Adjusting Scroll Speed in RadPdfViewer for WinForms

Environment

Product Version	Product	Author
2024.4.1113	RadPdfViewer for WinForms	Dinko Krastev

Description

Adjusting the default scroll speed of RadPdfViewer is essential when need to navigate through documents more quickly. This knowledge-base article also answers the following questions:

• How can I increase the mouse wheel scroll speed in RadPdfViewer?
• Is there a way to customize scrolling behavior in RadPdfViewer for WinForms?
• How to modify RadPdfViewer to scroll faster with the mouse wheel?

Solution

To change the scrolling speed in RadPdfViewer, create a custom RadPdfViewer control by overriding the ProcessMouseWheel method. This adjustment allows for a customized scrolling experience, enhancing navigation through documents.

Step 1: Create the Custom RadPdfViewer Control

First, implement the CustomPdfViewer class by extending RadPdfViewer. This class overrides the CreateViewerElement method to return an instance of a custom RadPdfViewerElement.

• C#

public class CustomPdfViewer : RadPdfViewer
{
    public override string ThemeClassName
    {
        get
        {
            return typeof(RadPdfViewer).FullName;
        }
    }
    protected override RadPdfViewerElement CreateViewerElement()
    {
        return new CustomRadPdfViewerElement();
    }
}

Step 2: Customize the RadPdfViewerElement

Next, define the CustomRadPdfViewerElement class by extending RadPdfViewerElement. Override the ProcessMouseWheel method to customize the scroll behavior. In this example, the scroll amount is multiplied by 5 to increase the scroll speed. Adjust this value as needed.

• C#

public class CustomRadPdfViewerElement : RadPdfViewerElement
{
    protected override Type ThemeEffectiveType
    {
        get
        {
            return typeof(RadPdfViewerElement);
        }
    }
    public override bool ProcessMouseWheel(MouseEventArgs e, bool shift, bool control)
    {
        if (this.Document == null)
        {
            return false;
        }

        float scale = this.ScaleFactor;

        if (control)
        {
            if (e.Delta > 0)
            {
                scale *= 1.1f;
            }
            else
            {
                scale *= 0.9f;
            }

            this.ScaleFactor = scale;
        }
        else
        {
            int newValue;
            if (this.Scroller.ScrollMode != ItemScrollerScrollModes.Discrete)
            {
                newValue = this.VScrollBar.Value + Math.Sign(e.Delta) * -30 * 5; // Adjust scroll speed here
            }
            else
            {
                newValue = this.VScrollBar.Value - Math.Sign(e.Delta);
            }
            newValue = Math.Max(0, Math.Min(this.VScrollBar.Maximum - this.VScrollBar.LargeChange + 1, newValue));
            this.VScrollBar.Value = newValue;
        }
        return false;
    }
}

Step 3: Replace RadPdfViewer with the Custom Control

In the Designer.cs file of your form, replace the RadPdfViewer control instance with the newly created CustomPdfViewer control. This change applies the customized scrolling functionality to your application.