Adjust sizes when snapping layout items to pixel grid

When "importing" the size hints into the cells, make sure that
the cells minimum sizes are ceiled up to the closest integer.

Change-Id: Id00177468e8b1e12bc1231c7351b2136f94f7300
Task-number: QTBUG-41216
Reviewed-by: Paul Olav Tvete <paul.tvete@theqtcompany.com>

2 files changed, 33 insertions, 14 deletions

diff --git a/src/gui/util/qgridlayoutengine.cpp b/src/gui/util/qgridlayoutengine.cpp
index ae8bde8910..20bc7166ab 100644
--- a/src/gui/util/qgridlayoutengine.cpp
+++ b/src/gui/util/qgridlayoutengine.cpp
@@ -416,8 +416,23 @@ void QGridLayoutRowData::calculateGeometries(int start, int end, qreal targetSiz
 #endif
     }
     if (snapToPixelGrid) {
-        for (int i = 0; i < n; ++i)
-            positions[i] = qround(positions[i]);
+        for (int i = 0; i < n; ++i) {
+            const qreal oldpos = positions[i];
+            positions[i] = qround(oldpos);
+            const qreal delta = positions[i] - oldpos;
+            sizes[i] -= delta;
+            if (i > 0)
+                sizes[i - 1] += delta;
+        }
+
+        sizes[n - 1] = targetSize - positions[n - 1];
+        // This loop serves two purposes:
+        // 1. round off the small epsilons produced by the above loop.
+        // 2. avoid that the above loop didn't make the cell width smaller than its minimum constraint.
+        for (int i = 0; i < n; ++i) {
+            const QGridLayoutBox &box = boxes.at(start + i);
+            sizes[i] = qMax(box.q_minimumSize, qround(sizes[i]));
+        }
     }
 
     if (descents) {
@@ -569,7 +584,7 @@ QLayoutPolicy::ControlTypes QGridLayoutItem::controlTypes(LayoutSide /*side*/) c
     return QLayoutPolicy::DefaultType;
 }
 
-QGridLayoutBox QGridLayoutItem::box(Qt::Orientation orientation, qreal constraint) const
+QGridLayoutBox QGridLayoutItem::box(Qt::Orientation orientation, bool snapToPixelGrid, qreal constraint) const
 {
     QGridLayoutBox result;
     QLayoutPolicy::Policy policy = sizePolicy(orientation);
@@ -584,6 +599,8 @@ QGridLayoutBox QGridLayoutItem::box(Qt::Orientation orientation, qreal constrain
         } else {
             result.q_minimumSize = result.q_preferredSize;
         }
+        if (snapToPixelGrid)
+            result.q_minimumSize = qCeil(result.q_minimumSize);
 
         if (policy & (QLayoutPolicy::GrowFlag | QLayoutPolicy::ExpandFlag)) {
             result.q_maximumSize = sizeHint(Qt::MaximumSize, constraintSize).width();
@@ -600,6 +617,8 @@ QGridLayoutBox QGridLayoutItem::box(Qt::Orientation orientation, qreal constrain
         } else {
             result.q_minimumSize = result.q_preferredSize;
         }
+        if (snapToPixelGrid)
+            result.q_minimumSize = qCeil(result.q_minimumSize);
 
         if (policy & (QLayoutPolicy::GrowFlag | QLayoutPolicy::ExpandFlag)) {
             result.q_maximumSize = sizeHint(Qt::MaximumSize, constraintSize).height();
@@ -623,7 +642,7 @@ QGridLayoutBox QGridLayoutItem::box(Qt::Orientation orientation, qreal constrain
 }
 
 QRectF QGridLayoutItem::geometryWithin(qreal x, qreal y, qreal width, qreal height,
-                                       qreal rowDescent, Qt::Alignment align) const
+                                       qreal rowDescent, Qt::Alignment align, bool snapToPixelGrid) const
 {
     const qreal cellWidth = width;
     const qreal cellHeight = height;
@@ -661,7 +680,7 @@ QRectF QGridLayoutItem::geometryWithin(qreal x, qreal y, qreal width, qreal heig
         break;
     case Qt::AlignBaseline: {
         width = qMin(effectiveMaxSize(QSizeF(-1,-1)).width(), width);
-        QGridLayoutBox vBox = box(Qt::Vertical);
+        QGridLayoutBox vBox = box(Qt::Vertical, snapToPixelGrid);
         const qreal descent = vBox.q_minimumDescent;
         const qreal ascent = vBox.q_minimumSize - descent;
         y += (cellHeight - rowDescent - ascent);
@@ -1027,7 +1046,7 @@ void QGridLayoutEngine::setGeometries(const QRectF &contentsGeometry, const QAbs
 
