fps display takes a very long time to stabilize

[illwieckz]

On my end the displayed fps value is adding up until it reaches its real value, and this takes a long time (around 10s on my end to reach 600fps).

This may be an unwanted side effect of:

• https://github.com/Unvanquished/Unvanquished/pull/2925

Smoothing the fps value to make it more readable is good but having to wait 10s to know the framerate is a bit too much.

[slipher]

The algorithm pretends the FPS has been 0 for an infinite amount of time in the past. So if you run at 600 FPS for 5 seconds then you get 600 * (1 - 2^-5) = 581 and after 10 seconds, 600 * (1 - 2^-10) = 599.4.

The easiest thing to try is decreasing the half-life (first parameter of UpdateFPSCounter). If we change it to 0.5 second instead of 1 second then it would take 5s to stabilize rather than 10.

We could try incorporating a 2nd number into the FPS tracking state to keep track of how long the process has been running, avoiding the period of assumed 0 FPS. Although if it turns out that the first measured frame includes some loading tasks this might not solve your issue.

[slipher]

If the first frame turns out to be equally fast, we could use an easy hack of assuming the speed was the same as during the first frame since forever.