June 23rd, 2011

What happens when applications try to copy text by sending Ctrl+C

Raymond Chen
Raymond Chen

I’m stealing this story from one of my colleagues.

I remember one app from a long time ago that had a feature where you could hit a global short cut key (or something like that) to launch the dictionary. It was also smart in that it would detect the current selected text and immediately search the dictionary for that term.

One day I was running a Perl script that took several hours to run. It was nearly done and for whatever I decided to launch the dictionary. It sent a Ctrl+C to my Perl script and killed it.

And that’s why you don’t send Ctrl+C to arbitrary applications.

Active Accessibility gives you access to the text under the cursor. There’s also a newer interface known as UI Automation which has a handy method called IText­Provider::Get­Selection. (On the managed side, you have System.Windows.Automation.Text­Pattern.Get­Selection.)

Update: Commenter parkrrrr points out the IText­Provider::Get­Selection. is the provider-side interface. The interface for applications wishing to read the selected text is IUI­Automation­Text­Pattern.

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Old New Thing
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Author

Raymond Chen

Raymond has been involved in the evolution of Windows for more than 30 years. In 2003, he began a Web site known as The Old New Thing which has grown in popularity far beyond his wildest imagination, a development which still gives him the heebie-jeebies. The Web site spawned a book, coincidentally also titled The Old New Thing (Addison Wesley 2007). He occasionally appears on the Windows Dev Docs Twitter account to tell stories which convey no useful information.

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