Feature Request: --scale command line option

[unwiredben]

Since the Pebble screen is so small, the emulator is often hard to view on high DPI displays. Looking at the qemu source, SDL supports scaling up the display area in response to keypresses and window resize events, but there's no way to pre-fill this scaling value on the command line.

ui/sdl.c provides a sdl_scale function to set the scaling factor. I'd propose adding a hook at SDL window creation time that would read a value provided by a --scale command line parameter and use that to pre-scale the window. This would also need to be pushed into the pebble tool to have it support passing that parameter through to qemu when it starts it.