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POWhy QWidget::paintEvent doesn't get called?
 

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  1. POWhy QWidget::paintEvent doesn't get called?
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    <p>I have a simple hierarchy of widgets: GraphWidget -> MotionWidget -> NodeWidget. I am new to Qt, so I am not quite sure about how some insides work yet. Basically, GraphWidget creates a single MotionWidget <em>M</em> and sets <em>M's</em> parent to itself. <em>M</em> then goes away and creates a bunch of NodeWidgets. However, NodeWidgets never get painted nor does their paintEvent() function gets called.</p> <p>I tried creating MotionWidget directly, without GraphWidget and everything works. So why does things break if I add GraphWidget to the hierarchy?</p> <p>Here is a paste with the relevant bits of code from my project. I also included the output from GraphWidget::dumpObjectTree() at the top.</p> <p>Edit: forgot to include the paste link ;) <a href="http://rafb.net/p/Zp39CF94.html" rel="nofollow noreferrer">http://rafb.net/p/Zp39CF94.html</a></p> <p>Update: I wrapped MotionWidget into a layout.</p> <p>Before:</p> <pre><code>GraphWidget :: GraphWidget( QWidget *parent ) : QWidget( parent ) { setFixedSize( 500, 500 ); MotionWidget *n = new MotionWidget( 5, this ); } </code></pre> <p>After</p> <pre><code>GraphWidget :: GraphWidget( QWidget *parent ) : QWidget( parent ) { setFixedSize( 500, 500 ); QVBoxLayout *l = new QVBoxLayout; MotionWidget *n = new MotionWidget( 5 ); l-&gt;addWidget( n ); setLayout( l ); } </code></pre> <p>Now, the latter works. I.e. everything gets drawn. The question then becomes... Why? Why didn't it work in the first case but worked in the second?</p>
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    1. COWould placing `this->setGeometry(parent->rect())` in the MotionWidget constructor remove the need for another layout? What if you call `n->show()` after creating it?
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      1. POWhy QWidget::paintEvent doesn't get called?
      1. USJudge Maygarden
 

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