ListView: add support for "pull back" header & footer

[ChangeLog][QtQuick][ListView] Introduced headerPositioning and
footerPositioning properties to control whether header and footer
are positioned inline, as overlays, or so that they slide away and
can be pulled back regardless of the content position.

Change-Id: Ifef1faf1ce6acf2b55cd1b6408e22ec2de841409
Reviewed-by: Alan Alpert <aalpert@blackberry.com>
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>

1 files changed, 139 insertions, 24 deletions

diff --git a/src/quick/items/qquicklistview.cpp b/src/quick/items/qquicklistview.cpp
index e8043804fb..1b268eccf3 100644
--- a/src/quick/items/qquicklistview.cpp
+++ b/src/quick/items/qquicklistview.cpp
@@ -125,6 +125,8 @@ public:
     virtual bool showFooterForIndex(int index) const;
     virtual void updateHeader();
     virtual void updateFooter();
+    bool hasStickyHeader() const;
+    bool hasStickyFooter() const;
 
     virtual void changedVisibleIndex(int newIndex);
     virtual void initializeCurrentItem();
@@ -143,6 +145,9 @@ public:
     qreal spacing;
     QQuickListView::SnapMode snapMode;
 
+    QQuickListView::HeaderPositioning headerPositioning;
+    QQuickListView::FooterPositioning footerPositioning;
+
     QSmoothedAnimation *highlightPosAnimator;
     QSmoothedAnimation *highlightWidthAnimator;
     QSmoothedAnimation *highlightHeightAnimator;
@@ -170,6 +175,8 @@ public:
         , visiblePos(0)
         , averageSize(100.0), spacing(0.0)
         , snapMode(QQuickListView::NoSnap)
+        , headerPositioning(QQuickListView::InlineHeader)
+        , footerPositioning(QQuickListView::InlineFooter)
         , highlightPosAnimator(0), highlightWidthAnimator(0), highlightHeightAnimator(0)
         , highlightMoveVelocity(400), highlightResizeVelocity(400), highlightResizeDuration(-1)
         , sectionCriteria(0), currentSectionItem(0), nextSectionItem(0)
@@ -1048,6 +1055,9 @@ void QQuickListViewPrivate::updateStickySections()
 
     bool isFlowReversed = isContentFlowReversed();
     qreal viewPos = isFlowReversed ? -position()-size() : position();
+    qreal startPos = hasStickyHeader() ? header->endPosition() : viewPos;
+    qreal endPos = hasStickyFooter() ? footer->position() : viewPos + size();
+
     QQuickItem *sectionItem = 0;
     QQuickItem *lastSectionItem = 0;
     int index = 0;
@@ -1059,18 +1069,18 @@ void QQuickListViewPrivate::updateStickySections()
             qreal sectionSize = orient == QQuickListView::Vertical ? section->height() : section->width();
             bool visTop = true;
             if (sectionCriteria->labelPositioning() & QQuickViewSection::CurrentLabelAtStart)
-                visTop = isFlowReversed ? -sectionPos-sectionSize >= viewPos : sectionPos >= viewPos;
+                visTop = isFlowReversed ? -sectionPos-sectionSize >= startPos : sectionPos >= startPos;
             bool visBot = true;
             if (sectionCriteria->labelPositioning() & QQuickViewSection::NextLabelAtEnd)
-                visBot = isFlowReversed ? -sectionPos <= viewPos + size() : sectionPos + sectionSize < viewPos + size();
+                visBot = isFlowReversed ? -sectionPos <= endPos : sectionPos + sectionSize < endPos;
             section->setVisible(visBot && visTop);
             if (visTop && !sectionItem)
                 sectionItem = section;
             if (isFlowReversed) {
-               if (-sectionPos <= viewPos + size())
+               if (-sectionPos <= endPos)
                     lastSectionItem = section;
             } else {
-                if (sectionPos + sectionSize < viewPos + size())
+                if (sectionPos + sectionSize < endPos)
                     lastSectionItem = section;
             }
         }
@@ -1092,14 +1102,14 @@ void QQuickListViewPrivate::updateStickySections()
         qreal sectionSize = orient == QQuickListView::Vertical ? currentSectionItem->height() : currentSectionItem->width();
         bool atBeginning = orient == QQuickListView::Vertical ? (isBottomToTop() ? vData.atEnd : vData.atBeginning) : (isRightToLeft() ? hData.atEnd : hData.atBeginning);
 
