Cocoa: Speed up fading out scroll bars.

This patch replaces QDateTime usage with msecs since epoch to calculate
scroll bars opacity. This eliminates lots of QDateTime::msecsTo calls.

Change-Id: Ic0c26806660c192c5fc6de0dafd86b4200e3cb4c
Reviewed-by: Morten Johan Sørvig <morten.sorvig@digia.com>

2 files changed, 18 insertions, 16 deletions

diff --git a/src/widgets/styles/qmacstyle_mac.mm b/src/widgets/styles/qmacstyle_mac.mm
index 3376c3cd52..ecb3e7f222 100644
--- a/src/widgets/styles/qmacstyle_mac.mm
+++ b/src/widgets/styles/qmacstyle_mac.mm
@@ -1836,6 +1836,7 @@ void QMacStylePrivate::animate()
     }
     if (!scrollBars.isEmpty()) {
         int i = 0;
+        const qint64 dt = QDateTime::currentMSecsSinceEpoch();
         while (i < scrollBars.size()) {
             QWidget *maybeScroll = scrollBars.at(i);
             if (!maybeScroll) {
@@ -1843,9 +1844,8 @@ void QMacStylePrivate::animate()
             } else {
                 if (QScrollBar *sb = qobject_cast<QScrollBar *>(maybeScroll)) {
                     const OverlayScrollBarInfo& info = scrollBarInfos[sb];
-                    const QDateTime dt = QDateTime::currentDateTime();
-                    const qreal elapsed = qMax(info.lastHovered.msecsTo(dt),
-                                               info.lastUpdate.msecsTo(dt));
+                    const qreal elapsed = qMax(dt - info.lastHovered,
+                                               dt - info.lastUpdate);
                     const CGFloat opacity = 1.0 - qMax(0.0, (elapsed - ScrollBarFadeOutDelay) /
                                                              ScrollBarFadeOutDuration);
                     if ((opacity > 0.0 || !info.cleared) && (elapsed > ScrollBarFadeOutDelay)) {
@@ -1888,7 +1888,8 @@ bool QMacStyle::eventFilter(QObject *o, QEvent *e)
         if (QSysInfo::MacintoshVersion >= QSysInfo::MV_10_7 &&
                 [NSScroller preferredScrollerStyle] == NSScrollerStyleOverlay && scrollArea) {
             QMacStylePrivate::OverlayScrollBarInfo& info = d->scrollBarInfos[sb];
-            const qreal elapsed = info.lastUpdate.msecsTo(QDateTime::currentDateTime());
+            const qint64 dt = QDateTime::currentMSecsSinceEpoch();
+            const qreal elapsed = dt - info.lastUpdate;
             const CGFloat opacity = 1.0 - qMax(0.0, (elapsed - QMacStylePrivate::ScrollBarFadeOutDelay)
                                                           / QMacStylePrivate::ScrollBarFadeOutDuration);
             switch (e->type()) {
@@ -1897,8 +1898,8 @@ bool QMacStyle::eventFilter(QObject *o, QEvent *e)
                 // the fade out is stopped and it's set to 100% opaque
                 if (opacity > 0.0) {
                     info.hovered = true;
-                    info.lastUpdate = QDateTime::currentDateTime();
-                    info.lastHovered = QDateTime::currentDateTime();
+                    info.lastUpdate = dt;
+                    info.lastHovered = info.lastUpdate;
                     sb->update();
                     break;
                 }
@@ -5113,6 +5114,7 @@ void QMacStyle::drawComplexControl(ComplexControl cc, const QStyleOptionComplex
             }
 
 #if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_7
+            const qint64 dt = QDateTime::currentMSecsSinceEpoch();
             if (QSysInfo::MacintoshVersion >= QSysInfo::MV_10_7 &&
                 [NSScroller preferredScrollerStyle] == NSScrollerStyleOverlay &&
                 scrollBarsScrollArea(qobject_cast<const QScrollBar *>(widget)) &&
@@ -5127,7 +5129,7 @@ void QMacStyle::drawComplexControl(ComplexControl cc, const QStyleOptionComplex
                     info.lastMinimum = slider->minimum;
                     info.lastSize = slider->rect.size();
                     info.lastMaximum = slider->maximum;
-                    info.lastUpdate = QDateTime::currentDateTime();
+                    info.lastUpdate = dt;
                     showSiblings = true;
                 }
 
@@ -5139,18 +5141,18 @@ void QMacStyle::drawComplexControl(ComplexControl cc, const QStyleOptionComplex
                                            d->scrollBarInfos.value(sibling).lastUpdate);
                     info.cleared = false;
                     if (d->scrollBarInfos.value(sibling).hovered)
-                        info.lastUpdate = QDateTime::currentDateTime();
+                        info.lastUpdate = dt;
                 }
 
-                qreal elapsed = info.lastHovered.msecsTo(QDateTime::currentDateTime());
+                qreal elapsed = dt - info.lastHovered;
                 CGFloat opacity = 1.0 - qMax(0.0,
                     (elapsed - QMacStylePrivate::ScrollBarFadeOutDelay) /
                     QMacStylePrivate::ScrollBarFadeOutDuration);
                 const bool isHorizontal = slider->orientation == Qt::Horizontal;
 
                 if (info.hovered) {
-                    info.lastHovered = QDateTime::currentDateTime();
-                    info.lastUpdate = QDateTime::currentDateTime();
+                    info.lastHovered = dt;
+                    info.lastUpdate = dt;
                     opacity = 1.0;
                     // if the current scroll bar is hovered, none of the others might fade out
                     Q_FOREACH (const QScrollBar *sibling, siblings) {
@@ -5206,7 +5208,7 @@ void QMacStyle::drawComplexControl(ComplexControl cc, const QStyleOptionComplex
 
                 // afterwards we draw the knob, since we cannot drow the know w/o the track,
                 // we simulate a scrollbar with a knob from 0.0 to 1.0
-                elapsed = info.lastUpdate.msecsTo(QDateTime::currentDateTime());
+                elapsed = dt - info.lastUpdate;
                 opacity = 1.0 - qMax(0.0, (elapsed - QMacStylePrivate::ScrollBarFadeOutDelay) /
                                           QMacStylePrivate::ScrollBarFadeOutDuration);
                 info.cleared = opacity <= 0.0;
diff --git a/src/widgets/styles/qmacstyle_mac_p.h b/src/widgets/styles/qmacstyle_mac_p.h
index 2c129aa49d..ac482b8fc7 100644
--- a/src/widgets/styles/qmacstyle_mac_p.h
+++ b/src/widgets/styles/qmacstyle_mac_p.h
@@ -215,18 +215,18 @@ public:
             : lastValue(-1),
               lastMinimum(-1),
               lastMaximum(-1),
-              lastUpdate(QDateTime::currentDateTime()),
+              lastUpdate(QDateTime::currentMSecsSinceEpoch()),
               hovered(false),
-              lastHovered(QDateTime::fromTime_t(0)),
+              lastHovered(0),
               cleared(false)
         {}
         int lastValue;
         int lastMinimum;
         int lastMaximum;
         QSize lastSize;
-        QDateTime lastUpdate;
+        qint64 lastUpdate;
         bool hovered;
-        QDateTime lastHovered;
+        qint64 lastHovered;
         bool cleared;
     };
     mutable QMap<const QWidget*, OverlayScrollBarInfo> scrollBarInfos;