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<td >Qt 5.12</td><td ><a href="qtgui-index.html">Qt GUI</a></td><td ><a href="qtgui-module.html">C++ Classes</a></td><td >QOpenGLPaintDevice</td></tr></table><table class="buildversion"><tr>
<td id="buildversion" width="100%" align="right"><a href="qtgui-index.html">Qt 5.12.6 Reference Documentation</a></td>
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<h3><a name="toc">Contents</a></h3>
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<li class="level1"><a href="#public-functions">Public Functions</a></li>
<li class="level1"><a href="#reimplemented-public-functions">Reimplemented Public Functions</a></li>
<li class="level1"><a href="#protected-functions">Protected Functions</a></li>
<li class="level1"><a href="#reimplemented-protected-functions">Reimplemented Protected Functions</a></li>
<li class="level1"><a href="#protected-variables">Protected Variables</a></li>
<li class="level1"><a href="#details">Detailed Description</a></li>
<li class="level2"><a href="#performance">Performance</a></li>
<li class="level2"><a href="#antialiasing-and-quality">Antialiasing and Quality</a></li>
<li class="level2"><a href="#state-changes">State Changes</a></li>
<li class="level2"><a href="#mixing-qpainter-and-opengl">Mixing QPainter and OpenGL</a></li>
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<h1 class="title">QOpenGLPaintDevice Class</h1>
<!-- $$$QOpenGLPaintDevice-brief -->
<p>The <a href="qopenglpaintdevice.html">QOpenGLPaintDevice</a> class enables painting to an OpenGL context using <a href="qpainter.html">QPainter</a>. <a href="#details">More...</a></p>
<!-- @@@QOpenGLPaintDevice -->
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<tr><td class="memItemLeft rightAlign topAlign"> Header:</td><td class="memItemRight bottomAlign">   <span class="preprocessor">#include &lt;QOpenGLPaintDevice&gt;</span>
</td></tr><tr><td class="memItemLeft rightAlign topAlign"> qmake:</td><td class="memItemRight bottomAlign"> QT += gui</td></tr><tr><td class="memItemLeft rightAlign topAlign"> Since:</td><td class="memItemRight bottomAlign">  Qt 5.0</td></tr><tr><td class="memItemLeft rightAlign topAlign"> Inherits:</td><td class="memItemRight bottomAlign"> <a href="qpaintdevice.html">QPaintDevice</a></td></tr></table></div><ul>
<li><a href="qopenglpaintdevice-members.html">List of all members, including inherited members</a></li>
</ul>
<a name="public-functions"></a>
<h2 id="public-functions">Public Functions</h2>
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qopenglpaintdevice.html#QOpenGLPaintDevice">QOpenGLPaintDevice</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qopenglpaintdevice.html#QOpenGLPaintDevice-1">QOpenGLPaintDevice</a></b>(const QSize &amp;<i>size</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qopenglpaintdevice.html#QOpenGLPaintDevice-2">QOpenGLPaintDevice</a></b>(int <i>width</i>, int <i>height</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> virtual </td><td class="memItemRight bottomAlign"><b><a href="qopenglpaintdevice.html#dtor.QOpenGLPaintDevice">~QOpenGLPaintDevice</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QOpenGLContext *</td><td class="memItemRight bottomAlign"><b><a href="qopenglpaintdevice.html#context">context</a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> qreal </td><td class="memItemRight bottomAlign"><b><a href="qopenglpaintdevice.html#dotsPerMeterX">dotsPerMeterX</a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> qreal </td><td class="memItemRight bottomAlign"><b><a href="qopenglpaintdevice.html#dotsPerMeterY">dotsPerMeterY</a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> virtual