From 9555b201fe47b4a74a432d3cb4fe7dba20cf894c Mon Sep 17 00:00:00 2001
From: outfoxxed <outfoxxed@outfoxxed.me>
Date: Wed, 31 Jul 2024 02:37:05 -0700
Subject: [PATCH] core/clock: fix instability causing timer to fire multiple
 times

If the signal was fired slightly before the scheduled time, it would
schedule itself again a couple ms in the future.
---
 src/core/clock.cpp | 80 +++++++++++++++++++++++++++++-----------------
 src/core/clock.hpp |  8 ++++-
 2 files changed, 58 insertions(+), 30 deletions(-)

diff --git a/src/core/clock.cpp b/src/core/clock.cpp
index 0af9762e..ee396ac8 100644
--- a/src/core/clock.cpp
+++ b/src/core/clock.cpp
@@ -8,7 +8,7 @@
 #include "util.hpp"
 
 SystemClock::SystemClock(QObject* parent): QObject(parent) {
-	QObject::connect(&this->timer, &QTimer::timeout, this, &SystemClock::update);
+	QObject::connect(&this->timer, &QTimer::timeout, this, &SystemClock::onTimeout);
 	this->update();
 }
 
@@ -30,41 +30,63 @@ void SystemClock::setPrecision(SystemClock::Enum precision) {
 	this->update();
 }
 
+void SystemClock::onTimeout() {
+	this->setTime(this->nextTime);
+	this->schedule(this->nextTime);
+}
+
 void SystemClock::update() {
-	auto time = QTime::currentTime();
-
 	if (this->mEnabled) {
-		auto secondPrecision = this->mPrecision >= SystemClock::Seconds;
-		auto secondChanged = this->setSeconds(secondPrecision ? time.second() : 0);
-
-		auto minutePrecision = this->mPrecision >= SystemClock::Minutes;
-		auto minuteChanged = this->setMinutes(minutePrecision ? time.minute() : 0);
-
-		auto hourPrecision = this->mPrecision >= SystemClock::Hours;
-		auto hourChanged = this->setHours(hourPrecision ? time.hour() : 0);
-
-		DropEmitter::call(secondChanged, minuteChanged, hourChanged);
-
-		auto nextTime = QTime(
-		    hourPrecision ? time.hour() : 0,
-		    minutePrecision ? time.minute() : 0,
-		    secondPrecision ? time.second() : 0
-		);
-
-		if (secondPrecision) nextTime = nextTime.addSecs(1);
-		else if (minutePrecision) nextTime = nextTime.addSecs(60);
-		else if (hourPrecision) nextTime = nextTime.addSecs(3600);
-
-		auto delay = time.msecsTo(nextTime);
-		// day rollover
-		if (delay < 0) delay += 86400000;
-
-		this->timer.start(delay);
+		this->setTime(QTime::currentTime());
+		this->schedule(QTime::currentTime());
 	} else {
 		this->timer.stop();
 	}
 }
 
+void SystemClock::setTime(QTime time) {
+	auto secondPrecision = this->mPrecision >= SystemClock::Seconds;
+	auto secondChanged = this->setSeconds(secondPrecision ? time.second() : 0);
+
+	auto minutePrecision = this->mPrecision >= SystemClock::Minutes;
+	auto minuteChanged = this->setMinutes(minutePrecision ? time.minute() : 0);
+
+	auto hourPrecision = this->mPrecision >= SystemClock::Hours;
+	auto hourChanged = this->setHours(hourPrecision ? time.hour() : 0);
+
+	DropEmitter::call(secondChanged, minuteChanged, hourChanged);
+}
+
+void SystemClock::schedule(QTime floor) {
+	auto secondPrecision = this->mPrecision >= SystemClock::Seconds;
+	auto minutePrecision = this->mPrecision >= SystemClock::Minutes;
+	auto hourPrecision = this->mPrecision >= SystemClock::Hours;
+
+setnext:
+	auto nextTime = QTime(
+	    hourPrecision ? floor.hour() : 0,
+	    minutePrecision ? floor.minute() : 0,
+	    secondPrecision ? floor.second() : 0
+	);
+
+	if (secondPrecision) nextTime = nextTime.addSecs(1);
+	else if (minutePrecision) nextTime = nextTime.addSecs(60);
+	else if (hourPrecision) nextTime = nextTime.addSecs(3600);
+
+	auto delay = QTime::currentTime().msecsTo(nextTime);
+
+	// If off by more than 2 hours we likely wrapped around midnight.
+	if (delay < -7200000) delay += 86400000;
+	else if (delay < 0) {
+		// Otherwise its just the timer being unstable.
+		floor = QTime::currentTime();
+		goto setnext;
+	}
+
+	this->timer.start(delay);
+	this->nextTime = nextTime;
+}
+
 DEFINE_MEMBER_GETSET(SystemClock, hours, setHours);
 DEFINE_MEMBER_GETSET(SystemClock, minutes, setMinutes);
 DEFINE_MEMBER_GETSET(SystemClock, seconds, setSeconds);
diff --git a/src/core/clock.hpp b/src/core/clock.hpp
index b3ac1228..7f0dbf74 100644
--- a/src/core/clock.hpp
+++ b/src/core/clock.hpp
@@ -1,5 +1,6 @@
 #pragma once
 
+#include <qdatetime.h>
 #include <qobject.h>
 #include <qqmlintegration.h>
 #include <qtimer.h>
@@ -49,7 +50,7 @@ signals:
 	void secondsChanged();
 
 private slots:
-	void update();
+	void onTimeout();
 
 private:
 	bool mEnabled = true;
@@ -58,6 +59,11 @@ private:
 	quint32 mMinutes = 0;
 	quint32 mSeconds = 0;
 	QTimer timer;
+	QTime nextTime;
+
+	void update();
+	void setTime(QTime time);
+	void schedule(QTime floor);
 
 	DECLARE_PRIVATE_MEMBER(SystemClock, hours, setHours, mHours, hoursChanged);
 	DECLARE_PRIVATE_MEMBER(SystemClock, minutes, setMinutes, mMinutes, minutesChanged);