| 1 | <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
|
|---|
| 2 | <!-- /home/espenr/tmp/qt-3.3.8-espenr-2499/qt-x11-free-3.3.8/examples/opengl/overlay_x11/overlay_x11.doc:1 -->
|
|---|
| 3 | <html>
|
|---|
| 4 | <head>
|
|---|
| 5 | <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
|
|---|
| 6 | <title>OpenGL Overlay X11 Example</title>
|
|---|
| 7 | <style type="text/css"><!--
|
|---|
| 8 | fn { margin-left: 1cm; text-indent: -1cm; }
|
|---|
| 9 | a:link { color: #004faf; text-decoration: none }
|
|---|
| 10 | a:visited { color: #672967; text-decoration: none }
|
|---|
| 11 | body { background: #ffffff; color: black; }
|
|---|
| 12 | --></style>
|
|---|
| 13 | </head>
|
|---|
| 14 | <body>
|
|---|
| 15 |
|
|---|
| 16 | <table border="0" cellpadding="0" cellspacing="0" width="100%">
|
|---|
| 17 | <tr bgcolor="#E5E5E5">
|
|---|
| 18 | <td valign=center>
|
|---|
| 19 | <a href="index.html">
|
|---|
| 20 | <font color="#004faf">Home</font></a>
|
|---|
| 21 | | <a href="classes.html">
|
|---|
| 22 | <font color="#004faf">All Classes</font></a>
|
|---|
| 23 | | <a href="mainclasses.html">
|
|---|
| 24 | <font color="#004faf">Main Classes</font></a>
|
|---|
| 25 | | <a href="annotated.html">
|
|---|
| 26 | <font color="#004faf">Annotated</font></a>
|
|---|
| 27 | | <a href="groups.html">
|
|---|
| 28 | <font color="#004faf">Grouped Classes</font></a>
|
|---|
| 29 | | <a href="functions.html">
|
|---|
| 30 | <font color="#004faf">Functions</font></a>
|
|---|
| 31 | </td>
|
|---|
| 32 | <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>
|
|---|
| 33 |
|
|---|
| 34 |
|
|---|
| 35 | <p>
|
|---|
| 36 | <b>Warning:</b> From version 5.0 onwards, the Qt OpenGL Extension includes
|
|---|
| 37 | direct support for use of OpenGL overlays. For many uses of overlays,
|
|---|
| 38 | this makes the technique described below redundant. See the <a href="opengl-overlay-example.html">overlay</a> example program. The
|
|---|
| 39 | following is a discussion on how to use non-QGL widgets in overlay
|
|---|
| 40 | planes.
|
|---|
| 41 | <p> Overlayrubber: An example program showing how to use Qt and Qt OpenGL
|
|---|
| 42 | Extension with X11 overlay visuals.
|
|---|
| 43 | <p> See <tt>$QTDIR/examples/opengl/overlay_x11</tt> for the source code.
|
|---|
| 44 | <p> Background information for this example can be found in the
|
|---|
| 45 | information on <a href="opengl-x11-overlays.html">overlays</a>.
|
|---|
| 46 | <p> The example program has three main parts:
|
|---|
| 47 | <p> <ol type=1>
|
|---|
| 48 | <li> <em>GearWidget</em> - a normal, simple <a href="qglwidget.html">QGLWidget</a>. This renders the usual
|
|---|
| 49 | gears. It has been modified to print a debug message every time it
|
|---|
| 50 | redraws (renders) itself. Thus, you can easily confirm that drawing in
|
|---|
| 51 | the overlay plane does not cause redrawings in the main plane where
|
|---|
| 52 | the QGLWidget resides.
|
|---|
| 53 | <p> <li> <em>RubberbandWidget</em> - Very simple standard (non-GL) Qt widget that
|
|---|
| 54 | implements rubberband drawing. Designed for use in an overlay plane.
|
|---|
| 55 | It takes the plane's transparent color as a constructor argument and
|
|---|
| 56 | uses that for its background color. Thus, the widget itself will be
|
|---|
| 57 | invisible, only the rubberbands it draws will be visible.