void </td><td class="memItemRight bottomAlign"><b><a href="qopenglpaintdevice.html#ensureActiveTarget">ensureActiveTarget</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qopenglpaintdevice.html#paintFlipped">paintFlipped</a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qopenglpaintdevice.html#setDevicePixelRatio">setDevicePixelRatio</a></b>(qreal <i>devicePixelRatio</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qopenglpaintdevice.html#setDotsPerMeterX">setDotsPerMeterX</a></b>(qreal <i>dpmx</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qopenglpaintdevice.html#setDotsPerMeterY">setDotsPerMeterY</a></b>(qreal <i>dpmy</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qopenglpaintdevice.html#setPaintFlipped">setPaintFlipped</a></b>(bool <i>flipped</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qopenglpaintdevice.html#setSize">setSize</a></b>(const QSize &amp;<i>size</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QSize </td><td class="memItemRight bottomAlign"><b><a href="qopenglpaintdevice.html#size">size</a></b>() const</td></tr>
</table></div>
<a name="reimplemented-public-functions"></a>
<h2 id="reimplemented-public-functions">Reimplemented Public Functions</h2>
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> virtual QPaintEngine *</td><td class="memItemRight bottomAlign"><b><a href="qopenglpaintdevice.html#paintEngine">paintEngine</a></b>() const override</td></tr>
</table></div>
<ul>
<li class="fn">14 public functions inherited from <a href="qpaintdevice.html#public-functions">QPaintDevice</a></li>
</ul>
<a name="protected-functions"></a>
<h2 id="protected-functions">Protected Functions</h2>
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qopenglpaintdevice.html#QOpenGLPaintDevice-4">QOpenGLPaintDevice</a></b>(<i>const QOpenGLPaintDevice &amp;</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QOpenGLPaintDevice &amp;</td><td class="memItemRight bottomAlign"><b><a href="qopenglpaintdevice.html#operator-eq">operator=</a></b>(<i>const QOpenGLPaintDevice &amp;</i>)</td></tr>
</table></div>
<a name="reimplemented-protected-functions"></a>
<h2 id="reimplemented-protected-functions">Reimplemented Protected Functions</h2>
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> virtual int </td><td class="memItemRight bottomAlign"><b><a href="qopenglpaintdevice.html#metric">metric</a></b>(QPaintDevice::PaintDeviceMetric <i>metric</i>) const override</td></tr>
</table></div>
<ul>
<li class="fn">1 protected function inherited from <a href="qpaintdevice.html#protected-functions">QPaintDevice</a></li>
</ul>
<a name="protected-variables"></a>
<h2 id="protected-variables">Protected Variables</h2>
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> int </td><td class="memItemRight bottomAlign"><b><a href="qopenglpaintdevice.html#d_ptr-var">d_ptr</a></b></td></tr>
</table></div>
<a name="details"></a>
<!-- $$$QOpenGLPaintDevice-description -->
<div class="descr">
<h2 id="details">Detailed Description</h2>
<p>The <a href="qopenglpaintdevice.html">QOpenGLPaintDevice</a> class enables painting to an OpenGL context using <a href="qpainter.html">QPainter</a>.</p>
<p>The <a href="qopenglpaintdevice.html">QOpenGLPaintDevice</a> uses the <b>current</b> QOpenGL context to render <a href="qpainter.html">QPainter</a> draw commands. The context is captured upon construction. It requires support for OpenGL (ES) 2.0 or higher.</p>
<a name="performance"></a>
<h3 id="performance">Performance</h3>
