The following example demonstrates a bug on MacOSX with 4.3.0.

Running on other platforms or with 4.2.x it works as expected:

#include <QtGui>

class Editor : public QWidget
{
Q_OBJECT

public:
Editor(QWidget * parent = 0)
: QWidget(parent)

{ QHBoxLayout *layout = new QHBoxLayout(this); layout->setMargin(0); layout->setSpacing(0); QLineEdit *lineEdit = new QLineEdit(this); lineEdit->setFrame(0); QPushButton *pushButton = new QPushButton(QString("..."), this); pushButton->setMaximumWidth(16); layout->addWidget(lineEdit); layout->addWidget(pushButton); }

};

class Delegate : public QItemDelegate
{
Q_OBJECT
public:
Delegate(QObject *parent = 0)
: QItemDelegate(parent)
{}
QWidget *createEditor(QWidget *parent, const QStyleOptionViewItem &, const QModelIndex &) const

{ return new Editor(parent); }

QSize sizeHint(const QStyleOptionViewItem & option, const QModelIndex & index) const

{ return QItemDelegate::sizeHint(option, index) + QSize(0, 4); }

};

#include "main.moc"

int main(int argc, char *argv[])
{
QApplication app(argc, argv);
QStandardItemModel model(4, 2);
QTreeView treeView;
treeView.setModel(&model);
Delegate delegate;
treeView.setItemDelegate(&delegate);
for (int row = 0; row < 4; ++row) {
for (int column = 0; column < 2; ++column)

{ QModelIndex index = model.index(row, column, QModelIndex()); model.setData(index, QVariant((row+1) * (column+1))); }

}
treeView.show();
return app.exec();
}

To reproduce:

start app
double click on a cell to start editing
notice how the lineedit doesn't use all the available space

This patch prevents the problem:

— /tmp/tmp.18648.11 2007-07-10 16:34:15.000000000 -0700
+++ /Users/anders/dev/qt-4.3/src/gui/kernel/qboxlayout.cpp 2007-07-10 16:24:34.000000000 -0700
@@ -132,6 +132,7 @@ void QBoxLayoutPrivate::effectiveMargins
int t = topMargin;
int r = rightMargin;
int b = bottomMargin;
+#if 0
#ifdef Q_WS_MAC
Q_Q(const QBoxLayout);
if (horz(dir))

{ @@ -221,6 +222,7 @@ void QBoxLayoutPrivate::effectiveMargins }

}
#endif
+#endif
if (left)
*left = l;
if (top)