Separate width and height info in the layouting code

By separating the width and height info, we can save some unnecessary
overhead in terms of memory and CPU cycles, and make the calculation of
the height of a row (or the width of a column in Compact View) a bit
simpler.

To achieve this, this patch extends the concept of "logical rows"
(which are actually columns in Compact View) to "logical width" and
"logical height" (which is the actual height and width, respectively, in
 Compact View). The distinction between rows/columns and "logical"
rows/columns may be a bit confusing, but the confusion is already in the
current code, and I hope that it will be mitigated a bit by prefixing
the corresponding variables with "logical".

REVIEW: 118454

8 files changed, 65 insertions, 60 deletions

diff --git a/src/kitemviews/kitemlistview.cpp b/src/kitemviews/kitemlistview.cpp
index 222a29cf5..281258898 100644
--- a/src/kitemviews/kitemlistview.cpp
+++ b/src/kitemviews/kitemlistview.cpp
@@ -459,9 +459,9 @@ int KItemListView::lastVisibleIndex() const
     return m_layouter->lastVisibleIndex();
 }
 
-void KItemListView::calculateItemSizeHints(QVector<QSizeF>& sizeHints) const
+void KItemListView::calculateItemSizeHints(QVector<qreal>& logicalHeightHints, qreal& logicalWidthHint) const
 {
-    widgetCreator()->calculateItemSizeHints(sizeHints, this);
+    widgetCreator()->calculateItemSizeHints(logicalHeightHints, logicalWidthHint, this);
 }
 
 void KItemListView::setSupportsItemExpanding(bool supportsExpanding)
diff --git a/src/kitemviews/kitemlistview.h b/src/kitemviews/kitemlistview.h
index 8a522a686..cf6f27c03 100644
--- a/src/kitemviews/kitemlistview.h
+++ b/src/kitemviews/kitemlistview.h
@@ -194,12 +194,14 @@ public:
     int lastVisibleIndex() const;
 
     /**
-     * @return Required size for all items in the model.
-     *         The returned value might be larger than KItemListView::itemSize().
+     * @return Calculates the required size for all items in the model.
+     *         It might be larger than KItemListView::itemSize().
      *         In this case the layout grid will be stretched to assure an
      *         unclipped item.
+     *         NOTE: the logical height (width) is actually the
+     *         width (height) if the scroll orientation is Qt::Vertical!
      */
-    void calculateItemSizeHints(QVector<QSizeF>& sizeHints) const;
+    void calculateItemSizeHints(QVector<qreal>& logicalHeightHints, qreal& logicalWidthHint) const;
 
     /**
      * If set to true, items having child-items can be expanded to show the child-items as
@@ -805,7 +807,7 @@ public:
 
     virtual void recycle(KItemListWidget* widget);
 
-    virtual void calculateItemSizeHints(QVector<QSizeF>& sizeHints, const KItemListView* view) const = 0;
+    virtual void calculateItemSizeHints(QVector<qreal>& logicalHeightHints, qreal& logicalWidthHint, const KItemListView* view) const = 0;
 
     virtual qreal preferredRoleColumnWidth(const QByteArray& role,
                                            int index,
@@ -824,7 +826,7 @@ public:
 
     virtual KItemListWidget* create(KItemListView* view);
 
-    virtual void calculateItemSizeHints(QVector<QSizeF>& sizeHints, const KItemListView* view) const;
+    virtual void calculateItemSizeHints(QVector<qreal>& logicalHeightHints, qreal& logicalWidthHint, const KItemListView* view) const;
 
     virtual qreal preferredRoleColumnWidth(const QByteArray& role,
                                            int index,
@@ -857,9 +859,9 @@ KItemListWidget* KItemListWidgetCreator<T>::create(KItemListView* view)
 }
 
 template<class T>
-void KItemListWidgetCreator<T>::calculateItemSizeHints(QVector<QSizeF>& sizeHints, const KItemListView* view) const
+void KItemListWidgetCreator<T>::calculateItemSizeHints(QVector<qreal>& logicalHeightHints, qreal& logicalWidthHint, const KItemListView* view) const
 {
-    return m_informant->calculateItemSizeHints(sizeHints, view);
+    return m_informant->calculateItemSizeHints(logicalHeightHints, logicalWidthHint, view);
 }
 
 template<class T>
diff --git a/src/kitemviews/kitemlistwidget.h b/src/kitemviews/kitemlistwidget.h
index cfb9155eb..a06bb5c9c 100644
--- a/src/kitemviews/kitemlistwidget.h
+++ b/src/kitemviews/kitemlistwidget.h
@@ -49,7 +49,7 @@ public:
     KItemListWidgetInformant();
     virtual ~KItemListWidgetInformant();
 
