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<title>Qt 4.6: QDirectPainter Class Reference</title>
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<td width="1"> </td><td class="postheader" valign="center"><a href="index.html"><font color="#004faf">Home</font></a> · <a href="classes.html"><font color="#004faf">All Classes</font></a> · <a href="functions.html"><font color="#004faf">All Functions</font></a> · <a href="overviews.html"><font color="#004faf">Overviews</font></a></td></tr></table><h1 class="title">QDirectPainter Class Reference<br /><span class="small-subtitle">[<a href="qtgui.html">QtGui</a> module]</span>
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<p>The QDirectPainter class provides direct access to the underlying hardware in Qt for Embedded Linux. <a href="#details">More...</a></p>
<pre> #include <QDirectPainter></pre><p>Inherits <a href="qobject.html">QObject</a>.</p>
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<li><a href="qdirectpainter-members.html">List of all members, including inherited members</a></li>
<li><a href="qdirectpainter-obsolete.html">Obsolete members</a></li>
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<a name="public-types"></a>
<h2>Public Types</h2>
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<tr><td class="memItemLeft" align="right" valign="top">enum </td><td class="memItemRight" valign="bottom"><b><a href="qdirectpainter.html#SurfaceFlag-enum">SurfaceFlag</a></b> { NonReserved, Reserved, ReservedSynchronous }</td></tr>
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<a name="public-functions"></a>
<h2>Public Functions</h2>
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<tr><td class="memItemLeft" align="right" valign="top"></td><td class="memItemRight" valign="bottom"><b><a href="qdirectpainter.html#QDirectPainter">QDirectPainter</a></b> ( QObject * <i>parent</i> = 0, SurfaceFlag <i>flag</i> = NonReserved )</td></tr>
<tr><td class="memItemLeft" align="right" valign="top"></td><td class="memItemRight" valign="bottom"><b><a href="qdirectpainter.html#dtor.QDirectPainter">~QDirectPainter</a></b> ()</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">QRegion </td><td class="memItemRight" valign="bottom"><b><a href="qdirectpainter.html#allocatedRegion">allocatedRegion</a></b> () const</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">void </td><td class="memItemRight" valign="bottom"><b><a href="qdirectpainter.html#endPainting">endPainting</a></b> ()</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">void </td><td class="memItemRight" valign="bottom"><b><a href="qdirectpainter.html#endPainting-2">endPainting</a></b> ( const QRegion & <i>region</i> )</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">void </td><td class="memItemRight" valign="bottom"><b><a href="qdirectpainter.html#flush">flush</a></b> ( const QRegion & <i>region</i> )</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">QRect </td><td class="memItemRight" valign="bottom"><b><a href="qdirectpainter.html#geometry">geometry</a></b> () const</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">void </td><td class="memItemRight" valign="bottom"><b><a href="qdirectpainter.html#lower">lower</a></b> ()</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">void </td><td class="memItemRight" valign="bottom"><b><a href="qdirectpainter.html#raise">raise</a></b> ()</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">virtual void </td><td class="memItemRight" valign="bottom"><b><a href="qdirectpainter.html#regionChanged">regionChanged</a></b> ( const QRegion & <i>newRegion</i> )</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">QRegion </td><td class="memItemRight" valign="bottom"><b><a href="qdirectpainter.html#requestedRegion">requestedRegion</a></b> () const</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">void </td><td class="memItemRight" valign="bottom"><b><a href="qdirectpainter.html#setGeometry">setGeometry</a></b> ( const QRect & <i>rectangle</i> )</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">void </td><td class="memItemRight" valign="bottom"><b><a href="qdirectpainter.html#setRegion">setRegion</a></b> ( const QRegion & <i>region</i> )</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">void </td><td class="memItemRight" valign="bottom"><b><a href="qdirectpainter.html#startPainting">startPainting</a></b> ( bool <i>lockDisplay</i> = true )</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">WId </td><td class="memItemRight" valign="bottom"><b><a href="qdirectpainter.html#winId">winId</a></b> () const</td></tr>
