Further work on improving stereo support in the OSG.

Renamed the osg::VisualsSettings to osg::DisplaySettings, and
osgUtil::VisualsRequirementsVisitor to osgUtil::DisplayRequirementsVisitor.

Added support for OSG_SCREEN_HEIGHT into osg::DisplaySettings, and added
a DisplaySettings* to the constructors of osg::SceneView and osg::Camera.

src/osg/DisplaySettings.cpp

@@ -0,0 +1,188 @@
+#include <osg/DisplaySettings>
+
+#include <algorithm>
+
+using namespace osg;
+
+DisplaySettings::DisplaySettings(const DisplaySettings& vs):Referenced()
+{
+    copy(vs);
+}
+
+DisplaySettings::~DisplaySettings()
+{
+}
+
+DisplaySettings& DisplaySettings::operator = (const DisplaySettings& vs)
+{
+    if (this==&vs) return *this;
+    copy(vs);
+    return *this;
+}
+
+void DisplaySettings::copy(const DisplaySettings& vs)
+{
+    _stereoMode = vs._stereoMode;
+    _eyeSeperation = vs._eyeSeperation;
+    _screenDistance = vs._screenDistance;
+    _screenHeight = vs._screenHeight;
+
+    _doubleBuffer = vs._doubleBuffer;
+    _RGB = vs._RGB;
+    _depthBuffer = vs._depthBuffer;
+    _minimumNumberAlphaBits = vs._minimumNumberAlphaBits;
+    _minimumNumberStencilBits = vs._minimumNumberStencilBits;
+}
+
+void DisplaySettings::merge(const DisplaySettings& vs)
+{
+    if (_stereo       || vs._stereo)        _stereo = true;
+    
+    // need to think what to do about merging the stereo mode.
+    
+    if (_doubleBuffer || vs._doubleBuffer)  _doubleBuffer = true;
+    if (_RGB          || vs._RGB)           _RGB = true;
+    if (_depthBuffer  || vs._depthBuffer)   _depthBuffer = true;
+    
+    if (vs._minimumNumberAlphaBits>_minimumNumberAlphaBits) _minimumNumberAlphaBits = vs._minimumNumberAlphaBits;
+    if (vs._minimumNumberStencilBits>_minimumNumberStencilBits) _minimumNumberStencilBits = vs._minimumNumberStencilBits;
+}
+
+void DisplaySettings::setDefaults()
+{
+    _stereo = false;
+    _stereoMode = ANAGLYPHIC;
+    _eyeSeperation = 0.05f;
+    _screenDistance = 0.5f;
+    _screenHeight = 0.26f;
+
+    _doubleBuffer = true;
+    _RGB = true;
+    _depthBuffer = true;
+    _minimumNumberAlphaBits = 0;
+    _minimumNumberStencilBits = 0;
+}
+
+void DisplaySettings::readEnvironmentalVariables()
+{
+    char *ptr;
+    if( (ptr = getenv("OSG_STEREO_MODE")) )
+    {
+        if (strcmp(ptr,"QUAD_BUFFER")==0)
+        {
+            _stereoMode = QUAD_BUFFER;
+        }
+        else
+        if (strcmp(ptr,"ANAGLYPHIC")==0)
+        {
+            _stereoMode = ANAGLYPHIC;
+        }
+        else
+        if (strcmp(ptr,"HORIZONTAL_SPLIT")==0)
+        {
+            _stereoMode = HORIZONTAL_SPLIT;
+        }
+        else
+        if (strcmp(ptr,"VERTICAL_SPLIT")==0)
+        {
+            _stereoMode = VERTICAL_SPLIT;
+        }
+    }
+
+    if( (ptr = getenv("OSG_STEREO")) )
+    {
+        if (strcmp(ptr,"OFF")==0)
+        {
+            _stereo = false;
+        }
+        else
+        if (strcmp(ptr,"ON")==0)
+        {
+            _stereo = true;
+        }
+    }
+
+    if( (ptr = getenv("OSG_EYE_SEPERATION")) )
+    {
+        _eyeSeperation = atof(ptr);
+    }
+
+    if( (ptr = getenv("OSG_SCREEN_DISTANCE")) )
+    {
+        _screenDistance = atof(ptr);
+    }
+
+    if( (ptr = getenv("OSG_SCREEN_HEIGHT")) )
+    {
+        _screenHeight = atof(ptr);
+    }
+}
+
+void DisplaySettings::readCommandLine(std::vector<std::string>& commandLine)
+{
+
+    bool found = true;
+    while (found)
+    {
+        found = false;
+
+        // check for stereo based options.
+        std::vector<std::string>::iterator itr = commandLine.begin();
+        for(;itr!=commandLine.end();++itr)
+        {
+            if (*itr=="-stereo") break;
+        }
+
+        if (itr!=commandLine.end())
+        {
+        
+            _stereo = true;
+
+            std::vector<std::string>::iterator start = itr; 
+            ++itr;
+            if (itr!=commandLine.end())
+            {
+                if (*itr=="ANAGLYPHIC") { _stereo = true;_stereoMode = ANAGLYPHIC; ++itr; }
+                else if (*itr=="QUAD_BUFFER") { _stereo = true;_stereoMode = QUAD_BUFFER; ++itr; }
+                else if (*itr=="HORIZONTAL_SPLIT") { _stereo = true;_stereoMode = HORIZONTAL_SPLIT; ++itr; }
+                else if (*itr=="VERTICAL_SPLIT") { _stereo = true;_stereoMode = VERTICAL_SPLIT; ++itr; }
+                else if (*itr=="ON") { _stereo = true; ++itr; }
+                else if (*itr=="OFF") { _stereo = false; ++itr; }
+            }
+
+            commandLine.erase(start,itr);
+            found = true;
+        }
+        
+        // check destination alpha
+        itr = commandLine.begin();
+        for(;itr!=commandLine.end();++itr)
+        {
+            if (*itr=="-rgba") break;
+        }
+
+        if (itr!=commandLine.end())
+        {
+            _RGB = true;
+            _minimumNumberAlphaBits = 1;
+            commandLine.erase(itr);
+            found = true;
+        }
+
+
+        // check stencil buffer
+        itr = commandLine.begin();
+        for(;itr!=commandLine.end();++itr)
+        {
+            if (*itr=="-stencil") break;
+        }
+
+        if (itr!=commandLine.end())
+        {
+            _minimumNumberStencilBits = 1;
+            commandLine.erase(itr);
+            found = true;
+        }
+
+    }    
+}