[Marble-bugs] [Bug 254000] MarbleWidget and Slider for the zoom causes the application to use 100% CPU.

[Dennis Nienhüser]

https://bugs.kde.org/show_bug.cgi?id=254000





--- Comment #5 from Dennis Nienhüser <earthwings gentoo org>  2010-10-13 20:50:50 ---
The implementation of our own slider has some interesting notes on this btw.
Also notice the blockSignals() calls.

    // There exists a circular signal/slot connection between MarbleWidget and
this widget's
    // zoom slider. MarbleWidget prevents recursion, but it still loops one
time unless
    // blocked here. Note that it would be possible to only connect the sliders
    // sliderMoved signal instead of its valueChanged signal above to break up
the loop.
    // This however means that the slider cannot be operated with the mouse
wheel, as this
    // does not emit the sliderMoved signal for some reason. Therefore the
signal is blocked
    // below before calling setValue on the slider to avoid that it calls back
to MarbleWidget,
    // and then un-blocked again to make user interaction possible.

    d->m_navigationUi.zoomSlider->blockSignals( true );

    d->m_navigationUi.zoomSlider->setValue( zoom );
    d->m_navigationUi.zoomSlider->setMinimum( minimumZoom() );
    // As we have disabled all zoomSlider Signals, we have to update our
buttons seperately.
    updateButtons( zoom );

    d->m_navigationUi.zoomSlider->blockSignals( false );

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