[osg-users] Viewport screen resolution not scaling properly in OSX retina

[OpenSceneGraph Users]

Hello,

The viewport dpi is different from the window dpi on OSX. Is there a way to 
fix the viewport dimensions, preferably by autodetecting the size of the 
frame buffer, so that the viewport size matches the window size? 

There must be a way to detect the frame buffer size in OSG, but I cannot 
find it.

The particular issue occurs with the FLTK sample program when compiled on 
my macbook.

//https://github.com/openscenegraph/OpenSceneGraph/blob/master/examples/osgviewerFLTK/osgviewerFLTK.cpp

On OSX, the viewport fills the bottom left  quarter of the window. I have 
read the scale factor to apply to the viewport is 2x the window size, but 
the resulting dimensions of the rescaled viewport are not exactly right. is 
there a way to access the framebuffer to get its dimensions?

On windows, I understand this issue could be fixed with a call to

///    ::SetProcessDPIAware();  //.. .alternately: SetProcessDpiAwareness()

but there seems to be no equivalent on for OSX.

I was unsuccessful accessing the function glfwGetFramebufferSize defined in 
<GLFW/glfw3.h> 

I have also tried to modify the sample code AdapterWidget() with the 
following commented lines to access the frame buffer size from OSG, with no 
luck. 

            AdapterWidget(x,y,w,h,label),xpixscale(1.0),ypixscale(1.0)
            {
                getCamera()->setViewport(new 
osg::Viewport(0,0,xpixscale*w,ypixscale*h));
                getCamera()->setProjectionMatrixAsPerspective(30.0f, 
static_cast<double>(w)/static_cast<double>(h), 1.0f, 10000.0f);
                getCamera()->setGraphicsContext(getGraphicsWindow());
                getCamera()->setDrawBuffer(GL_BACK);
                getCamera()->setReadBuffer(GL_BACK);
            
                setThreadingModel(osgViewer::Viewer::SingleThreaded);
 //           unsigned int swidth, sheight;
 //                  osgViewer::GraphicsWindow * _gw = getGraphicsWindow();
 //                  osg::GraphicsContext * gc = (osg::GraphicsContext*) 
_gw;
 //                  osg::GraphicsContext::WindowingSystemInterface * wsi = 
gc->getWindowingSystemInterface();
 //                  //yields wsi->Name == "Cocoa" but no other useful 
information
 //                  osg::DisplaySettings *ds = 
gc->getWindowingSystemInterface()->getDisplaySettings();  // This is NULL
 //                  sheight = ds->getScreenHeight();
 //                  swidth =  ds->getScreenWidth();
 //                  std::cout << sheight << " " << swidth << std::endl;
            }

There must be a solution to detecting the frame buffer size in OSG so the 
viewport size can be scaled to the window size. but I cannot find it. Does 
anyone have a solution?

Thanks

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