Fix custom error message feature

Author: vladimir-litvinchik

src/GroupDocs.Viewer.UI.API/README.md

@@ -125,5 +125,4 @@ builder.Services.AddSingleton<ISearchTermResolver, MySearchTermResolver>();
 
 ![GroupDocs.Viewer.UI - Custom search term](https://raw.githubusercontent.com/groupdocs-viewer/groupdocs-viewer.github.io/master/resources/image/ui/custom-search-term.png)
 
-**NOTE:** This feature works only when rendering to HTML. The service should be registered before you register the self-hosted or cloud API for it to take effect. By default, [SearchTermResolver.cs](./SearchTermResolution/Implementation/SearchTermResolver.cs) is registered. This class provides a default implementation that returns an empty string.
-
+**NOTE:** This feature works only when rendering to HTML and when `PreloadPages` is set to `0` which means all the pages are preloaded. The service should be registered before you register the self-hosted or cloud API for it to take effect. By default, [SearchTermResolver.cs](./SearchTermResolution/Implementation/SearchTermResolver.cs) is registered. This class provides a default implementation that returns an empty string.

src/GroupDocs.Viewer.UI.Core/Configuration/Config.cs

@@ -4,115 +4,151 @@ public class Config
     {
         /// <summary>
         /// Rendering mode for the UI.
-        /// Possible values: "RenderingMode.Html", "RenderingMode.Image".
-        /// Default value is "RenderingMode.Html".
+        /// Possible values: <c>RenderingMode.Html</c>, <c>RenderingMode.Image</c>.
+        /// Default value: <c>RenderingMode.Html</c>.
         /// </summary>
         public RenderingMode RenderingMode { get; set; } = RenderingMode.Html;
 
         /// <summary>
-        /// When enabled app will use pre-generated static content via GET requests.
-        /// Default value is false.
+        /// When enabled, the app uses pre-generated static content via GET requests.
+        /// Default value: <c>false</c>.
         /// </summary>
         public bool StaticContentMode { get; set; } = false;
 
         /// <summary>
-        /// File to load by default
+        /// File to load by default. Set this property to a relative file path or a file ID.
+        /// By default, no file is loaded unless this property is set or a file name is specified 
+        /// through the <c>file</c> query string parameter, e.g., <c>file=annual-review.docx</c>.
         /// </summary>
         public string InitialFile { get; set; }
 
         /// <summary>
-        ///  Number of pages to preload
-        /// </summary>
+        /// Number of pages to preload. Default value: <c>3</c>. 
+        /// Set to <c>0</c> to render all pages at once.
+        /// This property also determines how many pages are loaded in subsequent requests.
+        /// The UI respects scroll direction: when scrolling down, the next pages are loaded; 
+        /// when scrolling up, the previous pages are loaded.
+        /// </summary>
+        /// <remarks>
+        /// <para>If you're using the API without the UI, you can control this setting
+        /// in the service configuration:</para>
+        /// <code>
+        /// using GroupDocs.Viewer.UI.Core.Configuration;
+        ///
+        /// var builder = WebApplication.CreateBuilder(args);
+        ///
+        /// builder.Services
+        ///     .AddOptions&lt;Config&gt;()
+        ///     .Configure&lt;IConfiguration&gt;((config, configuration) =>
+        ///     {
+        ///         config.PreloadPages = 0; // Preload all pages at once
+        ///     });
+        /// </code>
+        /// </remarks>
         public int PreloadPages { get; set; } = 3;
 
         /// <summary>
-        // Initial zoom level. The default value is not specified; the UI automatically sets the zoom level.
+        /// Initial zoom level. If not specified, the UI automatically sets the zoom level.
         /// </summary>
         public ZoomLevel InitialZoom { get; set; }
 
         /// <summary>
-        /// Enable or disable right-click context menu
+        /// Enable or disable the right-click context menu.
+        /// Default value: <c>true</c>.
         /// </summary>
         public bool EnableContextMenu { get; set; } = true;
 
         /// <summary>
-        /// Enable or disable clickable links in documents
+        /// Enable or disable clickable links in documents.
+        /// Default value: <c>true</c>.
         /// </summary>
         public bool EnableHyperlinks { get; set; } = true;
 
         /* Control Visibility Settings */
 
         /// <summary>
-        /// Show or hide header
+        /// Show or hide the header.
+        /// Default value: <c>true</c>.
         /// </summary>
         public bool EnableHeader { get; set; } = true;
 
         /// <summary>
-        /// Show or hide header
+        /// Show or hide the toolbar.
+        /// Default value: <c>true</c>.
         /// </summary>
         public bool EnableToolbar { get; set; } = true;
 
         /// <summary>
-        /// Show or hide filename
+        /// Show or hide the file name.
+        /// Default value: <c>true</c>.
         /// </summary>
         public bool EnableFileName { get; set; } = true;
 
         /// <summary>
-        /// Show or hide thumbnails pane
+        /// Show or hide the thumbnails pane.
+        /// Default value: <c>true</c>.
         /// </summary>
         public bool EnableThumbnails { get; set; } = true;
 
         /// <summary>
-        /// Show or hide zoom controls
+        /// Show or hide the zoom controls.
+        /// Default value: <c>true</c>.
         /// </summary>
         public bool EnableZoom { get; set; } = true;
 
         /// <summary>
-        /// Show or hide page navigation menu
+        /// Show or hide the page navigation menu.
+        /// Default value: <c>true</c>.
         /// </summary>
         public bool EnablePageSelector { get; set; } = true;
 
         /// <summary>
-        /// Show or hide search control
+        /// Show or hide the search control.
+        /// Default value: <c>true</c>.
         /// </summary>
         public bool EnableSearch { get; set; } = true;
 
         /// <summary>
-        /// Show or hide "Print" button
+        /// Show or hide the "Print" button.
+        /// Default value: <c>true</c>.
         /// </summary>
         public bool EnablePrint { get; set; } = true;
 
         /// <summary>
-        /// Show or hide "Download PDF" button
+        /// Show or hide the "Download PDF" button.
+        /// Default value: <c>true</c>.
         /// </summary>
         public bool EnableDownloadPdf { get; set; } = true;
 
         /// <summary>
-        /// Show or hide "Present" button
+        /// Show or hide the "Present" button.
+        /// Default value: <c>true</c>.
         /// </summary>
         public bool EnablePresentation { get; set; } = true;
 
         /// <summary>
-        /// Show or hide "File Browser" button
+        /// Show or hide the "File Browser" button.
+        /// Default value: <c>true</c>.
         /// </summary>
         public bool EnableFileBrowser { get; set; } = true;
 
         /// <summary>
-        ///  Show or hide "Upload File" button
+        /// Show or hide the "Upload File" button.
+        /// Default value: <c>true</c>.
         /// </summary>
         public bool EnableFileUpload { get; set; } = true;
 
-     
-
         /* Language and Localization Settings */
 
         /// <summary>
-        /// Show or hide language menu
+        /// Show or hide the language menu.
+        /// Default value: <c>true</c>.
         /// </summary>
         public bool EnableLanguageSelector { get; set; } = true;
 
         /// <summary>
-        /// Default language code. Default value is "en".
+        /// Default language code.
+        /// Default value: <c>en</c>.
         /// </summary>
         public LanguageCode DefaultLanguage { get; set; } = LanguageCode.English;