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<li><div bar="2" class="fn"></div>29 public functions inherited from <a href="qobject.html#public-functions">QObject</a></li>
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<a name="static-public-members"></a>
<h2>Static Public Members</h2>
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<tr><td class="memItemLeft" align="right" valign="top">uchar * </td><td class="memItemRight" valign="bottom"><b><a href="qdirectpainter.html#frameBuffer">frameBuffer</a></b> ()</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">int </td><td class="memItemRight" valign="bottom"><b><a href="qdirectpainter.html#linestepx">linestep</a></b> ()</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">void </td><td class="memItemRight" valign="bottom"><b><a href="qdirectpainter.html#lock">lock</a></b> ()</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">int </td><td class="memItemRight" valign="bottom"><b><a href="qdirectpainter.html#screenDepth">screenDepth</a></b> ()</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">int </td><td class="memItemRight" valign="bottom"><b><a href="qdirectpainter.html#screenHeight">screenHeight</a></b> ()</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">int </td><td class="memItemRight" valign="bottom"><b><a href="qdirectpainter.html#screenWidth">screenWidth</a></b> ()</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">void </td><td class="memItemRight" valign="bottom"><b><a href="qdirectpainter.html#unlock">unlock</a></b> ()</td></tr>
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<li><div bar="2" class="fn"></div>5 static public members inherited from <a href="qobject.html#static-public-members">QObject</a></li>
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<h3>Additional Inherited Members</h3>
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<li><div class="fn"></div>1 property inherited from <a href="qobject.html#properties">QObject</a></li>
<li><div class="fn"></div>1 public slot inherited from <a href="qobject.html#public-slots">QObject</a></li>
<li><div class="fn"></div>1 signal inherited from <a href="qobject.html#signals">QObject</a></li>
<li><div class="fn"></div>7 protected functions inherited from <a href="qobject.html#protected-functions">QObject</a></li>
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<a name="details"></a>
<hr />
<h2>Detailed Description</h2>
<p>The QDirectPainter class provides direct access to the underlying hardware in Qt for Embedded Linux.</p>
<p>Note that this class is only available in <a href="qt-embedded-linux.html">Qt for Embedded Linux</a>.</p>
<p>QDirectPainter allows a client application to reserve a region of the framebuffer and render directly onto the screen. There are two ways of using the QDirectPainter class: You can either reserve a region using the provided static functions, or you can instantiate an object and make use of its more dynamic API.</p>
<ul><li><a href="#dynamic-allocation">Dynamic Allocation</a></li>
<li><a href="#static-allocation">Static Allocation</a></li>
<li><a href="#rendering">Rendering</a></li>
</ul>
<a name="dynamic-allocation"></a>
<h3>Dynamic Allocation</h3>
<p>By instantiating a QDirectPainter object using the default <a href="qdirectpainter.html#SurfaceFlag-enum">QDirectPainter::NonReserved</a> surface flag, the client application only gets some control over the reserved region, i.e., it can still render directly onto the screen but the allocated region may change (for example, if a window with a higher focus requests parts of the same region). The currently allocated region can be retrieved using the <a href="qdirectpainter.html#allocatedRegion">allocatedRegion</a>() function, while the <a href="qdirectpainter.html#requestedRegion">requestedRegion</a>() function returns the originally reserved region.</p>
<a name="static-allocation"></a>
<h3>Static Allocation</h3>
<p>Using the static approach, the client application gets complete control over the reserved region, i.e., the affected region will never be modified by the screen driver.</p>
