title: QScrollBar QPlaintextEdit setValue does not work
body: <p>I have a simple <code>QPlainTextEdit</code>. In <code>MainWindow</code> constructor:</p>
  
  <pre><code>for(int i = 0; i &lt; 100; ++i)
  {
      ui-&gt;plainTextEdit-&gt;appendPlainText("testing");
  }
  </code></pre>
  
  <p>And after that I want to scroll:</p>
  
  <pre><code>ui-&gt;plainTextEdit-&gt;verticalScrollBar()-&gt;setValue(30);
  </code></pre>
  
  <p>But it does not work. Although if I would create a button and in click-slot run the same code it would have worked:</p>
  
  <pre><code>connect(ui-&gt;pushButton, &amp;QPushButton::clicked, this, [this]()
  {
      ui-&gt;plainTextEdit-&gt;verticalScrollBar()-&gt;setValue(30); // it works
  });
  </code></pre>
  
  <p><strong>How to fix it?</strong></p>