.SetProperty(Property.MARGIN_TOP, UnitValue.CreatePointValue(50));
+            flexContainer.SetProperty(Property.BORDER, new SolidBorder(2));
+            flexContainer.SetProperty(Property.BACKGROUND, new Background(ColorConstants.LIGHT_GRAY));
+            Div child1 = CreateNewDiv();
+            child1.SetBackgroundColor(ColorConstants.CYAN);
+            child1.SetMargin(50);
+            Div child2 = CreateNewDiv();
+            child2.SetBackgroundColor(ColorConstants.CYAN);
+            child2.SetMargin(50);
+            flexContainer.Add(child1).Add(child2);
+            Div flexContainersSibling = CreateNewDiv();
+            flexContainersSibling.SetMarginBottom(40);
+            document.Add(flexContainersSibling).Add(flexContainer);
+            document.Close();
+            NUnit.Framework.Assert.IsNull(new CompareTool().CompareByContent(outFileName, cmpFileName, destinationFolder
+                , "diff"));
+        }
+
         private Div GetFlexContainer(OverflowPropertyValue? overflowX, Style style) {
             FlexContainer flexContainer = CreateFlexContainer();
             flexContainer.SetBackgroundColor(ColorConstants.GREEN).SetBorderRight(new SolidBorder(60));

itext.tests/itext.layout.tests/itext/layout/renderer/AbstractRendererUnitTest.cs

@@ -0,0 +1,29 @@
+using iText.IO.Source;
+using iText.Kernel.Geom;
+using iText.Kernel.Pdf;
+using iText.Kernel.Pdf.Canvas;
+using iText.Layout.Element;
+using iText.Layout.Layout;
+using iText.Layout.Properties;
+using iText.Test;
+using iText.Test.Attributes;
+
+namespace iText.Layout.Renderer {
+    public class BlockRendererUnitTest : ExtendedITextTest {
+        [NUnit.Framework.Test]
+        [LogMessage(iText.IO.LogMessageConstant.PAGE_WAS_FLUSHED_ACTION_WILL_NOT_BE_PERFORMED)]
+        public virtual void ClippedAreaFlushedPageTest() {
+            BlockRenderer blockRenderer = new DivRenderer(new Div());
+            blockRenderer.SetProperty(Property.OVERFLOW_X, OverflowPropertyValue.HIDDEN);
+            blockRenderer.occupiedArea = new LayoutArea(1, new Rectangle(100, 100));
+            PdfDocument pdfDocument = new PdfDocument(new PdfWriter(new ByteArrayOutputStream()));
+            pdfDocument.AddNewPage();
+            PdfCanvas pdfCanvas = new PdfCanvas(pdfDocument.AddNewPage());
+            DrawContext context = new DrawContext(pdfDocument, pdfCanvas);
+            pdfDocument.GetPage(1).Flush();
+            blockRenderer.Draw(context);
+            // This test checks that there is log message and there is no NPE so assertions are not required
+            NUnit.Framework.Assert.IsTrue(true);
+        }
+    }
+}

itext.tests/itext.layout.tests/itext/layout/renderer/BlockRendererUnitTest.cs

@@ -254,6 +254,8 @@ public const String IMAGE_HAS_INCORRECT_OR_UNSUPPORTED_BASE_COLOR_SPACE_IN_INDEX
 
         public const String PAGE_TREE_IS_BROKEN_FAILED_TO_RETRIEVE_PAGE = "Page tree is broken. Failed to retrieve page number {0}. Null will be returned.";
 
+        public const String PAGE_WAS_FLUSHED_ACTION_WILL_NOT_BE_PERFORMED = "Page was flushed. {0} will not be performed.";
+
         public const String PASSED_PAGE_SHALL_BE_ON_WHICH_CANVAS_WILL_BE_RENDERED = "The page passed to Canvas#enableAutoTagging(PdfPage) method shall be the one on which this canvas will be rendered. However the actual passed PdfPage instance sets not such page. This might lead to creation of malformed PDF document.";
 
         public const String PATH_KEY_IS_PRESENT_VERTICES_WILL_BE_IGNORED = "Path key is present. Vertices will be ignored";

itext.tests/itext.layout.tests/resources/itext/layout/FlexContainerTest/cmp_collapsingMarginsFlexContainerTest1.pdf

