Fabio Bracci wrote: > The problem is that this is the only working sequence: > performing a fl_read_image *after* fl_end_offscreen() simply causes an ugly > segmentation fault.
This is because fl_read_image() does not have any argument to specify from WHICH drawable the image pixels should be read, so it always reads from CURRENT drawable. Normally during Fl::flush() the drawable is a screen window. But outside this, there is no current drawable set so fl_read_image() does not know from where to read the pixels an it is probably accessing a NULL pointer. To read the pixels from your your offscreen, this offscreen needs to be current and you can set this as current by fl_begin_offscreen(my_ofscreen). The function fl_end_offscreen() sets back the previous active drawable as current, and if it happens to be 0, then fl_read_image() crashes. Your offscreen remains persistent until you call fl_delete_offscreen(my_offscreen), but to access it, you have to make it current again by encapsulating it within fl_begin_offscreen()/fl_end_offscreen() brackets like fl_begin_ofscreen(my_offscreen); // makes my_offscreen current fl_read_image(...); // reads from current drawable fl_end_offscreen(); //sets back previous drawable as current Roman _______________________________________________ fltk mailing list [email protected] http://lists.easysw.com/mailman/listinfo/fltk
