I got it working, seems that the only way to do it is to use the FlxG.camera.setScale() method. Using zoom or even upscaling the sprites wont work.
Here's detailed what I did:
- Set window size to 512x512 in the desktop application
- Set the screen resolution to 256x256 in the FlxGame core application
- In your FlxState set te camera scaling like so: FlxG.camera.setScale(4,4); That way you'll have a 64x64 grid in a 256x256 screen resolution.
Problem is that if you resize the window, you'll loose the 64x64 grid and achieve a full 256x256 resolution. But I guess that property can be disabled.