<p>The <a href="qopenglpaintdevice.html">QOpenGLPaintDevice</a> is almost always hardware accelerated and has the potential of being much faster than software rasterization. However, it is more sensitive to state changes, and therefore requires the drawing commands to be carefully ordered to achieve optimal performance.</p>
<a name="antialiasing-and-quality"></a>
<h3 id="antialiasing-and-quality">Antialiasing and Quality</h3>
<p>Antialiasing in the OpenGL paint engine is done using multisampling. Most hardware require significantly more memory to do multisampling and the resulting quality is not on par with the quality of the software paint engine. The OpenGL paint engine's strength lies in its performance, not its visual rendering quality.</p>
<a name="state-changes"></a>
<h3 id="state-changes">State Changes</h3>
<p>When painting to a <a href="qopenglpaintdevice.html">QOpenGLPaintDevice</a> using <a href="qpainter.html">QPainter</a>, the state of the current OpenGL context will be altered by the paint engine to reflect its needs. Applications should not rely upon the OpenGL state being reset to its original conditions, particularly the current shader program, OpenGL viewport, texture units, and drawing modes.</p>
<a name="mixing-qpainter-and-opengl"></a>
<h3 id="mixing-qpainter-and-opengl">Mixing QPainter and OpenGL</h3>
<p>When intermixing <a href="qpainter.html">QPainter</a> and OpenGL, it is important to notify <a href="qpainter.html">QPainter</a> that the OpenGL state may have been cluttered so it can restore its internal state. This is achieved by calling <a href="qpainter.html#beginNativePainting">QPainter::beginNativePainting</a>() before starting the OpenGL rendering and calling <a href="qpainter.html#endNativePainting">QPainter::endNativePainting</a>() after finishing.</p>
</div>
<p><b>See also </b><a href="qtgui-openglwindow-example.html">OpenGL Window Example</a>.</p>
<!-- @@@QOpenGLPaintDevice -->
<div class="func">
<h2>Member Function Documentation</h2>
<!-- $$$QOpenGLPaintDevice[overload1]$$$QOpenGLPaintDevice -->
<h3 class="fn" id="QOpenGLPaintDevice"><a name="QOpenGLPaintDevice"></a>QOpenGLPaintDevice::<span class="name">QOpenGLPaintDevice</span>()</h3>
<p>Constructs a <a href="qopenglpaintdevice.html">QOpenGLPaintDevice</a>.</p>
<p>The <a href="qopenglpaintdevice.html">QOpenGLPaintDevice</a> is only valid for the current context.</p>
<p><b>See also </b><a href="qopenglcontext.html#currentContext">QOpenGLContext::currentContext</a>().</p>
<!-- @@@QOpenGLPaintDevice -->
<!-- $$$QOpenGLPaintDevice$$$QOpenGLPaintDeviceconstQSize& -->
<h3 class="fn" id="QOpenGLPaintDevice-1"><a name="QOpenGLPaintDevice-1"></a>QOpenGLPaintDevice::<span class="name">QOpenGLPaintDevice</span>(const <span class="type"><a href="../qtcore/qsize.html">QSize</a></span> &amp;<i>size</i>)</h3>
<p>Constructs a <a href="qopenglpaintdevice.html">QOpenGLPaintDevice</a> with the given <i>size</i>.</p>
<p>The <a href="qopenglpaintdevice.html">QOpenGLPaintDevice</a> is only valid for the current context.</p>
<p><b>See also </b><a href="qopenglcontext.html#currentContext">QOpenGLContext::currentContext</a>().</p>
<!-- @@@QOpenGLPaintDevice -->
<!-- $$$QOpenGLPaintDevice$$$QOpenGLPaintDeviceintint -->
<h3 class="fn" id="QOpenGLPaintDevice-2"><a name="QOpenGLPaintDevice-2"></a>QOpenGLPaintDevice::<span class="name">QOpenGLPaintDevice</span>(<span class="type">int</span> <i>width</i>, <span class="type">int</span> <i>height</i>)</h3>
<p>Constructs a <a href="qopenglpaintdevice.html">QOpenGLPaintDevice</a> with the given <i>width</i> and <i>height</i>.</p>
<p>The <a href="qopenglpaintdevice.html">QOpenGLPaintDevice</a> is only valid for the current context.</p>