-    virtual void calculateItemSizeHints(QVector<QSizeF>& sizeHints, const KItemListView* view) const = 0;
+    virtual void calculateItemSizeHints(QVector<qreal>& logicalHeightHints, qreal& logicalWidthHint, const KItemListView* view) const = 0;
 
     virtual qreal preferredRoleColumnWidth(const QByteArray& role,
                                            int index,
diff --git a/src/kitemviews/kstandarditemlistwidget.cpp b/src/kitemviews/kstandarditemlistwidget.cpp
index 037226997..e0375480e 100644
--- a/src/kitemviews/kstandarditemlistwidget.cpp
+++ b/src/kitemviews/kstandarditemlistwidget.cpp
@@ -55,19 +55,19 @@ KStandardItemListWidgetInformant::~KStandardItemListWidgetInformant()
 {
 }
 
-void KStandardItemListWidgetInformant::calculateItemSizeHints(QVector<QSizeF>& sizeHints, const KItemListView* view) const
+void KStandardItemListWidgetInformant::calculateItemSizeHints(QVector<qreal>& logicalHeightHints, qreal& logicalWidthHint, const KItemListView* view) const
 {
     switch (static_cast<const KStandardItemListView*>(view)->itemLayout()) {
     case KStandardItemListWidget::IconsLayout:
-        calculateIconsLayoutItemSizeHints(sizeHints, view);
+        calculateIconsLayoutItemSizeHints(logicalHeightHints, logicalWidthHint, view);
         break;
 
     case KStandardItemListWidget::CompactLayout:
-        calculateCompactLayoutItemSizeHints(sizeHints, view);
+        calculateCompactLayoutItemSizeHints(logicalHeightHints, logicalWidthHint, view);
         break;
 
     case KStandardItemListWidget::DetailsLayout:
-        calculateDetailsLayoutItemSizeHints(sizeHints, view);
+        calculateDetailsLayoutItemSizeHints(logicalHeightHints, logicalWidthHint, view);
         break;
 
     default:
@@ -138,7 +138,7 @@ QFont KStandardItemListWidgetInformant::customizedFontForLinks(const QFont& base
     return baseFont;
 }
 
-void KStandardItemListWidgetInformant::calculateIconsLayoutItemSizeHints(QVector<QSizeF>& sizeHints, const KItemListView* view) const
+void KStandardItemListWidgetInformant::calculateIconsLayoutItemSizeHints(QVector<qreal>& logicalHeightHints, qreal& logicalWidthHint, const KItemListView* view) const
 {
     const KItemListStyleOption& option = view->styleOption();
     const QFont& normalFont = option.font;
@@ -154,8 +154,8 @@ void KStandardItemListWidgetInformant::calculateIconsLayoutItemSizeHints(QVector
     QTextOption textOption(Qt::AlignHCenter);
     textOption.setWrapMode(QTextOption::WrapAtWordBoundaryOrAnywhere);
 
-    for (int index = 0; index < sizeHints.count(); ++index) {
-        if (!sizeHints.at(index).isEmpty()) {
+    for (int index = 0; index < logicalHeightHints.count(); ++index) {
+        if (logicalHeightHints.at(index) > 0.0) {
             continue;
         }
 
@@ -186,11 +186,13 @@ void KStandardItemListWidgetInformant::calculateIconsLayoutItemSizeHints(QVector
         // Add one line for each additional information
         textHeight += additionalRolesSpacing;
 
-        sizeHints[index] = QSizeF(itemWidth, textHeight + spacingAndIconHeight);
+        logicalHeightHints[index] = textHeight + spacingAndIconHeight;
     }
+
+    logicalWidthHint = itemWidth;
 }
 
-void KStandardItemListWidgetInformant::calculateCompactLayoutItemSizeHints(QVector<QSizeF>& sizeHints, const KItemListView* view) const
+void KStandardItemListWidgetInformant::calculateCompactLayoutItemSizeHints(QVector<qreal>& logicalHeightHints, qreal& logicalWidthHint, const KItemListView* view) const
 {
     const KItemListStyleOption& option = view->styleOption();
     const QFontMetrics& normalFontMetrics = option.fontMetrics;
@@ -204,8 +206,8 @@ void KStandardItemListWidgetInformant::calculateCompactLayoutItemSizeHints(QVect
 
     const QFontMetrics linkFontMetrics(customizedFontForLinks(option.font));
 