-        currentSectionItem->setVisible(!atBeginning && (!header || header->endPosition() < viewPos));
-        qreal pos = isFlowReversed ? position() + size() - sectionSize : viewPos;
+        currentSectionItem->setVisible(!atBeginning && (!header || hasStickyHeader() || header->endPosition() < viewPos));
+        qreal pos = isFlowReversed ? position() + size() - sectionSize : startPos;
+        if (header)
+            pos = isFlowReversed ? qMin(-header->endPosition() - sectionSize, pos) : qMax(header->endPosition(), pos);
         if (sectionItem) {
             qreal sectionPos = orient == QQuickListView::Vertical ? sectionItem->y() : sectionItem->x();
             pos = isFlowReversed ? qMax(pos, sectionPos + sectionSize) : qMin(pos, sectionPos - sectionSize);
         }
-        if (header)
-            pos = isFlowReversed ? qMin(header->endPosition(), pos) : qMax(header->endPosition(), pos);
         if (footer)
             pos = isFlowReversed ? qMax(-footer->position(), pos) : qMin(footer->position() - sectionSize, pos);
         if (orient == QQuickListView::Vertical)
@@ -1125,13 +1135,15 @@ void QQuickListViewPrivate::updateStickySections()
 
         qreal sectionSize = orient == QQuickListView::Vertical ? nextSectionItem->height() : nextSectionItem->width();
         nextSectionItem->setVisible(!nextSection.isEmpty());
-        qreal pos = isFlowReversed ? position() : viewPos + size() - sectionSize;
+        qreal pos = isFlowReversed ? position() : endPos - sectionSize;
+        if (footer)
+            pos = isFlowReversed ? qMax(-footer->position(), pos) : qMin(footer->position() - sectionSize, pos);
         if (lastSectionItem) {
             qreal sectionPos = orient == QQuickListView::Vertical ? lastSectionItem->y() : lastSectionItem->x();
             pos = isFlowReversed ? qMin(pos, sectionPos - sectionSize) : qMax(pos, sectionPos + sectionSize);
         }
         if (header)
-            pos = isFlowReversed ? qMin(header->endPosition() - sectionSize, pos) : qMax(header->endPosition(), pos);
+            pos = isFlowReversed ? qMin(-header->endPosition() - sectionSize, pos) : qMax(header->endPosition(), pos);
         if (orient == QQuickListView::Vertical)
             nextSectionItem->setY(pos);
         else
@@ -1192,12 +1204,11 @@ void QQuickListViewPrivate::updateCurrentSection()
         return;
     }
     bool inlineSections = sectionCriteria->labelPositioning() & QQuickViewSection::InlineLabels;
-    qreal sectionThreshold = position();
-    if (currentSectionItem && !inlineSections)
-        sectionThreshold += orient == QQuickListView::Vertical ? currentSectionItem->height() : currentSectionItem->width();
+    qreal viewPos = isContentFlowReversed() ? -position()-size() : position();
+    qreal startPos = hasStickyHeader() ? header->endPosition() : viewPos;
     int index = 0;
     int modelIndex = visibleIndex;
-    while (index < visibleItems.count() && visibleItems.at(index)->endPosition() <= sectionThreshold) {
+    while (index < visibleItems.count() && visibleItems.at(index)->endPosition() <= startPos) {
         if (visibleItems.at(index)->index != -1)
             modelIndex = visibleItems.at(index)->index;
         ++index;
@@ -1220,7 +1231,7 @@ void QQuickListViewPrivate::updateCurrentSection()
         // section when that changes.  Clearing lastVisibleSection will also
         // force searching.
         QString lastSection = currentSection;
-        qreal endPos = isContentFlowReversed() ? -position() : position() + size();
+        qreal endPos = hasStickyFooter() ? footer->position() : viewPos + size();
         if (nextSectionItem && !inlineSections)
             endPos -= orient == QQuickListView::Vertical ? nextSectionItem->height() : nextSectionItem->width();
         while (index < visibleItems.count() && static_cast<FxListItemSG*>(visibleItems.at(index))->itemPosition() < endPos) {
@@ -1315,13 +1326,21 @@ void QQuickListViewPrivate::updateFooter()
 
     FxListItemSG *listItem = static_cast<FxListItemSG*>(footer);
     if (visibleItems.count()) {
-        qreal endPos = lastPosition();
-        if (findLastVisibleIndex() == model->count()-1) {
-            listItem->setPosition(endPos);
+        if (footerPositioning == QQuickListView::OverlayFooter) {
+            listItem->setPosition(isContentFlowReversed() ? -position() - footerSize() : position() + size() - footerSize());
+        } else if (footerPositioning == QQuickListView::PullBackFooter) {
+            qreal viewPos = isContentFlowReversed() ? -position() : position() + size();
+            qreal clampedPos = qBound(originPosition() - footerSize() + size(), listItem->position(), lastPosition());
+            listItem->setPosition(qBound(viewPos - footerSize(), clampedPos, viewPos));
         } else {
-            qreal visiblePos = position() + q->height();
-            if (endPos <= visiblePos || listItem->position() < endPos)
+            qreal endPos = lastPosition();
+            if (findLastVisibleIndex() == model->count()-1) {
                 listItem->setPosition(endPos);
+            } else {
+                qreal visiblePos = position() + q->height();
+                if (endPos <= visiblePos || listItem->position() < endPos)
+                    listItem->setPosition(endPos);
+            }
         }
     } else {
         listItem->setPosition(visiblePos);
@@ -1347,12 +1366,20 @@ void QQuickListViewPrivate::updateHeader()
     FxListItemSG *listItem = static_cast<FxListItemSG*>(header);
     if (listItem) {
         if (visibleItems.count()) {
-            qreal startPos = originPosition();
-            if (visibleIndex == 0) {
-                listItem->setPosition(startPos - headerSize());
+            if (headerPositioning == QQuickListView::OverlayHeader) {
+                listItem->setPosition(isContentFlowReversed() ? -position() - size() : position());
+            } else if (headerPositioning == QQuickListView::PullBackHeader) {
+                qreal viewPos = isContentFlowReversed() ? -position() - size() : position();
+                qreal clampedPos = qBound(originPosition() - headerSize(), listItem->position(), lastPosition() - headerSize() - size());
+                listItem->setPosition(qBound(viewPos - headerSize(), clampedPos, viewPos));
             } else {
-                if (position() <= startPos || listItem->position() > startPos - headerSize())
+                qreal startPos = originPosition();
+                if (visibleIndex == 0) {
                     listItem->setPosition(startPos - headerSize());
+                } else {
+                    if (position() <= startPos || listItem->position() > startPos - headerSize())
+                        listItem->setPosition(startPos - headerSize());
+                }
             }
         } else {
             listItem->setPosition(-headerSize());
@@ -1363,6 +1390,16 @@ void QQuickListViewPrivate::updateHeader()
         emit q->headerItemChanged();
 }
 
