Fix brightness and animation
Review Request #125156 - Created Sept. 11, 2015 and submitted
As described in https://bugs.kde.org/show_bug.cgi?id=350676#c5
There are two issue here:
1. m_cacheBrightness may not be updated after animation.
2. setStartValue and setEndValue may emit unwanted valueChanged even when animation is stopped. Though I don't agree that the bug is in Qt (see my https://bugs.kde.org/show_bug.cgi?id=350676#c7). But we need to skip this emit anyway.
1 is resolved by always query the brightness when animation emit finished(). slotScreenBrightnessChanged is reused for this purpose.
2 is resolved by disconnect and reconnect the signal to skip setStartValue and setEndValue.
not be able to reproduce 350676.