From 1f12ebeb663197ba956581869a12d7fb99d9f7fc Mon Sep 17 00:00:00 2001
From: cflip <cflip@cflip.net>
Date: Sat, 13 Nov 2021 11:28:28 -0700
Subject: Fix number of samples per step

Previously, the audio callback function would generate samples until it
was done, ignoring which step it was in. Now the audio callback function
will automatically increment the current step and generate the same
amount of samples for each step.

This also means the SDL window can be updated more often which fixes the
delayed input from before.
---
 main.cpp | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/main.cpp b/main.cpp
index de39d1c..1f3b6af 100644
--- a/main.cpp
+++ b/main.cpp
@@ -9,7 +9,8 @@ const int SAMPLE_RATE = 44100;
 const float sequence[8] = { 130.81f, 220.f, 130.81f, 440.f, 330.f, 440.f, 130.81f, 261.63f };
 
 struct CallbackInfo {
-	int sampleCount;
+	int samplesDone;
+	int samplesPerStep;
 	int currentStep;
 };
 
@@ -19,9 +20,15 @@ void AudioCallback(void *userData, Uint8 *rawBuffer, int bytes)
 	int length = bytes / sizeof(float);
 	CallbackInfo *info = (CallbackInfo*)userData;
 
-	for (int i = 0; i < length; i++, info->sampleCount++) {
+	for (int i = 0; i < length; i++, info->samplesDone++) {
 		float freq = sequence[info->currentStep];
-		float time = (float)info->sampleCount / (float)SAMPLE_RATE;
+		float time = (float)info->samplesDone / (float)SAMPLE_RATE;
+
+		if (info->samplesDone >= info->samplesPerStep) {
+			info->samplesDone = 0;
+			info->currentStep = (info->currentStep + 1) % 8;
+		}
+
 		buffer[i] = (sinf(2.0f * M_PI * freq * time)) * AMPLITUDE;
 	}
 }
@@ -60,7 +67,8 @@ int main(int argc, char** argv)
 	SDL_Event event;
 
 	CallbackInfo info;
-	info.sampleCount = 0;
+	info.samplesDone = 0;
+	info.samplesPerStep = SAMPLE_RATE * 0.2f;
 	info.currentStep = 0;
 
 	SDL_AudioSpec desiredSpec;
@@ -96,13 +104,12 @@ int main(int argc, char** argv)
 		SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
 		SDL_RenderClear(renderer);
 
-		info.currentStep = (info.currentStep + 1) % 8;
 		DrawInterface(renderer, info.currentStep);
 
 		SDL_RenderPresent(renderer);
 		SDL_UpdateWindowSurface(window);
 
-		SDL_Delay(200);
+		SDL_Delay(10);
 	}
 
 	SDL_PauseAudio(1);
-- 
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