diff options
Diffstat (limited to 'doc/html/opengl-overlay-x11-example.html')
| -rw-r--r-- | doc/html/opengl-overlay-x11-example.html | 105 |
1 files changed, 105 insertions, 0 deletions
diff --git a/doc/html/opengl-overlay-x11-example.html b/doc/html/opengl-overlay-x11-example.html new file mode 100644 index 0000000..6bc5136 --- /dev/null +++ b/doc/html/opengl-overlay-x11-example.html @@ -0,0 +1,105 @@ +<!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/examples/opengl/overlay_x11/overlay_x11.doc:1 --> +<html> +<head> +<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> +<title>OpenGL Overlay X11 Example</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>OpenGL Overlay X11 Example</h1> + + +<p> +<b>Warning:</b> From version 5.0 onwards, the Qt OpenGL Extension includes +direct support for 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-QGL widgets in overlay +planes. +<p> Overlayrubber: An example program showing how to use Qt and Qt OpenGL +Extension with X11 overlay visuals. +<p> See <tt>$QTDIR/examples/opengl/overlay_x11</tt> for the source code. +<p> Background information for this example can be found in the +information on <a href="opengl-x11-overlays.html">overlays</a>. +<p> The example program has three main parts: +<p> <ol type=1> +<li> <em>GearWidget</em> - a normal, simple <a href="qglwidget.html">QGLWidget</a>. This renders the usual +gears. It has been modified to print a debug message every time it +redraws (renders) itself. Thus, you can easily confirm that drawing in +the overlay plane does not cause redrawings in the main plane where +the QGLWidget resides. +<p> <li> <em>RubberbandWidget</em> - Very simple standard (non-GL) Qt widget that +implements rubberband drawing. Designed for use in an overlay plane. +It takes the plane's transparent color as a constructor argument and +uses that for its background color. Thus, the widget itself will be +invisible, only the rubberbands it draws will be visible. +<p> <li> <em>main.cpp</em> Creates a GearWidget and a Rubberbandwidget and puts the +latter on top of the former. Contains a routine that checks that the +default visual is in an overlay plane, and returns the transparent +color of that plane. +</ol> +<p> <h2> Running the Example +</h2> +<a name="1"></a><p> Start the <tt>overlayrubber</tt> executable. Click and drag with the left +mouse button to see rubberband drawing. Observe that the <a href="qglwidget.html">QGLWidget</a> +does not redraw itself (no redraw debug messages are output), and yet +the image is not destroyed. Marvel at the coolness of X11 overlays! +<p> <h2> Using this technique in a real application +</h2> +<a name="2"></a><p> For clarity, this example program has been kept very simple. Here are +some hints for real application usage: +<p> <ul> +<p> <li> <em>All normal widgets are in the overlay plane.</em> This means that you +can put all kinds of Qt widgets (your own or standard Qt widgets) on +top of the OpenGL image (widget), e.g. pushbuttons etc., and they can +be moved, resized, or removed without destroying the OpenGL image. +<p> <li> <em>Using with geometry management.</em> The <a href="qlayout.html">QLayout</a> classes don't permit +putting one widget (the overlay) on top of another (the OpenGL +widget); that would defy the whole purpose of the automatic layout. +The solution is to add just one of them to the QLayout object. Have it +keep a pointer to the other (i.e. the <a href="qglwidget.html">QGLWidget</a> knows about its +overlay widget or vice versa). Implement the resizeEvent() method of +the widget you put in the layout, and make it call setGeometry() on +the other widget with its own geometry as parameters, thus keeping the +two widgets' geometries synchronized. +<p> <li> <em>Using together with <a href="qpalette.html">QPalette</a> and <a href="qcolorgroup.html">QColorGroup</a>.</em> Instead of the +simplistic setBackgroundColor( transparentColor ), you can +use Qt's QPalette system to make your overlay widgets use +transparent color for what you want. This way, the normal Qt widgets +can be used as overlays for fancy effects. Just create a palette for +them with the transparent color for the relevant color roles, e.g. +Background and Base, in the Normal and/or Active modes. This way, you +can create see-through QPushButtons etc. +</ul> +<p> <p>See also <a href="opengl-examples.html">OpenGL Examples</a>. + +<!-- 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>Qt 3.3.8</div> +</table></div></address></body> +</html> |