emb-accel.html
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><!-- /home/reggie/tmp/qt-3.0-reggie-5401/qt-x11-commercial-3.0.5/doc/accel.doc:36 --><html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Adding an accelerated graphics driver to Qt/Embedded</title><style type="text/css"><!--h3.fn,span.fn { margin-left: 1cm; text-indent: -1cm; }a:link { color: #004faf; text-decoration: none }a:visited { color: #672967; text-decoration: none }body { background: #ffffff; color: black; }--></style></head><body><table border="0" cellpadding="0" cellspacing="0" width="100%"><tr bgcolor="#E5E5E5"><td 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="mainclasses.html"><font color="#004faf">Main Classes</font></a> | <a href="annotated.html"><font color="#004faf">Annotated</font></a> | <a href="groups.html"><font color="#004faf">Grouped Classes</font></a> | <a href="functions.html"><font color="#004faf">Functions</font></a></td><td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>Adding an accelerated graphics driver to Qt/Embedded</h1> <p> Qt/Embedded has the capacity to make use of hardware accelerators.To use a hardware accelerator for a PCI or AGP driver, you need toperform the following steps:<p> <ol type=1><li> Define an accelerated descendant of QLinuxFbScreen. <p> This should implement <tt>QVoodooScreen::connect()</tt> to map itsregisters. Use <tt>qt_probe_bus</tt> to get a pointer to the PCI configspace. This is where you should check that you're being pointed to theright device (using the PCI device/manufacturer ID information). Thenuse PCI config space to locate your device's accelerator registers inphysical memory and mmap the appropriate region from <tt>/dev/mem</tt>.There is no need to map the framebuffer, <tt>QLinuxFbScreen</tt> will dothis for you. Return <tt>FALSE</tt> if a problem occurs at any point. <tt>QVoodooScreen::initDevice()</tt> will be called only by the QWS server andis guaranteed to be called before any drawing is done (and so is agood place to set registers to known states). <tt>connect()</tt> will be calledby every connecting client.<p> <li> Define an accelerated descendant of QGfxRaster. <p> This is where the actual drawing code goes. Anything not implementedin hardware can be passed back to <tt>QGfxRaster</tt> to do in software. Usethe optype variable to make sure that accelerated and unacceleratedoperations are synchronised (if you start drawing via software into anarea where the hardware accelerator is still drawing then your drawingoperations will appear to be in the wrong order). optype is stored inshared memory and is set to 0 by unaccelerated operations; acceleratedoperations should set it to 1. When a software graphics operation isrequested and optype is 1, <tt>QGfxRaster::sync()</tt> is called; you shouldprovide your own implementation of this that waits for the graphicsengine to go idle. lastop is also available for optimisation and isstored in the shared space - this will not be set by the software-only<tt>QGfx</tt> and can be used to store the type of your last operation (e.g.drawing a rectangle) so that part of the setup for the next operationcan be avoided when many of the same operations are performed insequence.<p> All drawing operations should be protected via a <tt>QWSDisplay::grab()</tt>before any registers, lastop or optype are accessed, and <tt>ungrabbed()</tt> at the end. This prevents two applications trying toaccess the accelerator at once and possibly locking up the machine.It's possible that your source data is not on the graphics card so youshould check in such cases and fall back to software if necessary.Note that <tt>QGfxRaster</tt> supports some features not directly supportedby <a href="qpainter.html">QPainter</a> (for instance, alpha channels in 32-bit data andstretchBlt's). These features are used by Qt; stretchBlt speeds up <a href="qpixmap.html#xForm">QPixmap::xForm</a>() and <tt>drawPixmap()</tt> into a transformed <a href="qpainter.html">QPainter</a>,alpha channel acceleration is supported for 32-bit pixmaps.<p> <li>If you wish, define an accelerated descendant of <tt>QScreenCursor</tt>. <tt>restoreUnder()</tt>, <tt>saveUnder()</tt>, <tt>drawCursor()</tt> and <tt>draw()</tt> shouldbe defined as null operations. Implement <tt>set()</tt>, <tt>move()</tt>, <tt>show()</tt> and <tt>hide()</tt>. 4k is left for your cursor at the end of thevisible part of the framebuffer (i.e. at (width*height*depth)/8 )<p> <li>Implement <tt>initCursor()</tt> and <tt>createGfx()</tt> in your <a href="qscreen.html">QScreen</a>descendant. Implement <tt>useOffscreen()</tt> and return <tt>TRUE</tt> if you canmake use of offscreen graphics memory.<p> <li>Implement a small function <tt>qt_get_screen_mychip()</tt>, which simplyreturns a new <tt>QMychipScreen</tt><p> <li>Add your driver to the DriverTable table in <tt>qgfxraster_qws.cpp</tt>,e.g.<pre>{ "MyChip", qt_get_screen_mychip,1 },</pre> <p> The first parameter is the name used with QWS_DISPLAY to request youraccelerated driver.<p> <li>To run with your new driver,<pre>export QWS_DISPLAY=MyChip </pre> (optionally MyChip:/dev/fb<n> to request a different Linuxframebuffer than <tt>/dev/fb0</tt>), then run the program<p> </ol><p> If your driver is not PCI or AGP you'll need to inherit <a href="qscreen.html">QScreen</a>instead of <tt>QLinuxFbScreen</tt> and implement similar functionality to <tt>QLinuxFbScreen</tt>, but otherwise the process should be similar. The mostcomplete example driver is <tt>qgfxmach64_qws.cpp</tt>; <tt>qgfxvoodoo_qws.cpp</tt> may provide a smaller and easier-to-understanddriver.<p> <!-- eof --><p><address><hr><div align=center><table width=100% cellspacing=0 border=0><tr><td>Copyright © 2002 <a href="http://www.trolltech.com">Trolltech</a><td><a href="http://www.trolltech.com/trademarks.html">Trademarks</a><td align=right><div align=right>Qt version 3.0.5</div></table></div></address></body></html>⌨️ 快捷键说明
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