title: How to resize QDockWidget
body: <p>I have created one application without centralwidget in my mainwindows, and shown as maximized:</p>
  <pre><code>setCentralWidget(0);
  setWindowState(Qt::WindowMaximized);
  </code></pre>
  <p>In my mainwindow, I have three docks. The dock1 is set to be docked to leftDockWidgetArea, the dock2 and dock3 are set to be docked to the rightDockWidgetArea. Also, I arrange dock2 and dock3 by</p>
  <pre><code>splitDockWidget(ui-&gt;dock2, ui-&gt;dock3, Qt::Horizontal);
  </code></pre>
  <p>So I got a results that the ratio of the width of the three docks are <a href="https://i.stack.imgur.com/IqmW8.png" rel="nofollow noreferrer">2:1:1</a>.</p>
  <p>My question is <strong>how could I set the width of the three docks</strong> so that they can be arranged as <a href="https://i.stack.imgur.com/Pidxi.png" rel="nofollow noreferrer">1:4:1</a>.</p>
  <p>Suppose my screen's width is 1024. I have tried</p>
  <pre><code>ui-&gt;dockWidget_PrimeVis-&gt;resize(1000, 1000);
  </code></pre>
  <p>This does not work since I found some people say the size of docks are controlled by mainwindow. So I found I could call resizeDocks in mainwindow such as</p>
  <pre><code>resizeDocks({ ui-&gt;dock1, ui-&gt;dock2,ui-&gt;dock3}, { 150,600,150 }, Qt::Horizontal); 
  </code></pre>
  <p>And it does not work. Also, since each dock contains one subclassed widget, I also tried to set the size to each subclassed widget, again, does not work.</p>
  <p>Since we can manually change the size of each dock by GUI, so I believe there should be a way to set the size of each dock with codes, right? Anyone has a clue?</p>