<p>To create a static region, pass the <a href="qdirectpainter.html#SurfaceFlag-enum">QDirectPainter::Reserved</a> surface flag to the constructor. After the reserved region is reported through <a href="qdirectpainter.html#regionChanged">regionChanged</a>(), the allocated region will not change, unless <a href="qdirectpainter.html#setRegion">setRegion</a>() is called.</p>
<p>If <a href="qdirectpainter.html#SurfaceFlag-enum">QDirectPainter::ReservedSynchronous</a> is passed to the constructor, calls to <a href="qdirectpainter.html#setRegion">setRegion</a>() will block until the region is reserved, meaning that <a href="qdirectpainter.html#allocatedRegion">allocatedRegion</a>() will be available immediately. Note that in the current version <a href="qdirectpainter.html#setRegion">setRegion</a>() will cause the application event loop to be entered, potentially causing reentrancy issues.</p>
<a name="rendering"></a>
<h3>Rendering</h3>
<p>To draw on a given region, the application must first get hold of a pointer to the framebuffer. In most cases, this pointer can be retrieved using the <a href="qdirectpainter.html#frameBuffer">QDirectPainter::frameBuffer</a>() function. But note that if the current screen has subscreens, you must query the screen driver instead to identify the correct subscreen. A pointer to the current screen driver can always be retrieved using the static <a href="qscreen.html#instance">QScreen::instance</a>() function. Then use <a href="qscreen.html">QScreen</a>'s <a href="qscreen.html#subScreenIndexAt">subScreenIndexAt()</a> and <a href="qscreen.html#subScreens">subScreens()</a> functions to access the correct subscreen, and the subscreen's <a href="qscreen.html#base">base()</a> function to retrieve a pointer to the framebuffer.</p>
<p>Depending on the hardware, it might be necessary to lock the framebuffer for exclusive use while writing to it. This is possible using the <a href="qdirectpainter.html#lock">lock</a>() and <a href="qdirectpainter.html#unlock">unlock</a>() functions. Note that calling <a href="qdirectpainter.html#lock">lock</a>() will prevent all other applications from working until <a href="qdirectpainter.html#unlock">unlock</a>() is called.</p>
<p>In addition, QDirectPainter provides several functions returning information about the framebuffer: the <a href="qdirectpainter.html#linestepx">linestep</a>() function returns the length (in bytes) of each scanline of the framebuffer while the <a href="qdirectpainter.html#screenDepth">screenDepth</a>(), <a href="qdirectpainter.html#screenWidth">screenWidth</a>() and <a href="qdirectpainter.html#screenHeight">screenHeight</a>() function return the screen metrics.</p>
<p>See also <a href="qscreen.html">QScreen</a>, <a href="qwsembedwidget.html">QWSEmbedWidget</a>, and <a href="qt-embedded-architecture.html">Qt for Embedded Linux Architecture</a>.</p>
<hr />
<h2>Member Type Documentation</h2>
<a name="//apple_ref/cpp/tag/QDirectPainter/SurfaceFlag"></a>
<a name="//apple_ref/cpp/econst/QDirectPainter/NonReserved"></a>
<a name="//apple_ref/cpp/econst/QDirectPainter/Reserved"></a>
<a name="//apple_ref/cpp/econst/QDirectPainter/ReservedSynchronous"></a>
<h3 class="fn"><a name="SurfaceFlag-enum"></a>enum QDirectPainter::SurfaceFlag</h3>
<p>This enum describes the behavior of the region reserved by this <a href="qdirectpainter.html">QDirectPainter</a> object.</p>
<p><table class="valuelist" border="1" cellpadding="2" cellspacing="1" width="100%">
<tr><th width="25%">Constant</th><th width="15%">Value</th><th width="60%">Description</th></tr>
<tr><td valign="top"><tt>QDirectPainter::NonReserved</tt></td><td align="center" valign="top"><tt>0</tt></td><td valign="top">The allocated region may change, e.g., if a window with a higher focus requests parts of the same region. See also <a href="qdirectpainter.html#dynamic-allocation">Dynamic Allocation</a>.</td></tr>
<tr><td valign="top"><tt>QDirectPainter::Reserved</tt></td><td align="center" valign="top"><tt>1</tt></td><td valign="top">The allocated region will never change. See also <a href="qdirectpainter.html#static-allocation">Static Allocation</a>.</td></tr>
