add some command line switches for the gpu window

README.md

@@ -43,6 +43,27 @@ Options:
 -l LEVEL, --level LEVEL : Compression level (0-9). Higher compression levels are really slow.
 -o FILE, --output FILE  : Write the loaded and optionally packed cart back to disk.
 
+when using the native runtime:
+
+-m, --no-audio          : Disable audio, also reduces cpu load a bit
+--no-gpu                : Force old cpu-only window code
+--filter FILTER         : Select an upscale filter at startup
+--fullscreen            : Start in fullscreen mode
+
+Note that the cpu-only window does not support fullscreen nor upscale filters.
+
+Unless --no-gpu is given, uw8 will first try to open a gpu accelerated window, falling back to the old cpu-only window if that fails.
+Therefore you should rarely need to manually pass --no-gpu. If you prefer the old pixel doubling look to the now default crt filter,
+you can just pass "--filter nearest" or "--filter 1".
+
+The upscale filter options are:
+1, nearest              : Anti-aliased nearest filter
+2, fast_crt             : Very simple, cheap crt filter, not very good below a window size of 960x720
+3, ss_crt               : Super sampled crt filter, a little more demanding on the GPU but scales well to smaller window sizes
+4, chromatic_crt        : Variant of fast_crt with a slight offset of the three color dots of a pixel, still pretty cheap
+5, auto_crt (default)   : ss_crt below 960x720, chromatic_crt otherwise
+
+You can switch the upscale filter at any time using the keys 1-5. You can toggle fullscreen with F.
 
 uw8 pack [<options>] <infile> <outfile>