Robert Allan JamesandClaude Sonnet 5
1f3ec3554e
Scope decided with Captain Bob before implementation: ring buffer + recall on today's full-screen vt100 grid, not also confining REPL text to the 4.4o 640x480 box (that confinement stays open as its own future item, not a third silent deferral). No keyboard input path exists yet (M8 unstarted), so the trigger is two new FORTH words, SCROLL-BACK ( n -- ) / SCROLL-FWD ( n -- ), exercised via serial injection. vt100.c gains a text-only 1000-line ring buffer (kmalloc'd, tens of KB -- not pixel snapshots, which would be ~1000x larger for no benefit) plus a shadow buffer mirroring the current screen. scroll_up() now pushes evicted rows into the ring before the pixel scroll. History is one continuous sequence (ring then shadow); scrolling always redraws from that sequence -- no separate pixel-scroll path for scrollback, decided up front to avoid retrofitting later. New src/word_source/scroll_words.c (Module 31), thin wrappers over console_fb_scroll_back()/_fwd() -> vt100_scroll_back()/_fwd(). Bug caught during live testing: both words initially used an off-by-one underflow check (dsp < 1) copied from a different, older dsp convention elsewhere in this codebase; vm_pop() (which these words actually call) uses dsp as a 0-based top-of-stack index, so the check rejected every legitimate single-argument call. Fixed by removing the separate precheck and relying on vm_pop()'s own guard. Live-verified on all three architectures (exceeds this item's amd64-minimum bar): generated 50+ lines via a FORTH loop, confirmed SCROLL-BACK recovers correctly older content, and on amd64 confirmed SCROLL-FWD returns to genuinely live state (not a frozen snapshot) by showing the injected commands' own echo. Known limitation confirmed by direct pixel measurement: redrawn lines lose their original SGR color (not stored per-cell) -- text recovers exactly, color does not. Three-arch verified: Failed: 0, dict-hashes identical across all three (values changed correctly from prior items -- two new words were added). Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
53 lines
1.6 KiB
C
53 lines
1.6 KiB
C
/*
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StarForth — Steady-State Virtual Machine Runtime
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Copyright (c) 2023–2025 Robert A. James
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All rights reserved.
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Licensed under the StarForth License, Version 1.0
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*/
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/* scroll_words.c — REPL scrollback entry points (FABRIC.md item 4.4q).
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* Kernel-only; no-op on hosted builds. */
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#include "include/scroll_words.h"
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#include "../../include/log.h"
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#include "../../include/word_registry.h"
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#ifdef __STARKERNEL__
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#include "starkernel/console.h"
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/* SCROLL-BACK ( n -- ) -- move the REPL scrollback view back n lines.
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* Relies on vm_pop()'s own underflow guard (sets vm->error, logs, returns
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* 0) rather than a separate dsp precheck -- this codebase has more than
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* one dsp convention across older word_source files (some treat it as a
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* top-of-stack index, some as a raw count); vm_pop() is the one this word
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* actually calls, so deferring to its own check sidesteps the mismatch
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* entirely instead of risking silently picking the wrong one. */
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static void scroll_word_back(VM *vm) {
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cell_t n = vm_pop(vm);
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if (vm->error) return;
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if (n < 0) n = 0;
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console_fb_scroll_back((uint32_t)n);
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}
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/* SCROLL-FWD ( n -- ) -- move the REPL scrollback view forward n lines
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* (toward live). Same underflow-handling rationale as SCROLL-BACK above. */
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static void scroll_word_fwd(VM *vm) {
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cell_t n = vm_pop(vm);
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if (vm->error) return;
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if (n < 0) n = 0;
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console_fb_scroll_fwd((uint32_t)n);
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}
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#endif /* __STARKERNEL__ */
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void register_scroll_words(VM *vm)
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{
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#ifdef __STARKERNEL__
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register_word(vm, "SCROLL-BACK", scroll_word_back);
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register_word(vm, "SCROLL-FWD", scroll_word_fwd);
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#else
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(void) vm;
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#endif
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}
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