<tr><td valign="top"><tt>QDirectPainter::ReservedSynchronous</tt></td><td align="center" valign="top"><tt>3</tt></td><td valign="top">The allocated region will never change and each function that changes the allocated region will be blocking.</td></tr>
</table></p>
<p>See also <a href="qdirectpainter.html#allocatedRegion">allocatedRegion</a>().</p>
<hr />
<h2>Member Function Documentation</h2>
<a name="//apple_ref/cpp/instm/QDirectPainter/QDirectPainter"></a>
<h3 class="fn"><a name="QDirectPainter"></a>QDirectPainter::QDirectPainter ( <a href="qobject.html">QObject</a> * <i>parent</i> = 0, <a href="qdirectpainter.html#SurfaceFlag-enum">SurfaceFlag</a> <i>flag</i> = NonReserved )</h3>
<p>Constructs a <a href="qdirectpainter.html">QDirectPainter</a> object with the given <i>parent</i> and surface <i>flag</i>.</p>
<a name="//apple_ref/cpp/instm/QDirectPainter/~QDirectPainter"></a>
<h3 class="fn"><a name="dtor.QDirectPainter"></a>QDirectPainter::~QDirectPainter ()</h3>
<p>Destroys this <a href="qdirectpainter.html">QDirectPainter</a> object, releasing the reserved region.</p>
<p>See also <a href="qdirectpainter.html#allocatedRegion">allocatedRegion</a>().</p>
<a name="//apple_ref/cpp/instm/QDirectPainter/allocatedRegion"></a>
<h3 class="fn"><a name="allocatedRegion"></a><a href="qregion.html">QRegion</a> QDirectPainter::allocatedRegion () const</h3>
<p>Returns the currently reserved region.</p>
<p>Note that if the <a href="qdirectpainter.html#SurfaceFlag-enum">QDirectPainter::Reserved</a> flag is set, the region returned by this function will always be equivalent to the region returned by the <a href="qdirectpainter.html#requestedRegion">requestedRegion</a>() function. Otherwise they might differ (see <a href="qdirectpainter.html#dynamic-allocation">Dynamic Allocation</a> for details).</p>
<p>This function was introduced in Qt 4.2.</p>
<p>See also <a href="qdirectpainter.html#requestedRegion">requestedRegion</a>() and <a href="qdirectpainter.html#geometry">geometry</a>().</p>
<a name="//apple_ref/cpp/instm/QDirectPainter/endPainting"></a>
<h3 class="fn"><a name="endPainting"></a>void QDirectPainter::endPainting ()</h3>
<p>Call this function when you are done updating the screen. It will notify the hardware, if necessary, that your painting operations have ended.</p>
<p>This function was introduced in Qt 4.2.</p>
<h3 class="fn"><a name="endPainting-2"></a>void QDirectPainter::endPainting ( const <a href="qregion.html">QRegion</a> & <i>region</i> )</h3>
<p>This is an overloaded function.</p>
<p>This function will automatically call <a href="qdirectpainter.html#flush">flush</a>() to flush the <i>region</i> to the display before notifying the hardware, if necessary, that painting operations have ended.</p>
<p>This function was introduced in Qt 4.3.</p>
<a name="//apple_ref/cpp/instm/QDirectPainter/flush"></a>
<h3 class="fn"><a name="flush"></a>void QDirectPainter::flush ( const <a href="qregion.html">QRegion</a> & <i>region</i> )</h3>
<p>Flushes the <i>region</i> onto the screen.</p>
<p>This function was introduced in Qt 4.3.</p>
<a name="//apple_ref/cpp/clm/QDirectPainter/frameBuffer"></a>
<h3 class="fn"><a name="frameBuffer"></a><a href="qtglobal.html#uchar-typedef">uchar</a> * QDirectPainter::frameBuffer () <tt> [static]</tt></h3>
<p>Returns a pointer to the beginning of the display memory.</p>
<p>Note that it is the application's responsibility to limit itself to modifying only the reserved region.</p>
<p>Do not use this pointer if the current screen has subscreens, query the screen driver instead: A pointer to the current screen driver can always be retrieved using the static <a href="qscreen.html#instance">QScreen::instance</a>() function. Then use <a href="qscreen.html">QScreen</a>'s <a href="qscreen.html#subScreenIndexAt">subScreenIndexAt()</a> and <a href="qscreen.html#subScreens">subScreens()</a> functions to access the correct subscreen, and the subscreen's <a href="qscreen.html#base">base()</a> function to retrieve a pointer to the framebuffer.</p>
<p>See also <a href="qdirectpainter.html#requestedRegion">requestedRegion</a>(), <a href="qdirectpainter.html#allocatedRegion">allocatedRegion</a>(), and <a href="qdirectpainter.html#linestepx">linestep</a>().</p>
<a name="//apple_ref/cpp/instm/QDirectPainter/geometry"></a>
<h3 class="fn"><a name="geometry"></a><a href="qrect.html">QRect</a> QDirectPainter::geometry () const</h3>
