Cover layer related logic with tests.

Implemented during the second technical debt session.

Author: ars18wrw

kernel/src/test/java/com/itextpdf/kernel/pdf/layer/PdfLayerMembershipTest.java

@@ -0,0 +1,16 @@
+package com.itextpdf.kernel.pdf.layer;
+
+import com.itextpdf.kernel.pdf.canvas.PdfCanvas;
+
+class PdfLayerTestUtils {
+
+    public static void addTextInsideLayer(IPdfOCG layer, PdfCanvas canvas, String text, float x, float y) {
+        canvas
+                .beginLayer(layer)
+                .beginText()
+                .moveText(x, y)
+                .showText(text)
+                .endText()
+                .endLayer();
+    }
+}

kernel/src/test/java/com/itextpdf/kernel/pdf/layer/PdfLayerTestUtils.java

@@ -0,0 +1,131 @@
+/*
+    This file is part of the iText (R) project.
+    Copyright (c) 1998-2019 iText Group NV
+    Authors: iText Software.
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU Affero General Public License version 3
+    as published by the Free Software Foundation with the addition of the
+    following permission added to Section 15 as permitted in Section 7(a):
+    FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY
+    ITEXT GROUP. ITEXT GROUP DISCLAIMS THE WARRANTY OF NON INFRINGEMENT
+    OF THIRD PARTY RIGHTS
+
+    This program is distributed in the hope that it will be useful, but
+    WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+    or FITNESS FOR A PARTICULAR PURPOSE.
+    See the GNU Affero General Public License for more details.
+    You should have received a copy of the GNU Affero General Public License
+    along with this program; if not, see http://www.gnu.org/licenses or write to
+    the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+    Boston, MA, 02110-1301 USA, or download the license from the following URL:
+    http://itextpdf.com/terms-of-use/
+
+    The interactive user interfaces in modified source and object code versions
+    of this program must display Appropriate Legal Notices, as required under
+    Section 5 of the GNU Affero General Public License.
+
+    In accordance with Section 7(b) of the GNU Affero General Public License,
+    a covered work must retain the producer line in every PDF that is created
+    or manipulated using iText.
+
+    You can be released from the requirements of the license by purchasing
+    a commercial license. Buying such a license is mandatory as soon as you
+    develop commercial activities involving the iText software without
+    disclosing the source code of your own applications.
+    These activities include: offering paid services to customers as an ASP,
+    serving PDFs on the fly in a web application, shipping iText with a closed
+    source product.
+
+    For more information, please contact iText Software Corp. at this
+    address: [email protected]
+ */
+package com.itextpdf.kernel.pdf.layer;
+
+import com.itextpdf.kernel.pdf.PdfArray;
+import com.itextpdf.kernel.pdf.PdfDictionary;
+import com.itextpdf.kernel.pdf.PdfDocument;
+import com.itextpdf.kernel.pdf.PdfName;
+import com.itextpdf.kernel.pdf.PdfObject;
+import com.itextpdf.kernel.pdf.PdfWriter;
+import com.itextpdf.test.ExtendedITextTest;
+import com.itextpdf.test.annotations.type.UnitTest;
+import org.junit.Assert;
+import org.junit.Test;
+import org.junit.experimental.categories.Category;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+
+@Category(UnitTest.class)
+public class PdfVisibilityExpressionTest extends ExtendedITextTest {
+
+    @Test
+    public void expressionByArrayTest() {
+        PdfDocument tempDoc = new PdfDocument(new PdfWriter(new ByteArrayOutputStream()));
+
+        PdfArray array = new PdfArray();
+
+        // add the AND operator as the first parameter of the expression
+        array.add(PdfName.And);
+
+        // add two empty dictionaries as the other parameters
+        array.add(new PdfLayer((PdfDictionary) new PdfDictionary().makeIndirect(tempDoc)).getPdfObject());
+        array.add(new PdfLayer((PdfDictionary) new PdfDictionary().makeIndirect(tempDoc)).getPdfObject());
+
+        // create visibility expression
+        PdfVisibilityExpression expression = new PdfVisibilityExpression(array);
+
+        PdfObject expressionObject = expression.getPdfObject();
+        Assert.assertTrue(expressionObject instanceof PdfArray);
+        Assert.assertEquals(3, ((PdfArray) expressionObject).size());
+        Assert.assertEquals(PdfName.And, ((PdfArray) expressionObject).getAsName(0));
+    }
+
+    @Test
+    public void andExpressionTest() {
+        PdfDocument tempDoc = new PdfDocument(new PdfWriter(new ByteArrayOutputStream()));
+
+        // create expression with the AND operator as the first parameter
+        PdfVisibilityExpression expression = new PdfVisibilityExpression(PdfName.And);
+
+        // add two empty dictionaries as the other parameters
+        expression.addOperand(new PdfLayer((PdfDictionary) new PdfDictionary().makeIndirect(tempDoc)));
+        expression.addOperand(new PdfLayer((PdfDictionary) new PdfDictionary().makeIndirect(tempDoc)));
+
+        PdfObject expressionObject = expression.getPdfObject();
+        Assert.assertTrue(expressionObject instanceof PdfArray);
+        Assert.assertEquals(3, ((PdfArray) expressionObject).size());
+        Assert.assertEquals(PdfName.And, ((PdfArray) expressionObject).getAsName(0));
+    }
+
+    @Test
+    public void nestedExpressionTest() {
+        PdfDocument tempDoc = new PdfDocument(new PdfWriter(new ByteArrayOutputStream()));
+
+        // create expression with the OR operator as the first parameter
+        PdfVisibilityExpression expression = new PdfVisibilityExpression(PdfName.Or);
+
+        // add an empty dictionary as the second parameter
+        expression.addOperand(new PdfLayer((PdfDictionary) new PdfDictionary().makeIndirect(tempDoc)));
+
+        // create a nested expression with the AND operator and two empty dictionaries as parameters
+        PdfVisibilityExpression nestedExpression = new PdfVisibilityExpression(PdfName.And);
+        nestedExpression.addOperand(new PdfLayer((PdfDictionary) new PdfDictionary().makeIndirect(tempDoc)));
+        nestedExpression.addOperand(new PdfLayer((PdfDictionary) new PdfDictionary().makeIndirect(tempDoc)));
+
+        // add another expression as the third parameter
+        expression.addOperand(nestedExpression);
+
+        PdfObject expressionObject = expression.getPdfObject();
+        Assert.assertTrue(expressionObject instanceof PdfArray);
+        Assert.assertEquals(3, ((PdfArray) expressionObject).size());
+        Assert.assertEquals(PdfName.Or, ((PdfArray) expressionObject).getAsName(0));
+
+        PdfObject child = ((PdfArray) expressionObject).get(2);
+        Assert.assertTrue(child instanceof PdfArray);
+        Assert.assertEquals(3, ((PdfArray) child).size());
+        Assert.assertEquals(PdfName.And, ((PdfArray) child).get(0));
+    }
+
+}