1 files changed, 48 insertions(+), 8 deletions(-)

M main.c

@@ 36,6 36,12 @@ struct context {
 	int width;
 	int height;
 
+	bool dirty;
+	bool pending;
+
+	double val;
+	double peak;
+
 	struct wl_egl_window *wl_egl_window;
 	EGLConfig egl_config;
 	EGLContext egl_context;


@@ 198,7 204,29 @@ static void draw_vert(double val) {
 	glVertex2f(-1, 2*val-1);
 }
 
-static int draw(struct context *ctx, double val, double peak) {
+static int draw(struct context *ctx);
+static void frame_handle_done(void *data, struct wl_callback *callback,
+		uint32_t time) {
+	(void)time;
+	wl_callback_destroy(callback);
+	struct context *ctx = data;
+	ctx->pending = false;
+	draw(ctx);
+}
+
+const struct wl_callback_listener frame_listener = {
+	.done = frame_handle_done,
+};
+
+static int draw(struct context *ctx) {
+	if (ctx->pending) {
+		return 0;
+	}
+	if (!ctx->dirty) {
+		return 0;
+	}
+	ctx->dirty = false;
+
 	glClear(GL_COLOR_BUFFER_BIT);
 
 	void (*draw_bar)(double val);


@@ 208,20 236,24 @@ static int draw(struct context *ctx, double val, double peak) {
 		draw_bar = draw_horiz;
 	}
 
-	if (peak > 0.9) {
+	if (ctx->peak > 0.9) {
 		glColor3f(.5, 0.0, 0.0);
 	} else {
 		glColor3f(0.25, .25, 0.25);
 	}
 	glBegin(GL_POLYGON);
-	draw_bar(peak);
+	draw_bar(ctx->peak);
 	glEnd();
 
 	glColor3f(0.0, 1.0, 0.0);
 	glBegin(GL_POLYGON);
-	draw_bar(val);
+	draw_bar(ctx->val);
 	glEnd();
 
+	ctx->pending = true;
+	struct wl_callback *callback = wl_surface_frame(ctx->surface);
+	wl_callback_add_listener(callback, &frame_listener, ctx);
+
 	if (!eglSwapBuffers(ctx->egl_display, ctx->egl_surface)) {
 		fprintf(stderr, "eglSwapBuffers failed\n");
 		return -1;


@@ 231,7 263,7 @@ static int draw(struct context *ctx, double val, double peak) {
 }
 
 #define PEAK_DURATION 20
-#define HYSTERESIS 0.001
+#define HYSTERESIS 0.0005
 
 static int max_s16(void *buffer, int frames, int channels) {
 	int max = 0;


@@ 420,6 452,9 @@ int main(int argc, char **argv) {
 		.height = bar_width,
 		.width = 1024,
 		.running = true,
+		.val = 0.0,
+		.peak = 0.0,
+		.dirty = true,
 	};
 
 	void *buffer = NULL;


@@ 532,7 567,6 @@ int main(int argc, char **argv) {
 
 	eglSwapInterval(ctx.egl_display, 0);
 
-
 	int polln = snd_pcm_poll_descriptors_count(handle_capture) + 1;
 	struct pollfd *pfd = calloc(polln, sizeof(struct pollfd));
 	if (pfd == NULL) {


@@ 544,7 578,7 @@ int main(int argc, char **argv) {
 	// For some reason we must read at least once
 	snd_pcm_readi(handle_capture, buffer, frame_capacity);
 
-	draw(&ctx, 0.0, 0.0);
+	draw(&ctx);
 	
 	double peak;
 	int peak_timer = 0;


@@ 580,7 614,13 @@ int main(int argc, char **argv) {
 			peak_timer--;
 		}
 
-		draw(&ctx, val, peak);
+		if (val < ctx.val - HYSTERESIS || val > ctx.val + HYSTERESIS ||
+				peak < ctx.peak - HYSTERESIS || peak > ctx.peak + HYSTERESIS) {
+			ctx.dirty = true;
+			ctx.val = val;
+			ctx.peak = peak;
+			draw(&ctx);
+		}
 	}
 
 	snd_pcm_close(handle_capture);