Added support for subsititing $VAR_NAME entries in shaders to enable writing shaders that work across GLSL versions.

include/osg/DisplaySettings

@@ -20,6 +20,7 @@
 
 #include <string>
 #include <vector>
+#include <map>
 
 namespace osg {
 
@@ -319,7 +320,9 @@ class OSG_EXPORT DisplaySettings : public osg::Referenced
             SHADER_GLES3
         };
 
-        void setShaderHint(ShaderHint hint) { _shaderHint = hint; }
+        /** set the ShaderHint to tells shader generating cdoes  version to create.
+         * By default also OSG_GLSL_VERSION and OSG_PRECISION_FLOAT values that can get use directly in shaders using $OSG_GLSL_VERSION and $OSG_PRECISION_FLOAT respectively.*/
+        void setShaderHint(ShaderHint hint, bool setShaderValues=true);
         ShaderHint getShaderHint() const { return _shaderHint; }
 
 
@@ -358,6 +361,11 @@ class OSG_EXPORT DisplaySettings : public osg::Referenced
         /** helper function for computing the right eye view matrix.*/
         virtual osg::Matrixd computeRightEyeViewImplementation(const osg::Matrixd& view, double eyeSeperationScale=1.0) const;
 
+
+        void setValue(const std::string& name, const std::string& value);
+
+        bool getValue(const std::string& name, std::string& value, bool use_getenv_fallback=true) const;
+
     protected:
 
         virtual ~DisplaySettings();
@@ -422,6 +430,11 @@ class OSG_EXPORT DisplaySettings : public osg::Referenced
 
         OSXMenubarBehavior              _OSXMenubarBehavior;
 
+        typedef std::map<std::string, std::string> ValueMap;
+
+        mutable OpenThreads::Mutex      _valueMapMutex;
+        mutable ValueMap                _valueMap;
+
 };
 
 }

include/osg/State

@@ -823,9 +823,12 @@ class OSG_EXPORT State : public Referenced
           * during rendering. */
         inline void setDisplaySettings(DisplaySettings* vs) { _displaySettings = vs; }
 
-        /** Get the DisplaySettings */
+        /** Get the const DisplaySettings */
         inline const DisplaySettings* getDisplaySettings() const { return _displaySettings.get(); }
 
+        /** Get the const DisplaySettings that is current active DisplaySettings to be used by osg::State, - if DisplaySettings is not directly assigned then fallback to DisplaySettings::instance(). */
+        inline const DisplaySettings* getActiveDisplaySettings() const { return _displaySettings.valid() ? _displaySettings.get() : osg::DisplaySettings::instance().get(); }
+
 
 
         /** Set flag for early termination of the draw traversal.*/