The Great Flying Tortoise

It's easy to get confused about what points of extensibility exist and what layer provide what services. This isn't helped by the fact that we've lumped a bunch of things into the property system, but I'll try to diagram this out here and in future posts...

In the near future I'll be posting code examples that compile and run. In case you'd like to follow along, here's my personal setup. My code should compile on RC1 also, so go ahead and use RC1 if that's what you can get a hold of. Windows Vista...

The goal of this first expedition is to print lists of properties from items. This will give insight into the origins and capabilities of these different properties. Feel free to follow along and try out different things. There's a lot to explore. ...

PROPVARIANTs are easy to misuse . Because the data members are so cryptic, it is easy to get confused or to overlook errors. To help alleviate these and other problems (including readability), we provide a series of PROPVARIANT helpers for common uses...

In my first post , I described what the property system provides from an API perspective. But I used all these techno-wiggle-waggle-jibber-jabber that my friends couldn't follow. Ich. What feedback for a first post! So here it is minus the 133t-speak...

Reading properties is rather simple. First, bind to the item. SHCreateItemFromIDList and SHCreateItemFromParsingName are appropriate for this. Then read your properties. Be sure to clean up after yourself. IShellItem2 *psi; if (SUCCEEDED(SHCreateItemFromParsingName...

In general, PropVariantCompare performs a locale-sensitive comparison between two values and returns <0, 0, or >0 as appropriate. PropVariantCompare always tries to convert the values to the type of the first value. Thus if code tries to compare...

This coding expedition has developed a tool that can dump out all the properties on a file. If you are curious about the property system, I highly recommend you build this tool and run it on various file types. Coding to the Windows SDK Part 1 ...

I'm going to be talking about writable properties over the next few days. I know that some of you are itching to try this out yourselves, so here is an overly simplistic program that will write a single property to a file. I have omitted a lot of diagnostic...

One of the more prominent properties is PKEY_Keywords , e.g. "Tags". This is a vector property, and so it usually comes packaged in a PROPVARIANT with VT_VECTOR|VT_LPWSTR . If you deal with properties such as this, you may find the following helpers useful...

As I went through the property helper posts, I kept using those dense word combinations " locale sensitive " and " locale insensitive ". Why? Because locale tells your computer whether to display a number as "5.3" or "5,3". Should "5,305" be a big...

So if a property handler doesn't enumerate which properties it supports writing , then how does the explorer pick which properties to show? Well, the shell namespace extension containing the item specifies the list of properties it wants to show in a...

You'll recall that there are multiple layers in the property system . In particular, the GPS_DEFAULT property system stack for files in the filesystem namespace looks like this: [ Application using GPS_DEFAULT ] [ Coercion Layer ] [ Shell Item Layer...

[Edit: 2006/11/13 - My original post got this topic entirely backwards. I've fixed the title and will provide details about this tomorrow. ] -Ben Karas

You can, of course, wait for Windows Vista to ship before checking out the property system. But if you are curious or bored, here are a few other things you might do: Download the Windows Vista Platform SDK: The most recent Platform SDK . The SDK...

The property system is a new set of APIs for Microsoft Windows Vista that provides a general way to access metadata about files and items accessible through the shell namespace. This means you can ask for the dimensions of an image, or the size of a file...

Most of the property system uses PROPERTYKEY s to identify properties. But you can also identify a property using its canonical name. For instance, PKEY_DateModified corresponds to L"System.DateModified". Whereas a PROPERTYKEY was good for coding and...

I mentioned that one of the property system layers coerces values to be of the correct type. But how does the system know the expected type? The property system maintains a data structure describing each property on the machine. Each property description...

Last time we saw how to bind to a shell item and get its property store. Today, we loop through the store printing out known properties. HRESULT _PrintPropertyStore(IPropertyStore *pps) { DWORD cProps; HRESULT hr = pps-> GetCount (&cProps...

In parts one and two , I started writing a program to print out the properties on an item. But I saved the best for last -- printing a value. Discussion follows the code. HRESULT _PrintPropertyValue(__in REFPROPERTYKEY key, __in REFPROPVARIANT propvar...

The program itself is provided in parts 1 , 2 , and 3 . So I compiled my program and ran it from the command line. Here's a snippet of what I got back: Properties for 'scan0010.jpg' Folder name: propshow Type: JPEG Image Name: scan0010.jpg Size: 638...

In Part 4 , I discovered that WideCharToMultiByte converts certain invisible non-spacing Unicode characters to ?. This makes the output look really silly in a command line application. I want to keep this as a command line application, so I need to strip...

Using the tool I developed in this series, I know that my test photo has " Rating: 5 Stars ". But how is this value actually represented in the JPG itself? Let's answer that by adding some developer friendly output. Here's what I did: First, I need...

Values in the property system are stored in PROPVARIANT structures. Originally constructed for use in OLE structured storage, the property system reuses this structure to hold its data. As the name suggests, a PROPVARIANT can hold a variety of data...

As I mentioned yesterday, PROPVARIANT's hold data that gets piped through the property system. Early in our development cycle, we noticed is that even the most careful developer can easily make mistakes when initializing PROPVARIANTs. One common...