Add support to hardware scrolling under cpc

[poppichicken]

hi Marco.

I'm not sure if I have written this correctly, but rightScroll is not called.

BITMAP ENABLE(160,200,16)
BORDER OLIVE GREEN
CLS BLACK
DEFINE KEYBOARD ASYNC

ON SCROLL RIGHT COLUMN CALL rightScroll

PRINT "hello"
HSCROLL SCREEN RIGHT
END

rightScroll:
PRINT "rightScroll"
RETURN

Same thing happens if I use:

ON SCROLL RIGHT COLUMN GOSUB rightScroll

[spotlessmind1975]

Hi @poppichicken , and thank you for your bug report!

At first I thought it was a bug but, in fact, looking closely, it is not. In the sense that the ON...SCROLL instruction works with hardware scrolling (to be clear: what can be done pixel by pixel with some chipsets), but not with software scrolling (which is what can be done character by character). The reason is simple: it is a callback that is used to allow the program to fill the space not yet shown, before proceeding with the actual video shifting. Hardware scrolling is not implemented on the cpc target. So it is necessary to implement that type of operation first.

Thank you!

[poppichicken]

Ah, I see.
Thanks,