InternalTimer

Handles ticks/frames

  • requestAnimationFrame() is used to call a function before the next browser repaint --- this function performs all updates to the state of the game (hopefully) inbetween repaints
  • Every time an update happens, we record the timestamp in InternalTimer.lastTick_ms
  • When we next update, we see how much time has elapsed since the last update
  • From this, we can calculate how many of our ideal-world (GAME.FRAME_MS) frames have passed
  • If we aren't quite keeping up with the ideal frame rate, eg 2 frames' worth of time has passed since our last update, we can try to keep things looking smooth by moving obstacles twice as far as during a single-frame update
Author
  • Mark Mayes / mm-dev
License
  • GPL-3.0-only

Methods

(static) init()

Source
Main init

(static) nextTick()

Source
Call requestAnimationFrame() for the next opportunity to run InternalTimer.tick()

(static) secondsToFrames(_secs) → {number}

Source
Convert seconds to number of frames

Eg when an animation wants to run for 10secs, how many frames should it last for?

Parameters
Name Type Description
_secs number

How many seconds to convert
Returns
  number

The estimated number of frames it will take for _secs seconds to expire

(static) startTicking()

Source
Start the internal clock

(static) tick(_timestamp_ms)

Source
This function is given as a callback for requestAnimationFrame()
  • Calculate how many frames have passed since the last tick
  • Increment the internal frame count variable
  • Call the main game update function Game.updateByFrameCount(), passing it the number of frames
  • Start the next tick
Parameters
Name Type Description
_timestamp_ms DOMHighResTimeStamp

The time of the previous frame's rendering (automatically passed in by requestAnimationFrame())

(static) updateFpsAverage(_latestFps)

Source
Keep a rolling average of how many frames per second we are achieving
  • On each InternalTimer.tick() an estimate of FPS for the latest frame is calculated and passed in to this function
  • The most recent few (GAME.FPSDISPLAY_AVERAGE_FRAMES_SPAN) fps timings are kept in an array
  • The array is summed and the sum is divided by the array length to get an average (mean) which is stored as InternalTimer.currentFps
Parameters
Name Type Description
_latestFps number

The most recent FPS reading