The Old New Thing
Practical development throughout the evolution of Windows.
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Using the MNS_DRAGDROP style: Menu rearrangement
In order to do drag-drop rearrangement of menus, you need four things, most of which we already know how to do. Dragging an item out of a menu. Check. Dropping an item into a menu. Check. Connecting the drag with the drop. Rearranging menu items in response to the operation. Let's do step 4 first, just to mix things up. And since this is just a demonstration rather than production code, I'm only going to support string menu items of up to 255 characters in length. One thing you might not have noticed is that I inserted the copy before deleting the original. That way, we don't get st...
Using the MNS_DRAGDROP style: Dropping in
Last time, we looked at using the style for dragging items out of a menu. Today, we'll look at dropping them in. Take the program from last time and make the following additions. First, let's add a second item to the menu. Yes, I hard-coded another path. This is a demo, not production code. Anyway, it's time to hook up the message: To handle the message, you convert the , pair into a COM object, requesting the interface provided by the member, and putting the result into the member. (Exercise: Why is the member typed as rather than ?) When the user tries to drop on a menu item, we just give ...
Using the MNS_DRAGDROP style: Dragging out
Windows 2000 introduced the menu style, which permits drag/drop operations in a menu. Nobody uses this style, probably because it's totally undiscoverable by the end-user. But I'll write a sample program anyway. Mind you, I knew nothing about the menu style until I started writing this entry. But I simply read the documentation, which says that if you set this style, you will receive and messages. The message is sent when the user drags a menu item, so let's go with that first. The documentation says that you get information about the item that was dragged, and then you return a code that specifies w...
Introducing the for-if anti-pattern
Over the years, I've seen a bunch of coding anti-patterns. I figured maybe I'll share a few. Today, I'll introduce what I'm calling the for-if anti-pattern, also known as "We'll sell you the whole seat, but you'll only need the edge." This is a special case of the for-case anti-pattern, where all but one of the cases is null. This can naturally be simplified to The for-if anti-pattern arises in many forms. For example: This enumerates all the files in a directory looking for a specific one, and if it's found, it returns a stream on it. The slightly-less-crazy version would be Note that both version...
Celebrating the end of the gluttony season, but the effects linger
The Washington State Ferry system has reduced the rated carrying capacity of its fleet because people have gotten fatter: The average weight of an adult passenger has been officially revised from 160 pounds to 185 pounds. (That's from 11 stone 6 to 13 stone 3 in the UK, or from 73kg to 84kg for the rest of the world.) This has happened before: In 1999, the rated capacity of Washington State ferries dropped when the previous method for determining seating density was abandoned due to passengers' big butts. (I recall that The Seattle Times printed a ruler next to the article so that for readers could assess th...
Why is the file size reported incorrectly for files that are still being written to?
The shell team often gets questions like these from customers: Attached please find a sample program which continuously writes data to a file. If you open the folder containing the file in Explorer, you can see that the file size is reported as zero. Even manually refreshing the Explorer window does not update the file size. Even the command shows the file size as zero. On the other hand, calling reports the correct file size. If I close the file handle, then Explorer and the command both report the correct file size. We can observe this behavior on Windows Server 2008 R2, but on Windows Server 2003, the fi...
How do I get the full path for the target of a shortcut file?
A customer was having trouble obtaining information from a shortcut file. "Here is a sample program that tries to print the target of a shortcut file, but it only gets the file name without a directory. How do I get the full path?" Recall that the structure contains only a file name in the member. It doesn't have any path information. The structure was originally created for the function, and you already know the directory you are searching in because you passed it to . But we're not using the structure in conjunction with , so where do I get the directory from? In the customer's excitement over the ...
How do I determine programmatically whether a particular language is LTR or RTL?
Given an , how does one determine whether the language lays out left-to-right or right-to-left? One suggestion was simply to hard-code the list of known right-to-left languages, and if the language isn't on the list, then assume that it is left-to-right. This technique is clearly fragile, because Windows adds support for new languages not infrequently, and if one of those is a right-to-left language, then your table is now out of date. And besides, there are languages whose layout is neither left-to-right nor right-to-left. For example, Chinese and Japanese traditionally lay out top-to-bottom. To obtain the text...