On 03/18/2013 09:07 PM, Simon St James wrote: > Hi all, > > I am currently working on emscripten-qt > (http://vps2.etotheipiplusone.com:30176/redmine/projects/emscripten-qt/wiki/Demos/), > a project that uses Emscripten > (https://github.com/kripken/emscripten/wiki) to compile Qt 4.8.x to Javascript > and run in a browser using an HTML5 canvas for rendering. > > Currently, performance is surprisingly good considering we are still using the > "raster" graphics system where everything is plotted pixel by pixel by Qt and > then flushed to the canvas after pixel format conversion. However, we > suspect > that we can get significant gains in rendering speed by writing a Qt graphics > system that uses HTML5 Canvas drawing primitives. > > However however, it has been suggested that maybe using Qt's own "opengl" > graphics > system would be an even more performant approach. I started investigating > this by running stock Qt apps with stock Qt packages (on Kubuntu 12.04, Intel > HD Graphics card) with " -graphicssystem opengl", and every app I tried gave > only a black window, except for some more visually complex which were mostly > black with a few coloured rectangles scattered about When I compiled Qt > myself and tried with that, I noticed that using KDE's default "Oxygen" style > with -graphicssystem opengl actually triggered an assertion within Qt[1], and > while forcing the style to "plastique" no longer triggered it, I still just > had a black window. Other OpenGL apps work fine. > > So I was wondering whether using Qt's opengl graphics system is feasible? I > heard it was "experimental" and "not pixel-perfect", but I've not heard any > reports that that matched mine, which makes me wonder if I just got very > unlucky
True, it's experimental and not pixel-perfect, and not really well maintained at all for the desktop platforms. You could try to see if "export QT_GL_SWAPBUFFER_PRESERVE=1" fixes the issue with the black windows though. Were you planning on using WebGL? It might be possible, but I'd probably sooner recommend you to use HTML5 Canvas (i.e. a custom paint engine for QPainter). -- Samuel _______________________________________________ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
