Fix NullPointerException in AbstractRenderer class and update createXObject method

DEVSIX-4138

Autoported commit.
Original commit hash: [34efacbce]

Author: introfog

itext.tests/itext.layout.tests/itext/layout/renderer/AbstractRendererTest.cs

@@ -0,0 +1,39 @@
+using iText.IO.Source;
+using iText.Kernel.Colors;
+using iText.Kernel.Colors.Gradients;
+using iText.Kernel.Geom;
+using iText.Kernel.Pdf;
+using iText.Kernel.Pdf.Xobject;
+using iText.Test;
+
+namespace iText.Layout.Renderer {
+    public class AbstractRendererTest : ExtendedITextTest {
+        [NUnit.Framework.Test]
+        public virtual void CreateXObjectTest() {
+            AbstractLinearGradientBuilder gradientBuilder = new StrategyBasedLinearGradientBuilder().SetGradientDirectionAsStrategy
+                (StrategyBasedLinearGradientBuilder.GradientStrategy.TO_BOTTOM_LEFT).AddColorStop(new GradientColorStop
+                (ColorConstants.RED.GetColorValue(), 0d, GradientColorStop.OffsetType.RELATIVE)).AddColorStop(new GradientColorStop
+                (ColorConstants.GREEN.GetColorValue(), 0.5, GradientColorStop.OffsetType.RELATIVE));
+            PdfDocument pdfDocument = new PdfDocument(new PdfWriter(new ByteArrayOutputStream()));
+            PdfXObject pdfXObject = AbstractRenderer.CreateXObject(gradientBuilder, new Rectangle(0, 0, 20, 20), pdfDocument
+                );
+            NUnit.Framework.Assert.IsNotNull(pdfXObject.GetPdfObject().Get(PdfName.Resources));
+        }
+
+        [NUnit.Framework.Test]
+        public virtual void CreateXObjectWithNullLinearGradientTest() {
+            PdfDocument pdfDocument = new PdfDocument(new PdfWriter(new ByteArrayOutputStream()));
+            PdfXObject pdfXObject = AbstractRenderer.CreateXObject(null, new Rectangle(0, 0, 20, 20), pdfDocument);
+            NUnit.Framework.Assert.IsNull(pdfXObject.GetPdfObject().Get(PdfName.Resources));
+        }
+
+        [NUnit.Framework.Test]
+        public virtual void CreateXObjectWithInvalidColorTest() {
+            AbstractLinearGradientBuilder gradientBuilder = new StrategyBasedLinearGradientBuilder();
+            PdfDocument pdfDocument = new PdfDocument(new PdfWriter(new ByteArrayOutputStream()));
+            PdfXObject pdfXObject = AbstractRenderer.CreateXObject(gradientBuilder, new Rectangle(0, 0, 20, 20), pdfDocument
+                );
+            NUnit.Framework.Assert.IsNull(pdfXObject.GetPdfObject().Get(PdfName.Resources));
+        }
+    }
+}

itext/itext.layout/itext/layout/renderer/AbstractRenderer.cs

@@ -504,8 +504,8 @@ public virtual void DrawBackground(DrawContext drawContext) {
                         //  for gradient uses width and height = 1. For all othe cases the logic left as it was.
                         Rectangle imageRectangle;
                         if (backgroundXObject == null) {
-                            backgroundXObject = CreateXObject(backgroundImage.GetLinearGradientBuilder(), backgroundArea, drawContext.
-                                GetDocument());
+                            backgroundXObject = iText.Layout.Renderer.AbstractRenderer.CreateXObject(backgroundImage.GetLinearGradientBuilder
+                                (), backgroundArea, drawContext.GetDocument());
                             imageRectangle = new Rectangle(backgroundArea.GetX(), backgroundArea.GetTop() - backgroundXObject.GetHeight
                                 (), 1, 1);
                         }
@@ -548,17 +548,24 @@ public virtual void DrawBackground(DrawContext drawContext) {
             }
         }
 
-        public virtual PdfFormXObject CreateXObject(AbstractLinearGradientBuilder linearGradientBuilder, Rectangle
-             xObjectArea, PdfDocument document) {
-            if (linearGradientBuilder == null) {
-                return null;
-            }
+        /// <summary>
+        /// Create a
+        /// <see cref="iText.Kernel.Pdf.Xobject.PdfFormXObject"/>
+        /// with the given area and containing a linear gradient inside.
+        /// </summary>
+        /// <param name="linearGradientBuilder">the linear gradient builder</param>
+        /// <param name="xObjectArea">the result object area</param>
+        /// <param name="document">the pdf document</param>
+        /// <returns>the xObject with a specified area and a linear gradient</returns>
+        public static PdfFormXObject CreateXObject(AbstractLinearGradientBuilder linearGradientBuilder, Rectangle 
+            xObjectArea, PdfDocument document) {
             Rectangle formBBox = new Rectangle(0, 0, xObjectArea.GetWidth(), xObjectArea.GetHeight());
-            PdfFormXObject xObject = null;
-            Color gradientColor = linearGradientBuilder.BuildColor(formBBox, null);
-            if (gradientColor != null) {
-                xObject = new PdfFormXObject(formBBox);
-                new PdfCanvas(xObject, document).SetColor(gradientColor, true).Rectangle(formBBox).Fill();
+            PdfFormXObject xObject = new PdfFormXObject(formBBox);
+            if (linearGradientBuilder != null) {
+                Color gradientColor = linearGradientBuilder.BuildColor(formBBox, null);
+                if (gradientColor != null) {
+                    new PdfCanvas(xObject, document).SetColor(gradientColor, true).Rectangle(formBBox).Fill();
+                }
             }
             return xObject;
         }

port-hash

@@ -1 +1 @@
-fffd9ce335e05b267707f0ae3a5ce6093bf1d825
+34efacbce9d6048d19dd0efb6570d9a4ec9bc01f