Add column width and gap calculation

DEVSIX-7553

Author: Dmitry Radchuk

layout/src/main/java/com/itextpdf/layout/exceptions/LayoutExceptionMessageConstant.java

@@ -51,5 +51,8 @@ public final class LayoutExceptionMessageConstant {
     public static final String INLINE_VERTICAL_ALIGNMENT_DOESN_T_NEED_A_VALUE =
             "Inline vertical alignment \"{0}\" doesn't need a value";
 
+    public static final String INVALID_COLUMN_PROPERTIES =
+            "Invalid column-count/column-width/column-gap properties, they're absent or have negative value";
+
     private LayoutExceptionMessageConstant(){}
 }

layout/src/main/java/com/itextpdf/layout/properties/Property.java

@@ -68,6 +68,8 @@ public final class Property {
     public static final int COLLAPSING_MARGINS = 89;
     public static final int COLSPAN = 16;
     public static final int COLUMN_COUNT = 138;
+    public static final int COLUMN_WIDTH = 142;
+    public static final int COLUMN_GAP = 143;
     public static final int DESTINATION = 17;
     public static final int FILL_AVAILABLE_AREA = 86;
     public static final int FILL_AVAILABLE_AREA_ON_SPLIT = 87;
@@ -216,7 +218,7 @@ public final class Property {
      * related to textual operations. Indicates whether or not this type of property is inheritable.
      */
     private static final boolean[] INHERITED_PROPERTIES;
-    private static final int MAX_INHERITED_PROPERTY_ID = 140;
+    private static final int MAX_INHERITED_PROPERTY_ID = 143;
 
     static {
         INHERITED_PROPERTIES = new boolean[MAX_INHERITED_PROPERTY_ID + 1];

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

@@ -25,6 +25,7 @@ This file is part of the iText (R) project.
 import com.itextpdf.kernel.geom.Rectangle;
 import com.itextpdf.layout.borders.Border;
 import com.itextpdf.layout.element.MulticolContainer;
+import com.itextpdf.layout.exceptions.LayoutExceptionMessageConstant;
 import com.itextpdf.layout.layout.LayoutArea;
 import com.itextpdf.layout.layout.LayoutContext;
 import com.itextpdf.layout.layout.LayoutResult;
@@ -47,6 +48,7 @@ public class MulticolRenderer extends AbstractRenderer {
     private float columnWidth;
     private float approximateHeight;
     private Float heightFromProperties;
+    private float columnGap;
 
     /**
      * Creates a DivRenderer from its corresponding layout object.
@@ -80,9 +82,9 @@ public LayoutResult layout(LayoutContext layoutContext) {
         applyPaddings(actualBBox, false);
         applyBorderBox(actualBBox, false);
         applyMargins(actualBBox, false);
+        calculateColumnCountAndWidth(actualBBox.getWidth());
+
         heightFromProperties = determineHeight(actualBBox);
-        columnCount = (int) this.<Integer>getProperty(Property.COLUMN_COUNT);
-        columnWidth = actualBBox.getWidth() / columnCount;
         if (this.elementRenderer == null) {
             // initialize elementRenderer on first layout when first child represents renderer of element which
             // should be layouted in multicol, because on the next layouts this can have multiple children
@@ -259,6 +261,30 @@ private MulticolLayoutResult balanceContentAndLayoutColumns(LayoutContext prelay
         return result;
     }
 
