GUI: add a sample preview rate hint

src/engine/engine.cpp

@@ -2131,6 +2131,7 @@ void DivEngine::previewSample(int sample, int note, int pStart, int pEnd) {
   if (rate<100) rate=100;
   blip_set_rates(samp_bb,rate,got.rate);
   samp_prevSample=0;
+  sPreview.rate=rate;
   sPreview.pos=(sPreview.pBegin>=0)?sPreview.pBegin:0;
   sPreview.sample=sample;
   sPreview.wave=-1;
@@ -2164,6 +2165,7 @@ void DivEngine::previewWave(int wave, int note) {
   if (rate<100) rate=100;
   blip_set_rates(samp_bb,rate,got.rate);
   samp_prevSample=0;
+  sPreview.rate=rate;
   sPreview.pos=0;
   sPreview.sample=-1;
   sPreview.wave=wave;
@@ -2179,6 +2181,18 @@ void DivEngine::stopWavePreview() {
   BUSY_END;
 }
 
+bool DivEngine::isPreviewingSample() {
+  return (sPreview.sample>=0 && sPreview.sample<(int)song.sample.size());
+}
+
+int DivEngine::getSamplePreviewPos() {
+  return sPreview.pos;
+}
+
+double DivEngine::getSamplePreviewRate() {
+  return sPreview.rate;
+}
+
 String DivEngine::getConfigPath() {
   return configPath;
 }

src/engine/engine.h

@@ -387,12 +387,14 @@ class DivEngine {
   DivSystem sysFileMapDMF[256];
 
   struct SamplePreview {
+    double rate;
     int sample;
     int wave;
     int pos;
     int pBegin, pEnd;
     bool dir;
     SamplePreview():
+      rate(0.0),
       sample(-1),
       wave(-1),
       pos(0),
@@ -601,6 +603,11 @@ class DivEngine {
     // reset playback state
     void syncReset();
 
+    // sample preview query
+    bool isPreviewingSample();
+    int getSamplePreviewPos();
+    double getSamplePreviewRate();
+
     // trigger sample preview
     void previewSample(int sample, int note=-1, int pStart=-1, int pEnd=-1);
     void stopSamplePreview();