Do not trim leading spaces in single line and multiline text fields

Previously, leading spaces were trimmed because this is the default
layout behavior. However, Acrobat does not trim leading spaces and
thus there was a difference between the appearance generated by iText
and the one that Acrobat generates when you enter the field. We now
follow Acrobat and do not trim leading spaces

DEVSIX-3539

Author: Snipx

forms/src/main/java/com/itextpdf/forms/fields/FormFieldValueNonTrimmingTextRenderer.java

@@ -0,0 +1,74 @@
+/*
+    This file is part of the iText (R) project.
+    Copyright (c) 1998-2019 iText Group NV
+    Authors: iText Software.
+
+    This program is offered under a commercial and under the AGPL license.
+    For commercial licensing, contact us at https://itextpdf.com/sales.  For AGPL licensing, see below.
+
+    AGPL licensing:
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Affero General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    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 <https://www.gnu.org/licenses/>.
+ */
+package com.itextpdf.forms.fields;
+
+import com.itextpdf.layout.element.Text;
+import com.itextpdf.layout.layout.LayoutContext;
+import com.itextpdf.layout.layout.LayoutResult;
+import com.itextpdf.layout.layout.TextLayoutResult;
+import com.itextpdf.layout.renderer.IRenderer;
+import com.itextpdf.layout.renderer.TextRenderer;
+
+/**
+ * Custom implementation for rendering form field values. It makes sure that text value
+ * trimming strategy matches Acrobat's behavior
+ */
+class FormFieldValueNonTrimmingTextRenderer extends TextRenderer {
+    // Determines whether we want to trim leading space. In particular we don't want to trim
+    // the very first leading spaces of the text value. When text overflows to the next lines,
+    // whether we should trim the text depends on why the overflow happened
+    private boolean callTrimFirst = false;
+
+    public FormFieldValueNonTrimmingTextRenderer(Text textElement) {
+        super(textElement);
+    }
+
+    @Override
+    public IRenderer getNextRenderer() {
+        return new FormFieldValueNonTrimmingTextRenderer((Text) getModelElement());
+    }
+
+    @Override
+    public LayoutResult layout(LayoutContext layoutContext) {
+        LayoutResult baseLayoutResult = super.layout(layoutContext);
+        if (baseLayoutResult instanceof TextLayoutResult &&
+                baseLayoutResult.getOverflowRenderer() instanceof FormFieldValueNonTrimmingTextRenderer &&
+                !((TextLayoutResult) baseLayoutResult).isSplitForcedByNewline()) {
+            // In case the overflow to the next line happened naturally (without a forced line break),
+            // we don't want to preserve the extra spaces at the beginning of the next line
+            ((FormFieldValueNonTrimmingTextRenderer) baseLayoutResult.getOverflowRenderer()).setCallTrimFirst(true);
+        }
+        return baseLayoutResult;
+    }
+
+    @Override
+    public void trimFirst() {
+       if (callTrimFirst) {
+           super.trimFirst();
+       }
+    }
+
+    private void setCallTrimFirst(boolean callTrimFirst) {
+        this.callTrimFirst = callTrimFirst;
+    }
+}

forms/src/main/java/com/itextpdf/forms/fields/PdfFormField.java

@@ -90,6 +90,7 @@ This file is part of the iText (R) project.
 import com.itextpdf.layout.Canvas;
 import com.itextpdf.layout.Style;
 import com.itextpdf.layout.element.Paragraph;
+import com.itextpdf.layout.element.Text;
 import com.itextpdf.layout.layout.LayoutArea;
 import com.itextpdf.layout.layout.LayoutContext;
 import com.itextpdf.layout.layout.LayoutResult;
@@ -101,8 +102,6 @@ This file is part of the iText (R) project.
 import com.itextpdf.layout.property.TransparentColor;
 import com.itextpdf.layout.property.VerticalAlignment;
 import com.itextpdf.layout.renderer.IRenderer;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
@@ -113,6 +112,8 @@ This file is part of the iText (R) project.
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /**
  * This class represents a single field or field group in an {@link com.itextpdf.forms.PdfAcroForm
@@ -2668,7 +2669,7 @@ protected void drawTextAppearance(Rectangle rect, PdfFont font, float fontSize,
                 Logger logger = LoggerFactory.getLogger(PdfFormField.class);
                 logger.error(MessageFormatUtil.format(LogMessageConstant.COMB_FLAG_MAY_BE_SET_ONLY_IF_MAXLEN_IS_PRESENT));
             }
-            modelCanvas.showTextAligned(new Paragraph(value).addStyle(paragraphStyle).setPaddings(0, X_OFFSET, 0, X_OFFSET),
+            modelCanvas.showTextAligned(createParagraphForTextFieldValue(value).addStyle(paragraphStyle).setPaddings(0, X_OFFSET, 0, X_OFFSET),
                     x, rect.getHeight() / 2, textAlignment, VerticalAlignment.MIDDLE);
         }
         canvas.
@@ -2708,7 +2709,7 @@ protected void drawMultiLineTextAppearance(Rectangle rect, PdfFont font, String
         Canvas modelCanvas = new Canvas(canvas, getDocument(), areaRect);
         modelCanvas.setProperty(Property.APPEARANCE_STREAM_LAYOUT, true);
 
