RFC: Support arbitrary Cursor Positioning on VGA console?

[netzerohero]

VGA (ver-0.6) console supports ansi colors (select-graphic-rendition SGR) and cursor forward and backward (CUF and CUB).

Consider similar support for arbitrary Cursor Positioning (via ANSI escape codes).
Cursor Position == (ESC [ n ; m H) == CUP == Moves the cursor to row n, column m.

This could provide additional capability for the VGA-console; e.g., eventual support within C- and BASIC- environments in a user-friendly way.

For example (in BASIC dialects): VTAB n : HTAB m (Applesoft) or LOCATE n,m (GW-BASIC). The same feature would also be available in C via existing stdio printf(). This would open-up additional support to heritage BASIC code-bases and allow a c-programmer to use higher-level ansi standard stdio printfs without using lower-level calls to the VGA-graphics-pico directly (xreg calls).

[netzerohero]

Analysis:
Two approaches appear reasonable within rp6502 firmware:

1. Expand the Console-Canvas-Type to be similar to the Text-Canvas-Type in having a similar Text-Config-Structure containing a cursor x,y position. Given static-scoping limits of the term_state structures, accessor-functions could then provide x,y cursor positions, since direct xreg access is not available.

2. Expand function rp6502:src/vga/term/term.c :: term_out_state_CSI() to handle expanded CSI ansi-terminal-standard cases, including CUP - Cursor Position, and perhaps additional ansi=control-sequences as well (shown in yellow):
   

• Option-2 has the advantage of being "a standard driven" approach.
• Option-1 has the advantage of "growing into a solution" in that it aligns nicely to the existing Text-Canvas-Type (from C) and should low-level xreg access become available from EhBASIC.

[rumbledethumps]

If you want a mode 1 terminal emulator, write it on the 6502 side.

Adding mode 0 ANSI sequences has been low priority because there hasn't been a need. There's also a feature hold until picocomputer/rp6502#51 gets fixed.

[netzerohero]

Ah, thanks for the insights. For now I'm using minicom on the linux side.

[rumbledethumps]

Here's the supported ANSI sequences.
https://picocomputer.github.io/vga.html#terminal

[netzerohero]

RP6502 VGA (ver-0.12) adds additional CSI (Control Sequence Introducer) sequences to the VGA-console.
Nicely this includes: arbitrary Cursor Positioning (CUP):

• Cursor Position == (ESC [ n ; m H) == CUP == Moves the cursor to row n, column m.

Note that beginning with RP6502 firmware versions (ver-0.10) requires upgrading the RP6502's picos from the original (RP2040-based) Picos to the newer (RP2350-based) Pico2s:

• RP6502 VGA now requires a Raspberry Pi Pico 2
• RP6502 RIA requires either a Pico 2 (non-wifi) or a Pico 2 W (wifi)

[rumbledethumps]

What will you do with your newfound power... the power of the cursor? Will you move gently, like a Terran scribe? Or will you strike boldly—leaping lines, bending code, carving paths through the document as a true warrior of the interface?

Choose wisely. Qapla’.

[netzerohero]

As soon as Mouser beams-over a pair of pico2 multi-core super-computer, er, glue-HW-upgrades, the power of the cursor you unleashed in FW ver-0.12 will join the full pre-IEEE-754 floating-point power within EHBasic to run unfettered on the 65c02 accessing heritage BASIC code-bases to implement 1st generation spreadsheet sources mimicking VisiCalc long-trapped within the July-1982 issue of Softalk and the Feb-1983 issue of REMark. Can't do that with today's integer-only cc65 compiling Turbo-C MCALC demo sources. But a single 6502 in a stock A2 did it back-in-the-day as did the picocomputer's distant relative on a pair of Z80s in a H89 running SuperCalc. Alas, the original picos will be banished to the back of the parts drawer along with a long-forgotten slide-rule and a fondly thought of 1802.

Thank you for the upgrade. Live long and prosper.

[rumbledethumps]

Fascinating. You can do that project entirely on device. llvm-mos does floats but doesn't yet have a math library. You probably only need a handful of functions that are trivial for AI. Which got me thinking how trivial it is to "type in" a program these days.
BasiCalc.zip

[netzerohero]

Here's the full original Apple-II BasiCalc source from 1982:
BASICALC_A2_1982.txt

And here's my port.