the software centre flash

[longgangfan]

when I select a software in the software centre and click the button "install", the software centre and all the desktop will flash. I don't know why.

SRU TEST CASE:
1. Launch the current Ubuntu Software Center in Precise.
2. Watch the lobby view after launch. After about 10-15 seconds, notice that the view "flashes" a white screen for a very short moment.
4. Close Ubuntu Software Center.
5. Update to the version of software-center in precise-proposed.
6. Launch Ubuntu Software Center again and watch the lobby view. Verify that there is no longer a "flash" in the view after about 10-15 seconds.

SRU REGRESSION POTENTIAL:
Regression risk is very small and would likely be little more than a tiny, still-noticaeable "flash" in the UI after the 10-15 second period.

[Daniel Lawrence (dannyla)]

Thank you for taking the time to report this bug and helping to make Ubuntu better.

Please execute the following command, as it will automatically gather debugging information, in a terminal:

apport-collect 965093

When reporting bugs in the future please use apport by using 'ubuntu-bug' and the name of the package affected. You can learn more about this functionality at https://wiki.ubuntu.com/ReportingBugs.

[Dave Morley (davmor2)]

There is a very minor flash of USC alone when the install progress bar appears, like the page is redrawn.

[Michael Vogt (mvo)]

This happens when the update-software-center-agent finishes, you will see on th terminal:
2012-04-19 16:23:48,484 - softwarecenter.ui.gtk3.app - INFO - software-center-agent finished with status 0

when this happens. We need to investigate why we refresh the entire UI its certainly not needed to refresh e.g. the banners :)

[Natalia Bidart (nataliabidart)]

Once the db is reopened, 'reopen' signal is emitted and the following callbacks are executed:

softwarecenter/ui/gtk3/panes/availablepane.py(601)on_db_reopen()
-> self.refresh_apps()

the call above will set the whole SC screen (except for the toolbar) to white. This is caused by the call:

    415 self.show_appview_spinner()

and later (on_query_complete):

    285 self.hide_appview_spinner()

The same happens if the user is in the installed pane, when the callback for db_reopen does:

    652 self._build_categorised_installedview(keep_state)

(which shows and hides a spinner).

Michael, would it be safe to remove the showing and hiding of the spinner?

[Michael Vogt (mvo)]

Hello Natalia,

sorry for my slow reply and thanks a bunch for your analysis. The spinner is intended to only "unmask" itself when there
is a operation that takes a certain amount of time. The refresh is very quick so ideally it would be below this threshold.

The spinner is implemented as a "SpinnerNotebook" in ui/gtk3/widgets/spinner.py". Check the "show_spinner()" and
"hide_spinner()" and "_unmask_spinner()" code there. Unfortunately it appears like the implementation is buggy and
it will unconditionally switch to the notebook page with the spinner even if the operation is very quick.

I think the ideal fix is to ensure that the notebook page is only changed when the timeout happens and also that the
timeout id is saved in show_spinner and removed in hide_spinner if the
timeout has not yet fired. The current timeout of 100ms is probably a bit low, would be nice to know if there is
research data for a better one, my gutfeeling is that ~250ms - 500ms is a better default. Plus a test for this new
code :)

I hope this helps getting started, if there are any questions or concerns with the approach, I'm happy to talk about it on irc
or mumble.