ThemeReader.cs

/*
 * NanoXLSX is a small .NET library to generate and read XLSX (Microsoft Excel 2007 or newer) files in an easy and native way
 * Copyright Raphael Stoeckli © 2026
 * This library is licensed under the MIT License.
 * You find a copy of the license in project folder or on: http://opensource.org/licenses/MIT
 */
 
using System;
using System.IO;
using System.Xml;
using NanoXLSX.Colors;
using NanoXLSX.Interfaces;
using NanoXLSX.Interfaces.Reader;
using NanoXLSX.Registry;
using NanoXLSX.Registry.Attributes;
using NanoXLSX.Themes;
using IOException = NanoXLSX.Exceptions.IOException;
 
namespace NanoXLSX.Internal.Readers
{
    [NanoXlsxPlugIn(PlugInUUID = PlugInUUID.ThemeReader)]
    public class ThemeReader : IPluginBaseReader
    {
 
        private MemoryStream stream;
 
        #region properties
        public Workbook Workbook { get; set; }
        public IOptions Options { get; set; }
        public Action<MemoryStream, Workbook, string, IOptions, int?> InlinePluginHandler { get; set; }
        #endregion
 
        #region constructors
        internal ThemeReader()
        {
        }
        #endregion
 
        #region methods
        public void Init(MemoryStream stream, Workbook workbook, IOptions readerOptions, Action<MemoryStream, Workbook, string, IOptions, int?> inlinePluginHandler)
        {
            this.stream = stream;
            this.Workbook = workbook;
            this.Options = readerOptions;
            this.InlinePluginHandler = inlinePluginHandler;
        }

        public void Execute()
        {
            try
            {
                using (stream) // Close after processing
                {
                    XmlDocument xr = new XmlDocument() { XmlResolver = null };
                    using (XmlReader reader = XmlReader.Create(stream, new XmlReaderSettings() { XmlResolver = null }))
                    {
                        xr.Load(reader);
                        string prefix = ReaderUtils.DiscoverPrefix(xr, "theme");
                        XmlNodeList themes = ReaderUtils.GetElementsByTagName(xr, "theme", prefix);
                        string themeName = ReaderUtils.GetAttribute(themes[0], "name"); // If this fails, something is completely wrong
                        Workbook.WorkbookTheme = new Theme(themeName);
                        ColorScheme colorScheme = new ColorScheme();
                        Workbook.WorkbookTheme.Colors = colorScheme;
                        XmlNodeList colors = ReaderUtils.GetElementsByTagName(xr, "clrScheme", prefix);
 
                        foreach (XmlNode color in colors)
                        {
                            string colorSchemeName = ReaderUtils.GetAttribute(color, "name", "");
                            Workbook.WorkbookTheme.Colors.Name = colorSchemeName;
                            XmlNodeList colorNodes = color.ChildNodes;
                            foreach (XmlNode colorNode in colorNodes)
                            {
                                string name = colorNode.LocalName;
                                switch (name)
                                {
                                    case "dk1":
                                        colorScheme.Dark1 = ParseColor(colorNode.ChildNodes);
                                        break;
                                    case "lt1":
                                        colorScheme.Light1 = ParseColor(colorNode.ChildNodes);
                                        break;
                                    case "dk2":
                                        colorScheme.Dark2 = ParseColor(colorNode.ChildNodes);
                                        break;
                                    case "lt2":
                                        colorScheme.Light2 = ParseColor(colorNode.ChildNodes);
                                        break;
                                    case "accent1":
                                        colorScheme.Accent1 = ParseColor(colorNode.ChildNodes);
                                        break;
                                    case "accent2":
                                        colorScheme.Accent2 = ParseColor(colorNode.ChildNodes);
                                        break;
                                    case "accent3":
                                        colorScheme.Accent3 = ParseColor(colorNode.ChildNodes);
                                        break;
                                    case "accent4":
                                        colorScheme.Accent4 = ParseColor(colorNode.ChildNodes);
                                        break;
                                    case "accent5":
                                        colorScheme.Accent5 = ParseColor(colorNode.ChildNodes);
                                        break;
                                    case "accent6":
                                        colorScheme.Accent6 = ParseColor(colorNode.ChildNodes);
                                        break;
                                    case "hlink":
                                        colorScheme.Hyperlink = ParseColor(colorNode.ChildNodes);
                                        break;
                                    case "folHlink":
                                        colorScheme.FollowedHyperlink = ParseColor(colorNode.ChildNodes);
                                        break;
                                }
 
                            }
                        }
                        InlinePluginHandler?.Invoke(stream, Workbook, PlugInUUID.ThemeInlineReader, Options, null);
                    }
                }
            }
            catch (Exception ex)
            {
                throw new IOException("The XML entry could not be read from the input stream. Please see the inner exception:", ex);
            }
        }

        private static IColor ParseColor(XmlNodeList childNodes)
        {
            foreach (XmlNode node in childNodes)
            {
                if (node.LocalName == "sysClr")
                {
                    SystemColor.Value value = ParseSystemColor(node);
                    SystemColor systemColor = new SystemColor
                    {
                        ColorValue = value
                    };
                    string lastColor = ReaderUtils.GetAttribute(node, "lastClr");
                    if (lastColor != null)
                    {
                        systemColor.LastColor = lastColor;
                    }
                    return systemColor;
                }
                else if (node.LocalName == "srgbClr")
                {
                    SrgbColor srgbColor = new SrgbColor
                    {
                        ColorValue = ReaderUtils.GetAttribute(node, "val")
                    };
                    return srgbColor;
                }
            }
            return null;
        }

        private static SystemColor.Value ParseSystemColor(XmlNode innerNode)
        {
            string value = ReaderUtils.GetAttribute(innerNode, "val");
            if (string.IsNullOrEmpty(value))
            {
                throw new IOException("The system color entry was null or empty");
            }
            try
            {
                return SystemColor.MapStringToValue(value);
            }
            catch (Exception ex)
            {
                throw new IOException("The system color entry '" + value + "' could not be parsed", ex);
            }
        }
        #endregion
    }
}