-    for (int index = 0; index < sizeHints.count(); ++index) {
-        if (!sizeHints.at(index).isEmpty()) {
+    for (int index = 0; index < logicalHeightHints.count(); ++index) {
+        if (logicalHeightHints.at(index) > 0.0) {
             continue;
         }
 
@@ -232,22 +234,18 @@ void KStandardItemListWidgetInformant::calculateCompactLayoutItemSizeHints(QVect
             width = maxWidth;
         }
 
-        sizeHints[index] = QSizeF(width, height);
+        logicalHeightHints[index] = width;
     }
+
+    logicalWidthHint = height;
 }
 
-void KStandardItemListWidgetInformant::calculateDetailsLayoutItemSizeHints(QVector<QSizeF>& sizeHints, const KItemListView* view) const
+void KStandardItemListWidgetInformant::calculateDetailsLayoutItemSizeHints(QVector<qreal>& logicalHeightHints, qreal& logicalWidthHint, const KItemListView* view) const
 {
     const KItemListStyleOption& option = view->styleOption();
     const qreal height = option.padding * 2 + qMax(option.iconSize, option.fontMetrics.height());
-
-    for (int index = 0; index < sizeHints.count(); ++index) {
-        if (!sizeHints.at(index).isEmpty()) {
-            continue;
-        }
-
-        sizeHints[index] = QSizeF(-1, height);
-    }
+    logicalHeightHints.fill(height);
+    logicalWidthHint = -1.0;
 }
 
 KStandardItemListWidget::KStandardItemListWidget(KItemListWidgetInformant* informant, QGraphicsItem* parent) :
diff --git a/src/kitemviews/kstandarditemlistwidget.h b/src/kitemviews/kstandarditemlistwidget.h
index ba426d054..4f7a9136e 100644
--- a/src/kitemviews/kstandarditemlistwidget.h
+++ b/src/kitemviews/kstandarditemlistwidget.h
@@ -38,7 +38,7 @@ public:
     KStandardItemListWidgetInformant();
     virtual ~KStandardItemListWidgetInformant();
 
-    virtual void calculateItemSizeHints(QVector<QSizeF>& sizeHints, const KItemListView* view) const;
+    virtual void calculateItemSizeHints(QVector<qreal>& logicalHeightHints, qreal& logicalWidthHint, const KItemListView* view) const;
 
     virtual qreal preferredRoleColumnWidth(const QByteArray& role,
                                            int index,
@@ -73,9 +73,9 @@ protected:
     */
     virtual QFont customizedFontForLinks(const QFont& baseFont) const;
 
-    void calculateIconsLayoutItemSizeHints(QVector<QSizeF>& sizeHints, const KItemListView* view) const;
-    void calculateCompactLayoutItemSizeHints(QVector<QSizeF>& sizeHints, const KItemListView* view) const;
-    void calculateDetailsLayoutItemSizeHints(QVector<QSizeF>& sizeHints, const KItemListView* view) const;
+    void calculateIconsLayoutItemSizeHints(QVector<qreal>& logicalHeightHints, qreal& logicalWidthHint, const KItemListView* view) const;
+    void calculateCompactLayoutItemSizeHints(QVector<qreal>& logicalHeightHints, qreal& logicalWidthHint, const KItemListView* view) const;
+    void calculateDetailsLayoutItemSizeHints(QVector<qreal>& logicalHeightHints, qreal& logicalWidthHint, const KItemListView* view) const;
 
     friend class KStandardItemListWidget; // Accesses roleText()
 };
diff --git a/src/kitemviews/private/kitemlistsizehintresolver.cpp b/src/kitemviews/private/kitemlistsizehintresolver.cpp
index 029beddf9..1d8067026 100644
--- a/src/kitemviews/private/kitemlistsizehintresolver.cpp
+++ b/src/kitemviews/private/kitemlistsizehintresolver.cpp
@@ -23,7 +23,8 @@
 
