The Old New Thing

Thread affinity of user interface objects: Addendum

November 9, 2012 Nov 9, 2012 11/9/12

Raymond Chen

Some time ago, I discussed the thread affinity of device contexts, noting that the and functions must be called from the same thread. The same restriction also applies to printer DCs. Printer DCs must be created and destroyed on the same thread. The printing team imposed this additional rule in order to make it easier for printer driver ...

How do I get the tabbed dialog effect on my own custom tabbed dialog?

November 5, 2012 Nov 5, 2012 11/5/12

Raymond Chen

CJ observed that the standard tabbed dialogs provide an effect on the tab pages and want to know how to get the tabbed dialog effect on custom dialogs. fds242 noted this as well and wanted to know why the automatic tabbed dialog effect doesn't kick in until you put a static control on the child dialog box. Let's look at the first question...

When you synthesize input with SendInput, you are also synthesizing the timestamp

November 1, 2012 Nov 1, 2012 11/1/12

Raymond Chen

A customer was reporting a problem when they used the function to simulate a drag/drop operation for automated testing purposes. I see the mouse move from one location to another, and the starting and stopping locations are correct on the screen, but the mouse moves instantaneously rather than waiting 500ms between operations. Here's how ...

Keyboard layouts aren't like Beetlejuice – they won't appear just because you say their name

October 25, 2012 Oct 25, 2012 10/25/12

Raymond Chen

A customer reported a bug in Windows Vista Home Editions: We are handling a Ctrl+V keyboard event and want to interpret it in the context of a US-English keyboard. On Windows XP and versions of Windows Vista other than Home editions, the three calls all succeed, whereas on Windows Vista Home Editions, the calls fail. On the other ...

You can't use the WM_USER message in a dialog box

October 24, 2012 Oct 24, 2012 10/24/12

Raymond Chen

Today, I'm not actually going to say anything new. I'm just going to collate information I've already written under a better title to improve search engine optimization. A customer reported that they did the following but found that it didn't work: "I send the message to my dialog, but the value doesn't stick. At random times, the value...

Diversion: Generating a random color from JavaScript

October 23, 2012 Oct 23, 2012 10/23/12

Raymond Chen

A colleague posed a little puzzle for a fun little app he was writing in HTML: He wanted to generate a random color. If you search around the intertubes, you can find several possible attempts at a solution, like this collection, and an interesting example that has trouble with the pigeonhole principle. The original function to generate...

Using WM_COPYDATA to marshal message parameters since the window manager otherwise doesn’t know how

October 19, 2012 Oct 19, 2012 10/19/12

Raymond Chen

Miral asks for the recommended way of passing messages across processes if they require custom marshaling. There is no one recommended way of doing the custom marshaling, although some are hackier than others. Probably the most architecturally beautiful way of doing it is to use a mechanism that does perform automatic marshaling, like COM ...

What happens if you forget to pass an OVERLAPPED structure on an asynchronous handle?

October 12, 2012 Oct 12, 2012 10/12/12

Raymond Chen

It becomes synchronous, sort of.

Combo boxes have supported incremental searching for quite some time now

October 11, 2012 Oct 11, 2012 10/11/12

Raymond Chen

Back in August 2007, I promised to post a program the following day but it appears that I never did. Oops. I discovered this as I went through my "things to blog about" pile and figured better late than never. Though five years late is pretty bad. Here's a program which fills a combo box with some strings. Run this program and start ...