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diff --git a/doc/html/opengl-x11-overlays.html b/doc/html/opengl-x11-overlays.html new file mode 100644 index 000000000..381582890 --- /dev/null +++ b/doc/html/opengl-x11-overlays.html @@ -0,0 +1,115 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> +<!-- /home/espenr/tmp/qt-3.3.8-espenr-2499/qt-x11-free-3.3.8/doc/opengl-x11-overlays.doc:36 --> +<html> +<head> +<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> +<title>How to use X11 overlays with the TQt OpenGL extension</title> +<style type="text/css"><!-- +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>How to use X11 overlays with the TQt OpenGL extension</h1> + + + +<p> X11 overlays are a powerful mechanism for drawing +annotations etc., on top of an image without destroying it, thus saving +a great deal of image rendering time. For more information, consult the highly +recommended book <em>OpenGL Programming for the X Window System</em> (Mark +Kilgard, Addison Wesley Developers Press 1996). +<p> <b>Warning:</b> From version 5.0 onwards, the TQt OpenGL Extension includes +direct support for the use of OpenGL overlays. For many uses of +overlays, this makes the technique described below redundant. See the +<a href="opengl-overlay-example.html">overlay</a> example program. The +following is a discussion on how to use non-TQGL widgets in overlay +planes. +<p> In the typical case, X11 overlays can easily be used together with the +current version of TQt and the TQt OpenGL Extension. The following +retquirements apply: +<p> <ol type=1> +<li> Your X server and graphics card/hardware must support overlays. +For many X servers, overlay support can be turned on with +a configuration option; consult your X server installation +documentation. +<p> <li> Your X server must (be configured to) use an overlay visual as the +default visual. Most modern X servers do this, since this has the +added advantage that pop-up menus, overlapping windows etc., will +<em>not</em> destroy underlying images in the main plane, thereby +avoiding expensive redraws. +<p> <li> The best (deepest) visual for OpenGL rendering is in the main +plane. This is the normal case. Typically, X servers that support +overlays provide a 24 bit deep TrueColor visual in the main plane, +and an 8 bit PseudoColor (default) visual in the overlay plane. +</ol> +<p> The provided example program <a href="opengl-overlay-example.html">X11 +overlay</a> will check for these and report if anything is wrong. +See <a href="#x11visuals">About X11 Visuals</a>, below for more +information. +<p> <h2> How it works +</h2> +<a name="1"></a><p> Given the above, a <a href="qglwidget.html">TQGLWidget</a> will by default use the main plane +visual, while all other widgets will use the overlay visual. Thus, we +can place a normal widget on top of the TQGLWidget, and do drawing on +it, without destroying the image in the OpenGL window. In other words, +we can use all the drawing capabilities of <a href="qpainter.html">TQPainter</a> to draw the +annotations, rubberbands, etc. For the typical use of overlays, +this is much easier than using OpenGL for rendering the annotations. +<p> An overlay plane has a specific color called the transparent +color. Pixels drawn in this color will not be visible; instead the +underlying OpenGL image will show through. In the example program +<a href="opengl-overlay-example.html">X11 overlay</a>, the file +<tt>main.cpp</tt> contains a routine that returns a <a href="qcolor.html">TQColor</a> containing the +transparent color. For the overlay widget, you will typically want to +set the background color to the transparent color, so that the OpenGL +image shows through except where explicitly overpainted. +<p> Note: to use this technique, you must not use the "ManyColor" or +"TrueColor" ColorSpec for <a href="qapplication.html">TQApplication</a>, because this will force +the normal TQt widgets to use a TrueColor visual, which will typically +be in the main plane, not in the overlay plane as desired. +<p> <a name="x11visuals"></a> +<h2> About X11 visuals +</h2> +<a name="2"></a><p> The utilities directory contains two small programs that can help you +determine the capabilities of your X server. These programs are from +the OpenGL book mentioned above, see utilities/NOTICE for copyright +information. The full set of example programs from this book is +available at <a href="ftp://ftp.sgi.com/pub/opengl/opengl_for_x/">ftp://ftp.sgi.com/pub/opengl/opengl_for_x/</a>. +<p> <tt>glxvisuals</tt> will list all the GL-capable visuals the X server +provides, together with the depth and other GL-specific information +for each. Note especially the column "lvl"; a number in this column +means the visual is in an overlay plane. +<p> <tt>sovinfo</tt> will list all available visuals, and provides special +transparency information for overlay visuals. +<p> The <a href="opengl-overlay-example.html">X11 overlay</a> example +program will output what visual is used for the normal TQt widgets, and +what visual is used by the <a href="qglwidget.html">TQGLWidget</a>. +<p> +<!-- eof --> +<p><address><hr><div align=center> +<table width=100% cellspacing=0 border=0><tr> +<td>Copyright © 2007 +<a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a> +<td align=right><div align=right>TQt 3.3.8</div> +</table></div></address></body> +</html> |