         const Qt::Alignment align = effectiveAlignment(item);
         QRectF geom = item->geometryWithin(contentsGeometry.x() + x, contentsGeometry.y() + y,
-                                               width, height, q_descents[item->lastRow()], align);
+                                               width, height, q_descents[item->lastRow()], align, m_snapToPixelGrid);
         if (m_snapToPixelGrid) {
             // x and y should already be rounded, but the call to geometryWithin() above might
             // result in a geom with x,y at half-pixels (due to centering within the cell)
@@ -1407,9 +1426,9 @@ void QGridLayoutEngine::fillRowData(QGridLayoutRowData *rowData,
                         qreal length = colSizes[item->lastColumn(orientation)];
                         if (item->columnSpan(orientation) != 1)
                             length += colPositions[item->lastColumn(orientation)] - colPositions[item->firstColumn(orientation)];
-                        box->combine(item->box(orientation, length));
+                        box->combine(item->box(orientation, m_snapToPixelGrid, length));
                     } else {
-                        box->combine(item->box(orientation));
+                        box->combine(item->box(orientation, m_snapToPixelGrid));
                     }
 
                     if (effectiveRowSpan == 1) {
@@ -1477,8 +1496,8 @@ void QGridLayoutEngine::fillRowData(QGridLayoutRowData *rowData,
                         if (orientation == Qt::Horizontal) {
                             qreal width1 = rowData->boxes.at(prevRow).q_minimumSize;
                             qreal width2 = rowData->boxes.at(row).q_minimumSize;
-                            QRectF rect1 = item1->geometryWithin(0.0, 0.0, width1, FLT_MAX, -1.0, effectiveAlignment(item1));
-                            QRectF rect2 = item2->geometryWithin(0.0, 0.0, width2, FLT_MAX, -1.0, effectiveAlignment(item2));
+                            QRectF rect1 = item1->geometryWithin(0.0, 0.0, width1, FLT_MAX, -1.0, effectiveAlignment(item1), m_snapToPixelGrid);
+                            QRectF rect2 = item2->geometryWithin(0.0, 0.0, width2, FLT_MAX, -1.0, effectiveAlignment(item2), m_snapToPixelGrid);
                             spacing -= (width1 - (rect1.x() + rect1.width())) + rect2.x();
                         } else {
                             const QGridLayoutBox &box1 = rowData->boxes.at(prevRow);
@@ -1490,9 +1509,9 @@ void QGridLayoutEngine::fillRowData(QGridLayoutRowData *rowData,
                             qreal rowDescent2 = fixedDescent(box2.q_minimumDescent,
                                                              box2.q_minimumAscent, height2);
                             QRectF rect1 = item1->geometryWithin(0.0, 0.0, FLT_MAX, height1,
-                                                                 rowDescent1, effectiveAlignment(item1));
+                                                                 rowDescent1, effectiveAlignment(item1), m_snapToPixelGrid);
                             QRectF rect2 = item2->geometryWithin(0.0, 0.0, FLT_MAX, height2,
-                                                                 rowDescent2, effectiveAlignment(item2));
+                                                                 rowDescent2, effectiveAlignment(item2), m_snapToPixelGrid);
                             spacing -= (height1 - (rect1.y() + rect1.height())) + rect2.y();
                         }
                         rowSpacing = qMax(spacing, rowSpacing);
diff --git a/src/gui/util/qgridlayoutengine_p.h b/src/gui/util/qgridlayoutengine_p.h
index 1075a6f8f2..b3ed2d287b 100644
--- a/src/gui/util/qgridlayoutengine_p.h
+++ b/src/gui/util/qgridlayoutengine_p.h
@@ -314,8 +314,8 @@ public:
 
     virtual QLayoutPolicy::ControlTypes controlTypes(LayoutSide side) const;
 
-    QRectF geometryWithin(qreal x, qreal y, qreal width, qreal height, qreal rowDescent, Qt::Alignment align) const;
-    QGridLayoutBox box(Qt::Orientation orientation, qreal constraint = -1.0) const;
+    QRectF geometryWithin(qreal x, qreal y, qreal width, qreal height, qreal rowDescent, Qt::Alignment align, bool snapToPixelGrid) const;
+    QGridLayoutBox box(Qt::Orientation orientation, bool snapToPixelGrid, qreal constraint = -1.0) const;
 
 
     void transpose();