How do I get files in my own file format to have its own dynamic icon?

Question

Our application has a file format similar to the OpenDocument file format (see http://en.wikipedia.org/wiki/OpenDocument) - i.e. zipped with a manifest file, a thumbnail image, etc.

I notice that OpenOffice files have a preview image of the Open Office file as their icons, both in Windows and in Linux. Is there some way to accomplish this for our files: i.e. I want a dynamic icon based on the internal thumbnail.png?

Edit 1 Wow, thanks for all the quick answers. Thumbnailer looks great for the GNOME world. Windows I'll be looking into those links, thanks. As for the comment question: programmatically OR via our installer.

Edit 2 Oh, forgot Mac. How about on the Mac? (Sorry Mac lovers!) Also are there any links or info for how OpenOffice does their IconHandler stuff - since ours would be very similar?

Answer 1

Windows

What you need is an Icon Handler, also known as a Thumbnail Handler. Here is an example written as an active x control.

Another resource is to look up Property Handlers, which should also point to you to the latest and greatest way of having dynamic meta data handled correctly in windows.

These are dynamic solutions - they aren't needed if you just want an icon associated with all your files - they are only used when you want windows explorer to display an icon based on what's in the file, not just the extension, and when the file changes the icon is updated to reflect the changes. It doesn't have to be an image of the file itself, either, the thumbnail handler can generate any image based on the file contents.

The property handler updates other metadata, such as song or video length, so you can use all the metadata Windows Explorer supports.

Regarding MAC support, this page says, "The Mac and Windows operating systems have different methods of enabling this type of thumbnail, and in the case of the Mac OS, this support has been inconsistent from version to version so it hasn't been pursued [for Adobe InDesign]."

OS X

Icons for Mac OSX are determined by the Launch Services Database. However, it refers to a static icon file for all files handled by a registered application (it's not based on extension - each file has meta data attached that determines the application to which it belongs, although extensions give hints when the meta data doesn't exist, such as getting the file from a different OS or file system)

It appears that the dynamic icon functionality in OSX is provided by Finder, but searches aren't bringing up any easy pointers in this direction. Since Finder keeps changing over time, I can see why this target is hard to hit...

Gnome

For Gnome you use a thumbnailer. (thanks Dorward)

This is an extraordinarily simple program you write, which has 3 command line arguments:

• input file name, the file you are describing with the thumbnail (or URI if you accept those instead)
• output file name, where you need to write the PNG
• size, a number, in pixels, that describes the maximum square image size you should produce (128 --> 128x128 or smaller)

I wish all systems were this simple. On the other hand this doesn't support animation and a few other features that are provided by more difficult to implement plugins on other systems.

KDE

I'm a bit uncertain, but there are a few pointers that should get you started. First is that Konqueror is the file manager and displays the icons - it supports dynamic icons for some inbuilt types, but I don't know if these are hardcoded, or plugins you can write. Check out the Embedded Components Tutorial for a starting point.

There's a new (ish?) feature (or planned feature...) called Plasma which has a great deal to do with icons and icon functionality. Check out this announcment and this initial implementation.

You may need to dig into the source of Konqueror and check out how they did this for text files and others already implemented.

-Adam

Answer 2

Mac OSX since version 10.5 …

… has two approaches:

1. Your document is in the standard OSX bundle format and has a static image This can be done by creating a subfolder QuickLook and placing the Thumbnail/Preview.png/tiff/jpg inside.

2. Everything else needs a QuickLook generator plugin which can be stored in either /Library/QuickLook ~/Library/QuickLook or inside the YourApp.app/Contents/Library/QuickLook Folders.

This generator is being used to create Thumbnails and QuickLook previews on the fly. XCode offers a template for this. The template generates the needed ANSI C files which have to be implemented. If you want to write Object-C code you have to rename the GenerateThumbnailForURL.c and GeneratePreviewForURL.c to GenerateThumbnailForURL.m and GeneratePreviewForURL.m (and read the Apple Devel Docs carefully ;) )

---

Simple zip container based demo:

You will have to add the Cocoa.framework and Foundation.framework to your project In your GenerateThumbnailForURL.c (this is partly out of my head - so no guarantee that it works out of the box ;) ):

#include <Cocoa/Cocoa.h>
#include <Foundation/Foundation.h>

OSStatus GenerateThumbnailForURL(void *thisInterface, QLThumbnailRequestRef thumbnail, CFURLRef url, CFStringRef contentTypeUTI, CFDictionaryRef options, CGSize maxSize)
{
  NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

