From 886d923e30525e6bde1633a2261c9f21e5c5daba Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Mon, 10 Feb 2020 23:30:32 -0500
Subject: [PATCH] Attempts to permit fixed speed multiplication.

---
 ClockReceiver/ScanSynchroniser.hpp | 15 ++++++++++++---
 OSBindings/SDL/main.cpp            | 10 +++++++---
 2 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/ClockReceiver/ScanSynchroniser.hpp b/ClockReceiver/ScanSynchroniser.hpp
index aed4b67da..be2682c44 100644
--- a/ClockReceiver/ScanSynchroniser.hpp
+++ b/ClockReceiver/ScanSynchroniser.hpp
@@ -33,7 +33,7 @@ class ScanSynchroniser {
 				// Check out the machine's current frame time.
 				// If it's within 3% of a non-zero integer multiple of the
 				// display rate, mark this time window to be split over the sync.
-				ratio_ = frame_duration / scan_status.field_duration;
+				ratio_ = (frame_duration * base_multiplier_) / scan_status.field_duration;
 				const double integer_ratio = round(ratio_);
 				if(integer_ratio > 0.0) {
 					ratio_ /= integer_ratio;
@@ -54,13 +54,21 @@ class ScanSynchroniser {
 			//
 			// ... with one slight caveat, which is that it is desireable to adjust phase here, to align vertical sync points.
 			// So the set speed multiplier may be adjusted slightly to aim for that.
-			double speed_multiplier = 1.0 / ratio_;
+			double speed_multiplier = 1.0 / (ratio_ / base_multiplier_);
 			if(scan_status.current_position > 0.0) {
 				if(scan_status.current_position < 0.5) speed_multiplier /= phase_adjustment_ratio;
 				else speed_multiplier *= phase_adjustment_ratio;
 			}
 			speed_multiplier_ = (speed_multiplier_ * 0.95) + (speed_multiplier * 0.05);
-			return speed_multiplier_;
+			return speed_multiplier_ * base_multiplier_;
+		}
+
+		void set_base_speed_multiplier(double multiplier) {
+			base_multiplier_ = multiplier;
+		}
+
+		double get_base_speed_multiplier() {
+			return base_multiplier_;
 		}
 
 	private:
@@ -69,6 +77,7 @@ class ScanSynchroniser {
 
 		// Managed local state.
 		double speed_multiplier_ = 1.0;
+		double base_multiplier_ = 1.0;
 
 		// Temporary storage to bridge the can_synchronise -> next_speed_multiplier gap.
 		double ratio_ = 1.0;
diff --git a/OSBindings/SDL/main.cpp b/OSBindings/SDL/main.cpp
index 79757175e..3b683fa21 100644
--- a/OSBindings/SDL/main.cpp
+++ b/OSBindings/SDL/main.cpp
@@ -74,6 +74,10 @@ struct MachineRunner {
 		frame_lock_.clear();
 	}
 
+	void set_speed_multiplier(double multiplier) {
+		scan_synchroniser_.set_base_speed_multiplier(multiplier);
+	}
+
 	std::mutex *machine_mutex;
 	Machine::DynamicMachine *machine;
 
@@ -127,6 +131,7 @@ struct MachineRunner {
 
 				crt_machine->run_for(double(time_now - vsync_time) / 1e9);
 			} else {
+				crt_machine->set_speed_multiplier(scan_synchroniser_.get_base_speed_multiplier());
 				crt_machine->run_for(double(time_now - last_time_) / 1e9);
 			}
 			last_time_ = time_now;
@@ -565,13 +570,12 @@ int main(int argc, char *argv[]) {
 		char *end;
 		double speed = strtod(speed_string, &end);
 
-		if(end-speed_string != strlen(speed_string)) {
+		if(size_t(end - speed_string) != strlen(speed_string)) {
 			std::cerr << "Unable to parse speed: " << speed_string << std::endl;
 		} else if(speed <= 0.0) {
 			std::cerr << "Cannot run at speed " << speed_string << "; speeds must be positive." << std::endl;
 		} else {
-			machine->crt_machine()->set_speed_multiplier(speed);
-			// TODO: what if not a 'CRT' machine? Likely rests on resolving this project's machine naming policy.
+			machine_runner.set_speed_multiplier(speed);
 		}
 	}