[H-GEN] Why no keyboard with NO Window Manager ?

[ben.carlyle at invensys.com]

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G'day Mark,





Mark Corben <mcorben at bigpond.com>
Sent by: Majordomo <majordom at caliburn.humbug.org.au>
25/04/03 14:08
Please respond to general

 
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        Subject:        [H-GEN] Why no keyboard with NO Window Manager ?

>  I want to set up a number of Redhat 7.x Linux  boxes so that the user 
> logins and is presented with only a browser application (Phoenix). When 
> the user exits the browser either they are presented with a login xdm 
> screen or the application is restarted (I am still looking at 
alternatives).

<snip>

> When the user is logged in he/she is able to use the browser via the 
> buttons HOWEVER the user cannot use the keyboard to type any URL into 
> the application.

What probably we're talking about here is keyboard focus. When you click a 
button with your mouse it's reasonably clear to X exactly what the 
keypress should be associated with. It sends a click message to the widget 
under the X,Y coordinates of your mouse at the time of the click. A 
keyboard is a different matter.

Say you have five or six applications all of which can receive input from 
the keyboard. When you press the character 'y', who does it go to? 
Whomever has keyboard focus. Keyboard focus to a particular window is 
usually defined by the window-manager. Thus the traditional wars of 
Click-to-Focus vs Focus-follows-mouse, etc.

Within a particular window my understanding is that the individual widgets 
broker between themselves which has focus at any one time. Focus in this 
case may change because of a click somewhere, or tab keys, or a variety of 
other actions. The trouble is that none of this works if the larger window 
that maintains the widgets has focus granted by X.

In your case it sounds to me like X has given focus to something else 
(whatever that may be). I'm not sure of the exact policy here. I would 
guess that the first window to open would be the one that X would give 
focus, then some other policy would occur if that window ever closed. The 
important thing is that without a window-manager there's noone to decide 
who gets keyboard focus when you really don't want that window to have it. 
This also applies to some dialogues opened by the parent window which you 
won't be able to type into unless that dialogue window gets keyboard 
focus. This means that generally you don't want to run without a window 
manager unless you know that there will only ever be one window open, and 
that the app behind it will never ever try to open any kind of dialogue 
window :)

I hope that goes some way to explaining why it's probably better to run an 
unobtrusive window manager without any useful menu functionality than it 
is to run completely without a wm. In any case it might give you some 
search terms to help you read up on it ;)

Benjamin.



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