@@ -1887,11 +1887,11 @@ protected internal virtual void ApplyAction(PdfDocument document) {
         }
 
         protected internal virtual void ApplyLinkAnnotation(PdfDocument document) {
+            ILog logger = LogManager.GetLogger(typeof(iText.Layout.Renderer.AbstractRenderer));
             PdfLinkAnnotation linkAnnotation = this.GetProperty<PdfLinkAnnotation>(Property.LINK_ANNOTATION);
             if (linkAnnotation != null) {
                 int pageNumber = occupiedArea.GetPageNumber();
                 if (pageNumber < 1 || pageNumber > document.GetNumberOfPages()) {
-                    ILog logger = LogManager.GetLogger(typeof(iText.Layout.Renderer.AbstractRenderer));
                     String logMessageArg = "Property.LINK_ANNOTATION, which specifies a link associated with this element content area, see com.itextpdf.layout.element.Link.";
                     logger.Warn(MessageFormatUtil.Format(iText.IO.LogMessageConstant.UNABLE_TO_APPLY_PAGE_DEPENDENT_PROP_UNKNOWN_PAGE_ON_WHICH_ELEMENT_IS_DRAWN
                         , logMessageArg));
@@ -1905,7 +1905,15 @@ protected internal virtual void ApplyLinkAnnotation(PdfDocument document) {
                 Rectangle pdfBBox = CalculateAbsolutePdfBBox();
                 linkAnnotation.SetRectangle(new PdfArray(pdfBBox));
                 PdfPage page = document.GetPage(pageNumber);
-                page.AddAnnotation(linkAnnotation);
+                // TODO DEVSIX-1655 This check is necessary because, in some cases, our renderer's hierarchy may contain
+                //  a renderer from the different page that was already flushed
+                if (page.IsFlushed()) {
+                    logger.Error(MessageFormatUtil.Format(iText.IO.LogMessageConstant.PAGE_WAS_FLUSHED_ACTION_WILL_NOT_BE_PERFORMED
+                        , "link annotation applying"));
+                }
+                else {
+                    page.AddAnnotation(linkAnnotation);
+                }
             }
         }
 

itext.tests/itext.layout.tests/resources/itext/layout/FlexContainerTest/cmp_collapsingMarginsFlexContainerTest2.pdf

@@ -77,10 +77,11 @@ public class BlockFormattingContextUtil {
         /// <returns>true if given renderer creates a new "Block formatting context" in terms of CSS, false otherwise.
         ///     </returns>
         public static bool IsRendererCreateBfc(IRenderer renderer) {
-            return (renderer is RootRenderer) || (renderer is CellRenderer) || IsInlineBlock(renderer) || FloatingHelper
-                .IsRendererFloating(renderer) || IsAbsolutePosition(renderer) || IsFixedPosition(renderer) || IsCaption
-                (renderer) || AbstractRenderer.IsOverflowProperty(OverflowPropertyValue.HIDDEN, renderer, Property.OVERFLOW_X
-                ) || AbstractRenderer.IsOverflowProperty(OverflowPropertyValue.HIDDEN, renderer, Property.OVERFLOW_Y);
+            return (renderer is RootRenderer) || (renderer is CellRenderer) || IsInlineBlock(renderer) || renderer.GetParent
+                () is FlexContainerRenderer || FloatingHelper.IsRendererFloating(renderer) || IsAbsolutePosition(renderer
+                ) || IsFixedPosition(renderer) || IsCaption(renderer) || AbstractRenderer.IsOverflowProperty(OverflowPropertyValue
+                .HIDDEN, renderer, Property.OVERFLOW_X) || AbstractRenderer.IsOverflowProperty(OverflowPropertyValue.HIDDEN
+                , renderer, Property.OVERFLOW_Y);
         }
 
         private static bool IsInlineBlock(IRenderer renderer) {