- Changed canvas coordinate system to match UI coord system (origin at top left, y axis down)
- Changed mouse coordinate system to match UI and canvas
- No need to pass width/height to ui_begin_frame() anymore
- shorten str8_lit macro to STR8
- use strlen() in STR8 and remove str8_from_cstring(). Usage with string literal seem to always be optimized by compile-time constant, so there's little need for a confusing macro that only works with literals and breaks with pointers.
- replaced str8_unbox() with str8_lp/str8_ip
Martin Fouilleul