From WojciechLewandowski, Added DispaySettings::SwapMethod and support for it in GraphicsContext::Traits

include/osg/DisplaySettings

@@ -246,6 +246,19 @@ class OSG_EXPORT DisplaySettings : public osg::Referenced
         /** Get mask selecting default implict buffer attachments for Cameras secondary MULTISAMPLE FBOs. */
         ImplicitBufferAttachmentMask getImplicitBufferAttachmentResolveMask() const { return _implicitBufferAttachmentResolveMask;}
 
+        enum SwapMethod
+        {
+            SWAP_DEFAULT,   // Leave swap method at default returned by choose Pixel Format.
+            SWAP_EXCHANGE,  // Flip front / back buffer. 
+            SWAP_COPY,      // Copy back to front buffer. 
+            SWAP_UNDEFINED  // Move back to front buffer leaving contents of back buffer undefined.
+        };
+        
+        /** Select preferred swap method */
+        void setSwapMethod( SwapMethod swapMethod ) { _swapMethod = swapMethod; }
+
+        /** Get preferred swap method */
+        SwapMethod getSwapMethod( void ) { return _swapMethod; }
 
         /** Set the hint of which OpenGL version to attempt to create a graphics context for.*/
         void setGLContextVersion(const std::string& version) { _glContextVersion = version; }
@@ -315,6 +328,8 @@ class OSG_EXPORT DisplaySettings : public osg::Referenced
         std::string                     _glContextVersion;
         unsigned int                    _glContextFlags;
         unsigned int                    _glContextProfileMask;
+
+        SwapMethod                      _swapMethod;
 };
 
 }

include/osg/GraphicsContext

@@ -130,6 +130,8 @@ class OSG_EXPORT GraphicsContext : public Object
             
             // X11 hint whether to override the window managers window size/position redirection
             bool overrideRedirect;
+
+            DisplaySettings::SwapMethod swapMethod;
         };
 
         /** Simple resolution structure used by WindowingSystemInterface to get and set screen resolution.

src/osg/DisplaySettings.cpp

@@ -90,6 +90,7 @@ void DisplaySettings::setDisplaySettings(const DisplaySettings& vs)
     _glContextVersion = vs._glContextVersion;
     _glContextFlags = vs._glContextFlags;
     _glContextProfileMask = vs._glContextProfileMask;
+    _swapMethod = vs._swapMethod;
 }
 
 void DisplaySettings::merge(const DisplaySettings& vs)
@@ -120,6 +121,10 @@ void DisplaySettings::merge(const DisplaySettings& vs)
     // these are bit masks so merging them is like logical or 
     _implicitBufferAttachmentRenderMask |= vs._implicitBufferAttachmentRenderMask;
     _implicitBufferAttachmentResolveMask |= vs._implicitBufferAttachmentResolveMask;
+
+    // merge swap method to higher value
+    if( vs._swapMethod > _swapMethod )
+        _swapMethod = vs._swapMethod;
 }
 
 void DisplaySettings::setDefaults()
@@ -173,6 +178,8 @@ void DisplaySettings::setDefaults()
     _glContextVersion = "1.0";
     _glContextFlags = 0;
     _glContextProfileMask = 0;
+
+    _swapMethod = SWAP_DEFAULT;
 }
 
 void DisplaySettings::setMaxNumberOfGraphicsContexts(unsigned int num)
@@ -475,6 +482,30 @@ void DisplaySettings::readEnvironmentalVariables()
     {
         _glContextProfileMask = atoi(ptr);
     }
+
+    if ((ptr = getenv("OSG_SWAP_METHOD")) != 0)
+    {
+        if (strcmp(ptr,"DEFAULT")==0)
+        {
+            _swapMethod = SWAP_DEFAULT;
+        }
+        else
+        if (strcmp(ptr,"EXCHANGE")==0)
+        {
+            _swapMethod = SWAP_EXCHANGE;
+        }
+        else
+        if (strcmp(ptr,"COPY")==0)
+        {
+            _swapMethod = SWAP_COPY;
+        }
+        else
+        if (strcmp(ptr,"UNDEFINED")==0)
+        {
+            _swapMethod = SWAP_UNDEFINED;
+        }
+
+    }
 }
 
 void DisplaySettings::readCommandLine(ArgumentParser& arguments)
@@ -606,4 +637,13 @@ void DisplaySettings::readCommandLine(ArgumentParser& arguments)
     while (arguments.read("--gl-flags", _glContextFlags)) {}
     while (arguments.read("--gl-profile-mask", _glContextProfileMask)) {}
 
+    while(arguments.read("--swap-method",str))
+    {
+        if (str=="DEFAULT") _swapMethod = SWAP_DEFAULT;
+        else if (str=="EXCHANGE") _swapMethod = SWAP_EXCHANGE;
+        else if (str=="COPY") _swapMethod = SWAP_COPY;
+        else if (str=="UNDEFINED") _swapMethod = SWAP_UNDEFINED;
+    }
+
+
 }

src/osg/GraphicsContext.cpp

@@ -185,7 +185,8 @@ GraphicsContext::Traits::Traits(DisplaySettings* ds):
             glContextProfileMask(0),
             sharedContext(0),
             setInheritedWindowPixelFormat(false),
-            overrideRedirect(false)
+            overrideRedirect(false),
+            swapMethod( DisplaySettings::SWAP_DEFAULT )
 {
     if (ds)
     {
@@ -208,6 +209,8 @@ GraphicsContext::Traits::Traits(DisplaySettings* ds):
         glContextVersion = ds->getGLContextVersion();
         glContextFlags = ds->getGLContextFlags();
         glContextProfileMask = ds->getGLContextProfileMask();
+
+        swapMethod = ds->getSwapMethod();
     }
 }