[Interest] OpenGL Window Example: Terrible resize window performance

[Till Oliver Knoll]

Hi,

anyone else noticed that the performance is terrible when resizing the
window of the "OpenGL Window Example"? At least on OS X 10.9.4 (some
older MacBook Pro 2010) and OS X 10.8.5 (iMac 2011). Both in debug and
release mode.

When dragging the mouse the window reacts very sluggish: up to 1
second and more until the window changes its size (so it "lags behind
mouse movements").

Note that the triangle itself rotates smoothly, so it appears that
some timer is triggered when resizing the window, and the event is
handled much much later - or whatever. What is even more odd, while
the window resize doesn't happen, the triangle still continues to
rotate smoothly!

I have observed this behaviour in the past, but it is still there in
the latest Qt 5.3.1.


If this was just some random example, I wouldn't mind too much.
However I am (once again ;)) jumping into the "Modern OpenGL with Qt"
topic, and this example really seems to be the "entry point" for all
those new QOpenGL* classes (most other Qt OpenGL examples still use
the outdated QGL* classses and even worse: completely deprecated
glRotate, glVertex and other functions which have been removed from
modern OpenGL "core" context).

The funny thing is: all other OpenGL related example programs -
specifically "Scene Graph - OpenGL Under QML", which I guess uses the
same new QOpenGL classes and is also QWindow based - do not have this
odd "sluggish resize" behaviour: the window resizes immediatelly
(smoothly following the mouse movements) and the content is redrawn
instantaneously.


I haven't examined the source code too much in detail, so I currently
cannot tell from where this "sluggish resize behaviour" comes from (on
Mac only?), but once I know more I'll post it here ;)

In the meantime: anyone else has seen this behaviour? Possibly on
non-Mac platforms, too?

Cheers,
  Oliver