[Panel-devel] OpenGL applets

[Zack Rusin]

hey,

my flight leaves in the morning so i won't be able to commit this so if 
someone wants to play with it, here you go.

this code allows you to write fully OpenGL based plasma applets. simply 
inherit Plasma::GLApplet instead of Plasma::Applet and reimplement 
GLApplet::paintGLInterface instead of Applet::paintInterface

the whole concept is rather trivial - in glapplet i do some nasty behind the 
curtain hacks to redirect subsequent painting to a pbo, once the applets 
finishes the rendering, we blend the contents of the pbo to the actual 
qpainter invoked on the applet. 

it works really nicely for small/medium size applets. fullscreen applets won't 
work well due to fetches of the pbo contents. that could be eliminated by 
caling setViewport(new QGLWidget()); in CoronaView and then in the GLApplet 
checking whether the widget passed in paintInterface is a QGLWidget and if it 
is, instead of fetching the contents of the fbo we could just use its content 
as a texture (which would basically mean no slow-downs for applets of any 
size). unfortunately it will introduce a flicker of the entire desktop as the 
windows on top of the desktop are being moved (qglwidget doesn't handle well 
obscuring of its contents).

attached is the patch to libplasma and two sample opengl applets. the first 
one will fetch images from flicker and display them in a wheel. the other 
will display 4096 animating (in a wave like pattern) cubes with each side of 
a cube showing an animating svg (as you might guess that one is a little more 
computationally intensive).

obligatory screenshots:
http://chaos.troll.no/~zrusin/plasmagl1.png
http://chaos.troll.no/~zrusin/plasmagl2.png

z
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