Allow aligning items in a grid

This change introduces two new properties, horizontalItemAlignment and verticalItemAlignment to a
Grid element. This gives the user the possibility to align the items.

Change-Id: I7322a689f1bbc1da342bd618f6c30dd8c139ee29
Reviewed-by: Alan Alpert <aalpert@rim.com>

1 files changed, 109 insertions, 2 deletions

diff --git a/src/quick/items/qquickpositioners.cpp b/src/quick/items/qquickpositioners.cpp
index 2b03ed2dc4..df80e77bfa 100644
--- a/src/quick/items/qquickpositioners.cpp
+++ b/src/quick/items/qquickpositioners.cpp
@@ -1102,6 +1102,8 @@ QQuickGrid::QQuickGrid(QQuickItem *parent)
     , m_useRowSpacing(false)
     , m_useColumnSpacing(false)
     , m_flow(LeftToRight)
+    , m_hItemAlign(AlignLeft)
+    , m_vItemAlign(AlignTop)
 {
 }
 
@@ -1248,6 +1250,7 @@ void QQuickGrid::setLayoutDirection(Qt::LayoutDirection layoutDirection)
         prePositioning();
         emit layoutDirectionChanged();
         emit effectiveLayoutDirectionChanged();
+        emit effectiveHorizontalAlignmentChanged(effectiveHAlign());
     }
 }
 
@@ -1266,6 +1269,97 @@ Qt::LayoutDirection QQuickGrid::effectiveLayoutDirection() const
     return QQuickBasePositionerPrivate::getEffectiveLayoutDirection(this);
 }
 
+/*!
+    \qmlproperty enumeration QtQuick2::Grid::horizontalItmeAlignment
+    \qmlproperty enumeration QtQuick2::Grid::verticalItemAlignment
+    \qmlproperty enumeration QtQuick2::Grid::effectiveHorizontalItemAlignment
+
+    Sets the horizontal and vertical alignment of items in the Grid. By default,
+    the items are vertically aligned to the top. Horizontal
+    alignment follows the layoutDirection of the Grid, for example when having a layoutDirection
+    from LeftToRight, the items will be aligned on the left.
+
+    The valid values for \c horizontalItemAlignment are, \c Grid.AlignLeft, \c Grid.AlignRight and
+    \c Grid.AlignHCenter.
+
+    The valid values for \c verticalItemAlignment are \c Grid.AlignTop, \c Grid.AlignBottom
+    and \c Grid.AlignVCenter.
+
+    The below images show three examples of how to align items.
+
+    \table
+    \row
+        \li
+        \li \inlineimage gridLayout_aligntopleft.png
+        \li \inlineimage gridLayout_aligntop.png
+        \li \inlineimage gridLayout_aligncenter.png
+    \row
+        \li Horizontal alignment
+        \li AlignLeft
+        \li AlignHCenter
+        \li AlignHCenter
+    \row
+        \li Vertical alignment
+        \li AlignTop
+        \li AlignTop
+        \li AlignVCenter
+    \endtable
+
+
+    When mirroring the layout using either the attached property LayoutMirroring::enabled or
+    by setting the layoutDirection, the horizontal alignment of items will be mirrored as well.
+    However, the property \c horizontalItemAlignment will remain unchanged.
+    To query the effective horizontal alignment of items, use the read-only property
+    \c effectiveHorizontalItemAlignment.
+
+    \sa Grid::layoutDirection, {LayoutMirroring}{LayoutMirroring}
+*/
+QQuickGrid::HAlignment QQuickGrid::hItemAlign() const
+{
+    return m_hItemAlign;
+}
+void QQuickGrid::setHItemAlign(HAlignment align)
+{
+    if (m_hItemAlign != align) {
+        m_hItemAlign = align;
+        prePositioning();
+        emit horizontalAlignmentChanged(align);
+        emit effectiveHorizontalAlignmentChanged(effectiveHAlign());
+    }
+}
+
+QQuickGrid::HAlignment QQuickGrid::effectiveHAlign() const
+{
+    HAlignment effectiveAlignment = m_hItemAlign;
+    if (effectiveLayoutDirection() == Qt::RightToLeft) {
+        switch (hItemAlign()) {
+        case AlignLeft:
+            effectiveAlignment = AlignRight;
+            break;
+        case AlignRight:
+            effectiveAlignment = AlignLeft;
+            break;
+        default:
+            break;
+        }
+    }
+    return effectiveAlignment;
+}
+
+
+QQuickGrid::VAlignment QQuickGrid::vItemAlign() const
+{
+    return m_vItemAlign;
+}
+void QQuickGrid::setVItemAlign(VAlignment align)
+{
+    if (m_vItemAlign != align) {
+        m_vItemAlign = align;
+        prePositioning();
+        emit verticalAlignmentChanged(align);
+    }
+}
+
 void QQuickGrid::doPositioning(QSizeF *contentSize)
 {
     //Precondition: All items in the positioned list have a valid item pointer and should be positioned
@@ -1362,9 +1456,22 @@ void QQuickGrid::doPositioning(QSizeF *contentSize)
     for (int i = 0; i < positionedItems.count(); ++i) {
         PositionedItem &child = positionedItems[i];
         qreal childXOffset = xoffset;
+
+        if (effectiveHAlign() == AlignRight)
+            childXOffset += maxColWidth[curCol] - child.item->width();
+        else if (hItemAlign() == AlignHCenter)
+            childXOffset += (maxColWidth[curCol] - child.item->width())/2.0;
+
         if (!d->isLeftToRight())
-            childXOffset -= child.item->width();
-        positionItem(childXOffset, yoffset, &child);
+            childXOffset -= maxColWidth[curCol];
+
+        qreal alignYOffset = yoffset;
+        if (m_vItemAlign == AlignVCenter)
+            alignYOffset += (maxRowHeight[curRow] - child.item->height())/2.0;
+        else if (m_vItemAlign == AlignBottom)
+            alignYOffset += maxRowHeight[curRow] - child.item->height();
+
+        positionItem(childXOffset, alignYOffset, &child);
 
         if (m_flow == LeftToRight) {
             if (d->isLeftToRight())