Scale smooth scroll durations according to the global animation speed

Now people who don't like animations can set thenm to "Instant" globally
and smooth scrolling will be effectively disabled off in Okular.

There is no change in speed for people using the default global
animation duration.

BUG: 420755
FIXED-IN: 1.12.0

ui/pageview.cpp

@@ -439,6 +439,13 @@ PageView::PageView(QWidget *parent, Okular::Document *document)
     horizontalScrollBar()->setCursor(Qt::ArrowCursor);
     horizontalScrollBar()->setSingleStep(20);
 
+    // make the smooth scroll animation durations respect the global animation
+    // scale
+    KConfigGroup kdeglobalsConfig = KConfigGroup(KSharedConfig::openConfig(), QStringLiteral("KDE"));
+    const qreal globalAnimationScale = qMax(0.0, kdeglobalsConfig.readEntry("AnimationDurationFactor", 1.0));
+    d->smoothScrollShortDuration *= globalAnimationScale;
+    d->smoothScrollLongDuration *= globalAnimationScale;
+
     // connect the padding of the viewport to pixmaps requests
     connect(horizontalScrollBar(), &QAbstractSlider::valueChanged, this, &PageView::slotRequestVisiblePixmaps);
     connect(verticalScrollBar(), &QAbstractSlider::valueChanged, this, &PageView::slotRequestVisiblePixmaps);