title: Qt remove empty space between widgets on QVBoxLayout
body: <p>I have annoying problem. I created QVBoxLayout on which I added my widgets. 
  This is sample from my constructor:</p>
  
  <pre><code>layout = new QVBoxLayout;
  layout-&gt;setMargin(0);
  layout-&gt;setContentsMargins(QMargins(0,0,0,0));
  layout-&gt;setSpacing(0);
  </code></pre>
  
  <p>And then I have function to add widgets.</p>
  
  <pre><code>layout-&gt;addWidget(_wave);
  </code></pre>
  
  <p>_wave is my own widget. But you can add whatever you want, for example QButton.</p>
  
  <p>What do I want achieve? 
  <a href="http://doc.qt.digia.com/4.6/images/qvboxlayout-with-5-children.png" rel="noreferrer">Similar like this</a> but without any spaces beetween widgets added to layout. Just only QButtons or other widget, sticked each other.</p>
  
  <p>I added everywhere setMargins, setSpacing etc.
  Please help me with that, I don't really have an idea what should I do.</p>
  
  <p><img src="https://i.stack.imgur.com/Way1M.jpg" alt="enter image description here"></p>
  
  <p>Sorry for colors, but I wanted to mentioned what I want to achieve. I have mainWindow on which I added QWidget. This widget have blue background. Then to the layout, Im addding some widgets, which are orange on this image. I just want to be sure, that this blue background between widget isnt visible. I want to have widget under widget, without any space.</p>