<p><b>See also </b><a href="qopenglcontext.html#currentContext">QOpenGLContext::currentContext</a>().</p>
<!-- @@@QOpenGLPaintDevice -->
<!-- $$$QOpenGLPaintDevice$$$QOpenGLPaintDeviceconstQOpenGLPaintDevice& -->
<h3 class="fn" id="QOpenGLPaintDevice-4"><a name="QOpenGLPaintDevice-4"></a><code>[protected] </code>QOpenGLPaintDevice::<span class="name">QOpenGLPaintDevice</span>(<i>const QOpenGLPaintDevice &amp;</i>)</h3>
<p>Default constructs an instance of QOpenGLPaintDevice.</p><!-- @@@QOpenGLPaintDevice -->
<!-- $$$~QOpenGLPaintDevice[overload1]$$$~QOpenGLPaintDevice -->
<h3 class="fn" id="dtor.QOpenGLPaintDevice"><a name="dtor.QOpenGLPaintDevice"></a><code>[virtual] </code>QOpenGLPaintDevice::<span class="name">~QOpenGLPaintDevice</span>()</h3>
<p>Destroys the <a href="qopenglpaintdevice.html">QOpenGLPaintDevice</a>.</p>
<!-- @@@~QOpenGLPaintDevice -->
<!-- $$$context[overload1]$$$context -->
<h3 class="fn" id="context"><a name="context"></a><span class="type"><a href="qopenglcontext.html">QOpenGLContext</a></span> *QOpenGLPaintDevice::<span class="name">context</span>() const</h3>
<p>Returns the OpenGL context associated with the paint device.</p>
<!-- @@@context -->
<!-- $$$dotsPerMeterX[overload1]$$$dotsPerMeterX -->
<h3 class="fn" id="dotsPerMeterX"><a name="dotsPerMeterX"></a><span class="type"><a href="../qtcore/qtglobal.html#qreal-typedef">qreal</a></span> QOpenGLPaintDevice::<span class="name">dotsPerMeterX</span>() const</h3>
<p>Returns the number of pixels per meter horizontally.</p>
<p><b>See also </b><a href="qopenglpaintdevice.html#setDotsPerMeterX">setDotsPerMeterX</a>().</p>
<!-- @@@dotsPerMeterX -->
<!-- $$$dotsPerMeterY[overload1]$$$dotsPerMeterY -->
<h3 class="fn" id="dotsPerMeterY"><a name="dotsPerMeterY"></a><span class="type"><a href="../qtcore/qtglobal.html#qreal-typedef">qreal</a></span> QOpenGLPaintDevice::<span class="name">dotsPerMeterY</span>() const</h3>
<p>Returns the number of pixels per meter vertically.</p>
<p><b>See also </b><a href="qopenglpaintdevice.html#setDotsPerMeterY">setDotsPerMeterY</a>().</p>
<!-- @@@dotsPerMeterY -->
<!-- $$$ensureActiveTarget[overload1]$$$ensureActiveTarget -->
<h3 class="fn" id="ensureActiveTarget"><a name="ensureActiveTarget"></a><code>[virtual] </code><span class="type">void</span> QOpenGLPaintDevice::<span class="name">ensureActiveTarget</span>()</h3>
<p>This virtual method is provided as a callback to allow re-binding a target frame buffer object or context when different <a href="qopenglpaintdevice.html">QOpenGLPaintDevice</a> instances are issuing draw calls alternately.</p>
<p><a href="qpainter.html#beginNativePainting">beginNativePainting()</a> will also trigger this method.</p>
<p>The default implementation does nothing.</p>
<!-- @@@ensureActiveTarget -->
<!-- $$$metric[overload1]$$$metricQPaintDevice::PaintDeviceMetric -->
<h3 class="fn" id="metric"><a name="metric"></a><code>[override virtual protected] </code><span class="type">int</span> QOpenGLPaintDevice::<span class="name">metric</span>(<span class="type"><a href="qpaintdevice.html#PaintDeviceMetric-enum">QPaintDevice::PaintDeviceMetric</a></span> <i>metric</i>) const</h3>
<p>Reimplemented from <a href="qpaintdevice.html#metric">QPaintDevice::metric</a>().</p>
<!-- @@@metric -->
<!-- $$$paintEngine[overload1]$$$paintEngine -->
<h3 class="fn" id="paintEngine"><a name="paintEngine"></a><code>[override virtual] </code><span class="type"><a href="qpaintengine.html">QPaintEngine</a></span> *QOpenGLPaintDevice::<span class="name">paintEngine</span>() const</h3>
<p>Reimplemented from <a href="qpaintdevice.html#paintEngine">QPaintDevice::paintEngine</a>().</p>
<!-- @@@paintEngine -->
