Adds comment explaining window position change in GuiCanvas.

Engine/source/gui/core/guiCanvas.cpp

@@ -1762,6 +1762,8 @@ void GuiCanvas::renderFrame(bool preRenderOnly, bool bufferSwap /* = true */)
       mode.antialiasLevel = 0;
       Point2I winPos = mPlatformWindow->getPosition(); // Save position so we can put window back.
       mPlatformWindow->setVideoMode(mode);
+      // setVideoMode (above) will center the window on the display device. If the window had been positioned
+      // by the user or from script, put it back where it was before the light manager change.
       mPlatformWindow->setPosition(winPos);
 
       Con::printf( "AntiAliasing has been disabled; it is not compatible with AdvancedLighting." );
@@ -1776,6 +1778,8 @@ void GuiCanvas::renderFrame(bool preRenderOnly, bool bufferSwap /* = true */)
          mode.parseFromString( pref );
          Point2I winPos = mPlatformWindow->getPosition(); // Save position so we can put window back.
          mPlatformWindow->setVideoMode(mode);
+         // setVideoMode (above) will center the window on the display device. If the window had been positioned
+         // by the user or from script, put it back where it was before the light manager change.
          mPlatformWindow->setPosition(winPos);
 
          Con::printf( "AntiAliasing has been enabled while running BasicLighting." );