 KItemListSizeHintResolver::KItemListSizeHintResolver(const KItemListView* itemListView) :
     m_itemListView(itemListView),
-    m_sizeHintCache(),
+    m_logicalHeightHintCache(),
+    m_logicalWidthHint(0.0),
     m_needsResolving(false)
 {
 }
@@ -35,7 +36,7 @@ KItemListSizeHintResolver::~KItemListSizeHintResolver()
 QSizeF KItemListSizeHintResolver::sizeHint(int index)
 {
     updateCache();
-    return m_sizeHintCache.at(index);
+    return QSizeF(m_logicalWidthHint, m_logicalHeightHintCache.at(index));
 }
 
 void KItemListSizeHintResolver::itemsInserted(const KItemRangeList& itemRanges)
@@ -45,15 +46,15 @@ void KItemListSizeHintResolver::itemsInserted(const KItemRangeList& itemRanges)
         insertedCount += range.count;
     }
 
-    const int currentCount = m_sizeHintCache.count();
-    m_sizeHintCache.reserve(currentCount + insertedCount);
+    const int currentCount = m_logicalHeightHintCache.count();
+    m_logicalHeightHintCache.reserve(currentCount + insertedCount);
 
     // We build the new list from the end to the beginning to mimize the
     // number of moves.
-    m_sizeHintCache.insert(m_sizeHintCache.end(), insertedCount, QSizeF());
+    m_logicalHeightHintCache.insert(m_logicalHeightHintCache.end(), insertedCount, 0.0);
 
     int sourceIndex = currentCount - 1;
-    int targetIndex = m_sizeHintCache.count() - 1;
+    int targetIndex = m_logicalHeightHintCache.count() - 1;
     int itemsToInsertBeforeCurrentRange = insertedCount;
 
     for (int rangeIndex = itemRanges.count() - 1; rangeIndex >= 0; --rangeIndex) {
@@ -62,33 +63,33 @@ void KItemListSizeHintResolver::itemsInserted(const KItemRangeList& itemRanges)
 
         // First: move all existing items that must be put behind 'range'.
         while (targetIndex >= itemsToInsertBeforeCurrentRange + range.index + range.count) {
-            m_sizeHintCache[targetIndex] = m_sizeHintCache[sourceIndex];
+            m_logicalHeightHintCache[targetIndex] = m_logicalHeightHintCache[sourceIndex];
             --sourceIndex;
             --targetIndex;
         }
 
         // Then: insert QSizeF() for the items which are inserted into 'range'.
         while (targetIndex >= itemsToInsertBeforeCurrentRange + range.index) {
-            m_sizeHintCache[targetIndex] = QSizeF();
+            m_logicalHeightHintCache[targetIndex] = 0.0;
             --targetIndex;
         }
     }
 
     m_needsResolving = true;
 
-    Q_ASSERT(m_sizeHintCache.count() == m_itemListView->model()->count());
+    Q_ASSERT(m_logicalHeightHintCache.count() == m_itemListView->model()->count());
 }
 
 void KItemListSizeHintResolver::itemsRemoved(const KItemRangeList& itemRanges)
 {
-    const QVector<QSizeF>::iterator begin = m_sizeHintCache.begin();
-    const QVector<QSizeF>::iterator end = m_sizeHintCache.end();
+    const QVector<qreal>::iterator begin = m_logicalHeightHintCache.begin();
+    const QVector<qreal>::iterator end = m_logicalHeightHintCache.end();
 
     KItemRangeList::const_iterator rangeIt = itemRanges.constBegin();
     const KItemRangeList::const_iterator rangeEnd = itemRanges.constEnd();
 
-    QVector<QSizeF>::iterator destIt = begin + rangeIt->index;
-    QVector<QSizeF>::iterator srcIt = destIt + rangeIt->count;
+    QVector<qreal>::iterator destIt = begin + rangeIt->index;
+    QVector<qreal>::iterator srcIt = destIt + rangeIt->count;
 
     ++rangeIt;
 
@@ -104,33 +105,33 @@ void KItemListSizeHintResolver::itemsRemoved(const KItemRangeList& itemRanges)
         }
     }
 
-    m_sizeHintCache.erase(destIt, end);
+    m_logicalHeightHintCache.erase(destIt, end);
 