  /* unzip the thumbnail and put it into an NSData object */
  // Create temporary path and writing handle for extraction
  NSString *tmpPath = [NSTemporaryDirectory() stringByAppendingFormat: [NSString stringWithFormat: @"%.0f.%@" , [NSDate timeIntervalSinceReferenceDate] * 1000.0, @"png"]];
  [[NSFileManager defaultManager] createFileAtPath: tmpPath contents: [NSData alloc] attributes:nil];
  NSFileHandle *writingHandle = [NSFileHandle fileHandleForWritingAtPath: tmpPath];


  // Use task to unzip - create command: /usr/bin/unzip -p <pathToFile> <fileToExtract>
  NSTask *unzipTask = [[NSTask alloc] init];
  [unzipTask setLaunchPath: @"/usr/bin/unzip"];

  // -p -> output to StandardOut, added File to extract, nil to terminate Array
  [unzipTask setArguments: [NSArray arrayWithObjects: @"-p", [(NSURL *) url path], @"Thumbnails/thumbnail.png", nil]];

  // redirect standardOut to writingHandle
  [unzipTask setStandardOutput: writingHandle];

  // Unzip - run task
  [unzipTask launch];
  [unzipTask waitUntilExit];

  // Read Image Data and remove File
  NSData *thumbnailData = [NSData dataWithContentsOfFile: tmpPath];
  [[NSFileManager defaultManager] removeFileAtPath: tmpPath handler:nil];


  if ( thumbnailData == nil || [thumbnailData length] == 0 ) {
     // Nothing Found. Don't care.
     [pool release];
     return noErr;
  }

  // That is the Size our image should have - create a dictionary too
  CGSize size = CGSizeMake(256, 256);
  NSDictionary *properties = [NSDictionary dictionaryWithObjectsAndKeys:
      [NSNumber numberWithInt:size.width],kQLPreviewPropertyWidthKey,
      [NSNumber numberWithInt:size.height],kQLPreviewPropertyHeightKey,
      nil];

  // Get CGContext for Thumbnail
  CGContextRef CGContext = QLThumbnailRequestCreateContext(thumbnail, size, TRUE, (CFDictionaryRef)properties);
  if(CGContext) {
     NSGraphicsContext* context = [NSGraphicsContext graphicsContextWithGraphicsPort:(void *)CGContext flipped:size.width > size.height];
     if(context) {
        //These two lines of code are just good safe programming…
       [NSGraphicsContext saveGraphicsState];
       [NSGraphicsContext setCurrentContext:context];

       NSBitmapImageRep *thumbnailBitmap = [NSBitmapImageRep imageRepWithData:thumbnailData];
       [thumbnailBitmap draw];

       //This line sets the context back to what it was when we're done
       [NSGraphicsContext restoreGraphicsState];
    }

    // When we are done with our drawing code QLThumbnailRequestFlushContext() is called to flush the context
    QLThumbnailRequestFlushContext(thumbnail, CGContext);

    // Release the CGContext
    CFRelease(CGContext);
  }

  [pool release];
  return noErr;
}

---

Info.plist

You will have to modify your info.plist file too - when you open it up it has a lot of fields pre-set. Most of them are self-explaning (or will not have to be changed) but I had to add the following structure (copy paste should do - copy the text, go into the plist editor and just paste.):

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<array>
   <dict>
     <key>UTTypeConformsTo</key>
     <array>
       <string>com.pkware.zip-archive</string>
     </array>
     <key>UTTypeDescription</key>
     <string>i-net Crystal-Clear Report File</string>
     <key>UTTypeIconName</key>
     <string>generic</string>
     <key>UTTypeIdentifier</key>
     <string>com.company.product</string>
     <key>UTTypeReferenceURL</key>
     <string>http://your-url.com</string>
     <key>UTTypeTagSpecification</key>
     <dict>
       <key>public.filename-extension</key>
         <array>
           <string>$fileEXT$</string>
         </array>
     </dict>
  </dict>
</array>
</plist>

This will register your filetype $fileExt$ and tell the system that your filetype is a zipy format type. A nice refference, that I used here is the QuickLook IPA Plugin from googlecode

Answer 3

In Windows, what you need is to implement an Icon Handler. I did this many moons ago and it is not difficult as long as you know the basics of COM.

See: http://msdn.microsoft.com/en-us/library/bb776857(VS.85).aspx