June 2015 | Page 2 of 3 | The Old New Thing

How come the technique for launching an unelevated process from an elevated process doesn’t work?

Raymond ChenJune 18, 2015Jun 18, 201506/18/15

A customer was following the Execute in Explorer sample to launch an unelevated process from an elevated process. (A sample which I rehashed some time ago.) The customer reported that the resulting process was still elevated. Upon closer inspection, the customer had disabled User Account Control (UAC). If UAC is disabled, then the ability ...

When you think you found a problem with a function, make sure you’re actually calling the function

Raymond ChenJune 17, 2015Jun 17, 201506/17/15

On an internal mailing list, a tester asked if there were any known problems with the FindFirstFileEx function preventing a directory from being deleted and recreated. Our code creates a test folder, then calls FindFirstFileEx to look inside the test folder. When we're done, we call FindClose, then delete ...

One way to make sure nobody reports problems with your Web site

Raymond ChenJune 16, 2015Jun 16, 201506/16/15

I had ordered a service online, and the Web site said, "Do not close this window until you are done, because once you close the window, you won't be able to come back." Okay, fine. I just need to make sure I get everything I need before I close the window. I click a link to download some of the information I had ordered, and I get the error ...

How can I reposition my window so it isn’t covered by the touch keyboard?

Raymond ChenJune 15, 2015Jun 15, 201506/15/15

Last week, we saw how we could rearrange our window contents to avoid having the touch keyboard cover the edit control. But what if the touch keyboard covers the entire window? No amount of rearranging will help. We'll have to move our window. Let's make these changes to the DoLayout function: If there are at least 50 pixels of the edit...

How can I force a CreateFile call to hang, in order to test something?

Raymond ChenJune 12, 2015Jun 12, 201506/12/15

A customer was doing some testing and wanted to know if there was a way to force a call to CreateFile to hang, so that they can test their program's hang detection and recovery code. You can ceate these scenarios with careful use of opportunistic locks (also known as oplocks). The sample program I wrote some time ago can be used, for ...

Keep your eye on the code page: Is this string CP_ACP or UTF-8?

Raymond ChenJune 11, 2015Jun 11, 201506/11/15

A customer had a problem with strings and code pages. The customer has a password like "Müllwagen" for a particular user. Note the umlaut over the u. That character is encoded as the two bytes C3 BC according to UTF-8. When the customer passes this password to the LogonUser function in order to authenticate the user, the call fails...

Taking ownership of a file doesn’t give you access, yet

Raymond ChenJune 10, 2015Jun 10, 201506/10/15

A colleague of mine accidentally ran a command from an elevated command prompt rather than a normal unelevated command prompt. By default, files created from an elevated command prompt are owned by the Administrators group, on the theory that you are doing work in the elevated command prompt in your rôle as the system administrator, so ...

How can I reposition my controls so they aren’t covered by the touch keyboard?

Raymond ChenJune 8, 2015Jun 8, 201506/8/15

Last week, we saw how to tell the Windows 8 touch keyboard to appear automatically in a desktop program when focus enters an edit control. But we did nothing to prevent the touch keyboard from covering the edit control. To find out when the touch keyboard appears and disappears, you register with the framework input pane. The framework input ...

There is no /8TB flag on 64-bit Windows

Raymond ChenJune 5, 2015Jun 5, 201506/5/15

A customer reported that their 64-bit application was crashing on Windows 8.1. They traced the problem back to the fact that the user-mode address space for 64-bit applications on Windows 8.1 is 128TB, whereas it was only 8TB on earlier versions of Windows for x64. They wanted to know whether there was a compatibility mode that they could set ...

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