Why is my call to ChangeTimerQueueTimer having no effect? (And another case of looking past the question to solve the problem.)

Raymond ChenDecember 30, 2015Dec 30, 201512/30/15

A customer had a question about the Change­Timer­Queue­Timer function, and they shared a sample program that demonstrated the issue. (Hooray for reduction.) The customer asked, "Why aren't we getting the ticks after calling Change­Timer­Queue­Timer?" This is explained down in the documentation for the Change­Timer...

Determining how each Explorer window is sorted

Raymond ChenDecember 28, 2015Dec 28, 201512/28/15

Today's Little Program lists all the open Explorer windows and their current sort criteria. (I will refrain from mentioning how auto-sort makes this meaningful.) Remember that Little Programs do little to no error checking. To process a window, we first ask for the top-level browser, and from that we ask for the active shell view, then ...

When is the correct time to call FreeLibraryWhenCallbackReturns?

Raymond ChenDecember 25, 2015Dec 25, 201512/25/15

When is the correct time to call Free­Library­When­Callback­Returns, or any of the other ...When­Callback­Returns functions? In practice, many people call the function immediately before returning from the callback. Is this a requirement? No. You can call the ...When­Callback­Returns function at any time during...

Why does my in-place tooltip dismiss itself as soon as it appears?

Raymond ChenDecember 24, 2015Dec 24, 201512/24/15

One subtlety in the use of in-place tooltips is that you should create the tooltip with the WS_EX_TRANSPARENT extended style. This style makes the window invisible to hit-testing, which is a good thing here. The code that decides when to show and hide an in-place tooltip goes like this: If the mouse enters the thing that needs a tooltip, ...

Confusing gotcha: PSECURITY_DESCRIPTOR is not a pointer to a SECURITY_DESCRIPTOR

Raymond ChenDecember 23, 2015Dec 23, 201512/23/15

There is a structure called a SECURITY_DESCRIPTOR. It describes the layout of an absolute security descriptor. There is also a structure called a SECURITY_DESCRIPTOR_RELATIVE. It describes the layout of a relative security descriptor. And then there is a type called PSECURITY_DESCRIPTOR. You might think based on its name that it is a pointer...

Allocating page file space without allocating RAM

Raymond ChenDecember 21, 2015Dec 21, 201512/21/15

The Windows Server 2003 Resource Kit comes with a tool called consume.exe, and one of the things you can ask it to do is to suck up space in your swap file. If you run the program in that mode, you see that it manages to do its job without consuming physical memory. (The amount of Free Pages in Task Manager remains constant.) How is that ...

Are views of memory-mapped files coherent within a single process? (And how this was the wrong question.)

Raymond ChenDecember 18, 2015Dec 18, 201512/18/15

A customer wanted some clarification. An MSDN article says This means that changes made to a page in the memory-mapped file via one process's view are automatically reflected in a common view of the memory-mapped file in another process. "The above paragraph says that the views are coherent across processes, but what about within a single ...