[Thinlinc-technical] multiple modifiers

Peter Astrand astrand at cendio.se
Mon Jan 28 16:43:45 CET 2013

Follow up with bug reports for the issues below:

>> I didn't consciously do anything to cause this (though I have to confess
>> that at one point I did modify the session starter code to pass +kb, but
>> took that out again).
> Yes, the shipped default configuration is actually to use a Swedish keyboard 
> in the server side session. The reason for this is that such a keyboard 
> layout "should" be a superset of a US keyboard. In general, the server layout 
> should not matter unless you use applications which interprets the raw 
> keycode. So the idea was that having Swedish by default would make things 
> works out of the box for both US and Nordic customers.
> But, now it seems that there's a regression between 3.4.0 and 4.0.0 wrt the 
> Swedish layout.

It turns out that the problem with stuck modifiers is caused by a problem 
with the Xserver Xvnc. It's present in both 3.4.0 and 4.0.0. We have 
opened up a bug for this problem: 

However, normally you only experience the problem in 4.0.0 since it has a 
new default keyboard layout; one with some modifiers in multiple 
locations. We have another bug for this:

I've already fixed that one; the fix will be in 4.1.0. In the mean time, 
if you suffer from this problem, you can workaround it by executing this 
command in the session:

xmodmap -e "keycode 204 = NoSymbol NoSymbol"

>>> This is ok; this is what will happen on a local workstation as well,
>>> if you lift Shift before the symbol key. Applications should not care.
>> This causes trouble because I have different keybindings for
>> Mod4-semicolon and Mod4-Shift-semicolon. The result of the spurious
>> 'shift' being set in the modifier bits (it's an XCB application reading
>> the key presses) is that the wrong binding is executed.
> I see. Yes, that can be a problem. With a Swedish layout in the session, it 
> is not possible to generate Mod4-semicolon without shift. You would need to 
> add an unshifted mapping for this to work, ie something like:
> xmodmap -e "keycode 250 = semicolon"
> I haven't thought of this before. This means that the Swedish layout is not a 
> correct superset of the US map after all.

We will consider shipping ThinLinc with a default layout of US in the 
future. We have a bug for this as well: 

Peter Astrand		ThinLinc Chief Developer
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