+    //algorithm is based on pseudo algorithm from https://www.w3.org/TR/css-multicol-1/#propdef-column-span
+    private void calculateColumnCountAndWidth(float initialWidth) {
+        final Integer columnCount = (Integer)this.<Integer>getProperty(Property.COLUMN_COUNT);
+        final Float columnWidth = (Float)this.<Float>getProperty(Property.COLUMN_WIDTH);
+        final Float columnGap = (Float)this.<Float>getProperty(Property.COLUMN_GAP);
+        this.columnGap = columnGap != null ? columnGap.floatValue() : 0;
+        if ((columnCount == null && columnWidth == null)
+            || (columnCount != null && columnCount.intValue() < 0)
+            || (columnWidth != null && columnWidth.floatValue() < 0)) {
+            throw new IllegalStateException(LayoutExceptionMessageConstant.INVALID_COLUMN_PROPERTIES);
+        }
+        if (columnWidth == null) {
+            this.columnCount = columnCount.intValue();
+        } else if (columnCount == null) {
+            this.columnCount = Math.max(1, (int) Math.floor((double)((initialWidth + this.columnGap)
+                    / (columnWidth.floatValue() + this.columnGap))));
+        } else {
+            this.columnCount = Math.min((int) columnCount,
+                    Math.max(1, (int) Math.floor((double) ((initialWidth + this.columnGap)
+                            / (columnWidth.floatValue() + this.columnGap)))));
+        }
+        this.columnWidth = Math.max(0.0f, ((initialWidth + this.columnGap)/this.columnCount - this.columnGap));
+    }
+
     private void clearOverFlowRendererIfNeeded(MulticolLayoutResult result) {
         //When we have a height set on the element but the content doesn't fit in the given height
         //we don't want to render the overflow renderer as it would be rendered in the next area
@@ -309,7 +335,7 @@ private MulticolLayoutResult layoutColumnsAndReturnOverflowRenderer(LayoutContex
             LayoutArea tempArea = preLayoutContext.getArea().clone();
             tempArea.getBBox().setWidth(columnWidth);
             tempArea.getBBox().setHeight(workingHeight);
-            tempArea.getBBox().setX(actualBBox.getX() + columnWidth * i);
+            tempArea.getBBox().setX(actualBBox.getX() + (columnWidth + columnGap) * i);
             tempArea.getBBox().setY(actualBBox.getY() + actualBBox.getHeight() - tempArea.getBBox().getHeight());
 
             LayoutContext columnContext = new LayoutContext(tempArea, preLayoutContext.getMarginsCollapseInfo(),

layout/src/test/java/com/itextpdf/layout/element/MulticolContainerTest.java

@@ -25,6 +25,7 @@ This file is part of the iText (R) project.
 import com.itextpdf.commons.utils.PlaceHolderTextUtil;
 import com.itextpdf.commons.utils.PlaceHolderTextUtil.PlaceHolderTextBy;
 import com.itextpdf.io.image.ImageDataFactory;
+import com.itextpdf.io.source.ByteArrayOutputStream;
 import com.itextpdf.io.util.UrlUtil;
 import com.itextpdf.kernel.colors.Color;
 import com.itextpdf.kernel.colors.ColorConstants;
@@ -35,6 +36,7 @@ This file is part of the iText (R) project.
 import com.itextpdf.layout.Document;
 import com.itextpdf.layout.borders.Border;
 import com.itextpdf.layout.borders.SolidBorder;
+import com.itextpdf.layout.exceptions.LayoutExceptionMessageConstant;
 import com.itextpdf.layout.logs.LayoutLogMessageConstant;
 import com.itextpdf.layout.properties.Background;
 import com.itextpdf.layout.properties.HorizontalAlignment;
@@ -994,8 +996,89 @@ public void continuousColumContainerSetHeightSmaller() throws IOException, Inter
         });
     }
 
