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Custom Document Presenter

Document presenters in RadPdfViewer are responsible for displaying the pages of a PDF document, as well as navigating the file and manipulating it. There are two presenters that come out-of-the-box and you can find more information about them here.

Additionally, RadPDFViewer offers you the ability to create your own document presenter, which helps you design the presentational functionality of the document as you want.

This article covers the following topics:

Implementing the IFixedDocumentPresenter Interface

Implementing this interface allows you to create a fully functioning document presenter in RadPdfViewer. The interface contains the following members:

  • Owner:Đ¢his property is of type Telerik.Windows.Documents.UI.IFixedDocumentViewer and is implemented by RadPdfViewer. The owner of your document presenter is the instance of RadPdfViewer that uses the presenter.

  • PointerHandlersController: This property is of type Telerik.Windows.Documents.Fixed.UI.PointerHandlers.PointerHandlersController and the member is responsible for the behavior of RadPdfViewer after mouse or touch events.

  • CurrentPage: The property gets the current RadFixedPage.

  • ShowSelectionMarkers(): The method shows the selection markers.

  • HideSelectionMarkers(): The method hides the selection markers.

  • GetLocationFromViewPoint(Point viewpoint, out RadFixedPage page, out Point location): This method obtains the page and document location from the provided view point.

  • GetViewPointFromLocation(RadFixedPage page, Point location, out Point viewpoint): This method obtains the view point from the provided page and document location.

  • PageUp(): This method navigates to the previous page.

  • PageDown(): This method navigates to the next page.

  • GoToPage (int pageNumber): This method navigates to the provided page number.

  • GoToDestination(Destination destination): This method navigates to the provided destination.

  • InvalidateMeasure(): This method invalidates the measurement state.

  • InvalidateArrange(): This method invalidates the arrangement state.

  • __UpdatePresenterLayout():__This method updates the presenter layout.

  • Initialize(IFixedDocumentViewer owner): This method initializes the document presenter with the provided owner.

  • Initialize(IFixedDocumentViewer owner, IFixedDocumentPresenter presenter): This method initializes the document presenter with the provided owner and another document presenter.

  • Release(): This method releases the resources used by the document presenter.

  • CurrentPageChanged: This event is fired when the current page is changed.

Inheriting FixedDocumentPresenterBase

The FixedDocumentPresenterBase class implements all the members from IFixedDocumentPresenter but it allows the inheriting class to override those members with custom functionality. Some members of this class are abstract and need to be overridden in the inheriting classes:

  • PagesLayoutManager: The property is of type Telerik.Windows.Documents.Fixed.Layout.PagesLayoutManagerBase and is responsible for the way pages are laid out in the document.

  • CurrentNo: The number of the current page.

  • GetLocationFromViewPoint(Point viewpoint, out RadFixedPage page, out Point location): This method obtains the document location from the provided view point.

  • UpdateScrollOffsetFromPosition(TextPosition position): This method updates the scroll offset from the provided position.

PagesLayoutManagerBase is an abstract class responsible for the layout of the document pages. The class provides the following abstract members:

  • UpdateLayout(Size viewportSize): This method updates the page layout based on the provided view port.

  • GetPagesLayoutInfos(): This method returns a collection of the layout information for all the pages in the document.

  • Release(): This method releases the resources of the layout manager.

Creating a Custom Presenter

The following steps illustrate what you need to do to create and register a custom document presenter:

Step 1: Create a class that inherits the abstract FixedPageLayoutInfo class. This class is responsible for the page layout and should hold information about how to visualize a single page. Implement the base constructor and add your preferences.

[C#] Example 1: Implement FixedPageLayoutInfo

public class SinglePageInfo : FixedPageLayoutInfo
{
    public SinglePageInfo(Telerik.Windows.Documents.Fixed.Model.RadFixedPage page, System.Windows.Rect positionInView)
        : base(page, positionInView)
    {
        //...
    }
}

Step 2: Create a class that inherits the abstract PagesLayoutManagerBase class, and will be responsible for the layout of the document pages. Implement all abstract members of the class and override them according to your scenario.

[C#] Example 2: Implement PagesLayoutManagerBase

public class SinglePageLayoutManager : PagesLayoutManagerBase
{
    private SinglePageInfo visiblePage;
    private readonly List<SinglePageInfo> pageLayoutInfos;

    public SinglePageLayoutManager(IFixedDocumentPresenter presenter)
        : base(presenter)
    {
        this.pageLayoutInfos = new List<SinglePageInfo>();
    }

    protected override List<FixedPageLayoutInfo> GetPagesLayoutInfos()
    {
        List<FixedPageLayoutInfo> result = new List<FixedPageLayoutInfo>();
        foreach (var info in this.pageLayoutInfos)
        {
            result.Add(info);
        }

        return result;
    }

    public override void Release()
    {
        // Release pageLayoutInfos here.
    }

    public override void UpdateLayout(Size viewportSize)
    {
        // Update pageLayoutInfos here.
    }
}

Step 3: Add a new class for your custom presenter that inherits the abstract FixedDocumentPresenterBase class which, in turn, inherits the IFixedDocumentPresenter interface.

Step 4: Implement all the members of the FixedDocumentPresenterBase class to create a fully functional document presenter. Some members of the FixedDocumentPresenterBase class are abstract and need to be overridden with custom functionality.

To ensure that the content is loaded, verify that the VisiblePages property of FixedDocumentPresenterBase is set every time the visible pages in the presenter are changed.

Step 5: Register the custom document presenter as demonstrated in Example 3.

[C#] Example 3: Register a custom document presenter

        this.pdfViewer.RegisterPresenter("CustomPresenterName", new CustomSinglePagePresenter());

You can download an example that demonstrates how to create and register a custom document presenter from our SDK repository on GitHub.

See Also