title: Qt 5.7 -> 5.8 add QIcon to QListwidget
body: <p>I want to upgrade my project from Qt 5.7 to Qt5.8. I have a function which shows an image on a <code>QListWidget</code>.</p>
  
  <p>My project, a viewer makes a thumbnail from image and convert it to a <code>QIcon</code>.  After creating the <code>QIcon</code> it is added to the <code>QListWidget</code> by inserting a new <code>QListwidgetItem</code>.</p>
  
  <p>In 5.7 that worked well, but in 5.8 thumbnails are not shown.</p>
  
  <p>Belows are codes </p>
  
  <p><code>QIcon</code> to <code>QListWidget</code>:</p>
  
  <pre><code>QIcon tmpIcon(pathOfImage);
  
  ui.listWidget-&gt;addItem(new QListWidgetItem(tmpIcon, pathOfImage));
  </code></pre>
  
  <p>What makes this happen? How can I adjust to 5.8?</p>
  
  <hr>
  
  <ul>
  <li><p>In 5.7 it works:</p>
  
  <p><img src="https://i.stack.imgur.com/f42SL.png" alt="In 5.7 it works! "></p></li>
  <li><p>In 5.8 it doesnt:</p>
  
  <p><img src="https://i.stack.imgur.com/VAxMF.png" alt="In 5.8 .... "></p></li>
  </ul>
  
  <hr>
  
  <p>But right now, I found that small size of PNG can be shown in 5.8. </p>
  
  <p>I don't know what is the problem. Maybe the size or the format of the image?</p>
  
  <p>In 5.7 that didn't affect the <code>QListwidget</code>!</p>