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

MapGenericMask is just a convenience function for converting generic access to specific access, according to the instructions you provide

Raymond Chen May 15, 2015 May 15, 2015 05/15/15

For some reason, people call the MapGenericMask function in order to calculate what access mask to pass to request access to something. That's not what MapGenericMask is for. The MapGenericMask function is to assist the server side of the access, not the client side. As the documentation says, the MapGeneric...

Low-level hooks have thread affinity, so make sure you keep an eye on the thread

Raymond Chen May 14, 2015 May 14, 2015 05/14/15

A customer was having a problem with their automated testing tool. We have an automation testing tool that, among other things, installs a low-level mouse hook. Sometimes, the hook takes too long to process an action, and it gets unhooked. We have a watchdog thread that tries to detect when this has happened, and in response, it kicks off a ...

Why don't you forward WM_GETMINMAXINFO and clamp the results?

Raymond Chen May 13, 2015 May 13, 2015 05/13/15

In my illustration of how to make a window resizable in only one direction, commenter Josua asks, "Why don't you forward WM_GETMINMAXINFO and clamp the results?" I'm going to assume the question is really "Why don't you forward WM_GETMINMAXINFO before clamping the results?" rather than "Why did you bother ...

How does Task Manager compute Up Time, and why doesn't it agree with GetTickCount?

Raymond Chen May 12, 2015 May 12, 2015 05/12/15

Task Manager shows a piece of information called "Up time". How is this value calculated, and why doesn't it agree with the value reported by GetTickCount/GetTickCount64? Task Manager calculates "up time" by subtracting the system boot time from the current time. In other words, it is misnamed; it really should be called ...

Can I run a service executable from a network location?

Raymond Chen May 11, 2015 May 11, 2015 05/11/15

A customer liaison wanted to know whether it is possible to run a service executable from a network location. The customer was doing so and running into problems, and they wanted to know whether it is a legal scenario. Running a service from a network location is a bad idea. If the computer lose network connectivity momentarily, the service ...

Documentation creates contract, which is why you need to be very careful what you document

Raymond Chen May 8, 2015 May 8, 2015 05/8/15

A person with a rude name asks, "Why does MS not document the system metrics used by classic/pre-uxtheme windows and common controls? This image is really useful and I wish all of this was actually documented." Actually, that picture explains why it isn't documented. Suppose such a picture existed in the Windows 2000 documentation. I don't ...

Hidden message in a T-shirt, it's been done before

Raymond Chen May 7, 2015 May 7, 2015 05/7/15

While everybody is trying to figure out the hidden message in Joe Belfiore's T-shirt,¹ I figure I'd give you an easier puzzle. Here is the pattern of 0's and 1's printed on the T-shirt handed given out at the Windows 8 kick-off meeting. Because you don't have a project until you have a T-shirt. The actual shirt clipped many of the...

Why is there an invisible U+202A at the start of my file name?

Raymond Chen May 6, 2015 May 6, 2015 05/6/15

There's something strange about this property sheet page: To change permissions, click Edit. Edit... Advanced... For special permissions or advanced settings, click Advanced. Apply Cancel OK...

What does it mean when the Advanced Security Settings dialog says that an ACE was inherited from "Parent Object" without naming the specific parent?

Raymond Chen May 5, 2015 May 5, 2015 05/5/15

The Advanced Security Settings dialog shows the ACEs in an object's ACL, and one of the pieces of information is a column labeled Inherited from which identifies whether the ACE was inherited, and if so, from where. A customer observed that when they opened the Advanced Security Settings dialog, one of their objects had an ACE that showed ...

Creating a window that can be resized in only one direction

Raymond Chen May 4, 2015 May 4, 2015 05/4/15

Today's Little Program shows a window that can be resized in only one direction, let's say vertically but not horizontally. Start with the scratch program and make these changes: We accomplish this by removing horizontal resize behavior from the left and right edges and corners. For the corners, we remove the horizontal resizing, but leave ...

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