Why isn't my file type plugin showing a preview thumbnail in Explorer?

[aybe]

Just noticed that the plugin I quickly wrote to open TIM files does not show a thumbnail preview in Windows Explorer, in the following screenshot both PNG and TIM are associated to be opened by the software, PNG shows a preview thumbnail but TIM doesn't:

 

 

Is there something I'm missing in order to get thumbnail previews in Explorer ?

 

This is the current code:

 

using System.IO;
using System.Text;
using PaintDotNet;
using PaintDotNet.PropertySystem;

namespace TimFileType;
#pragma warning disable CA1416 // Validate platform compatibility

public sealed class TimFileTypeFactory : IFileTypeFactory2
{
    public FileType[] GetFileTypeInstances(IFileTypeHost host)
    {
        return new FileType[] { new TimFileTypeClass(host.Services) };
    }
}

[PluginSupportInfo(typeof(PluginSupportInfo))]
public class TimFileTypeClass : PropertyBasedFileType
{
    public TimFileTypeClass(IServiceProvider serviceProvider)
        : base("TIM: Screen Image Data", new FileTypeOptions { LoadExtensions = new[] { ".tim" } })
    {
        ServiceProvider = serviceProvider;
    }

    private IServiceProvider ServiceProvider { get; }

    protected override unsafe Document OnLoad(Stream input)
    {
        using var reader = new BinaryReader(input, Encoding.Default, true);

        reader.ReadByte();
        reader.ReadByte();
        reader.ReadInt16();

        var flags   = reader.ReadInt32();
        var format  = flags & 0b111;
        var palette = (flags & 0b1000) != 0;

        if (palette)
        {
            var length = reader.ReadInt32();
            reader.BaseStream.Position += length - 4;
        }

        // 24-bit only for now

        var pixelDataSize = reader.ReadInt32();
        var frameBufferX  = reader.ReadInt16();
        var frameBufferY  = reader.ReadInt16();
        var pixelWidth    = reader.ReadInt16();
        var pixelHeight   = reader.ReadInt16();
        var pixelData     = reader.ReadBytes(pixelDataSize - 12);

        pixelWidth = (short)(pixelWidth * 2 / 3);
        var layer = Layer.CreateBackgroundLayer(pixelWidth, pixelHeight);

        var pointer = layer.Surface.GetRowPointer(0);

        for (var i = 0; i < pixelWidth * pixelHeight; i ++)
        {
            pointer->R = pixelData[i*3 + 0];
            pointer->G = pixelData[i*3 + 1];
            pointer->B = pixelData[i*3 + 2];
            pointer->A = byte.MaxValue;
            pointer++;
        }

        var document = new Document(pixelWidth, pixelHeight);

        document.Layers.Add(layer);

        return document;
    }

    protected override void OnSaveT(Document input, Stream output, PropertyBasedSaveConfigToken token, Surface scratchSurface, ProgressEventHandler progressCallback)
    {
        throw new NotImplementedException();
    }

    public override PropertyCollection OnCreateSavePropertyCollection()
    {
        throw new NotImplementedException();
    }
}

 

Any suggestions are welcome! 😃

[midora]

You have to write your own thumbnail shell extension for the file type and install it.

Like here 'GIF Animations and Images' FileType Plugin

[aybe]

Amazing, thank you! 😃

[Rick Brewster]

Paint.NET doesn't handle thumbnails for plugins, unfortunately. This would be very complex, for one, but also it's important to note that it would require loading all of the plugins into the process that handles thumbnails. This could cause thumbnails to generate very slowly, and if a plugin contains a bug* it could jeopardize all thumbnail generation. It's also difficult to correctly handle registration of new file types with the shell (Explorer). It's a big Pandora's box of trouble, in other words. Would be nice if it weren't, though.

 

* yes, it happens ... a lot, in fact

[aybe]

Makes perfect sense, SharpShell is pretty easy to implement even though some may say it's very baaaaad to write managed shell extensions😅.

[Rick Brewster]

It depends on the type of shell extension. For extensions that are hosted out-of-process, like thumbnail providers, it should be fine. However, there are still some open questions about how Explorer re-uses the process(es) for extensions. You can only load .NET into a process once, and if Explorer recycles the process then it may not work, particularly if extensions need different versions of .NET. I haven't seen any reports of issues stemming from this, however, so I just have to assume right now that it's safe.

[aybe]

Yes, I've actually coded the plugin and can successfully load any TIM file. However, I'm currently having conceptual issues that, unless I'm mistaken, won't be solvable through the actual PDN interface. This obviously makes sense as PDN is a general image editor and doesn't intend to support a very specific feature for a specific format.

 

Not sure what to do next... I've uploaded my work in case someone has an idea, if that ever makes sense.😁

 

https://forums.getpaint.net/topic/119542-any-possibility-of-load-options-for-a-plugin/?do=findComment&comment=592590