uc8151: add FillRectangle() and SetScroll() functions to satisfy tinyterm.Displayer interface

[deadprogram]

This PR adds to the uc8151 display by implementing the FillRectangle() and SetScroll() functions in order to satisfy the tinyterm.Displayer interface.

[deadprogram]

Once this can get merged, I have some related changes to tinyterm that allows it to work on the badger2040 display.

[ydnar]

Do you want to add an assertion that it satisfies the interface?

[deadprogram]

@ydnar what would be the best way to do that? The interface is defined in package that consumes this package here: https://github.com/tinygo-org/tinyterm/blob/release/tinyterm.go#L27

[ydnar]

@ydnar what would be the best way to do that? The interface is defined in package that consumes this package here: https://github.com/tinygo-org/tinyterm/blob/release/tinyterm.go#L27

Can you define it elsewhere and have tinyterm import that and alias it?

[ydnar]

Seems like a big lift for little value...

[deadprogram]

I'll think about a way to do it in a future PR. Thanks for review @ydnar now merging.

[aykevl]

You have a program that calls SetScroll without first calling SetScrollArea? I think that won't work on other displays like ST7789.

[deadprogram]

This is for interface compatibility with tinyterm which does not call SetScrollArea(). See https://github.com/tinygo-org/tinyterm/blob/release/tinyterm.go#L27-L31

Actually, in the case of the uc8151 tinyterm only uses the software scroll, which is why the implementation here just returns without doing anything.