<!-- $$$paintFlipped[overload1]$$$paintFlipped -->
<h3 class="fn" id="paintFlipped"><a name="paintFlipped"></a><span class="type">bool</span> QOpenGLPaintDevice::<span class="name">paintFlipped</span>() const</h3>
<p>Returns <code>true</code> if painting is flipped around the Y-axis.</p>
<p><b>See also </b><a href="qopenglpaintdevice.html#setPaintFlipped">setPaintFlipped</a>().</p>
<!-- @@@paintFlipped -->
<!-- $$$setDevicePixelRatio[overload1]$$$setDevicePixelRatioqreal -->
<h3 class="fn" id="setDevicePixelRatio"><a name="setDevicePixelRatio"></a><span class="type">void</span> QOpenGLPaintDevice::<span class="name">setDevicePixelRatio</span>(<span class="type"><a href="../qtcore/qtglobal.html#qreal-typedef">qreal</a></span> <i>devicePixelRatio</i>)</h3>
<p>Sets the device pixel ratio for the paint device to <i>devicePixelRatio</i>.</p>
<!-- @@@setDevicePixelRatio -->
<!-- $$$setDotsPerMeterX[overload1]$$$setDotsPerMeterXqreal -->
<h3 class="fn" id="setDotsPerMeterX"><a name="setDotsPerMeterX"></a><span class="type">void</span> QOpenGLPaintDevice::<span class="name">setDotsPerMeterX</span>(<span class="type"><a href="../qtcore/qtglobal.html#qreal-typedef">qreal</a></span> <i>dpmx</i>)</h3>
<p>Sets the number of pixels per meter horizontally to <i>dpmx</i>.</p>
<p><b>See also </b><a href="qopenglpaintdevice.html#dotsPerMeterX">dotsPerMeterX</a>().</p>
<!-- @@@setDotsPerMeterX -->
<!-- $$$setDotsPerMeterY[overload1]$$$setDotsPerMeterYqreal -->
<h3 class="fn" id="setDotsPerMeterY"><a name="setDotsPerMeterY"></a><span class="type">void</span> QOpenGLPaintDevice::<span class="name">setDotsPerMeterY</span>(<span class="type"><a href="../qtcore/qtglobal.html#qreal-typedef">qreal</a></span> <i>dpmy</i>)</h3>
<p>Sets the number of pixels per meter vertically to <i>dpmy</i>.</p>
<p><b>See also </b><a href="qopenglpaintdevice.html#dotsPerMeterY">dotsPerMeterY</a>().</p>
<!-- @@@setDotsPerMeterY -->
<!-- $$$setPaintFlipped[overload1]$$$setPaintFlippedbool -->
<h3 class="fn" id="setPaintFlipped"><a name="setPaintFlipped"></a><span class="type">void</span> QOpenGLPaintDevice::<span class="name">setPaintFlipped</span>(<span class="type">bool</span> <i>flipped</i>)</h3>
<p>Sets whether painting should be flipped around the Y-axis or not to <i>flipped</i>.</p>
<p><b>See also </b><a href="qopenglpaintdevice.html#paintFlipped">paintFlipped</a>().</p>
<!-- @@@setPaintFlipped -->
<!-- $$$setSize[overload1]$$$setSizeconstQSize& -->
<h3 class="fn" id="setSize"><a name="setSize"></a><span class="type">void</span> QOpenGLPaintDevice::<span class="name">setSize</span>(const <span class="type"><a href="../qtcore/qsize.html">QSize</a></span> &amp;<i>size</i>)</h3>
<p>Sets the pixel size of the paint device to <i>size</i>.</p>
<p><b>See also </b><a href="qopenglpaintdevice.html#size">size</a>().</p>
<!-- @@@setSize -->
<!-- $$$size[overload1]$$$size -->
<h3 class="fn" id="size"><a name="size"></a><span class="type"><a href="../qtcore/qsize.html">QSize</a></span> QOpenGLPaintDevice::<span class="name">size</span>() const</h3>
<p>Returns the pixel size of the paint device.</p>
<p><b>See also </b><a href="qopenglpaintdevice.html#setSize">setSize</a>().</p>
<!-- @@@size -->
<!-- $$$operator=[overload1]$$$operator=constQOpenGLPaintDevice& -->
<h3 class="fn" id="operator-eq"><a name="operator-eq"></a><code>[protected] </code><span class="type"><a href="qopenglpaintdevice.html#QOpenGLPaintDevice">QOpenGLPaintDevice</a></span> &amp;QOpenGLPaintDevice::<span class="name">operator=</span>(<i>const QOpenGLPaintDevice &amp;</i>)</h3>
<p>Copy-assignment operator.</p><!-- @@@operator= -->
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