title: QTextEdit how to keep currently selected text line at the same position on the screen
body: <p>I want my text cursor to be always at the same vertical position of <strong>QTextEdit</strong>.</p>
  
  <p>As an example lets say i have (*I* = cursor, ==== delimit the edit box). Lets say <strong>*I*</strong> is 20 pixels from top.</p>
  
  <pre><code>============================================
  Today is a nice weather
  I wanted to go *I*for a walk. 
  But finaly got caught in a rain.
  ============================================
  </code></pre>
  
  <p>now if i move my cursor down.</p>
  
  <pre><code>============================================
  I wanted to go for a walk. 
  But finaly got *I*caught in a rain.
  Damn it.
  ============================================
  </code></pre>
  
  <p>Not that i can not simply count lines from, because i have embedded tables and the font size is different too. </p>