[Interest] Reduce maximum frame rate with Qt5.3 beta

[Sean Harmer]

On Saturday 19 April 2014 23:58:42 Joshua Kolden wrote:
> A  60hz refresh rate is very common, but it is by no means the only sync
> rate in use.  

Of course. That's why the QPA architecture abstracts this via the 
QPlatformScreen::refeshRate() function. Each platform can use this to return 
the refresh rate of a given screen.

> I would hope that qt does noting to limit frame rate! Only
> the user or os/display driver know if frame rate should be bound to the
> display refresh (“vertical sync”) AND if the refresh rate is 60hz or
> something else.  It’s handy if Qt provides access to limiting frame rate
> for specific applications / testing, but by default neither the app nor the
> tool kit should set frame rate to a hard limit.

The swapInterval() mentioned by Laszlo combined with this controls the refresh 
rate in the common case.

Setting swapInterval to:

* 1 enforces vsync
* 0 turns vsync off
* -1 uses adaptive vsync (if framerate is > rfresh rate then use vsync. If 
framerate is < refresh rate do not wait for vsync).

See http://www.opengl.org/wiki/Swap_Interval for more info.

Of course all of this can be overriden by the user if they force some settings 
in the driver's control panel.

Cheers,

Sean

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