Document with invalid cross-reference stream is not loaded correctly

WPF controls are used to visualize the form fields in PdfViewer. However, these controls inherit the background defined in the PdfViewer's theme instead of a background of the form field control. This leads to wrong visualization mostly in the dark themes as the content inside the form field might get unreadable.

The character is visualized as '3'. The same issue is also reproducible when the content is copied from Adobe.

We should implement the logic for getting character codes from Unicode when using CFFFontSource.
Workaround: The font may be changed by creating a similar font with FontsRepository.TryCreateFont(...) method.

Workaround for documents generated with PdfProcessing: When drawing lines using the FixedContentEditor the IsFilled graphic property should be set to false:

RadFixedDocument document = new RadFixedDocument();

Rect rect = new Rect(0, 0, 50, 50);
FixedContentEditor editor = new FixedContentEditor(document.Pages.AddPage());
editor.GraphicProperties.IsFilled = false;
editor.GraphicProperties.IsStroked = true;

editor.Position.Translate(50, 50);
editor.GraphicProperties.StrokeColor = new RgbColor(255, 0, 0);
editor.DrawText("Lines");
editor.DrawLine(rect.TopLeft, rect.TopRight);
editor.DrawLine(rect.TopRight, rect.BottomRight);
editor.DrawLine(rect.BottomRight, rect.BottomLeft);
editor.DrawLine(rect.BottomLeft, rect.TopLeft);

WPF allows running multiple UI threads in a single process. When RadPdfViewer is used in such scenarios, sometimes InvalidOperationException: 'The calling thread cannot access this object because a different thread owns it.' is thrown. 

Scenarios:
- Show Find dialog (or any other of the dialogs available for register in ExtensibilityManager class) for the first instance, the for the second instance.

The exception is thrown while decoding TIFF images. Although the document is properly loaded and the end user is not impacted, the DivideByZeroException is logged and present in the OnException event handler parameters. 

This is not quite a valid PDF file scenario according to PDF file specification. However, we may try handling it in order to show the correct number of pages. When the kid is of type Pages, it should be added to the pages traversal recursion only the first time it is met.

Default RadPdfViewer presenters load image sources async which allows to render the rest PDF content faster. However, FixedDocumentSinglePagePresenter loads images syncrhonously and all page content is rendered right after all images on the page are loaded.

Setting DocumentSource throws NullReferenceException when PdfViewer is hosted in ElementHost. When setting the DocumentSource, the Application.Dispatcher is used, but in Winforms app, the Application is not instantiated. 

Steps to reproduce:
1. Host PdfViewer in ElementHost in a WinForms application
2. Set the DocumentSource property
3. Run
Expected: The document is opened
Actual: NullReferenceException is thrown

Workaround: the document could be set to the Document property of PdfViewer. Or instead hosting the PdfViewer for WPF in ElementHost, use WinForms version of the control.

Tint transformation function is used to transform Device N color in Alternate colorspace.

There is a similar question in FAQ for FontForge (https://fontforge.github.io/faq.html#mingliu) where it is described that kaiu.ttf (and probably mingliu.ttf) font does not store the correct outlines and its outlines need special treatment in order to be rendered correctly. The Chinese glyphs are rendered wrong in RadPdfViewer as well. However, Adobe Reader, FoxitReader and ChromeViewer render the glyphs correctly.

The performance of loading the thumbnails is decreased with the removing of the cache in PdfViewer. 

Possible reason is that the pages are no longer loaded asynchronously.

Steps to reproduce:
- Open the SDK with the thumbnails for PDFViewer.
- Notice that the load of the thumbnails is slow.

The ActionsManager.ExecuteUri method throws exception when tries to open relative Uri. As the exception is caught, with the current state no action is observed when interacting with such link in RadPdfViewer.

GoToPage() method is not working correctly in some cases when called in DocumentChanged event handler. The known cases are described below:

   1. When RadPdfViewer and the document are loaded initially and document is set through the RadPdfViewer.Document property.
Workaround: DocumentSource property could be set (in XAML or in code-behind) instead of the Document property. If the Document property is used, this should be done after RadPdfViewer is loaded.

    2. When the ScaleMode is changed in DocumentChanged event handler and then GoToPage() method is called in the same event handler.

When clicking on link annotations pointing to destinations in the document, and the "Fit one full page to window" mode is activated, the document is not scrolled exactly to the destination.

The issue can be reproduced only in Single Page Presenter mode and when the Top and Left values of the passed parameter are greater than 0.

The problem can also be observed by invoking directly GoToDestination method, as the problem is inside it.

The ColorSpace element is not required for images which are using JPXDecode filter.

Some colors are changed due to incorrect import of some graphic state colors.

The slow performance when creating thumbnail is only reproducible with specific documents.