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Switched away from tracking absolute time to tracking relative.

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This commit is contained in:
Thomas Harte 2016-04-06 20:46:00 -04:00
parent d4be4c4769
commit 28e6517234
1 changed files with 11 additions and 13 deletions
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24
OSBindings/Mac/Clock Signal/Documents/MachineDocument.swift
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@ -28,25 +28,23 @@ class MachineDocument: NSDocument, CSOpenGLViewDelegate, CSOpenGLViewResponderDe
}
var intendedCyclesPerSecond: Int64 = 0
private var lastCycleCount: Int64?
private var cycleCountError: Int64 = 0
private var lastTime: CVTimeStamp?
final func openGLView(view: CSOpenGLView, didUpdateToTime time: CVTimeStamp) {
// TODO: treat time as a delta from old time, work out how many cycles that is plus error
if let lastTime = lastTime {
// perform (time passed in seconds) * (intended cycles per second), converting and
// maintaining an error count to deal with underflow
let videoTimeScale64 = Int64(time.videoTimeScale)
let videoTimeCount = ((time.videoTime - lastTime.videoTime) * intendedCyclesPerSecond) + cycleCountError
cycleCountError = videoTimeCount % videoTimeScale64
let numberOfCycles = videoTimeCount / videoTimeScale64
// this slightly elaborate dance is to avoid overflow
let videoTimeScale64 = Int64(time.videoTimeScale)
let cycleCountLow = ((time.videoTime % videoTimeScale64) * intendedCyclesPerSecond) / videoTimeScale64
let cycleCountHigh = (time.videoTime / videoTimeScale64) * intendedCyclesPerSecond
let cycleCount = cycleCountLow + cycleCountHigh
if let lastCycleCount = lastCycleCount {
let elapsedTime = cycleCount - lastCycleCount
// if the emulation has fallen too far behind then silently limit the request;
// some actions — e.g. the host computer waking after sleep — may give us a
// prohibitive backlog
runForNumberOfCycles(min(Int32(elapsedTime), Int32(intendedCyclesPerSecond / 25)))
runForNumberOfCycles(min(Int32(numberOfCycles), Int32(intendedCyclesPerSecond / 25)))
}
lastCycleCount = cycleCount
lastTime = time
}
func openGLView(view: CSOpenGLView, drawViewOnlyIfDirty onlyIfDirty: Bool) {}