Windows Forms: January 2007 Archives

The latest Crystal Toolkit version 0.70 has an early alpha version of classes to help you build image viewers using thumbnails. You may have seen the Microsoft Office Picture Viewer, which has a nice filmstrip view of thumbnails in a splitter like view. I wanted to build an image grid view control that has that nice look and feel, but I also wanted to build it in a classic model-view-controller pattern. And I also wanted to have my control use other tools to automatically thumbnail image folders that I need to browse.

CrystalImageGridView does all of this, working with CrystalImageGridModel, CrystalFileCollector, and the CrystalThumbnailer to provide all of these features. You can see from the screenshots (this demo is included in the zip file on the Downloads page) that you can view the thumbnails docked in the split container on the bottom. Click on the left hand button on the upper toolbar and the split container expands the thumbnail view to fill the client area.

I'll have more bug fixes, little features, and documentation to write later. If you want to play around with this control, do the following:

1. Build Crystal Toolkit and add a reference to your Form project.
2. Drag CrystalImageGridView from the toolbox to your Form, preferrably to a split container.
3. Hook up the Load event to your Form and add this code to the method:

CrystalFileCollector _collector = 

    new CrystalFileCollector();

_collector = new CrystalFileCollector();

_collector.AddView(crystalImageGridView1);

_collector.CollectImages();

It's that easy. Run this simple form you just made, and the image grid starts previewing images from your MyPictures folder. The CrystalFileCollector spins off a background thread and pops the images into the grid as they are thumbnailed. If you don't like that location, you can modify the ImageLocation property.

More later, much more, I hope. If you have any comments, bug fixes, or whatever, contact me at richard {at} attilan [dot] com.

A little over a week ago, a user named MG reported a problem that I couldn't duplicate until now. When he ran the demo program CrystalTrackBarDemo.exe, all the CrystalTrackBar objects were invisible. No trackbar, no ticks, no thumb, only the gradient background remained on the non-transparent objects. After a second user reported this bug on the CodeProject article, I suddenly remembered about my usage of TrackBarRenderer.IsSupported in CrystalTrackBar OnPaint:

protected override void OnPaint(PaintEventArgs e)
{
    if (!TrackBarRenderer.IsSupported)
    {
        this.Parent.Text = 
            "CrystalTrackBar Disabled";
        return;
    }

    DrawTrackBar(e.Graphics);
    DrawTicks(e.Graphics);
    DrawThumb(e.Graphics);
}

On the MSDN Forum, Mick Doherty pointed out that TrackBarRenderer.IsSupported == VisualStylesRenderer.IsSupported. According to the documentation, one of the things that can make the VisualStylesRenderer is the VisualStyleInformation.IsEnabledByUser property. Users can enable visual styles in the Appearance tab of the Display option in Control Panel.

I was able to reenact the bug by setting my Appearance setting for Windows and Buttons to Windows Classic Style (on XP: Control Panel->Display->Appearance tab). As some people are addicted to the old Windows NT look and feel, it makes sense this how they ran into the bug. When I ran my application again, TrackBarRenderer.IsSupported returned false and all I got was the rectangles, no trackbar or ticks.

I'll need to draw the TrackBar and Ticks myself if TrackBarRenderer isn't supported. I'm already drawing the Thumb, so this should be an easy bug to fix. I hope to have it posted in a few days.