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UI controls in emulator

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Dejvino 2026-02-27 20:20:06 +01:00
parent 2b6e1d2c6b
commit 5240eb990b
3 changed files with 204 additions and 18 deletions
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140
main.cpp
View File

@ -3,6 +3,7 @@
#include <SDL2/SDL.h>
#include <vector>
#include <atomic>
#include <math.h>
#include "synth_engine.h" // Include our portable engine
#include <stdio.h>
@ -18,6 +19,15 @@ const size_t VIS_BUFFER_SIZE = 8192;
std::vector<int16_t> vis_buffer(VIS_BUFFER_SIZE, 0);
std::atomic<size_t> vis_write_index{0};
// --- Control State ---
const float MIN_FREQ = 20.0f;
const float MAX_FREQ = 20000.0f;
float knob_freq_val = 440.0f;
float knob_vol_val = 0.5f;
SynthEngine::Waveform current_waveform = SynthEngine::SAWTOOTH;
const char* waveform_names[] = {"Saw", "Square", "Sine"};
// --- Global Synth Engine Instance ---
// The audio callback needs access to our synth, so we make it global.
SynthEngine engine(SAMPLE_RATE);
@ -47,6 +57,78 @@ void data_callback(ma_device* pDevice, void* pOutput, const void* pInput, ma_uin
vis_write_index.store(idx, std::memory_order_relaxed);
}
// --- UI Drawing Helpers ---
void DrawCircle(SDL_Renderer * renderer, int32_t centreX, int32_t centreY, int32_t radius) {
const int32_t diameter = (radius * 2);
int32_t x = (radius - 1);
int32_t y = 0;
int32_t tx = 1;
int32_t ty = 1;
int32_t error = (tx - diameter);
while (x >= y) {
SDL_RenderDrawPoint(renderer, centreX + x, centreY - y);
SDL_RenderDrawPoint(renderer, centreX + x, centreY + y);
SDL_RenderDrawPoint(renderer, centreX - x, centreY - y);
SDL_RenderDrawPoint(renderer, centreX - x, centreY + y);
SDL_RenderDrawPoint(renderer, centreX + y, centreY - x);
SDL_RenderDrawPoint(renderer, centreX + y, centreY + x);
SDL_RenderDrawPoint(renderer, centreX - y, centreY - x);
SDL_RenderDrawPoint(renderer, centreX - y, centreY + x);
if (error <= 0) {
++y;
error += ty;
ty += 2;
}
if (error > 0) {
--x;
tx += 2;
error += (tx - diameter);
}
}
}
void drawKnob(SDL_Renderer* renderer, int x, int y, int radius, float value) {
// Draw outline
SDL_SetRenderDrawColor(renderer, 100, 100, 100, 255);
DrawCircle(renderer, x, y, radius);
DrawCircle(renderer, x, y, radius-1);
// Draw indicator
float angle = (value * (270.0f * M_PI / 180.0f)) - (135.0f * M_PI / 180.0f);
int x2 = x + (int)(sin(angle) * (radius - 2));
int y2 = y - (int)(cos(angle) * (radius - 2));
SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255);
SDL_RenderDrawLine(renderer, x, y, x2, y2);
}
void drawWaveformIcon(SDL_Renderer* renderer, int x, int y, int w, int h, SynthEngine::Waveform wf) {
SDL_SetRenderDrawColor(renderer, 200, 200, 200, 255);
switch(wf) {
case SynthEngine::SAWTOOTH:
SDL_RenderDrawLine(renderer, x, y+h, x+w, y); // Ramp up
SDL_RenderDrawLine(renderer, x+w, y, x+w, y+h); // Drop down
break;
case SynthEngine::SQUARE:
SDL_RenderDrawLine(renderer, x, y+h, x, y); // Rise
SDL_RenderDrawLine(renderer, x, y, x+w, y); // High
SDL_RenderDrawLine(renderer, x+w, y, x+w, y+h); // Drop
break;
case SynthEngine::SINE: {
int prev_x = x, prev_y = y + h/2;
for (int i = 1; i <= w; ++i) {
int px = x + i;
int py = y + h/2 - (int)(sin(i * 2.0 * M_PI / w) * h/2.0f);
