WPF Accelerator Keys like Visual Studio

Question

Hello all,

I'm developing a large line of business app with C# and WPF. Our standard is to include accelerator keys for buttons on all forms (Save, Cancel, Search, etc.). I've recently noticed that when a form is loaded, the accelerator key is active even when the user does not press the "Alt" key. For example, our Search button uses "Alt-H" as the accelerator, but the user can initiate a search by simply pressing "H". I'm using the standard "_" in the button content to create the accelerator key.

<Button Content="Searc_h"/>

Has anyone else noticed this behavior and has anyone found a suitable workaround that requires the "Alt" key to be pressed?

Answer 1

There is a Windows setting that displays the "_" without the Alt key being pressed. You might want to check if that is enabled.

In Display Properties -> Appearance -> Effects -> 'Hide Underlined Letters for Keyboard Navigation until I press Alt key". This is for XP - not sure where it is at for Vista.

EDIT: This at least is true in that it will display the mnemonic without first pressing the Alt key. I just re-read your post and noticed that it will automatically launch when you press the 'H' key without Alt. Not sure what is going on there.

Answer 2

This behavior seems to be normal on Windows. At least I just tried it with a Winforms window and pressing the accelerator without Alt did indeed invoke a button or shifted focus to the appropriate control.

Answer 3

This article on Sara Ford's Weblog discusses this phenomenon.

A commenter mentions this as a solution:

"If you're writing an application and you don't like this behavior, look up WM_CHANGEUISTATE and specifically the UISF_HIDEFOCUS flag."

Answer 4

Actually, the Command pattern in WPF allows you more granular control over what keyboard shortcuts are allowed. It goes a step further than the "_" in your button text.

Check the following link for more information:

http://www.switchonthecode.com/tutorials/wpf-tutorial-command-bindings-and-custom-commands

Edit: previous link was dead - provided a new link.

-Doug