Btw, Edge Overlay on slows down booting to play... 
Seems a bit solved, && edited with some cosmetics
..., SX280 lib.c tells:
int vid_get_viewport_yoffset() {
// this seems to be always 0, buffer always begins with actual display data (widescreen or not)
return 0;
vid_get_viewport_image_offset(); // offset into viewport for when image size != viewport size (e.g. 16:9 image on 4:3 LCD)
seems always 0, too. Some #THUMB_FW lines to save some bytes didn´t disturb so far ...
Edit: Now it´s fluid, with ...
static int key_check(int x)
{
return camera_info.state.mode_play|x
&& camera_info.state.kbd_last_clicked_time - get_tick_count()>-300;
}
