snark13
49a87b4d02
palette.h/video/palette.c wrap BIOS $A4 PIC_SET_PAL/PIC_GET_PAL and $A6 SET_PAL_INIT for the 8 palette pages (0-3 graphics, 4-7 text planes). gfx_palette.c and conio/text_palette.c are thin per-domain wrappers; text_palette.c maps the text "plane" 0..3 (paper/ink/blink-paper/ blink-ink) onto BIOS pages 4..7. Covered by tests/text_palette. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
90 lines
3.9 KiB
C
90 lines
3.9 KiB
C
/*
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* palette.h — Sprinter palette (low-level).
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*
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* The Sprinter has eight 256-colour palette pages, shared by graphics and
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* text modes:
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*
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* pal_num 0..3 — graphics palettes. Each character cell selects which
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* of the four it uses through bits 7..6 of its mode byte.
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* Used by graphics modes 0x81 / 0x82.
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* pal_num 4..7 — text-mode planes — together they form the colour table
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* of the text-mode attribute byte:
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* 4 = paper (background, non-blink phase)
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* 5 = ink (foreground, non-blink phase)
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* 6 = paper-blink (background during blink half-cycle)
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* 7 = ink-blink (foreground during blink half-cycle)
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* Each plane holds 256 BGR colours indexed directly by
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* the 8-bit attribute byte of the cell.
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*
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* Entry format — 4 bytes per colour, in Blue-Green-Red-pad order; the pad
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* byte is reserved and must be 0.
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*
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* Notes on the underlying BIOS ($A4):
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* - `count = 0` means 256 entries (full plane).
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* - On write, data is AND-masked against `pal_mask` before reaching
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* VRAM. pal_load/pal_set_color hard-code mask = 0xFF (no masking).
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*
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* Blink semantics (text planes):
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* The hardware constantly alternates between planes 4↔6 (paper) and
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* 5↔7 (ink). To DISABLE blink everywhere in IBM-CGA style, copy plane
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* 4 → 6 and 5 → 7 (so both phases show the same colour). To ENABLE
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* ZX-Spectrum style flash, swap entries 6 ↔ 7 for the desired attrs.
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* The system default (PAL_CGA) leaves flash visible only for attribute
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* bytes with bit 7 set.
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*
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* Backed by BIOS PIC_SET_PAL/PIC_GET_PAL ($A4) and SET_PAL_INIT ($A6).
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* Higher-level wrappers live in <conio.h> (text_pal_*) and <gfx.h>
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* (gfx_pal_*); use those directly unless you need raw plane control.
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*/
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#ifndef PALETTE_H
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#define PALETTE_H
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#include <stdint.h>
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/* Default-palette types for pal_reset(). Values match BIOS $A6 B-register. */
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#define PAL_GRAPH 1 /* graphics palette (planes 0..3) */
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#define PAL_SINCLAIR 2 /* Spectrum palette (text planes 4..7, ZX colours) */
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#define PAL_CGA 3 /* CGA text palette (text planes 4..7, IBM CGA) */
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/* Load a contiguous block of palette entries.
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* pal_num: 0..7 (0..3 graphics, 4..7 text)
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* start: first slot (0..255)
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* count: number of slots (0 means 256)
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* bgr0: pointer to count entries of 4 bytes each: Blue, Green, Red, 0 */
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void pal_load(uint8_t pal_num, uint8_t start, uint8_t count,
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const uint8_t *bgr0);
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/* Read a contiguous block of palette entries back into RAM.
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* Same parameter shape as pal_load — bgr0 here is a write buffer of
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* count*4 bytes that receives B,G,R,0 quadruples. */
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void pal_get (uint8_t pal_num, uint8_t start, uint8_t count,
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uint8_t *bgr0);
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/* Convenience: set one entry from an RGB triple. */
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void pal_set_color(uint8_t pal_num, uint8_t slot,
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uint8_t r, uint8_t g, uint8_t b);
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/* Convenience: read one entry into R,G,B pointers (any may be NULL). */
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void pal_get_color(uint8_t pal_num, uint8_t slot,
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uint8_t *r, uint8_t *g, uint8_t *b);
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/* Restore a built-in default palette (BIOS $A6 SET_PAL_INIT).
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* type: PAL_GRAPH / PAL_SINCLAIR / PAL_CGA.
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* Internally:
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* PAL_GRAPH → A=0, E=0, B=1 (resets graphics palette 0)
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* PAL_SINCLAIR → A=0, E=0, B=2
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* PAL_CGA → A=0, E=0, B=3 (resets all text planes 4..7)
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*
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* Use pal_reset_at() if you need a non-zero page or a non-zero graphics
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* palette index. */
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void pal_reset(uint8_t type);
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/* Full-control variant of pal_reset.
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* pal_page: BIOS A register — "palette page" hardware index.
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* graph_pal: BIOS E register — for PAL_GRAPH, target palette 0..3.
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* type: BIOS B register — PAL_GRAPH / PAL_SINCLAIR / PAL_CGA. */
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void pal_reset_at(uint8_t type, uint8_t pal_page, uint8_t graph_pal);
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#endif
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