[maemo-developers] Qt application crashes after 2 minutes if started from app grid

[From: Thomas Perl]

Hi,

2011/5/10 Cornelius Hald <hald at icandy.de>:
> On Tue, 2011-05-10 at 18:24 +0300, Eero Tamminen wrote:
>> On 05/09/2011 08:44 PM, ext Timur Kristóf wrote:
>> > On 05/09/2011 04:43 PM, Kimmo Hämäläinen wrote:
>> >> If you don't use D-Bus at all, you need to implement this
>> >> single-instance and window raising yourself.
>>  >
>>  > This can be easily done with the QtSingleApplication class.
>>
>> If that works by starting a new instance of the application
>> which them notices that it's already running and exits,
>> that makes window topping a really heavy operation...
>
> Actually for me the single-instance thing works even with a normal
> QApplication. I've removed the .service file and the service line in
> the .desktop file. Still I can have only one instance.

I think on Maemo 5, hildon-desktop is keeping track of which window
belongs to which .desktop file (or: launcher icon) and if the
application is already running, hildon-desktop simply switches to the
application instead of instantiating a new one. That doesn't mean that
it will work the same on any other environment (e.g. N900 MeeGo DE,
etc..). It's a good idea though if most applications are
single-instance, because it makes switching instantaneous, because
hildon-desktop simply has to present the window without creating
another process.

The code is in src/launcher/hd-app-mgr.c in hildon-desktop's source -
it should be in the function hd_app_mgr_launch() and
hd_app_mgr_activate() if I'm not mistaken.

The user could still start two instances if (s)he would start your
application from X Terminal. If you want to prevent that, I'd suggest
using D-Bus.

HTH.
Thomas