|
|---|
| 58 | <p> <li> <em>main.cpp</em> Creates a GearWidget and a Rubberbandwidget and puts the
|
|---|
| 59 | latter on top of the former. Contains a routine that checks that the
|
|---|
| 60 | default visual is in an overlay plane, and returns the transparent
|
|---|
| 61 | color of that plane.
|
|---|
| 62 | </ol>
|
|---|
| 63 | <p> <h2> Running the Example
|
|---|
| 64 | </h2>
|
|---|
| 65 | <a name="1"></a><p> Start the <tt>overlayrubber</tt> executable. Click and drag with the left
|
|---|
| 66 | mouse button to see rubberband drawing. Observe that the <a href="qglwidget.html">QGLWidget</a>
|
|---|
| 67 | does not redraw itself (no redraw debug messages are output), and yet
|
|---|
| 68 | the image is not destroyed. Marvel at the coolness of X11 overlays!
|
|---|
| 69 | <p> <h2> Using this technique in a real application
|
|---|
| 70 | </h2>
|
|---|
| 71 | <a name="2"></a><p> For clarity, this example program has been kept very simple. Here are
|
|---|
| 72 | some hints for real application usage:
|
|---|
| 73 | <p> <ul>
|
|---|
| 74 | <p> <li> <em>All normal widgets are in the overlay plane.</em> This means that you
|
|---|
| 75 | can put all kinds of Qt widgets (your own or standard Qt widgets) on
|
|---|
| 76 | top of the OpenGL image (widget), e.g. pushbuttons etc., and they can
|
|---|
| 77 | be moved, resized, or removed without destroying the OpenGL image.
|
|---|
| 78 | <p> <li> <em>Using with geometry management.</em> The <a href="qlayout.html">QLayout</a> classes don't permit
|
|---|
| 79 | putting one widget (the overlay) on top of another (the OpenGL
|
|---|
| 80 | widget); that would defy the whole purpose of the automatic layout.
|
|---|
| 81 | The solution is to add just one of them to the QLayout object. Have it
|
|---|
| 82 | keep a pointer to the other (i.e. the <a href="qglwidget.html">QGLWidget</a> knows about its
|
|---|
| 83 | overlay widget or vice versa). Implement the resizeEvent() method of
|
|---|
| 84 | the widget you put in the layout, and make it call setGeometry() on
|
|---|
| 85 | the other widget with its own geometry as parameters, thus keeping the
|
|---|
| 86 | two widgets' geometries synchronized.
|
|---|
| 87 | <p> <li> <em>Using together with <a href="qpalette.html">QPalette</a> and <a href="qcolorgroup.html">QColorGroup</a>.</em> Instead of the
|
|---|
| 88 | simplistic setBackgroundColor( transparentColor ), you can
|
|---|
| 89 | use Qt's QPalette system to make your overlay widgets use
|
|---|
| 90 | transparent color for what you want. This way, the normal Qt widgets
|
|---|
| 91 | can be used as overlays for fancy effects. Just create a palette for
|
|---|
| 92 | them with the transparent color for the relevant color roles, e.g.
|
|---|
| 93 | Background and Base, in the Normal and/or Active modes. This way, you
|
|---|
| 94 | can create see-through QPushButtons etc.
|
|---|
| 95 | </ul>
|
|---|
| 96 | <p> <p>See also <a href="opengl-examples.html">OpenGL Examples</a>.
|
|---|
| 97 |
|
|---|
| 98 | <!-- eof -->
|
|---|
| 99 | <p><address><hr><div align=center>
|
|---|
| 100 | <table width=100% cellspacing=0 border=0><tr>
|
|---|
| 101 | <td>Copyright © 2007
|
|---|
| 102 | <a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a>
|
|---|
| 103 | <td align=right><div align=right>Qt 3.3.8</div>
|
|---|
| 104 | </table></div></address></body>
|
|---|
| 105 | </html>
|
|---|
