Fix crash on Xpressive when using integrate function

plugins/Xpressive/ExprSynth.cpp

@@ -83,6 +83,7 @@ struct IntegrateFunction : public exprtk::ifunction<T>
 
 	IntegrateFunction(const unsigned int* frame, unsigned int sample_rate,unsigned int max_counters) :
 	exprtk::ifunction<T>(1),
+    m_first_value(0),
 	m_frame(frame),
 	m_sample_rate(sample_rate),
 	m_max_counters(max_counters),
@@ -96,15 +97,26 @@ struct IntegrateFunction : public exprtk::ifunction<T>
 
 	inline T operator()(const T& x) override
 	{
-		if (*m_frame == 0)
+        if (m_frame)
 		{
-			++m_nCountersCalls;
-			if (m_nCountersCalls > m_max_counters)
-			{
-				return 0;
-			}
-			m_cc = m_nCounters;
-			++m_nCounters;
+            if (m_nCountersCalls == 0)
+            {
+                m_first_value = *m_frame;
+            }
+            if (m_first_value == *m_frame)
+            {
+                ++m_nCountersCalls;
+                if (m_nCountersCalls > m_max_counters)
+                {
+                    return 0;
+                }
+                m_cc = m_nCounters;
+                ++m_nCounters;
+            }
+            else // we moved to the next frame
+            {
+                m_frame = 0; // this will indicate that we are no longer in init phase.
+            }
 		}
 
 		T res = 0;
@@ -116,12 +128,15 @@ struct IntegrateFunction : public exprtk::ifunction<T>
 		m_cc = (m_cc + 1) % m_nCountersCalls;
 		return res / m_sample_rate;
 	}
-
-	const unsigned int* const m_frame;
+    unsigned int m_first_value;
+    const unsigned int* m_frame;
 	const unsigned int m_sample_rate;
-	const unsigned int m_max_counters;
-	unsigned int m_nCounters;
-	unsigned int m_nCountersCalls;
+    // number of counters allocated
+    const unsigned int m_max_counters;
+    // number of integrate instances that has counters allocated
+    unsigned int m_nCounters;
+    // real number of integrate instances
+    unsigned int m_nCountersCalls;
 	unsigned int m_cc;
 	double *m_counters;
 };

plugins/Xpressive/Xpressive.cpp

@@ -553,7 +553,7 @@ void XpressiveView::expressionChanged() {
 		ExprFront expr(text.constData(),sample_rate);
 		float t=0;
 		const float f=10,key=5,v=0.5;
-		unsigned int i;
+        unsigned int frame_counter = 0;
 		expr.add_variable("t", t);
 
 		if (m_output_expr)
@@ -572,20 +572,21 @@ void XpressiveView::expressionChanged() {
 			expr.add_cyclic_vector("W2",e->graphW2().samples(),e->graphW2().length());
 			expr.add_cyclic_vector("W3",e->graphW3().samples(),e->graphW3().length());
 		}
-		expr.setIntegrate(&i,sample_rate);
+        expr.setIntegrate(&frame_counter,sample_rate);
 		expr.add_constant("srate",sample_rate);
 
 		const bool parse_ok=expr.compile();
 
 		if (parse_ok) {
 			e->exprValid().setValue(0);
-			const auto length = static_cast<std::size_t>(m_raw_graph->length());
+            const unsigned int length = static_cast<unsigned int>(m_raw_graph->length());
 			auto const samples = new float[length];
-			for (auto i = std::size_t{0}; i < length; i++) {
-				t = i / (float) length;
-				samples[i] = expr.evaluate();
-				if (std::isinf(samples[i]) != 0 || std::isnan(samples[i]) != 0)
-					samples[i] = 0;
+            // frame_counter's reference is used in the integrate function.
+            for ( frame_counter = 0; frame_counter < length; ++frame_counter) {
+                t = frame_counter / (float) length;
+                samples[frame_counter] = expr.evaluate();
+                if (std::isinf(samples[frame_counter]) != 0 || std::isnan(samples[frame_counter]) != 0)
+                    samples[frame_counter] = 0;
 			}
 			m_raw_graph->setSamples(samples);
 			delete[] samples;