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PODerived QPainterPath, QPainter performance degrading quickly
 

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  1. PODerived QPainterPath, QPainter performance degrading quickly
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    <p>I am currently trying to encapsulate my QPainter objects into reusable classes, possibly deriving each other. This enables them to transform the painter around any way they like, have their own children to draw etc:</p> <p>I have <code>DrawArc</code> derived from <code>QPainterPath</code></p> <pre><code>DrawArc::DrawArc() : QPainterPath() {} void DrawArc::paint(QPainter* painter) { painter-&gt;save(); //... arcTo(/*...*/); lineTo(/*...*/); painter-&gt;translate(QPoint(100,100)); painter-&gt;drawPath(*dynamic_cast&lt;QPainterPath*&gt;(this)); painter-&gt;restore(); } </code></pre> <p>and <code>DrawBeam</code> derived from <code>DrawArc</code></p> <pre><code>DrawBeam::DrawBeam() : DrawArc() {} void DrawBeam::paint(QPainter* painter) { painter-&gt;save(); //... painter-&gt;setPen(QPen(color, 4)); painter-&gt;setBrush(brush); DrawArc::paint(painter); painter-&gt;restore(); } </code></pre> <p>In the actual Widget I am doing the following</p> <pre><code>BeamWidget::BeamWidget(QWidget* parent) : QWidget(parent) { DrawBeam* mybeam = new DrawBeam(); } void BeamWidget::paintEvent(QPaintEvent * /* event */) { QPainter painter(this); painter.setRenderHint(QPainter::Antialiasing, true); mybeam-&gt;paint(&amp;painter); } </code></pre> <p>However I am seeing dramatic performance losses in <code>painter-&gt;drawPath(*dynamic_cast&lt;QPainterPath*&gt;(this));</code> after a few seconds (or few hundred redraws). Everything else in the remaining procedure seems to run fine but when I enable that line the performance degrades quickly.</p> <p>Also all elements deriving from <code>DrawArc</code> painting seem to sometimes lose their QBrush styles and remain visible even though <code>setAutoFillBackground(true);</code> is set...</p>
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    1. USNils Werner
    1. USNils Werner
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    1. CO`Also all elements deriving from DrawArc painting seem to sometimes lose their QBrush styles` you are saving the painter...
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      1. USUmNyobe
    2. COto my knowledge `painter->save()` and `painter->restore()` let me take a snapshot of my painter so I can unroll back to it when I am done, undoing all transformations and unsetting the picked pens, brushes etc.
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      1. PODerived QPainterPath, QPainter performance degrading quickly
      1. USNils Werner
    3. COit opens the possibility of using different styles during painting.
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      1. USUmNyobe
 

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