Add uniformCellWidths and uniformCellHeights to QGridLayoutEngine

Some users wish to make layouts with uniform column widths or
uniform row heights, ignoring the sizeHints of individual items.
This patch enables this mode in the QGridLayoutEngine, used
by the QuickLayout.

The sizeHints are aggregated and their average preferred size
and extreme minimum and maximum sizes are respected in the
layout.

Change-Id: Ibb9409eb0a11a1ce8bb305f44a4cb0071c871ec9
Reviewed-by: Jan Arve Sæther <jan-arve.saether@qt.io>

2 files changed, 59 insertions, 0 deletions

diff --git a/src/gui/util/qgridlayoutengine.cpp b/src/gui/util/qgridlayoutengine.cpp
index 1cc42d3260..9d64c87bde 100644
--- a/src/gui/util/qgridlayoutengine.cpp
+++ b/src/gui/util/qgridlayoutengine.cpp
@@ -758,6 +758,8 @@ QGridLayoutEngine::QGridLayoutEngine(Qt::Alignment defaultAlignment, bool snapTo
     m_visualDirection = Qt::LeftToRight;
     m_defaultAlignment = defaultAlignment;
     m_snapToPixelGrid = snapToPixelGrid;
+    m_uniformCellWidths = false;
+    m_uniformCellHeights = false;
     invalidate();
 }
 
@@ -875,6 +877,34 @@ qreal QGridLayoutEngine::rowSizeHint(Qt::SizeHint which, int row, Qt::Orientatio
     return q_infos[orientation].boxes.value(row).q_sizes(which);
 }
 
+bool QGridLayoutEngine::uniformCellWidths() const
+{
+    return m_uniformCellWidths;
+}
+
+void QGridLayoutEngine::setUniformCellWidths(bool uniformCellWidths)
+{
+    if (m_uniformCellWidths == uniformCellWidths)
+        return;
+
+    m_uniformCellWidths = uniformCellWidths;
+    invalidate();
+}
+
+bool QGridLayoutEngine::uniformCellHeights() const
+{
+    return m_uniformCellHeights;
+}
+
+void QGridLayoutEngine::setUniformCellHeights(bool uniformCellHeights)
+{
+    if (m_uniformCellHeights == uniformCellHeights)
+        return;
+
+    m_uniformCellHeights = uniformCellHeights;
+    invalidate();
+}
+
 void QGridLayoutEngine::setRowAlignment(int row, Qt::Alignment alignment,
                                         Qt::Orientation orientation)
 {
@@ -1499,6 +1529,27 @@ void QGridLayoutEngine::fillRowData(QGridLayoutRowData *rowData,
             rowSpacing = qMax(windowMargin, rowSpacing);
         }
     }
+
+    if (rowData->boxes.size() > 1 &&
+        ((orientation == Qt::Horizontal && m_uniformCellWidths) ||
+        (orientation == Qt::Vertical && m_uniformCellHeights))) {
+        qreal averagePreferredSize = 0.;
+        qreal minimumMaximumSize = std::numeric_limits<qreal>::max();
+        qreal maximumMinimumSize = 0.;
+        for (const auto &box : rowData->boxes) {
+            averagePreferredSize += box.q_preferredSize;
+            minimumMaximumSize = qMin(minimumMaximumSize, box.q_maximumSize);
+            maximumMinimumSize = qMax(maximumMinimumSize, box.q_minimumSize);
+        }
+        averagePreferredSize /= rowData->boxes.size();
+        minimumMaximumSize = qMax(minimumMaximumSize, maximumMinimumSize);
+        averagePreferredSize = qBound(maximumMinimumSize, averagePreferredSize, minimumMaximumSize);
+        for (auto &box : rowData->boxes) {
+            box.q_preferredSize = averagePreferredSize;
+            box.q_minimumSize = maximumMinimumSize;
+            box.q_maximumSize = minimumMaximumSize;
+        }
+    }
 }
 
 void QGridLayoutEngine::ensureEffectiveFirstAndLastRows() const
diff --git a/src/gui/util/qgridlayoutengine_p.h b/src/gui/util/qgridlayoutengine_p.h
index 8344d488c1..e21d89dd2e 100644
--- a/src/gui/util/qgridlayoutengine_p.h
+++ b/src/gui/util/qgridlayoutengine_p.h
@@ -334,6 +334,12 @@ public:
     qreal rowSizeHint(Qt::SizeHint which, int row,
                       Qt::Orientation orientation = Qt::Vertical) const;
 
+    bool uniformCellWidths() const;
+    void setUniformCellWidths(bool uniformCellWidths);
+
+    bool uniformCellHeights() const;
+    void setUniformCellHeights(bool uniformCellHeights);
+
     void setRowAlignment(int row, Qt::Alignment alignment, Qt::Orientation orientation);
     Qt::Alignment rowAlignment(int row, Qt::Orientation orientation) const;
 
@@ -415,6 +421,8 @@ private:
     // Configuration
     Qt::Alignment m_defaultAlignment;
     unsigned m_snapToPixelGrid : 1;
+    unsigned m_uniformCellWidths : 1;
+    unsigned m_uniformCellHeights : 1;
 
     // Lazily computed from the above user input
     mutable QHVContainer<int> q_cachedEffectiveFirstRows;