Keyboard handling

Some special web browser keyboard hotkeys could trigger some undesirable behaviors.

You can find some of them here

Preventing some web browser behaviors

For instance, if you need the F1 keys in your game, it actually trigger the browser help openning a new page.

Here is a javascript example you can use to prevent it. Note that your game still receive the event.

window.onkeydown =
    function(event) {
        // prevent web browser to open the help page (F1 key)
        if(event.keyCode == 112){
            event.preventDefault();
            return false;
        }                
    };

Preventing all possible browser hotkeys is not a good idea. Sometimes you want some to occur (F12 to open dev tools, F5 to refresh, Ctrl+T to open a new tab).

It’s then recommended to just prevent browser hotkeys you’re really using in your game.

Preventing page scrolling

Browser implements page scrolling hotkeys that could conflicts with your game :

Space, Page Down, Arrow Down – Scroll down a frame.
Shift+Space, Page Up, Arrow Up – Scroll up a frame.
Home – Top of page.
End – Bottom of page.
Arrow Left – Scroll left a frame.
Arrow right – Scroll right a frame.

Note that the space key is a special case : prevent it from key down event would prevent the key press event to occur and the space character won’t be typed in the TextField widget.

Here is a javascript template you can use to prevent page scrolling without messing with TextField widget :

window.onkeypress =
    function(event) {
        // prevent the space key (page scroll down)
        if(event.keyCode == 32){
            event.preventDefault();
            return false;
        }
    };

window.onkeydown =
    function(event) {
        // prevent all navigation keys except the space key
        if(event.keyCode >= 33 && event.keyCode <= 40){
            event.preventDefault();
            return false;
        }                
    };