Add Plugin::isDummyInstance() method, useful for some plugins

Signed-off-by: falkTX <falktx@falktx.com>

distrho/DistrhoPlugin.hpp

@@ -845,6 +845,14 @@ public:
     */
     const char* getBundlePath() const noexcept;
 
+   /**
+      Check if this plugin instance is a "dummy" one used for plugin meta-data/information export.@n
+      When true no processing will be done, the plugin is created only to extract information.@n
+      In DPF, LADSPA/DSSI, VST2 and VST3 formats create one global instance per plugin binary
+      while LV2 creates one when generating turtle meta-data.
+    */
+    bool isDummyInstance() const noexcept;
+
 #if DISTRHO_PLUGIN_WANT_TIMEPOS
    /**
       Get the current host transport time position.@n

distrho/src/DistrhoPlugin.cpp

@@ -24,6 +24,7 @@ START_NAMESPACE_DISTRHO
 uint32_t    d_nextBufferSize = 0;
 double      d_nextSampleRate = 0.0;
 const char* d_nextBundlePath = nullptr;
+bool        d_nextPluginIsDummy = false;
 bool        d_nextCanRequestParameterValueChanges = false;
 
 /* ------------------------------------------------------------------------------------------------------------
@@ -106,6 +107,11 @@ const char* Plugin::getBundlePath() const noexcept
     return pData->bundlePath;
 }
 
+bool Plugin::isDummyInstance() const noexcept
+{
+    return pData->isDummy;
+}
+
 #if DISTRHO_PLUGIN_WANT_TIMEPOS
 const TimePosition& Plugin::getTimePosition() const noexcept
 {

distrho/src/DistrhoPluginInternal.hpp

@@ -34,6 +34,7 @@ static const uint32_t kMaxMidiEvents = 512;
 extern uint32_t    d_nextBufferSize;
 extern double      d_nextSampleRate;
 extern const char* d_nextBundlePath;
+extern bool        d_nextPluginIsDummy;
 extern bool        d_nextCanRequestParameterValueChanges;
 
 // -----------------------------------------------------------------------
@@ -84,6 +85,8 @@ static void fillInPredefinedPortGroupData(const uint32_t groupId, PortGroup& por
 // Plugin private data
 
 struct Plugin::PrivateData {
+    const bool canRequestParameterValueChanges;
+    const bool isDummy;
     bool isProcessing;
 
 #if DISTRHO_PLUGIN_NUM_INPUTS+DISTRHO_PLUGIN_NUM_OUTPUTS > 0
@@ -124,10 +127,11 @@ struct Plugin::PrivateData {
     uint32_t bufferSize;
     double   sampleRate;
     char*    bundlePath;
-    bool     canRequestParameterValueChanges;
 
     PrivateData() noexcept
-        : isProcessing(false),
+        : canRequestParameterValueChanges(d_nextCanRequestParameterValueChanges),
+          isDummy(d_nextPluginIsDummy),
+          isProcessing(false),
 #if DISTRHO_PLUGIN_NUM_INPUTS+DISTRHO_PLUGIN_NUM_OUTPUTS > 0
           audioPorts(nullptr),
 #endif
@@ -153,8 +157,7 @@ struct Plugin::PrivateData {
           requestParameterValueChangeCallbackFunc(nullptr),
           bufferSize(d_nextBufferSize),
           sampleRate(d_nextSampleRate),
-          bundlePath(d_nextBundlePath != nullptr ? strdup(d_nextBundlePath) : nullptr),
-          canRequestParameterValueChanges(d_nextCanRequestParameterValueChanges)
+          bundlePath(d_nextBundlePath != nullptr ? strdup(d_nextBundlePath) : nullptr)
     {
         DISTRHO_SAFE_ASSERT(bufferSize != 0);
         DISTRHO_SAFE_ASSERT(d_isNotZero(sampleRate));

distrho/src/DistrhoPluginLADSPA+DSSI.cpp

@@ -553,9 +553,11 @@ static const struct DescriptorInitializer
         // Create dummy plugin to get data from
         d_nextBufferSize = 512;
         d_nextSampleRate = 44100.0;
+        d_nextPluginIsDummy = true;
         const PluginExporter plugin(nullptr, nullptr, nullptr);
         d_nextBufferSize = 0;
         d_nextSampleRate = 0.0;
+        d_nextPluginIsDummy = false;
 
         // Get port count, init
         ulong port = 0;

distrho/src/DistrhoPluginLV2export.cpp

@@ -231,9 +231,11 @@ void lv2_generate_ttl(const char* const basename)
     // Dummy plugin to get data from
     d_nextBufferSize = 512;
     d_nextSampleRate = 44100.0;
+    d_nextPluginIsDummy = true;
     PluginExporter plugin(nullptr, nullptr, nullptr);
     d_nextBufferSize = 0;
     d_nextSampleRate = 0.0;
+    d_nextPluginIsDummy = false;
 
     const String pluginDLL(basename);
     const String pluginTTL(pluginDLL + ".ttl");

distrho/src/DistrhoPluginVST2.cpp

@@ -1406,6 +1406,7 @@ static intptr_t vst_dispatcherCallback(AEffect* effect, int32_t opcode, int32_t
         // set valid but dummy values
         d_nextBufferSize = 512;
         d_nextSampleRate = 44100.0;
+        d_nextPluginIsDummy = true;
         d_nextCanRequestParameterValueChanges = true;
     }
 
@@ -1417,6 +1418,7 @@ static intptr_t vst_dispatcherCallback(AEffect* effect, int32_t opcode, int32_t
         // unset
         d_nextBufferSize = 0;
         d_nextSampleRate = 0.0;
+        d_nextPluginIsDummy = false;
         d_nextCanRequestParameterValueChanges = false;
 
         *(PluginExporter**)ptr = &plugin;

distrho/src/DistrhoPluginVST3.cpp

@@ -3544,10 +3544,12 @@ static const PluginExporter& _getPluginInfo()
 {
     d_nextBufferSize = 512;
     d_nextSampleRate = 44100.0;
+    d_nextPluginIsDummy = true;
     d_nextCanRequestParameterValueChanges = true;
     static const PluginExporter gPluginInfo(nullptr, nullptr, nullptr);
     d_nextBufferSize = 0;
     d_nextSampleRate = 0.0;
+    d_nextPluginIsDummy = false;
     d_nextCanRequestParameterValueChanges = false;
 
     return gPluginInfo;