Showing tag results for Code

Sep 5, 2013
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Why are my posted messages getting lost when the user drags my window around?

Raymond Chen

This question was inspired by an actual customer question, but I changed a lot of it around to make for a more interesting story. (Trust me, the original story was even more boring.) A customer's background thread posted a message to the main UI thread to signal something (details not important). They found that the posted message was never rece...

Code
Aug 30, 2013
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Can an x64 function repurpose parameter home space as general scratch space?

Raymond Chen

We saw some time ago that the x64 calling convention in Windows reserves space for the register parameters on the stack, in case the called function wants to spill them. But can the called function use the memory for other purposes, too? You sort of already know the answer to this question. Consider this function: How would a naïve comp...

Code
Aug 29, 2013
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How can I write to a file only as long as nobody's looking?

Raymond Chen

A customer wanted to know how to detect that the user has opened Notepad to view a particular file. They had come up with method based on polling and sniffing the Notepad title bar, but they found that it consumed a lot of CPU. (They hadn't noticed yet that it doesn't localize, and that it can trigger false positives since Notepad shows only the fi...

Code
Aug 28, 2013
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The format of data and custom resources

Raymond Chen

Continuing the highly-sporadic series of Win32 resource formats, today we'll look at the format of resources, which are declared in resource files as . Also the format of custom resources, which are declared in resource files by just giving the custom resource name or ordinal as the second word on the declaration. The format is very simple: It's ...

Code
Aug 26, 2013
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Why doesn't the "Automatically move pointer to the default button in a dialog box" work for nonstandard dialog boxes, and how do I add it to my own nonstandard dialog boxes?

Raymond Chen

The Mouse control panel has a setting called Automatically move pointer to the default button in a dialog box, known informally as Snap to default button or simply Snap To. You may have discovered that it doesn't work for all dialog boxes. Why not? The Snap To feature is implemented by the dialog manager. When the window is shown and the setting...

CodeTips/Support
Aug 23, 2013
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If I attach a file to an existing completion port, do I have to close the completion port handle a second time?

Raymond Chen

There are two ways of calling the function. You can pass a null pointer as the parameter, indicating that you would like to create a brand new completion port, associated with the file handle you passed (if you passed one). Or you can pass the handle of an existing completion port, and the file handle you passed will be associated with that por...

Code
Aug 22, 2013
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All I/O on a synchronous file handle is serialized; that's why it's called a synchronous file handle

Raymond Chen

File handles are synchronous by default. If you want asynchronous file handles, you need to pass the flag when you create the handle. And all operations on a synchronous file handle are serialized. You'd think this was a simple and obvious rule, but "Someone" finds it "very surprising that operations can block which only handle file metadata." I...

Code
Aug 19, 2013
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The tiny table sorter – or – you can write LINQ in JavaScript

Raymond Chen

I had a little side project that displayed status information in a table, and I figured, hey, let me add sorting. And it was a lot easier than I thought. I just put the header row in the and the table contents in the , then I could use this code to sort the table: Each cell can have an optional custom attribute which specifies how the item sh...

Code
Aug 16, 2013
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If I signal an auto-reset event and there is a thread waiting on it, is it guaranteed that the event will be reset and the waiting thread released before SetEvent returns?

Raymond Chen

Let's go straight to the question: I have two programs that take turns doing something. Right now, I manage the hand-off with two auto-reset events. In Thread A, after it finishes doing some work, it signals Event B and then immediately waits on Event A. Thread B does the converse: When its wait on Event B completes, it...

Code
Aug 15, 2013
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How do I control the order of the pages in property sheets from my shell extension?

Raymond Chen

A customer wanted to know whether a shell extension can control the order of the property sheet pages in a property sheet. The interface lets you add pages and replace pages, but nothing about rearranging them. Naturally a shell extension can control the relative order of its own pages (by changing in the order in which it calls ) but how can it...

Code