From d796c9dd933ab96ec83b9a634feedd5d32e1ba3f Mon Sep 17 00:00:00 2001 From: Timothy Pearson Date: Tue, 8 Nov 2011 12:31:36 -0600 Subject: Test conversion to TQt3 from Qt3 8c6fc1f8e35fd264dd01c582ca5e7549b32ab731 --- doc/html/opengl-overlay-x11-example.html | 105 +++++++++++++++++++++++++++++++ 1 file changed, 105 insertions(+) create mode 100644 doc/html/opengl-overlay-x11-example.html (limited to 'doc/html/opengl-overlay-x11-example.html') diff --git a/doc/html/opengl-overlay-x11-example.html b/doc/html/opengl-overlay-x11-example.html new file mode 100644 index 000000000..554f6e79b --- /dev/null +++ b/doc/html/opengl-overlay-x11-example.html @@ -0,0 +1,105 @@ + + + + + +OpenGL Overlay X11 Example + + + + + + + +

OpenGL Overlay X11 Example

+ + +

+Warning: From version 5.0 onwards, the TQt OpenGL Extension includes +direct support for use of OpenGL overlays. For many uses of overlays, +this makes the technique described below redundant. See the overlay example program. The +following is a discussion on how to use non-TQGL widgets in overlay +planes. +

Overlayrubber: An example program showing how to use TQt and TQt OpenGL +Extension with X11 overlay visuals. +

See $QTDIR/examples/opengl/overlay_x11 for the source code. +

Background information for this example can be found in the +information on overlays. +

The example program has three main parts: +

GearWidget - a normal, simple TQGLWidget. 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 TQGLWidget resides. +
RubberbandWidget - Very simple standard (non-GL) TQt 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. +
main.cpp 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. +

Running the Example +

Start the overlayrubber executable. Click and drag with the left +mouse button to see rubberband drawing. Observe that the TQGLWidget +does not redraw itself (no redraw debug messages are output), and yet +the image is not destroyed. Marvel at the coolness of X11 overlays! +

Using this technique in a real application +

For clarity, this example program has been kept very simple. Here are +some hints for real application usage: +

All normal widgets are in the overlay plane. This means that you +can put all kinds of TQt widgets (your own or standard TQt 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. +
Using with geometry management. The TQLayout 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 TQLayout object. Have it +keep a pointer to the other (i.e. the TQGLWidget 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. +
Using together with TQPalette and TQColorGroup. Instead of the +simplistic setBackgroundColor( transparentColor ), you can +use TQt's TQPalette system to make your overlay widgets use +transparent color for what you want. This way, the normal TQt 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 TQPushButtons etc. +