From 48f397f168ba32965e209c498643413a1533f468 Mon Sep 17 00:00:00 2001
From: AnyOldName3 <krizdjali+github@gmail.com>
Date: Thu, 3 Dec 2020 21:06:02 +0000
Subject: [PATCH] Remove existing shader when no longer required

---
 components/shader/shadervisitor.cpp | 20 ++++++++++++++++++++
 components/shader/shadervisitor.hpp |  1 +
 2 files changed, 21 insertions(+)

diff --git a/components/shader/shadervisitor.cpp b/components/shader/shadervisitor.cpp
index 10e9e606e..e908b6aaa 100644
--- a/components/shader/shadervisitor.cpp
+++ b/components/shader/shadervisitor.cpp
@@ -294,7 +294,10 @@ namespace Shader
     void ShaderVisitor::createProgram(const ShaderRequirements &reqs)
     {
         if (!reqs.mShaderRequired && !mForceShaders)
+        {
+            ensureFFP(*reqs.mNode);
             return;
+        }
 
         osg::Node& node = *reqs.mNode;
         osg::StateSet* writableStateSet = nullptr;
@@ -333,6 +336,19 @@ namespace Shader
         }
     }
 
+    void ShaderVisitor::ensureFFP(osg::Node& node)
+    {
+        if (!node.getStateSet() || !node.getStateSet()->getAttribute(osg::StateAttribute::PROGRAM))
+            return;
+        osg::StateSet* writableStateSet = nullptr;
+        if (mAllowedToModifyStateSets)
+            writableStateSet = node.getStateSet();
+        else
+            writableStateSet = getWritableStateSet(node);
+
+        writableStateSet->removeAttribute(osg::StateAttribute::PROGRAM);
+    }
+
     bool ShaderVisitor::adjustGeometry(osg::Geometry& sourceGeometry, const ShaderRequirements& reqs)
     {
         bool useShader = reqs.mShaderRequired || mForceShaders;
@@ -380,6 +396,8 @@ namespace Shader
 
             createProgram(reqs);
         }
+        else
+            ensureFFP(geometry);
 
         if (needPop)
             popRequirements();
@@ -414,6 +432,8 @@ namespace Shader
                     morph->setSourceGeometry(sourceGeometry);
             }
         }
+        else
+            ensureFFP(drawable);
 
         if (needPop)
             popRequirements();
diff --git a/components/shader/shadervisitor.hpp b/components/shader/shadervisitor.hpp
index 6b2353b66..6031dbfe6 100644
--- a/components/shader/shadervisitor.hpp
+++ b/components/shader/shadervisitor.hpp
@@ -94,6 +94,7 @@ namespace Shader
         std::string mDefaultFsTemplate;
 
         void createProgram(const ShaderRequirements& reqs);
+        void ensureFFP(osg::Node& node);
         bool adjustGeometry(osg::Geometry& sourceGeometry, const ShaderRequirements& reqs);
     };