-        Paragraph paragraph = new Paragraph(value).setFont(font)
+        Paragraph paragraph = createParagraphForTextFieldValue(value).setFont(font)
                 .setMargin(0)
                 .setPadding(3)
                 .setMultipliedLeading(1);
@@ -3687,4 +3688,10 @@ private Color appearancePropToColor(PdfDictionary appearanceCharacteristics, Pdf
         }
         return null;
     }
+
+    private static Paragraph createParagraphForTextFieldValue(String value) {
+        Text text = new Text(value);
+        text.setNextRenderer(new FormFieldValueNonTrimmingTextRenderer(text));
+        return new Paragraph(text);
+    }
 }

forms/src/test/java/com/itextpdf/forms/PdfFormFieldMultilineTextTest.java

@@ -30,21 +30,20 @@ This file is part of the iText (R) project.
 import com.itextpdf.kernel.font.PdfFontFactory;
 import com.itextpdf.kernel.geom.Rectangle;
 import com.itextpdf.kernel.pdf.PdfDocument;
+import com.itextpdf.kernel.pdf.PdfPage;
 import com.itextpdf.kernel.pdf.PdfReader;
 import com.itextpdf.kernel.pdf.PdfWriter;
 import com.itextpdf.kernel.utils.CompareTool;
-import com.itextpdf.layout.Document;
 import com.itextpdf.test.ExtendedITextTest;
 import com.itextpdf.test.annotations.type.IntegrationTest;
 
+import java.io.IOException;
+import java.util.Map;
 import org.junit.Assert;
 import org.junit.BeforeClass;
 import org.junit.Test;
 import org.junit.experimental.categories.Category;
 
-import java.io.IOException;
-import java.util.Map;
-
 @Category(IntegrationTest.class)
 public class PdfFormFieldMultilineTextTest extends ExtendedITextTest {
 
@@ -243,4 +242,54 @@ public void formFieldFilledWithStringTest() throws IOException, InterruptedExcep
         Assert.assertNull(new CompareTool().compareByContent(destinationFolder + "formFieldWithStringTest.pdf",
                 sourceFolder + "cmp_formFieldWithStringTest.pdf", destinationFolder, "diff_"));
     }
+
+    @Test
+    public void multilineTextFieldLeadingSpacesAreNotTrimmedTest() throws IOException, InterruptedException {
+        String filename = destinationFolder + "multilineTextFieldLeadingSpacesAreNotTrimmed.pdf";
+        PdfDocument pdfDoc = new PdfDocument(new PdfWriter(filename));
+        pdfDoc.addNewPage();
+
+        PdfAcroForm form = PdfAcroForm.getAcroForm(pdfDoc, true);
+
+        PdfPage page = pdfDoc.getFirstPage();
+        Rectangle rect = new Rectangle(210, 490, 300, 200);
+
+        PdfTextFormField field = PdfFormField.createMultilineText(pdfDoc, rect,
+                "TestField", "        value\n      with\n    leading\n    space");
+
+        form.addField(field, page);
+
+        pdfDoc.close();
+
+        CompareTool compareTool = new CompareTool();
+        String errorMessage = compareTool.compareByContent(filename, sourceFolder + "cmp_multilineTextFieldLeadingSpacesAreNotTrimmed.pdf", destinationFolder, "diff_");
+        if (errorMessage != null) {
+            Assert.fail(errorMessage);
+        }
+    }
+
+    @Test
+    public void multilineTextFieldRedundantSpacesAreTrimmedTest() throws IOException, InterruptedException {
+        String filename = destinationFolder + "multilineTextFieldRedundantSpacesAreTrimmedTest.pdf";
+        PdfDocument pdfDoc = new PdfDocument(new PdfWriter(filename));
+        pdfDoc.addNewPage();
+
+        PdfAcroForm form = PdfAcroForm.getAcroForm(pdfDoc, true);
+
+        PdfPage page = pdfDoc.getFirstPage();
+        Rectangle rect = new Rectangle(210, 490, 90, 200);
+
+        PdfTextFormField field = PdfFormField.createMultilineText(pdfDoc, rect,
+                "TestField", "before spaces           after spaces");
+
+        form.addField(field, page);
+
+        pdfDoc.close();
+
+        CompareTool compareTool = new CompareTool();
+        String errorMessage = compareTool.compareByContent(filename, sourceFolder + "cmp_multilineTextFieldRedundantSpacesAreTrimmedTest.pdf", destinationFolder, "diff_");
+        if (errorMessage != null) {
+            Assert.fail(errorMessage);
+        }
+    }
 }

forms/src/test/java/com/itextpdf/forms/PdfFormFieldTest.java

@@ -175,6 +175,30 @@ public void formFieldTest04() throws IOException, InterruptedException {
         }
     }
 
+    @Test
+    public void textFieldLeadingSpacesAreNotTrimmedTest() throws IOException, InterruptedException {
+        String filename = destinationFolder + "textFieldLeadingSpacesAreNotTrimmed.pdf";
+        PdfDocument pdfDoc = new PdfDocument(new PdfWriter(filename));
+        pdfDoc.addNewPage();
+
+        PdfAcroForm form = PdfAcroForm.getAcroForm(pdfDoc, true);
+
+        PdfPage page = pdfDoc.getFirstPage();
+        Rectangle rect = new Rectangle(210, 490, 300, 22);
+
+        PdfTextFormField field = PdfFormField.createText(pdfDoc, rect, "TestField", "        value with leading space");
+
+        form.addField(field, page);
+
+        pdfDoc.close();
+
+        CompareTool compareTool = new CompareTool();
+        String errorMessage = compareTool.compareByContent(filename, sourceFolder + "cmp_textFieldLeadingSpacesAreNotTrimmed.pdf", destinationFolder, "diff_");
+        if (errorMessage != null) {
+            Assert.fail(errorMessage);
+        }
+    }
+
     @Test
     public void unicodeFormFieldTest() throws IOException {
         String filename = sourceFolder + "unicodeFormFieldFile.pdf";