From 2abb46b83d37f3cb83bf16d8d87bab5a454fb2ba Mon Sep 17 00:00:00 2001
From: "stevethefiddle@gmail.com"
 <stevethefiddle@gmail.com@47890b92-0858-11df-a26f-8b716316a5bc>
Date: Sun, 26 Oct 2014 20:30:22 +0000
Subject: [PATCH] Allow generator effects to use preview without requiring a
 selection to be made. Documentation: This does not affect any currently
 shipped effects. This will need documenting on the wiki for writing Nyquist
 plug-ins.

---
 src/effects/Effect.cpp          | 3 ++-
 src/effects/Effect.h            | 6 ++++++
 src/effects/nyquist/Nyquist.cpp | 6 ++++++
 src/effects/nyquist/Nyquist.h   | 3 ++-
 4 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/effects/Effect.cpp b/src/effects/Effect.cpp
index 2502af84b..7f2dc9ca7 100644
--- a/src/effects/Effect.cpp
+++ b/src/effects/Effect.cpp
@@ -1409,7 +1409,8 @@ void Effect::Preview(bool dryOnly)
    if (t1 > mT1)
       t1 = mT1;
 
-   if (t1 <= t0)
+   // Generators can run without a selection.
+   if (!GeneratorPreview() && (t1 <= t0))
       return;
 
    bool success = ::MixAndRender(mTracks, mFactory, rate, floatSample, t0, t1,
diff --git a/src/effects/Effect.h b/src/effects/Effect.h
index 67aa36fa0..f2f934623 100644
--- a/src/effects/Effect.h
+++ b/src/effects/Effect.h
@@ -181,6 +181,12 @@ class AUDACITY_DLL_API Effect : public EffectHostInterface
       return (mFlags & BUILTIN_EFFECT) != 0;
    }
 
+   // Preview normally requires a selection, but INSERT_EFFECTs do not.
+   // Return true to override the need for a selection.
+   virtual bool GeneratorPreview(){
+      return false;
+   }
+
    // Called to set or retrieve parameter values.  Return true if successful.
    virtual bool TransferParameters( Shuttle & WXUNUSED(shuttle) ) {
       return true;
diff --git a/src/effects/nyquist/Nyquist.cpp b/src/effects/nyquist/Nyquist.cpp
index 2f7436040..652ce4bc9 100644
--- a/src/effects/nyquist/Nyquist.cpp
+++ b/src/effects/nyquist/Nyquist.cpp
@@ -508,6 +508,12 @@ bool EffectNyquist::TransferParameters( Shuttle & shuttle )
    return true;
 }
 
+bool EffectNyquist::GeneratorPreview()
+{
+   // Enable Nyquist generator plug-ins to create preview without a selection
+   return (mEnablePreview && (GetEffectFlags() & INSERT_EFFECT));
+}
+
 bool EffectNyquist::PromptUser()
 {
    while (mInteractive) {
diff --git a/src/effects/nyquist/Nyquist.h b/src/effects/nyquist/Nyquist.h
index de2be7418..9d036e2f0 100644
--- a/src/effects/nyquist/Nyquist.h
+++ b/src/effects/nyquist/Nyquist.h
@@ -112,7 +112,8 @@ class AUDACITY_DLL_API EffectNyquist:public Effect
       return mAction;
    }
 
-   virtual bool PromptUser();
+   virtual bool GeneratorPreview();
+   virtual bool PromptUser(); 
 
    virtual bool Process();