Support for overlay-scrollbars on Mac

On Lion scroll bars are within the scroll area itself and are not being
shown as long as the user is not scrolling.

This patch draws the new scroll bars and makes them fade away. Further
it introduces a pixel metric checking for this behaviour. It's used by
QAbstractScrollArea to put the viewport to the correct place.

Task-number: QTBUG-21673

Change-Id: Id530265043549318ac420b392de6b8642deaa4c6
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>
Reviewed-by: Gabriel de Dietrich <gabriel.dietrich-de@nokia.com>

1 files changed, 30 insertions, 8 deletions

diff --git a/src/widgets/widgets/qabstractscrollarea.cpp b/src/widgets/widgets/qabstractscrollarea.cpp
index d97b03128e..faa6933e75 100644
--- a/src/widgets/widgets/qabstractscrollarea.cpp
+++ b/src/widgets/widgets/qabstractscrollarea.cpp
@@ -52,6 +52,7 @@
 #include "qboxlayout.h"
 #include "qpainter.h"
 #include "qmargins.h"
+#include "qheaderview.h"
 
 #include <QDebug>
 
@@ -327,6 +328,11 @@ void QAbstractScrollAreaPrivate::layoutChildren()
     bool needv = (vbarpolicy == Qt::ScrollBarAlwaysOn
                   || (vbarpolicy == Qt::ScrollBarAsNeeded && vbar->minimum() < vbar->maximum()));
 
+    QStyleOption opt(0);
+    opt.init(q);
+    const int scrollOverlap = q->style()->pixelMetric(QStyle::PM_ScrollView_ScrollBarOverlap,
+                                                      &opt, q);
+
 #ifdef Q_WS_MAC
     QWidget * const window = q->window();
 
@@ -365,8 +371,6 @@ void QAbstractScrollAreaPrivate::layoutChildren()
     const QSize extSize(vsbExt, hsbExt);
 
     const QRect widgetRect = q->rect();
-    QStyleOption opt(0);
-    opt.init(q);
 
     const bool hasCornerWidget = (cornerWidget != 0);
 
@@ -394,7 +398,7 @@ void QAbstractScrollAreaPrivate::layoutChildren()
     }
 #endif
 
-    QPoint cornerOffset(needv ? vsbExt : 0, needh ? hsbExt : 0);
+    QPoint cornerOffset((needv && scrollOverlap == 0) ? vsbExt : 0, (needh && scrollOverlap == 0) ? hsbExt : 0);
     QRect controlsRect;
     QRect viewportRect;
 
@@ -403,7 +407,7 @@ void QAbstractScrollAreaPrivate::layoutChildren()
     if ((frameStyle != QFrame::NoFrame) &&
         q->style()->styleHint(QStyle::SH_ScrollView_FrameOnlyAroundContents, &opt, q)) {
         controlsRect = widgetRect;
-        const int extra = q->style()->pixelMetric(QStyle::PM_ScrollView_ScrollBarSpacing, &opt, q);
+        const int extra = scrollOverlap;
         const QPoint cornerExtra(needv ? extra : 0, needh ? extra : 0);
         QRect frameRect = widgetRect;
         frameRect.adjust(0, 0, -cornerOffset.x() - cornerExtra.x(), -cornerOffset.y() - cornerExtra.y());
@@ -418,9 +422,11 @@ void QAbstractScrollAreaPrivate::layoutChildren()
         viewportRect = QRect(controlsRect.topLeft(), controlsRect.bottomRight() - cornerOffset);
     }
 
+    cornerOffset = QPoint(needv ? vsbExt : 0, needh ? hsbExt : 0);
+
     // If we have a corner widget and are only showing one scroll bar, we need to move it
     // to make room for the corner widget.
-    if (hasCornerWidget && (needv || needh))
+    if (hasCornerWidget && (needv || needh) && scrollOverlap == 0)
         cornerOffset =  extPoint;
 
 #ifdef Q_WS_MAC
@@ -436,7 +442,7 @@ void QAbstractScrollAreaPrivate::layoutChildren()
     // Some styles paints the corner if both scorllbars are showing and there is
     // no corner widget. Also, on the Mac we paint if there is a native
     // (transparent) sizegrip in the area where a corner widget would be.
-    if ((needv && needh && hasCornerWidget == false)
+    if ((needv && needh && hasCornerWidget == false && scrollOverlap == 0)
         || ((needv || needh) 
 #ifdef Q_WS_MAC
         && hasMacSizeGrip
@@ -455,8 +461,24 @@ void QAbstractScrollAreaPrivate::layoutChildren()
         reverseCornerPaintingRect = QRect();
 #endif
 
+    // move the scrollbars away from top/left headers
+    int vHeaderRight = 0;
+    int hHeaderBottom = 0;
+    if (scrollOverlap > 0 && (needv || needh)) {
+        const QList<QHeaderView *> headers = q->findChildren<QHeaderView*>();
+        if (headers.count() <= 2) {
+            Q_FOREACH (const QHeaderView *header, headers) {
+                const QRect geo = header->geometry();
+                if (header->orientation() == Qt::Vertical && header->isVisible() && QStyle::visualRect(opt.direction, opt.rect, geo).left() <= opt.rect.width() / 2)
+                    vHeaderRight = QStyle::visualRect(opt.direction, opt.rect, geo).right();
+                else if (header->orientation() == Qt::Horizontal && header->isVisible() && geo.top() <= q->frameWidth())
+                    hHeaderBottom = geo.bottom();
+             }
+         }
+    }
+
     if (needh) {
-        QRect horizontalScrollBarRect(QPoint(controlsRect.left(), cornerPoint.y()), QPoint(cornerPoint.x() - 1, controlsRect.bottom()));
+        QRect horizontalScrollBarRect(QPoint(controlsRect.left() + vHeaderRight, cornerPoint.y()), QPoint(cornerPoint.x() - 1, controlsRect.bottom()));
 #ifdef Q_WS_MAC
         if (hasMacReverseSizeGrip)
             horizontalScrollBarRect.adjust(vsbExt, 0, 0, 0);
@@ -466,7 +488,7 @@ void QAbstractScrollAreaPrivate::layoutChildren()
     }
 
     if (needv) {
-        const QRect verticalScrollBarRect  (QPoint(cornerPoint.x(), controlsRect.top()),  QPoint(controlsRect.right(), cornerPoint.y() - 1));
+        const QRect verticalScrollBarRect  (QPoint(cornerPoint.x(), controlsRect.top() + hHeaderBottom),  QPoint(controlsRect.right(), cornerPoint.y() - 1));
         scrollBarContainers[Qt::Vertical]->setGeometry(QStyle::visualRect(opt.direction, opt.rect, verticalScrollBarRect));
         scrollBarContainers[Qt::Vertical]->raise();
     }