<p>Returns the bounding rectangle of the requested region.</p>
<p>This function was introduced in Qt 4.2.</p>
<p>See also <a href="qdirectpainter.html#setGeometry">setGeometry</a>() and <a href="qdirectpainter.html#requestedRegion">requestedRegion</a>().</p>
<a name="//apple_ref/cpp/clm/QDirectPainter/linestep"></a>
<h3 class="fn"><a name="linestepx"></a>int QDirectPainter::linestep () <tt> [static]</tt></h3>
<p>Returns the length (in bytes) of each scanline of the framebuffer.</p>
<p>See also <a href="qdirectpainter.html#frameBuffer">frameBuffer</a>().</p>
<a name="//apple_ref/cpp/clm/QDirectPainter/lock"></a>
<h3 class="fn"><a name="lock"></a>void QDirectPainter::lock () <tt> [static]</tt></h3>
<p>Locks access to the framebuffer.</p>
<p>Note that calling this function will prevent all other applications from updating the display until <a href="qdirectpainter.html#unlock">unlock</a>() is called.</p>
<p>See also <a href="qdirectpainter.html#unlock">unlock</a>().</p>
<a name="//apple_ref/cpp/instm/QDirectPainter/lower"></a>
<h3 class="fn"><a name="lower"></a>void QDirectPainter::lower ()</h3>
<p>Lowers the reserved region to the bottom of the widget stack.</p>
<p>After this call the reserved region will be visually behind (and therefore obscured by) any overlapping widgets.</p>
<p>This function was introduced in Qt 4.2.</p>
<p>See also <a href="qdirectpainter.html#raise">raise</a>() and <a href="qdirectpainter.html#requestedRegion">requestedRegion</a>().</p>
<a name="//apple_ref/cpp/instm/QDirectPainter/raise"></a>
<h3 class="fn"><a name="raise"></a>void QDirectPainter::raise ()</h3>
<p>Raises the reserved region to the top of the widget stack.</p>
<p>After this call the reserved region will be visually in front of any overlapping widgets.</p>
<p>This function was introduced in Qt 4.2.</p>
<p>See also <a href="qdirectpainter.html#lower">lower</a>() and <a href="qdirectpainter.html#requestedRegion">requestedRegion</a>().</p>
<a name="//apple_ref/cpp/instm/QDirectPainter/regionChanged"></a>
<h3 class="fn"><a name="regionChanged"></a>void QDirectPainter::regionChanged ( const <a href="qregion.html">QRegion</a> & <i>newRegion</i> ) <tt> [virtual]</tt></h3>
<p>This function is called when the allocated region changes.</p>
<p>This function is not called for region changes that happen while the <a href="qdirectpainter.html#startPainting">startPainting</a>() function is executing.</p>
<p>Note that the given region, <i>newRegion</i>, is not guaranteed to be correct at the time you access the display. To prevent reentrancy problems you should always call <a href="qdirectpainter.html#startPainting">startPainting</a>() before updating the display and then use <a href="qdirectpainter.html#allocatedRegion">allocatedRegion</a>() to retrieve the correct region.</p>
<p>This function was introduced in Qt 4.2.</p>
<p>See also <a href="qdirectpainter.html#allocatedRegion">allocatedRegion</a>(), <a href="qdirectpainter.html#startPainting">startPainting</a>(), and <a href="qdirectpainter.html#dynamic-allocation">Dynamic Allocation</a>.</p>
<a name="//apple_ref/cpp/instm/QDirectPainter/requestedRegion"></a>
<h3 class="fn"><a name="requestedRegion"></a><a href="qregion.html">QRegion</a> QDirectPainter::requestedRegion () const</h3>
<p>Returns the region requested by this <a href="qdirectpainter.html">QDirectPainter</a>.</p>
<p>Note that if the <a href="qdirectpainter.html#SurfaceFlag-enum">QDirectPainter::Reserved</a> flag is set, the region returned by this function will always be equivalent to the region returned by the <a href="qdirectpainter.html#allocatedRegion">allocatedRegion</a>() function. Otherwise they might differ (see <a href="qdirectpainter.html#dynamic-allocation">Dynamic Allocation</a> for details).</p>
<p>This function was introduced in Qt 4.2.</p>
<p>See also <a href="qdirectpainter.html#geometry">geometry</a>(), <a href="qdirectpainter.html#setRegion">setRegion</a>(), and <a href="qdirectpainter.html#allocatedRegion">allocatedRegion</a>().</p>
<a name="//apple_ref/cpp/clm/QDirectPainter/screenDepth"></a>
<h3 class="fn"><a name="screenDepth"></a>int QDirectPainter::screenDepth () <tt> [static]</tt></h3>
<p>Returns the bit depth of the display.</p>
<p>See also <a href="qdirectpainter.html#screenHeight">screenHeight</a>() and <a href="qdirectpainter.html#screenWidth">screenWidth</a>().</p>
