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debuggingfirefox-os

What's the difference between the frame rate numbers?

In the Firefox OS 1.1.1 debug settings, I can enable an option to show frames per second. Quote from MDN:

Enabling this option adds two indicators at the top of the Firefox OS display, indicating the rate at which screen redraws is occurring, in frames per second.

Why two indicators, what's the difference between them?

Solution

  • From the MDN page about Performance in Firefox OS:

    The framerate monitor continuously reports two numbers. […] The left number is the "composition rate": the estimated number of times per second Firefox OS is drawing frames to the hardware framebuffer. […] The rightmost number is the "layer transaction rate", the estimated number of times per second processes are repainting and notifying the compositor.

    In Firefox OS ≥ 1.2, there is a third number that measures the fill rate (thanks paa).