Add an example of how to write a custom layout for QGraphicsLayouts.

Flowlayout...  Documentation will follow.

1 files changed, 169 insertions, 0 deletions

diff --git a/examples/graphicsview/flowlayout/flowlayout.cpp b/examples/graphicsview/flowlayout/flowlayout.cpp
new file mode 100644
index 0000000..d1676bc
--- /dev/null
+++ b/examples/graphicsview/flowlayout/flowlayout.cpp
@@ -0,0 +1,169 @@
+#include "flowlayout.h"
+#include <QtGui/qwidget.h>
+#include <QtCore/qmath.h>
+
+FlowLayout::FlowLayout()
+{
+    m_spacing[0] = 6;
+    m_spacing[1] = 6;
+    QSizePolicy sp = sizePolicy();
+    sp.setHeightForWidth(true);
+    setSizePolicy(sp);
+}
+
+void FlowLayout::insertItem(int index, QGraphicsLayoutItem *item)
+{
+    item->setParentLayoutItem(this);
+    if (uint(index) > uint(m_items.count()))
+        index = m_items.count();
+    m_items.insert(index, item);
+    invalidate();
+}
+
+int FlowLayout::count() const
+{
+    return m_items.count();
+}
+
+QGraphicsLayoutItem *FlowLayout::itemAt(int index) const
+{
+    return m_items.value(index);
+}
+
+void FlowLayout::removeAt(int index)
+{
+    m_items.removeAt(index);
+}
+
+qreal FlowLayout::spacing(Qt::Orientation o) const
+{
+    return m_spacing[int(o) - 1];
+}
+
+void FlowLayout::setSpacing(Qt::Orientations o, qreal spacing)
+{
+    if (o & Qt::Horizontal)
+        m_spacing[0] = spacing;
+    if (o & Qt::Vertical)
+        m_spacing[1] = spacing;
+}
+
+void FlowLayout::setGeometry(const QRectF &geom)
+{
+    QGraphicsLayout::setGeometry(geom);
+    doLayout(geom, true);
+}
+
+qreal FlowLayout::doLayout(const QRectF &geom, bool applyNewGeometry)
+{
+    QPointF tl = geom.topLeft();
+    qreal maxw = geom.width();
+
+    qreal left, top, right, bottom;
+    getContentsMargins(&left, &top, &right, &bottom);
+    maxw = maxw - left - right;
+    qreal x = 0;
+    qreal y = 0;
+    qreal maxRowHeight = 0;
+    QSizeF pref;
+    for (int i = 0; i < m_items.count(); ++i) {
+        QGraphicsLayoutItem *item = m_items.at(i);
+        pref = item->effectiveSizeHint(Qt::PreferredSize);
+        maxRowHeight = qMax(maxRowHeight, pref.height());
+
+        qreal next_x;
+        next_x = x + pref.width();
+        if (next_x > maxw) {
+            if (x == 0) {
+                pref.setWidth(maxw);
+            } else {
+                x = 0;
+                next_x = pref.width();
+            }
+            y += maxRowHeight + spacing(Qt::Vertical);
+            maxRowHeight = 0;
+        }
+
+        if (applyNewGeometry)
+            item->setGeometry(QRectF(QPointF(left + x, top + y), pref));
+        x = next_x + spacing(Qt::Horizontal);
+    }
+    maxRowHeight = qMax(maxRowHeight, pref.height());
+    return top + y + maxRowHeight + bottom;
+}
+
+QSizeF FlowLayout::minSize(const QSizeF &constraint) const
+{
+    QSizeF size(0, 0);
+    qreal left, top, right, bottom;
+    getContentsMargins(&left, &top, &right, &bottom);
+    if (constraint.width() > 0) {   // height for width
+        FlowLayout *that = const_cast<FlowLayout *>(this);
+        qreal height = that->doLayout(QRectF(QPointF(0,0), constraint), false);
+        size = QSizeF(constraint.width(), height);
+    } else {
+        QGraphicsLayoutItem *item;
+        foreach (item, m_items)
+            size = size.expandedTo(item->effectiveSizeHint(Qt::MinimumSize));
+        size += QSize(left + right, top + bottom);
+    }        
+    return size;
+}
+
+QSizeF FlowLayout::prefSize() const
+{
+    qreal left, top, right, bottom;
+    getContentsMargins(&left, &top, &right, &bottom);
+
+    QGraphicsLayoutItem *item;
+    qreal maxh = 0;
+    qreal totalWidth = 0;
+    foreach (item, m_items) {
+        if (totalWidth > 0)
+            totalWidth += spacing(Qt::Horizontal);
+        QSizeF pref = item->effectiveSizeHint(Qt::PreferredSize);
+        totalWidth += pref.width();
+        maxh = qMax(maxh, pref.height());
+    }
+    maxh += spacing(Qt::Vertical);
+
+    const qreal goldenAspectRatio = 1.61803399;
+    qreal w = qSqrt(totalWidth * maxh * goldenAspectRatio) + left + right;
+
+    return minSize(QSizeF(w, -1));
+}
+
+QSizeF FlowLayout::maxSize() const
+{
+    QGraphicsLayoutItem *item;
+    qreal totalWidth = 0;
+    qreal totalHeight = 0;
+    foreach (item, m_items) {
+        if (totalWidth > 0)
+            totalWidth += spacing(Qt::Horizontal);
+        if (totalHeight > 0)
+            totalHeight += spacing(Qt::Vertical);
+        QSizeF pref = item->effectiveSizeHint(Qt::PreferredSize);
+        totalWidth += pref.width();
+        totalHeight += pref.height();
+    }
+
+    qreal left, top, right, bottom;
+    getContentsMargins(&left, &top, &right, &bottom);
+    return QSizeF(left + totalWidth + right, top + totalHeight + bottom);
+}
+
+QSizeF FlowLayout::sizeHint(Qt::SizeHint which, const QSizeF &constraint) const
+{
+    switch (which) {
+    case Qt::PreferredSize:
+        return prefSize();
+    case Qt::MinimumSize:
+        return minSize(constraint);
+    case Qt::MaximumSize:
+        return maxSize();
+    default:
+        break;
+    }
+    return constraint;
+}