[Development] Bug#874054: Setting QT_LINUX_ACCESSIBILITY_ALWAYS_ON=1 has a huge negative performance impact, should not be always on

[Allan Sandfeld Jensen]

On Sonntag, 3. September 2017 18:15:15 CEST Samuel Thibault wrote:
> On the long run, it really should.  Just hiding issues is not the way
> forward :)
> 
> Also, note that if the performance is so bad, it means something *needs*
> to be fixed, otherwise blind users will get the bad performance, and
> nobody will be there to fix it, because nobody notices it except blind
> users, who are left with little hope to fix it by themselves.

It is not a issue or a bug. The performance impact comes from sending 
everything the mouse hovers over to the accessibility framework (for instance 
to be spoken aloud), when there is not any accessibility tools running.

You are deliberately crippling Qt to always send dbus events even when no one 
is listening.

Note the performance impact is the same in all applications regardless of 
framework. Running accessibility tools has a substantional performance cost on 
mouse movements, but a mouse rendered or text scrolling at 60 fps is 
completely pointless to blind people, but rather important to everybody else.

'Allan