Thursday, December 09, 2010

 

Multiple-Key down: 3 keys held down, 2 show up

When holding down multiple keyboard keys some keys may not register. You can test your keyboard by doing the following.

1. Open up a text editor (MS Word, Notepad or vi)
2. Hold the UP ARROW
3. Hold the LEFT ARROW
4. Keep those held and now press the SPACEBAR

If you did happen to see a space show up, your keyboard likely cost a pretty penny. Most people, however, use the cheapest keyboard they can get. This "No Space shows up" error is called "Masking" or "Ghosting" and is explained throughly here: http://www.dribin.org/dave/keyboard/one_html/

Some keyboard manufacturers worked around this by moving where the Masking happens. For example, some keyboards don't show a space bar press if you're already holding down S and D.

The best work around for this issue when developing software that utilizes multiple keys(such as games) is to either allow the user to assign keys or map two sets of keys to each software event. For example, allow them to use WASD instead of the Arrow keys.

Original source: http://www.­tage7.­net/­devblog/­2010/­01/­17/­the-­multiple-­key-­down-­problem/­ google cached

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