From http://www.jwz.org/xscreensaver/xscreensaver-5.17.tar.gz

[xscreensaver] / OSX / XScreenSaverGLView.m

diff --git a/OSX/XScreenSaverGLView.m b/OSX/XScreenSaverGLView.m
index f7a58c481bd4f04d2c287fde7092d5ac2e6d9ac1..da155211a3c058f32d5f7a5424179cf519be41c8 100644 (file)
--- a/OSX/XScreenSaverGLView.m
+++ b/OSX/XScreenSaverGLView.m
@@ -371,6 +371,9 @@ init_GL (ModeInfo *mi)
       [NSNumber numberWithBool:!dbuf_p], kEAGLDrawablePropertyRetainedBacking,
       nil];
 
+    // Without this, the GL frame buffer is half the screen resolution!
+    eagl_layer.contentsScale = [UIScreen mainScreen].scale;
+
     ogl_ctx = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES1];
   }