fix: apply colors from conditional formatting

vaadin-spreadsheet-flow-parent/vaadin-spreadsheet-flow/src/main/java/com/vaadin/flow/component/spreadsheet/ColorConverterUtil.java

@@ -14,16 +14,19 @@ public class ColorConverterUtil implements Serializable {
 
     public static String toRGBA(byte[] argb) {
         int rgba[] = new int[3];
-        for (int i = 1; i < argb.length; i++) {
+        boolean hasAlpha = argb.length == 4;
+        float alpha = hasAlpha ? argb[0] : 1.0f;
+        int channelOffset = hasAlpha ? 1 : 0;
+
+        for (int i = channelOffset; i < argb.length; i++) {
             int x = argb[i];
             if (x < 0) {
                 x += 256;
             }
-            rgba[i - 1] = x;
+            rgba[i - channelOffset] = x;
         }
 
-        float x = argb[0];
-        return buildRgba(rgba, x);
+        return buildRgba(rgba, alpha);
     }
 
     public static String toRGBA(String hexARGB) {

vaadin-spreadsheet-flow-parent/vaadin-spreadsheet-flow/src/main/java/com/vaadin/flow/component/spreadsheet/XSSFColorConverter.java

@@ -14,6 +14,7 @@
 import org.apache.poi.ss.usermodel.BorderFormatting;
 import org.apache.poi.ss.usermodel.CellStyle;
 import org.apache.poi.ss.usermodel.ConditionalFormattingRule;
+import org.apache.poi.ss.usermodel.IndexedColors;
 import org.apache.poi.xssf.model.ThemesTable;
 import org.apache.poi.xssf.usermodel.XSSFBorderFormatting;
 import org.apache.poi.xssf.usermodel.XSSFCellStyle;
@@ -24,7 +25,6 @@
 import org.apache.poi.xssf.usermodel.extensions.XSSFCellBorder.BorderSide;
 import org.apache.poi.xssf.usermodel.extensions.XSSFCellFill;
 import org.openxmlformats.schemas.spreadsheetml.x2006.main.CTBorder;
-import org.openxmlformats.schemas.spreadsheetml.x2006.main.CTCfRule;
 import org.openxmlformats.schemas.spreadsheetml.x2006.main.CTColor;
 import org.openxmlformats.schemas.spreadsheetml.x2006.main.CTDxf;
 import org.openxmlformats.schemas.spreadsheetml.x2006.main.CTFont;
@@ -288,6 +288,11 @@ public String getBackgroundColorCSS(ConditionalFormattingRule rule) {
 
                 // CF rules have tint in bgColor but not the XSSFColor.
                 return styleColor(themeColor, bgColor.getTint());
+            } else if (bgColor.isSetIndexed()) {
+                XSSFColor mappedColor = new XSSFColor(
+                        IndexedColors.fromInt((int) bgColor.getIndexed()),
+                        workbook.getStylesSource().getIndexedColors());
+                return styleColor(mappedColor, bgColor.getTint());
             } else {
                 byte[] rgb = bgColor.getRgb();
                 return rgb == null ? null : ColorConverterUtil.toRGBA(rgb);
@@ -320,6 +325,11 @@ public String getFontColorCSS(ConditionalFormattingRule rule) {
                     .getThemeColor((int) ctColor.getTheme());
 
             return styleColor(themeColor, ctColor.getTint());
+        } else if (ctColor.isSetIndexed()) {
+            XSSFColor mappedColor = new XSSFColor(
+                    IndexedColors.fromInt((int) ctColor.getIndexed()),
+                    workbook.getStylesSource().getIndexedColors());
+            return styleColor(mappedColor, ctColor.getTint());
         } else {
             byte[] rgb = ctColor.getRgb();
             return rgb == null ? null : ColorConverterUtil.toRGBA(rgb);
@@ -405,16 +415,12 @@ private byte applyTint(int lum, double tint) {
      */
     private CTDxf getXMLColorDataWithReflection(
             XSSFConditionalFormattingRule rule) {
-        CTCfRule realRule = null;
-
         Method declaredMethod = null;
         try {
-            declaredMethod = rule.getClass().getDeclaredMethod("getCTCfRule");
+            declaredMethod = rule.getClass().getDeclaredMethod("getDxf",
+                    boolean.class);
             declaredMethod.setAccessible(true);
-            realRule = (CTCfRule) declaredMethod.invoke(rule);
-            CTDxf dxf = workbook.getStylesSource().getCTStylesheet().getDxfs()
-                    .getDxfArray((int) realRule.getDxfId());
-            return dxf;
+            return (CTDxf) declaredMethod.invoke(rule, false);
         } catch (Exception e) {
             LOGGER.debug(e.getMessage());
             return null;

