New feature idea: draw bad lines, borders etc.

[r1me]

How about drawing something else than text and would be helpful for coders and artists, like:

• bad lines (no doubt coders would like to have this feature) ignore FLD or whatever can delay bad lines, simply draw a dotted line where they normally occur
• borders of foreground (i.e. with same foreground and background color it's hard to tell if something is off center)
• margins of visible area (customizable x1, y1, x2, y2) once set that can be later used for calibrating projectors/CRTs for C64 video output, like https://csdb.dk/release/?id=201894 does

More or less that's what came to my mind.

[hbekel]

Those ideas are nice, but unfortunately they are not really feasible for a simple project like this.

1. Drawing bad lines -- this is completely out of scope for this hardware. The overlay64 only sees a PAL signal, and knows nothing about the C64 or the VIC. Even if some other device, say an FPGA VIC implementation, would provide an additional output line and assert it for the duration of a bad line, the overlay would not be able to pick it up and mark it in realtime. It is either completely busy bitbanging on the luminance signal for displaying the current (previously calculated) text buffer, OR it is sampling input lines and preparing the text buffer for display, but it can't do both simultaneously.

2. Drawing horizontal or vertical lines could be achieved by using a custom font and preparing a static text screen. However, since the overlay produces a higher horizontal resolution than the VIC (about 53*8=424 pixels), you probably wont be able to line it up exactly with something like the edge of the VIC border.

[hbekel]

By the way, if you had an fpga VIC or some other magical device providing such a hypothetical output line (that would go high during badlines), you wouldn't even need the overlay to mark that line, you'd just have to switch a transistor to pull the luminance signal high. Limit the current with a resistor to make it semi-transparent, and you could still see what happens on the actual VIC line.