Remove all spacing in QGridLayout

I'm trying to build programmaticaly (with Qt 4.6) a 开发者_Python百科window containing a series of QPushButton's, all packed together. It should look like so (which I call a toolbox):

toolbox image http://img99.imageshack.us/img99/9853/examplezk.png

So, I created a Toolbox class, deriving from QWidget, that has the following constructor:

Toolbox::Toolbox (void)
  : QWidget (0, Qt::Tool)
{
  setWindowTitle (tr ("Toolbox"));

  QGridLayout *group = new QGridLayout (this);
  group->setSpacing (0);
  group->setContentsMargins (0, 0, 0, 0);
  group->setSizeConstraint (QLayout::SetFixedSize);
  setLayout (group);

  unsigned k = 0;
  QPushButton *buttons = new QPushButton[6];
  for (unsigned i = 0; i < 3; i++)
    for (unsigned j = 0; j < 2; j++)
    {
      buttons[k].setIcon (QIcon ("test.png"));
      buttons[k].setIconSize (QSize (32, 32));
      buttons[k].setContentsMargins (0, 0, 0, 0);
      buttons[k].setCheckable (true);
      buttons[k].setAutoExclusive (true);

      group->addWidget (&buttons[k], i, j);
      k++;
    }
  buttons[1].setChecked (true);

Somehow, it does not work and my buttons don't end up packed together:

result http://img9.imageshack.us/img9/774/resultr.png

I can't manage to remove this vertical spacing (and the margins surrounding the entire array). Any help is welcome.

Apparently, this is considered a normal thing: see the corresponding bug report, which was closed. The workaround reported there doesn't seem to work for me.

Since you've set the size constraint on the layout to QLayout::SetFixedSize, Qt will use the size hint of the widget as its fixed size. You might have to override QWidget::sizeHint() in the Toolbox class to make the widget exactly as large as it needs to be to fit all the buttons (in the case of your six buttons, the width would be 64 and the height would be 96).

If you are using the the plastique style which is now standard in Qt4.6 the borders of QPushButtons are drawn inside the widget. Try using one of the other styles. e.g.:

#include <QGtkStyle>

QApplication a(argc, argv, true);
a.setStyle("gtk");

A style can also be set on an individual widget using the QWidget::setStyle() function.