vaadin-spreadsheet-flow-parent/vaadin-spreadsheet-flow/src/test/java/com/vaadin/flow/component/spreadsheet/tests/XSSFColorConverterTest.java

@@ -0,0 +1,89 @@
+/**
+ * Copyright 2000-2024 Vaadin Ltd.
+ *
+ * This program is available under Vaadin Commercial License and Service Terms.
+ *
+ * See {@literal <https://vaadin.com/commercial-license-and-service-terms>} for the full
+ * license.
+ */
+package com.vaadin.flow.component.spreadsheet.tests;
+
+import org.apache.poi.ss.usermodel.ComparisonOperator;
+import org.apache.poi.ss.usermodel.ConditionalFormattingRule;
+import org.apache.poi.ss.usermodel.IndexedColors;
+import org.apache.poi.xssf.usermodel.XSSFColor;
+import org.apache.poi.xssf.usermodel.XSSFWorkbook;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+import com.vaadin.flow.component.spreadsheet.Spreadsheet;
+import com.vaadin.flow.component.spreadsheet.XSSFColorConverter;
+
+public class XSSFColorConverterTest {
+
+    private Spreadsheet spreadsheet;
+    private XSSFColorConverter converter;
+
+    @Before
+    public void setUp() {
+        spreadsheet = new Spreadsheet();
+        converter = new XSSFColorConverter(
+                (XSSFWorkbook) spreadsheet.getWorkbook());
+    }
+
+    @Test
+    public void getFontColorCSS_withIndexedColor() {
+        var rule = createRule();
+        var font = rule.createFontFormatting();
+        font.setFontColorIndex(IndexedColors.RED.index);
+
+        var cssColor = converter.getFontColorCSS(rule);
+
+        Assert.assertEquals("rgba(255, 0, 0, 1.0);", cssColor);
+    }
+
+    @Test
+    public void getFontColorCSS_withRgbColor() {
+        var rule = createRule();
+        var font = rule.createFontFormatting();
+        var color = new XSSFColor(
+                new byte[] { (byte) 255, (byte) 128, (byte) 64 });
+        font.setFontColor(color);
+
+        var cssColor = converter.getFontColorCSS(rule);
+
+        Assert.assertEquals("rgba(255, 128, 64, 1.0);", cssColor);
+    }
+
+    @Test
+    public void getBackgroundColorCSS_withIndexedColor() {
+        var rule = createRule();
+        var pattern = rule.createPatternFormatting();
+        pattern.setFillBackgroundColor(IndexedColors.RED.index);
+
+        var cssColor = converter.getBackgroundColorCSS(rule);
+
+        Assert.assertEquals("rgba(255, 0, 0, 1.0);", cssColor);
+    }
+
+    @Test
+    public void getBackgroundColorCSS_withRgbColor() {
+        var rule = createRule();
+        var pattern = rule.createPatternFormatting();
+        var color = new XSSFColor(
+                new byte[] { (byte) 255, (byte) 128, (byte) 64 });
+        pattern.setFillBackgroundColor(color);
+
+        var cssColor = converter.getBackgroundColorCSS(rule);
+
+        Assert.assertEquals("rgba(255, 128, 64, 1.0);", cssColor);
+    }
+
+    private ConditionalFormattingRule createRule() {
+        var conditionalFormatting = spreadsheet.getActiveSheet()
+                .getSheetConditionalFormatting();
+        return conditionalFormatting
+                .createConditionalFormattingRule(ComparisonOperator.LT, "0");
+    }
+}