     // Note that the cache size might temporarily not match the model size if
     // this function is called from KItemListView::setModel() to empty the cache.
-    if (!m_sizeHintCache.isEmpty() && m_itemListView->model()) {
-        Q_ASSERT(m_sizeHintCache.count() == m_itemListView->model()->count());
+    if (!m_logicalHeightHintCache.isEmpty() && m_itemListView->model()) {
+        Q_ASSERT(m_logicalHeightHintCache.count() == m_itemListView->model()->count());
     }
 }
 
 void KItemListSizeHintResolver::itemsMoved(const KItemRange& range, const QList<int>& movedToIndexes)
 {
-    QVector<QSizeF> newSizeHintCache(m_sizeHintCache);
+    QVector<qreal> newLogicalHeightHintCache(m_logicalHeightHintCache);
 
     const int movedRangeEnd = range.index + range.count;
     for (int i = range.index; i < movedRangeEnd; ++i) {
         const int newIndex = movedToIndexes.at(i - range.index);
-        newSizeHintCache[newIndex] = m_sizeHintCache.at(i);
+        newLogicalHeightHintCache[newIndex] = m_logicalHeightHintCache.at(i);
     }
 
-    m_sizeHintCache = newSizeHintCache;
+    m_logicalHeightHintCache = newLogicalHeightHintCache;
 }
 
 void KItemListSizeHintResolver::itemsChanged(int index, int count, const QSet<QByteArray>& roles)
 {
     Q_UNUSED(roles);
     while (count) {
-        m_sizeHintCache[index] = QSizeF();
+        m_logicalHeightHintCache[index] = 0.0;
         ++index;
         --count;
     }
@@ -140,14 +141,14 @@ void KItemListSizeHintResolver::itemsChanged(int index, int count, const QSet<QB
 
 void KItemListSizeHintResolver::clearCache()
 {
-    m_sizeHintCache.fill(QSizeF());
+    m_logicalHeightHintCache.fill(0.0);
     m_needsResolving = true;
 }
 
 void KItemListSizeHintResolver::updateCache()
 {
     if (m_needsResolving) {
-        m_itemListView->calculateItemSizeHints(m_sizeHintCache);
+        m_itemListView->calculateItemSizeHints(m_logicalHeightHintCache, m_logicalWidthHint);
         m_needsResolving = false;
     }
 }
diff --git a/src/kitemviews/private/kitemlistsizehintresolver.h b/src/kitemviews/private/kitemlistsizehintresolver.h
index 86580bf7b..a0ad033f3 100644
--- a/src/kitemviews/private/kitemlistsizehintresolver.h
+++ b/src/kitemviews/private/kitemlistsizehintresolver.h
@@ -48,7 +48,8 @@ public:
 
 private:
     const KItemListView* m_itemListView;
-    mutable QVector<QSizeF> m_sizeHintCache;
+    mutable QVector<qreal> m_logicalHeightHintCache;
+    mutable qreal m_logicalWidthHint;
     bool m_needsResolving;
 };
 
diff --git a/src/kitemviews/private/kitemlistviewlayouter.cpp b/src/kitemviews/private/kitemlistviewlayouter.cpp
index 9da5384d4..04325c7d0 100644
--- a/src/kitemviews/private/kitemlistviewlayouter.cpp
+++ b/src/kitemviews/private/kitemlistviewlayouter.cpp
@@ -239,6 +239,7 @@ QRectF KItemListViewLayouter::itemRect(int index) const
         // to get the physical horizontal direction
         QPointF pos(y, x);
         pos.rx() -= m_scrollOffset;
+        sizeHint.transpose();
         return QRectF(pos, sizeHint);
     }
 
@@ -282,7 +283,9 @@ QRectF KItemListViewLayouter::groupHeaderRect(int index) const
                 break;
             }
 
-            const qreal itemWidth = m_sizeHintResolver->sizeHint(index).width();
+            const qreal itemWidth = (m_scrollOrientation == Qt::Vertical)
+                                     ? m_sizeHintResolver->sizeHint(index).width()
+                                     : m_sizeHintResolver->sizeHint(index).height();
 
             if (itemWidth > headerWidth) {
                 headerWidth = itemWidth;
@@ -461,7 +464,7 @@ void KItemListViewLayouter::doLayout()
             while (index < itemCount && column < m_columnCount) {
                 qreal requiredItemHeight = itemSize.height();
                 const QSizeF sizeHint = m_sizeHintResolver->sizeHint(index);
-                const qreal sizeHintHeight = horizontalScrolling ? sizeHint.width() : sizeHint.height();
+                const qreal sizeHintHeight = sizeHint.height();
                 if (sizeHintHeight > requiredItemHeight) {
                     requiredItemHeight = sizeHintHeight;
                 }