<a name="//apple_ref/cpp/clm/QDirectPainter/screenHeight"></a>
<h3 class="fn"><a name="screenHeight"></a>int QDirectPainter::screenHeight () <tt> [static]</tt></h3>
<p>Returns the height of the display in pixels.</p>
<p>See also <a href="qdirectpainter.html#screenWidth">screenWidth</a>() and <a href="qdirectpainter.html#screenDepth">screenDepth</a>().</p>
<a name="//apple_ref/cpp/clm/QDirectPainter/screenWidth"></a>
<h3 class="fn"><a name="screenWidth"></a>int QDirectPainter::screenWidth () <tt> [static]</tt></h3>
<p>Returns the width of the display in pixels.</p>
<p>See also <a href="qdirectpainter.html#screenHeight">screenHeight</a>() and <a href="qdirectpainter.html#screenDepth">screenDepth</a>().</p>
<a name="//apple_ref/cpp/instm/QDirectPainter/setGeometry"></a>
<h3 class="fn"><a name="setGeometry"></a>void QDirectPainter::setGeometry ( const <a href="qrect.html">QRect</a> & <i>rectangle</i> )</h3>
<p>Request to reserve the given <i>rectangle</i> of the framebuffer.</p>
<p>Note that the actually allocated region might differ from the requested one, e.g., if the given region overlaps with the region of another <a href="qdirectpainter.html">QDirectPainter</a> object.</p>
<p>This function was introduced in Qt 4.2.</p>
<p>See also <a href="qdirectpainter.html#geometry">geometry</a>(), <a href="qdirectpainter.html#allocatedRegion">allocatedRegion</a>(), and <a href="qdirectpainter.html#setRegion">setRegion</a>().</p>
<a name="//apple_ref/cpp/instm/QDirectPainter/setRegion"></a>
<h3 class="fn"><a name="setRegion"></a>void QDirectPainter::setRegion ( const <a href="qregion.html">QRegion</a> & <i>region</i> )</h3>
<p>Requests to reserve the given <i>region</i> of the framebuffer.</p>
<p>Note that the actually allocated region might differ from the requested one, e.g., if the given region overlaps with the region of another <a href="qdirectpainter.html">QDirectPainter</a> object.</p>
<p>This function was introduced in Qt 4.2.</p>
<p>See also <a href="qdirectpainter-obsolete.html#region" class="obsolete">region</a>(), <a href="qdirectpainter.html#requestedRegion">requestedRegion</a>(), <a href="qdirectpainter.html#allocatedRegion">allocatedRegion</a>(), and <a href="qdirectpainter.html#dynamic-allocation">Dynamic Allocation</a>.</p>
<a name="//apple_ref/cpp/instm/QDirectPainter/startPainting"></a>
<h3 class="fn"><a name="startPainting"></a>void QDirectPainter::startPainting ( bool <i>lockDisplay</i> = true )</h3>
<p>Call this function before you start updating the pixels in the allocated region. The hardware will be notified, if necessary, that you are about to start painting operations.</p>
<p>Set <i>lockDisplay</i> if you want startPainting() and <a href="qdirectpainter.html#endPainting">endPainting</a>() to <a href="qdirectpainter.html#lock">lock</a>() and <a href="qdirectpainter.html#unlock">unlock</a>() the display automatically.</p>
<p>Note that for a <a href="qdirectpainter.html#SurfaceFlag-enum">NonReserved</a> direct painter, you must call <a href="qdirectpainter.html#allocatedRegion">allocatedRegion</a>() after calling this function, since the allocated region is only guaranteed to be correct after this function has returned.</p>
<p>The <a href="qdirectpainter.html#regionChanged">regionChanged</a>() function will not be called between startPainting() and <a href="qdirectpainter.html#endPainting">endPainting</a>().</p>
<p>This function was introduced in Qt 4.2.</p>
<p>See also <a href="qdirectpainter.html#endPainting">endPainting</a>() and <a href="qdirectpainter.html#flush">flush</a>().</p>
<a name="//apple_ref/cpp/clm/QDirectPainter/unlock"></a>
<h3 class="fn"><a name="unlock"></a>void QDirectPainter::unlock () <tt> [static]</tt></h3>
<p>Unlocks the lock on the framebuffer (set using the <a href="qdirectpainter.html#lock">lock</a>() function), allowing other applications to access the screen.</p>
<p>See also <a href="qdirectpainter.html#lock">lock</a>().</p>
<a name="//apple_ref/cpp/instm/QDirectPainter/winId"></a>
<h3 class="fn"><a name="winId"></a><a href="qwidget.html#WId-typedef">WId</a> QDirectPainter::winId () const</h3>
<p>Returns the window system identifier of the widget.</p>
<p>This function was introduced in Qt 4.2.</p>
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