QT4 apps slooooow in ssh

[T.C. Hollingsworth]

On Tue, May 8, 2012 at 1:10 PM, Roberto Ragusa <mail at robertoragusa.it> wrote:
> On 05/08/2012 09:40 PM, T.C. Hollingsworth wrote:
>> On Tue, May 8, 2012 at 8:47 AM, Roberto Ragusa <mail at robertoragusa.it> wrote:
>>> An additional test, on the F16 machine:
>>> - "kate" is normally fast
>>> - "ssh -Y localhost kate" is slooooooooooooooooooow
>>>
>>> What is happening here????
>>
>> Is `ssh -Y localhost kate -graphicssystem native` faster?
>
> Absolutely yes! The speed is normal again.
>
> I also tried "-graphicssystem raster" which is sloooow,
> and "-graphicssystem opengl" which is bugged (pieces of the GUI are
> missing).
>
> Why is the default so bad for ssh?

The default is the "raster" graphics engine, which works somewhat like
you described in your original e-mail:
http://labs.qt.nokia.com/2009/12/18/qt-graphics-and-performance-the-raster-engine/

The "native" graphics engine uses regular X11, which will probably
always be best over SSH.

Qt also respects the QT_GRAPHICSSYSTEM environment variable to
configure this, so you can add `export QT_GRAPHICSSYSTEM=native` to
your ~/.profile or wherever to make it your "default".

-T.C.