Define animated smooth scroll durations in a central location

This will make it easy to adjust the durations in the future.

ui/pageview.cpp

@@ -176,6 +176,12 @@ public:
     double lastSourceLocationViewportNormalizedX;
     double lastSourceLocationViewportNormalizedY;
     int controlWheelAccumulatedDelta;
+
+    // for everything except PgUp/PgDn and scroll to arbitrary locations
+    int smoothScrollShortDuration;
+    // for PgUp/PgDn and scroll to arbitrary locations
+    int smoothScrollLongDuration;
+
     // auto scroll
     int scrollIncrement;
     QTimer *autoScrollTimer;
@@ -330,6 +336,8 @@ PageView::PageView(QWidget *parent, Okular::Document *document)
     d->lastSourceLocationViewportNormalizedX = 0.0;
     d->lastSourceLocationViewportNormalizedY = 0.0;
     d->controlWheelAccumulatedDelta = 0;
+    d->smoothScrollShortDuration = 100;
+    d->smoothScrollLongDuration = d->smoothScrollShortDuration * 2;
     d->scrollIncrement = 0;
     d->autoScrollTimer = nullptr;
     d->annotator = nullptr;
@@ -1886,7 +1894,7 @@ void PageView::keyPressEvent(QKeyEvent *e)
             int next_page = d->document->currentPage() - viewColumns();
             d->document->setViewportPage(next_page);
         } else {
-            d->scroller->scrollTo(d->scroller->finalPosition() + QPoint(-horizontalScrollBar()->singleStep(), 0), 100);
+            d->scroller->scrollTo(d->scroller->finalPosition() + QPoint(-horizontalScrollBar()->singleStep(), 0), d->smoothScrollShortDuration);
         }
         break;
     case Qt::Key_Right:
@@ -1896,7 +1904,7 @@ void PageView::keyPressEvent(QKeyEvent *e)
             int next_page = d->document->currentPage() + viewColumns();
             d->document->setViewportPage(next_page);
         } else {
-            d->scroller->scrollTo(d->scroller->finalPosition() + QPoint(horizontalScrollBar()->singleStep(), 0), 100);
+            d->scroller->scrollTo(d->scroller->finalPosition() + QPoint(horizontalScrollBar()->singleStep(), 0), d->smoothScrollShortDuration);
         }
         break;
     case Qt::Key_Escape:
@@ -4023,7 +4031,7 @@ void PageView::scrollTo(int x, int y, bool smoothMove)
     d->blockPixmapsRequest = true;
 
     if (smoothMove)
-        d->scroller->scrollTo(QPoint(x, y));
+        d->scroller->scrollTo(QPoint(x, y), d->smoothScrollLongDuration);
     else
         d->scroller->scrollTo(QPoint(x, y), 0);
 
@@ -4745,10 +4753,10 @@ void PageView::slotScrollUp(int nSteps)
     // if in single page mode and at the top of the screen, go to \ page
     if (Okular::Settings::viewContinuous() || verticalScrollBar()->value() > verticalScrollBar()->minimum()) {
         if (nSteps) {
-            d->scroller->scrollTo(d->scroller->finalPosition() + QPoint(0, -100 * nSteps), 100);
+            d->scroller->scrollTo(d->scroller->finalPosition() + QPoint(0, -100 * nSteps), d->smoothScrollShortDuration);
         } else {
             if (d->scroller->finalPosition().y() > verticalScrollBar()->minimum())
-                d->scroller->scrollTo(d->scroller->finalPosition() + QPoint(0, -verticalScrollBar()->rect().height()));
+                d->scroller->scrollTo(d->scroller->finalPosition() + QPoint(0, -verticalScrollBar()->rect().height()), d->smoothScrollLongDuration);
         }
     } else if (d->document->currentPage() > 0) {
         // more optimized than document->setPrevPage and then move view to bottom
@@ -4767,10 +4775,10 @@ void PageView::slotScrollDown(int nSteps)
     // if in single page mode and at the bottom of the screen, go to next page
     if (Okular::Settings::viewContinuous() || verticalScrollBar()->value() < verticalScrollBar()->maximum()) {
         if (nSteps) {
-            d->scroller->scrollTo(d->scroller->finalPosition() + QPoint(0, 100 * nSteps), 100);
+            d->scroller->scrollTo(d->scroller->finalPosition() + QPoint(0, 100 * nSteps), d->smoothScrollShortDuration);
         } else {
             if (d->scroller->finalPosition().y() < verticalScrollBar()->maximum())
-                d->scroller->scrollTo(d->scroller->finalPosition() + QPoint(0, verticalScrollBar()->rect().height()));
+                d->scroller->scrollTo(d->scroller->finalPosition() + QPoint(0, verticalScrollBar()->rect().height()), d->smoothScrollLongDuration);
         }
     } else if ((int)d->document->currentPage() < d->items.count() - 1) {
         // more optimized than document->setNextPage and then move view to top