+bool QQuickListViewPrivate::hasStickyHeader() const
+{
+    return header && headerPositioning != QQuickListView::InlineHeader;
+}
+
+bool QQuickListViewPrivate::hasStickyFooter() const
+{
+    return footer && footerPositioning != QQuickListView::InlineFooter;
+}
+
 void QQuickListViewPrivate::itemGeometryChanged(QQuickItem *item, const QRectF &newGeometry, const QRectF &oldGeometry)
 {
     Q_Q(QQuickListView);
@@ -2443,6 +2480,80 @@ void QQuickListView::setSnapMode(SnapMode mode)
 */
 
 /*!
+    \qmlproperty enumeration QtQuick::ListView::headerPositioning
+    \since Qt 5.4
+
+    This property determines the positioning of the \l{headerItem}{header item}.
+
+    The possible values are:
+    \list
+    \li ListView.InlineHeader (default) - the header is positioned in the beginning
+    of the content and moves together with the content like an ordinary item.
+    \li ListView.OverlayHeader - the header is positioned in the beginning of the view.
+    \li ListView.PullBackHeader - the header is positioned in the beginning of the view.
+    The header can be pushed away by moving the content forwards, and pulled back by
+    moving the content backwards.
+    \endlist
+*/
+QQuickListView::HeaderPositioning QQuickListView::headerPositioning() const
+{
+    Q_D(const QQuickListView);
+    return d->headerPositioning;
+}
+
+void QQuickListView::setHeaderPositioning(QQuickListView::HeaderPositioning positioning)
+{
+    Q_D(QQuickListView);
+    if (d->headerPositioning != positioning) {
+        d->applyPendingChanges();
+        d->headerPositioning = positioning;
+        if (isComponentComplete()) {
+            d->updateHeader();
+            d->updateViewport();
+            d->fixupPosition();
+        }
+        emit headerPositioningChanged();
+    }
+}
+
+/*!
+    \qmlproperty enumeration QtQuick::ListView::footerPositioning
+    \since Qt 5.4
+
+    This property determines the positioning of the \l{footerItem}{footer item}.
+
+    The possible values are:
+    \list
+    \li ListView.InlineFooter (default) - the footer is positioned in the end
+    of the content and moves together with the content like an ordinary item.
+    \li ListView.OverlayFooter - the footer is positioned in the end of the view.
+    \li ListView.PullBackFooter - the footer is positioned in the end of the view.
+    The footer can be pushed away by moving the content backwards, and pulled back by
+    moving the content forwards.
+    \endlist
+*/
+QQuickListView::FooterPositioning QQuickListView::footerPositioning() const
+{
+    Q_D(const QQuickListView);
+    return d->footerPositioning;
+}
+
+void QQuickListView::setFooterPositioning(QQuickListView::FooterPositioning positioning)
+{
+    Q_D(QQuickListView);
+    if (d->footerPositioning != positioning) {
+        d->applyPendingChanges();
+        d->footerPositioning = positioning;
+        if (isComponentComplete()) {
+            d->updateFooter();
+            d->updateViewport();
+            d->fixupPosition();
+        }
+        emit footerPositioningChanged();
+    }
+}
+
+/*!
     \qmlproperty Transition QtQuick::ListView::populate
 
     This property holds the transition to apply to the items that are initially created
@@ -2816,6 +2927,10 @@ void QQuickListView::viewportMoved(Qt::Orientations orient)
         }
         d->inFlickCorrection = false;
     }
+    if (d->hasStickyHeader())
+        d->updateHeader();
+    if (d->hasStickyFooter())
+        d->updateFooter();
     if (d->sectionCriteria) {
         d->updateCurrentSection();
         d->updateStickySections();