+    @Test
+    public void paragraphWithColumnWidthTest() throws IOException, InterruptedException {
+        String outFileName = DESTINATION_FOLDER + "paragraphWithColumnWidthTest.pdf";
+        String cmpFileName = SOURCE_FOLDER + "cmp_paragraphWithColumnWidthTest.pdf";
+
+        try (Document document = new Document(new PdfDocument(new PdfWriter(outFileName)))) {
+            Div columnContainer = new MulticolContainer();
+            columnContainer.setProperty(Property.COLUMN_WIDTH, 200.0f);
+            Paragraph paragraph = createDummyParagraph();
+            columnContainer.add(paragraph);
+            document.add(columnContainer);
+        }
+        //expecting 2 columns with ~260px width each
+        Assert.assertNull(new CompareTool().compareByContent(outFileName, cmpFileName, DESTINATION_FOLDER, "diff"));
+    }
+
+    @Test
+    public void paragraphWithColumnWidthAndColumnCountTest() throws IOException, InterruptedException {
+        String outFileName = DESTINATION_FOLDER + "paragraphWithColumnWidthAndColumnCountTest.pdf";
+        String cmpFileName = SOURCE_FOLDER + "cmp_paragraphWithColumnWidthAndColumnCountTest.pdf";
+
+        try (Document document = new Document(new PdfDocument(new PdfWriter(outFileName)))) {
+            Div columnContainer = new MulticolContainer();
+            //column width is ignored in this case, because column-count requires higher width
+            columnContainer.setProperty(Property.COLUMN_WIDTH, 100.0f);
+            columnContainer.setProperty(Property.COLUMN_COUNT, 2);
+            Paragraph paragraph = createDummyParagraph();
+            columnContainer.add(paragraph);
+            document.add(columnContainer);
+        }
+        Assert.assertNull(new CompareTool().compareByContent(outFileName, cmpFileName, DESTINATION_FOLDER, "diff"));
+    }
+
+    @Test
+    public void paragraphWithInvalidColumnValuesTest() {
+
+        try (Document document = new Document(new PdfDocument(new PdfWriter(new ByteArrayOutputStream())))) {
+            Div columnContainer = new MulticolContainer();
+            //column width is ignored in this case, because column-count requires higher width
+            columnContainer.setProperty(Property.COLUMN_WIDTH, -30.0f);
+            columnContainer.setProperty(Property.COLUMN_COUNT, -2);
+            columnContainer.setProperty(Property.COLUMN_GAP, -20.0f);
+            Paragraph paragraph = createDummyParagraph();
+            columnContainer.add(paragraph);
+            Throwable exception = Assert.assertThrows(IllegalStateException.class, () -> document.add(columnContainer));
+            Assert.assertEquals(LayoutExceptionMessageConstant.INVALID_COLUMN_PROPERTIES, exception.getMessage());
+        }
+    }
+
+    @Test
+    public void paragraphWithColumnWidthAndGapTest() throws IOException, InterruptedException {
+        String outFileName = DESTINATION_FOLDER + "paragraphWithColumnWidthAndGapTest.pdf";
+        String cmpFileName = SOURCE_FOLDER + "cmp_paragraphWithColumnWidthAndGapTest.pdf";
+
+        try (Document document = new Document(new PdfDocument(new PdfWriter(outFileName)))) {
+            Div columnContainer = new MulticolContainer();
+            columnContainer.setProperty(Property.COLUMN_WIDTH, 100.0f);
+            columnContainer.setProperty(Property.COLUMN_GAP, 100.0f);
+            Paragraph paragraph = createDummyParagraph();
+            columnContainer.add(paragraph);
+            document.add(columnContainer);
+        }
+        Assert.assertNull(new CompareTool().compareByContent(outFileName, cmpFileName, DESTINATION_FOLDER, "diff"));
+    }
+
+    @Test
+    public void paragraphWithColumnCountAndGapTest() throws IOException, InterruptedException {
+        String outFileName = DESTINATION_FOLDER + "paragraphWithColumnCountAndGapTest.pdf";
+        String cmpFileName = SOURCE_FOLDER + "cmp_paragraphWithColumnCountAndGapTest.pdf";
+
+        try (Document document = new Document(new PdfDocument(new PdfWriter(outFileName)))) {
+            Div columnContainer = new MulticolContainer();
+            columnContainer.setProperty(Property.COLUMN_COUNT, 5);
+            columnContainer.setProperty(Property.COLUMN_GAP, 50.0f);
+            Paragraph paragraph = createDummyParagraph();
+            columnContainer.add(paragraph);
+            document.add(columnContainer);
+        }
+        Assert.assertNull(new CompareTool().compareByContent(outFileName, cmpFileName, DESTINATION_FOLDER, "diff"));
+    }
+
 
