Question

Good morning,
I have to layout some QWidgets and layouts into a main layout, but I have a problem with a space that I can not remove.
Basically what I would achieve is a horizzontal layout containing a grid layout and some buttons ( all in a horizontal line ). The grid layout (2×2) contains 2 QLabels and 2 QLeds.
Unfortunately Qt place a space between the grid layout and the first button as you can see in the attached image here http://img413.imageshack.us/img413/9132/problemhu.png
I would remove such space.
Here the code I wrote:

QGridLayout* gl = new QGridLayout();
gl->setAlignment(Qt::AlignLeft);
gl->setContentsMargins(0, 0, 0, 0);
gl->addWidget(activeLabel, 0, 0);
gl->addWidget(m_focusLed, 0, 1);
gl->addWidget(encodingLabel, 1, 0);
gl->addWidget(m_encodingLed, 1, 1);

This created the grid layout and added the QLabels and QLeds on it.
Then I add the buttons into the horizontal layout so:

  /* layout buttons */
  QHBoxLayout* lo = new QHBoxLayout();
  lo->setSpacing(0);
  lo->addLayout(gl); // <--here I add the grid layout
  lo->addWidget(m_goToBeginBtn);
  lo->addWidget(m_goToEndBtn);
  lo->addWidget(m_frewBtn);
  lo->addWidget(m_fforBtn);
  lo->addSpacing( 10 );
  lo->addWidget(m_ffrewBtn);
  lo->addWidget(m_ffforBtn);
  lo->addSpacing(10);
  lo->addWidget(m_prevBtn);
  lo->addWidget(m_nextBtn);
  lo->addWidget(m_playBtn);
  lo->addWidget(m_stopBtn);
  lo->addWidget(m_cutBtn);
  lo->addSpacing(10);
  lo->addWidget(m_zoomInBtn);
  lo->addWidget(m_zoomOutBtn);
  lo->addSpacing(10);
  lo->addWidget(m_bgSndCheckBox);
  lo->addWidget( m_showPanelBtn);

I don’t know why Qt place such space between the grid layout and the first button. I would remove it. How can I do? I didn’t get help from the Qt mailing list.

Best Regards

Answer 1

How to fix this largely depends on what behavior you want to see. I’m guessing what you want is for the labels and the Leds to stay exactly where they are, and keep their size.

What is happening is that the grid layout is resizing with your window, (like your buttons), but the left alignment is keeping the controls stuck to the left, thus the space.

First, remove the gl->setAlignment(Qt::AlignLeft) line.

Secondly, you want to make sure you set the sizePolicy properly on both your QLabels and your QLeds, because otherwise your QLeds will start to resize horizontally. What you want is a fixed horizontal size policy. Here is an example:

QSizePolicy sizePolicy(QSizePolicy::Fixed, QSizePolicy::Preferred);
sizePolicy.setHeightForWidth(label->sizePolicy().hasHeightForWidth());
label->setSizePolicy(sizePolicy);

A completely different way to accomplish the same thing would be to add a bunch of calls to setStretch() on your horizontal layout. But you would have to do this for each column in your layout that you want to stretch. Basically each for each button, but skipping the grid layout in the first column. Like this…

lo->setStretch(1, 1);  // Column 1 is your first button
lo->setStretch(2, 1);
...
lo->setStretch(19, 1)l  // 19 columns in total, 15 buttons plus 4 spacing.