SDL_RenderDrawLine(renderer, prev_x, prev_y, px, py);
prev_x = px; prev_y = py;
}
break;
}
}
}
int main(int argc, char* argv[]) {
(void)argc; (void)argv;
@ -81,6 +163,9 @@ int main(int argc, char* argv[]) {
ma_device_start(&device);
engine.setVolume(knob_vol_val);
engine.setFrequency(knob_freq_val);
// --- Main Loop ---
bool quit = false;
SDL_Event e;
@ -89,14 +174,50 @@ int main(int argc, char* argv[]) {
while (SDL_PollEvent(&e) != 0) {
if (e.type == SDL_QUIT) {
quit = true;
} else if (e.type == SDL_MOUSEWHEEL) {
int mouseX, mouseY;
SDL_GetMouseState(&mouseX, &mouseY);
if (mouseX < WINDOW_WIDTH / 2) { // Left knob (frequency)
if (e.wheel.y > 0) knob_freq_val *= 1.05f;
else if (e.wheel.y < 0) knob_freq_val /= 1.05f;
if (knob_freq_val < MIN_FREQ) knob_freq_val = MIN_FREQ;
if (knob_freq_val > MAX_FREQ) knob_freq_val = MAX_FREQ;
engine.setFrequency(knob_freq_val);
} else { // Right knob (volume)
if (e.wheel.y > 0) knob_vol_val += 0.05f;
else if (e.wheel.y < 0) knob_vol_val -= 0.05f;
if (knob_vol_val > 1.0f) knob_vol_val = 1.0f;
if (knob_vol_val < 0.0f) knob_vol_val = 0.0f;
engine.setVolume(knob_vol_val);
}
} else if (e.type == SDL_MOUSEBUTTONDOWN) {
int mouseX, mouseY;
SDL_GetMouseState(&mouseX, &mouseY);
if (e.button.button == SDL_BUTTON_LEFT && mouseX < WINDOW_WIDTH / 2) {
// Left knob click emulates encoder switch: cycle waveform
current_waveform = (SynthEngine::Waveform)(((int)current_waveform + 1) % 3);
engine.setWaveform(current_waveform);
}
}
}
// Update window title with current values
char title[128];
snprintf(title, sizeof(title), "NoiceSynth Scope | Freq: %.1f Hz | Vol: %.0f%% | Wave: %s",
knob_freq_val,
knob_vol_val * 100.0f,
waveform_names[(int)current_waveform]);
SDL_SetWindowTitle(window, title);
// Clear screen
SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
SDL_RenderClear(renderer);
// Draw Waveform
// --- Draw Waveform (Oscilloscope) ---
// Draw in the top half of the window
SDL_SetRenderDrawColor(renderer, 0, 255, 0, 255); // Green
// Determine read position (snapshot atomic write index)
@ -121,24 +242,31 @@ int main(int argc, char* argv[]) {
}
// Draw points
int prev_x = 0;
int prev_y = WINDOW_HEIGHT / 2;
int prev_x = -1;
int prev_y = -1;
for (int x = 0; x < WINDOW_WIDTH; ++x) {
int16_t sample = vis_buffer[read_idx];
read_idx = (read_idx + 1) % VIS_BUFFER_SIZE;
// Map 16-bit sample (-32768 to 32767) to screen height
// Invert Y because screen Y grows downwards
int y = WINDOW_HEIGHT / 2 - (sample * (WINDOW_HEIGHT / 2) / 32768);
// Use top half of window, so divide height by 4 (2 for half, 2 for +/-)
int y = WINDOW_HEIGHT / 4 - (sample * (WINDOW_HEIGHT / 4) / 32768);
if (x > 0) {
if (prev_x != -1) {
SDL_RenderDrawLine(renderer, prev_x, prev_y, x, y);
}
prev_x = x;
prev_y = y;
}
// --- Draw Controls ---
// Draw in the bottom half of the window
float normalized_freq = (log(knob_freq_val) - log(MIN_FREQ)) / (log(MAX_FREQ) - log(MIN_FREQ));
drawKnob(renderer, WINDOW_WIDTH / 4, WINDOW_HEIGHT * 3 / 4, 50, normalized_freq);
drawWaveformIcon(renderer, WINDOW_WIDTH / 4 - 25, WINDOW_HEIGHT * 3 / 4 + 60, 50, 20, current_waveform);
drawKnob(renderer, WINDOW_WIDTH * 3 / 4, WINDOW_HEIGHT * 3 / 4, 50, knob_vol_val);
SDL_RenderPresent(renderer);
}

