Accumulate Control+Wheel Deltas until they reach QWheelEvent::DefaultDeltasPerStep

This way zooming in/out with a touchpad is easier to control

BUGS: 377128

ui/pageview.cpp

@@ -166,6 +166,7 @@ public:
     double lastSourceLocationViewportNormalizedX;
     double lastSourceLocationViewportNormalizedY;
     QTimer * viewportMoveTimer;
+    int controlWheelAccumulatedDelta;
     // auto scroll
     int scrollIncrement;
     QTimer * autoScrollTimer;
@@ -312,6 +313,7 @@ PageView::PageView( QWidget *parent, Okular::Document *document )
     d->lastSourceLocationViewportNormalizedX = 0.0;
     d->lastSourceLocationViewportNormalizedY = 0.0;
     d->viewportMoveTimer = 0;
+    d->controlWheelAccumulatedDelta = 0;
     d->scrollIncrement = 0;
     d->autoScrollTimer = 0;
     d->annotator = 0;
@@ -1971,6 +1973,8 @@ void PageView::tabletEvent( QTabletEvent * e )
 
 void PageView::mouseMoveEvent( QMouseEvent * e )
 {
+    d->controlWheelAccumulatedDelta = 0;
+
     // don't perform any mouse action when no document is shown
     if ( d->items.isEmpty() )
         return;
@@ -2159,6 +2163,8 @@ void PageView::mouseMoveEvent( QMouseEvent * e )
 
 void PageView::mousePressEvent( QMouseEvent * e )
 {
+    d->controlWheelAccumulatedDelta = 0;
+
     // don't perform any mouse action when no document is shown
     if ( d->items.isEmpty() )
         return;
@@ -2392,6 +2398,8 @@ void PageView::mousePressEvent( QMouseEvent * e )
 
 void PageView::mouseReleaseEvent( QMouseEvent * e )
 {
+    d->controlWheelAccumulatedDelta = 0;
+
     // stop the drag scrolling
     d->dragScrollTimer.stop();
 
@@ -3192,6 +3200,8 @@ void PageView::guessTableDividers()
 
 void PageView::mouseDoubleClickEvent( QMouseEvent * e )
 {
+    d->controlWheelAccumulatedDelta = 0;
+
     if ( e->button() == Qt::LeftButton )
     {
         const QPoint eventPos = contentAreaPoint( e->pos() );
@@ -3254,43 +3264,55 @@ void PageView::wheelEvent( QWheelEvent *e )
         vScroll = verticalScrollBar()->value();
     e->accept();
     if ( (e->modifiers() & Qt::ControlModifier) == Qt::ControlModifier ) {
-        if ( e->delta() < 0 )
+        d->controlWheelAccumulatedDelta += delta;
+        if ( d->controlWheelAccumulatedDelta <= -QWheelEvent::DefaultDeltasPerStep )
+        {
             slotZoomOut();
-        else
+            d->controlWheelAccumulatedDelta = 0;
+        }
+        else if ( d->controlWheelAccumulatedDelta >= QWheelEvent::DefaultDeltasPerStep )
+        {
             slotZoomIn();
+            d->controlWheelAccumulatedDelta = 0;
+        }
     }
-    else if ( delta <= -120 && !Okular::Settings::viewContinuous() && vScroll == verticalScrollBar()->maximum() )
+    else
     {
-        // go to next page
-        if ( (int)d->document->currentPage() < d->items.count() - 1 )
+        d->controlWheelAccumulatedDelta = 0;
+
+        if ( delta <= -QWheelEvent::DefaultDeltasPerStep && !Okular::Settings::viewContinuous() && vScroll == verticalScrollBar()->maximum() )
         {
-            // more optimized than document->setNextPage and then move view to top
-            Okular::DocumentViewport newViewport = d->document->viewport();
-            newViewport.pageNumber += viewColumns();
-            if ( newViewport.pageNumber >= (int)d->items.count() )
-                newViewport.pageNumber = d->items.count() - 1;
-            newViewport.rePos.enabled = true;
-            newViewport.rePos.normalizedY = 0.0;
-            d->document->setViewport( newViewport );
+            // go to next page
+            if ( (int)d->document->currentPage() < d->items.count() - 1 )
+            {
+                // more optimized than document->setNextPage and then move view to top
+                Okular::DocumentViewport newViewport = d->document->viewport();
+                newViewport.pageNumber += viewColumns();
+                if ( newViewport.pageNumber >= (int)d->items.count() )
+                    newViewport.pageNumber = d->items.count() - 1;
+                newViewport.rePos.enabled = true;
+                newViewport.rePos.normalizedY = 0.0;
+                d->document->setViewport( newViewport );
+            }
         }
-    }
-    else if ( delta >= 120 && !Okular::Settings::viewContinuous() && vScroll == verticalScrollBar()->minimum() )
-    {
-        // go to prev page
-        if ( d->document->currentPage() > 0 )
+        else if ( delta >= QWheelEvent::DefaultDeltasPerStep && !Okular::Settings::viewContinuous() && vScroll == verticalScrollBar()->minimum() )
         {
-            // more optimized than document->setPrevPage and then move view to bottom
-            Okular::DocumentViewport newViewport = d->document->viewport();
-            newViewport.pageNumber -= viewColumns();
-            if ( newViewport.pageNumber < 0 )
-                newViewport.pageNumber = 0;
-            newViewport.rePos.enabled = true;
-            newViewport.rePos.normalizedY = 1.0;
-            d->document->setViewport( newViewport );
+            // go to prev page
+            if ( d->document->currentPage() > 0 )
+            {
+                // more optimized than document->setPrevPage and then move view to bottom
+                Okular::DocumentViewport newViewport = d->document->viewport();
+                newViewport.pageNumber -= viewColumns();
+                if ( newViewport.pageNumber < 0 )
+                    newViewport.pageNumber = 0;
+                newViewport.rePos.enabled = true;
+                newViewport.rePos.normalizedY = 1.0;
+                d->document->setViewport( newViewport );
+            }
         }
+        else
+            QAbstractScrollArea::wheelEvent( e );
     }
-    else
-        QAbstractScrollArea::wheelEvent( e );
 
     updateCursor();
 }