Previewing images in a SuperToolTip

In my previous post I mentioned the possibility of displaying a PDF page thumbnail in a tooltip to show a larger preview when the user hovers over it. Here’s what our end goal looks like:

Pdf Page SuperToolTip
The thumbnail displays a larger preview of itself when the mouse hovers above a page.

To accomplish this, we’ll add upon the PdfThumbnails solution from the last post to create this new functionality.

First, drop a ToolTipController onto the frmMain form. This component can be used to provide tooltips for DevExpress which implement the IToolTipControlClient interface necessary for displaying tooltips. Don’t worry about the nitty-gritty: DevExpress controls all seem to implement this interface allowing you to customize and create tooltips.

Once you drop the ToolTipController onto your form, make sure that you then set the grdThumbnails GridControl’s ToolTipController property to this new ToolTipController instance.

To provide our tooltips we’ll need to handle an event that is fired when the user hovers over a control (or event an element within a control, such as a single grid cell). This event comes in the form of the ToolTipController’s GetActiveObjectInfo event. Let’s create a handler for this event:


/// Get active object info event handler for the ToolTipController
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void toolTipController1_GetActiveObjectInfo(object sender, DevExpress.Utils.ToolTipControllerGetActiveObjectInfoEventArgs e)
WinExplorerViewHitInfo hitInfo = wvThumbnails.CalcHitInfo(e.ControlMousePosition);

if (hitInfo.IsValid == false || hitInfo.InItem == false)

ToolTipControlInfo toolTipInfo = null;
SuperToolTip toolTip = new SuperToolTip();

toolTipInfo = new ToolTipControlInfo(hitInfo.RowHandle.ToString(), "Page Preview");
ToolTipItem item1 = new ToolTipItem();
item1.Image = PdfPage.ScaleThumbnailImage(hitInfo.ItemInfo.Image, 640, 480);

toolTipInfo.SuperTip = toolTip;
e.Info = toolTipInfo;

} //End the toolTipController1_GetActiveObjectInfo() method

Our tooltip will be pretty simple–it’s just an image with no text, hyperlinks etc… We construct a SuperToolTip object, and more importantly, a ToolTipControlInfo object. The ToolTipControlInfo object is what is responsible for holding the information we’d like to show in a tooltip. That is, we can set a Title, Text or Image property, all of which are the basis of any tooltip, be it a standard tooltip or SuperToolTip.

One important thing to note is that the ToolTipControlInfo object itself has a property called “Object” (of datatype Object… a little confusing, I agree) which needs to be set to a unique value to identify what the tooltip is associated with. I do this by simply setting the property to the row handle of the WinExplorerView, since it will be unique.

The last bit of code isn’t really DevExpress-centric, but we need a way to scale the image to a manageable size because we don’t want to actually show the full size page image:

/// <summary>
/// Returns a thumbnail scaled to fit within the provided width and height ratio
/// </summary>
/// <param name="ImageToScale">Image to be scaled</param>
/// <param name="MaxWidth">New image maximum width</param>
/// <param name="MaxHeight">New image maximum height</param>
/// <returns>Scaled image</returns>
static internal Image ScaleThumbnailImage(Image ImageToScale, int MaxWidth, int MaxHeight)
    double ratioX = (double)MaxWidth / ImageToScale.Width;
    double ratioY = (double)MaxHeight / ImageToScale.Height;
    double ratio = Math.Min(ratioX, ratioY);

    int newWidth = (int)(ImageToScale.Width * ratio);
    int newHeight = (int)(ImageToScale.Height * ratio);

    Image newImage = new Bitmap(newWidth, newHeight);
    Graphics.FromImage(newImage).DrawImage(ImageToScale, 0, 0, newWidth, newHeight);

    return newImage;

}   //End the ScaleThumbnailImage() method

This method just takes the thumbnail image (which itself is actually a full-sized Bitmap of the page–the WinExplorerView scales it internally to a smaller graphic) and scales it to a new Bitmap of the dimensions requested in the MaxWidth & MaxHeight parameters.

In the future, we’ll get back to our Xpo Contact List project and use this image tooltip functionality to show preview images of our contacts in the program grids. This functionality can be helpful anywhere in your application where you display a small image and want to provide the user with a quick way to view a larger version of that image.

Download the PdfThumbnails_NEW source for our project and see it in action for yourself!

Previewing images in a SuperToolTip