-    private <T extends IBlockElement> void executeTest(String testName, T container, Consumer<T> executor)
+    private void executeTest(String testName, MulticolContainer container, Consumer<MulticolContainer> executor)
             throws IOException, InterruptedException {
         String filename = DESTINATION_FOLDER + testName + ".pdf";
         String cmpName = SOURCE_FOLDER + "cmp_" + testName + ".pdf";
@@ -1012,6 +1095,35 @@ private <T extends IBlockElement> void executeTest(String testName, T container,
         Assert.assertNull(compareTool.compareByContent(filename, cmpName, DESTINATION_FOLDER, "diff_"));
     }
 
+    private static Paragraph createDummyParagraph() {
+        return new Paragraph("Lorem ipsum dolor sit amet, consectetur adipiscing elit, " +
+                "sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, " +
+                "quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute " +
+                "irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. " +
+                "Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim " +
+                "id est laborum.");
+    }
+
+    private static String generateLongString(int amountOfWords) {
+        StringBuilder sb = new StringBuilder();
+        int random = 1;
+        for (int i = 0; i < amountOfWords; i++) {
+            random = getPseudoRandomInt(i + random);
+            for (int j = 1; j <= random; j++) {
+                sb.append('a');
+            }
+            sb.append(' ');
+        }
+        return sb.toString();
+    }
+
+    private static int getPseudoRandomInt(int prev) {
+        final int first = 93840;
+        final int second = 1929;
+        final int max = 7;
+        return (prev * first + second) % max;
+    }
+
     private static Div createFirstPageFiller() {
         Div firstPageFiller = new Div();
         firstPageFiller.setProperty(Property.MARGIN_TOP, UnitValue.createPointValue(50));

layout/src/test/resources/com/itextpdf/layout/MulticolContainerTest/cmp_paragraphWithColumnCountAndGapTest.pdf

@@ -892,8 +892,16 @@ public class CommonCssConstants {
      */
     public static final String COLUMN_REVERSE = "column-reverse";
 
+    /**
+     * The Constant COLUMN_COUNT.
+     */
     public static final String COLUMN_COUNT = "column-count";
 
+    /**
+     * The Constant COLUMN_WIDTH.
+     */
+    public static final String COLUMN_WIDTH = "column-width";
+
     /**
      * The Constant CONTAIN.
      */

layout/src/test/resources/com/itextpdf/layout/MulticolContainerTest/cmp_paragraphWithColumnWidthAndColumnCountTest.pdf

@@ -111,6 +111,12 @@ public CssDefaultValidator() {
         defaultValidators.put(CommonCssConstants.COLUMN_GAP, new MultiTypeDeclarationValidator(
                 new CssLengthValueValidator(false), new CssPercentageValueValidator(false), normalValidator,
                 inheritInitialUnsetValidator));
+        defaultValidators.put(CommonCssConstants.COLUMN_WIDTH, new MultiTypeDeclarationValidator(
+                new CssLengthValueValidator(false), new CssPercentageValueValidator(false),
+                new CssEnumValidator(CommonCssConstants.AUTO), inheritInitialUnsetValidator));
+        defaultValidators.put(CommonCssConstants.COLUMN_COUNT, new MultiTypeDeclarationValidator(
+                new CssNumberValueValidator(false), new CssEnumValidator(CommonCssConstants.AUTO),
+                inheritInitialUnsetValidator));
         defaultValidators.put(CommonCssConstants.ROW_GAP, new MultiTypeDeclarationValidator(
                 new CssLengthValueValidator(false), new CssPercentageValueValidator(false), normalValidator,
                 inheritInitialUnsetValidator));