screen mode 8 problem, does not clear line at the bottom

[tallLeRoy]

May be a ROM problem or an emulator problem using x16emu. Here is a simple Prog8 program to show the problem line.

%import textio
%zeropage basicsafe
%option no_sysinit

main {

    sub start() {
        txt.color2(0,1)
;        txt.clear_screen()
        void cx16.set_screen_mode(8)  ; 64x50
        cx16.VERA_DC_BORDER = 1
    }
}

If txt.clear_screen() is called before screen mode 8, the screen is all white. If txt.clear_screen() is called after screen mode 8 the problem line remains.

[tallLeRoy]

Those Prog8 library calls, just call the ROM routines

[mooinglemur]

I believe this is an Emulator scaling (or HSTOP/HSTART) rounding error. It may not be either. Whatever its cause, a workaround until this is fixed would be to set mode 0, clear the screen, then change to your desired mode.