62
synth_engine.cpp
View File

@ -1,35 +1,73 @@
#include "synth_engine.h"
#include <math.h>
// A simple sine lookup table for the sine oscillator
const int SINE_TABLE_SIZE = 256;
static int16_t sine_table[SINE_TABLE_SIZE];
static bool sine_table_filled = false;
/**
* @brief Fills the global sine table. Called once on startup.
*/
void fill_sine_table() {
if (sine_table_filled) return;
for (int i = 0; i < SINE_TABLE_SIZE; ++i) {
// M_PI is not standard C++, but it's common. If it fails, use 3.1415926535...
sine_table[i] = static_cast<int16_t>(sin(2.0 * M_PI * i / SINE_TABLE_SIZE) * 32767.0);
}
sine_table_filled = true;
}
SynthEngine::SynthEngine(uint32_t sampleRate)
: _sampleRate(sampleRate),
_phase(0),
_increment(0)
_increment(0),
_volume(0.5f),
_waveform(SAWTOOTH)
{
fill_sine_table();
// Initialize with a default frequency
setFrequency(440.0f);
}
void SynthEngine::setFrequency(float freq) {
// Calculate the phase increment for a given frequency.
// The phase accumulator is a 32-bit unsigned integer (0 to 2^32 - 1).
// The phase accumulator is a 32-bit unsigned integer (0 to 2^32-1).
// One full cycle of the accumulator represents one cycle of the waveform.
// increment = (frequency * 2^32) / sampleRate
// We use a 64-bit intermediate calculation to prevent overflow.
_increment = static_cast<uint32_t>((static_cast<uint64_t>(freq) << 32) / _sampleRate);
// The original calculation was incorrect for float frequencies.
_increment = static_cast<uint32_t>((double)freq * (4294967296.0 / (double)_sampleRate));
}
void SynthEngine::setVolume(float vol) {
if (vol < 0.0f) vol = 0.0f;
if (vol > 1.0f) vol = 1.0f;
_volume = vol;
}
void SynthEngine::setWaveform(Waveform form) {
_waveform = form;
}
void SynthEngine::process(int16_t* buffer, uint32_t numFrames) {
for (uint32_t i = 0; i < numFrames; ++i) {
// 1. Advance the phase. Integer overflow automatically wraps it,
// which is exactly what we want for a continuous oscillator.
_phase += _increment;
// 2. Generate the sample. For a sawtooth wave, the sample value is
// directly proportional to the phase. We take the top 16 bits
// of the 32-bit phase accumulator to get a signed 16-bit sample.
int16_t sample = static_cast<int16_t>(_phase >> 16);
int16_t sample = 0;
switch (_waveform) {
case SAWTOOTH:
sample = static_cast<int16_t>(_phase >> 16);
break;
case SQUARE:
sample = (_phase < 0x80000000) ? 32767 : -32768;
break;
case SINE:
// Use top 8 bits of phase as index into sine table
sample = sine_table[(_phase >> 24) & 0xFF];
break;
}
// 3. Write the sample to the buffer.
buffer[i] = sample;
// Apply volume and write to buffer
buffer[i] = static_cast<int16_t>(sample * _volume);
}
}

20
synth_engine.h
View File

@ -17,6 +17,12 @@
*/
class SynthEngine {
public:
enum Waveform {
SAWTOOTH,
SQUARE,
SINE
};
/**
* @brief Constructs the synthesizer engine.
* @param sampleRate The audio sample rate in Hz (e.g., 44100).
@ -36,10 +42,24 @@ public:
*/
void setFrequency(float freq);
/**
* @brief Sets the output volume.
* @param vol Volume from 0.0 (silent) to 1.0 (full).
*/
void setVolume(float vol);
/**
* @brief Sets the oscillator's waveform.
* @param form The waveform to use.
*/
void setWaveform(Waveform form);
private:
uint32_t _sampleRate;
uint32_t _phase; // Phase accumulator for the oscillator.
uint32_t _increment; // Phase increment per sample, determines frequency.
float _volume;
Waveform _waveform;
};
#endif // SYNTH_ENGINE_H