mirror of
https://github.com/RetroPortingToolKit/psxrecomp
synced 2026-10-26 10:19:47 -04:00
Alexandros Mandravillis
107 lines
3.7 KiB
C
107 lines
3.7 KiB
C
/* display_scanout.h — small, renderer-neutral CRTC presentation helpers. */
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#ifndef PSXRECOMP_DISPLAY_SCANOUT_H
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#define PSXRECOMP_DISPLAY_SCANOUT_H
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#include <stdint.h>
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/* PAL active video is 288 lines per field and 576 rows when the interlaced
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* display bit is set. CPU presentation buffers must preserve that full
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* canvas even though PS1 VRAM itself remains 512 rows and wraps on access. */
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#define PSX_DISPLAY_PRESENT_MAX_HEIGHT 576u
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typedef struct {
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uint32_t canvas_height;
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uint32_t canvas_origin_y;
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uint32_t source_skip_y;
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uint32_t source_height;
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int offset_y;
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int range_set;
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int valid;
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} PsxDisplayVerticalLayout;
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/* Depth24 staging expands the visible source into the full active-video
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* canvas. Every presentation backend must therefore consume the canvas
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* height, while ordinary 15-bit display keeps its source height. */
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static inline uint32_t psx_display_present_height(
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int depth24, uint32_t source_height, uint32_t canvas_height)
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{
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return depth24 && canvas_height != 0u ? canvas_height : source_height;
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}
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static inline uint32_t psx_display_interlaced_rows(
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uint32_t rows, int interlaced)
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{
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return interlaced ? rows * 2u : rows;
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}
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/* Canvas-origin clipping belongs only to staged depth24 presentation.
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* Ordinary 15-bit renderers read their source rectangle directly. */
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static inline uint32_t psx_display_clip_source_height(
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int depth24, uint32_t source_height, uint32_t canvas_height,
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uint32_t canvas_origin_y)
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{
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if (!depth24)
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return source_height;
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if (canvas_origin_y >= canvas_height)
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return 0u;
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const uint32_t available = canvas_height - canvas_origin_y;
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return source_height < available ? source_height : available;
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}
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/* Preserve the legacy default for an unset/degenerate GP1(07h) range. A
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* programmed increasing range that has no active-video intersection owns a
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* zero height instead, so presentation fails closed to black. */
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static inline uint32_t psx_display_source_height(
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PsxDisplayVerticalLayout layout, uint32_t fallback_height)
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{
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return layout.range_set ? layout.source_height : fallback_height;
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}
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/* Intersect a GP1(07h) range with the PAL or NTSC active region. The canvas
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* preserves the television scanout position without discarding visible VRAM
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* rows. source_skip_y owns rows before the active region; canvas_origin_y owns
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* black rows before the visible source. */
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static inline PsxDisplayVerticalLayout psx_display_vertical_layout(
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int pal, uint32_t raw_y1, uint32_t raw_y2)
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{
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const int ymin = pal ? 20 : 16;
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const int ymax = pal ? 308 : 256;
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const int centre = pal ? 0xA3 : 0x88;
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PsxDisplayVerticalLayout out = {0};
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int y1 = (int)raw_y1;
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int y2 = (int)raw_y2;
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if (raw_y2 <= raw_y1)
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return out;
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out.range_set = 1;
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out.canvas_height = (uint32_t)(ymax - ymin);
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if (y1 < ymin) y1 = ymin;
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if (y1 > ymax) y1 = ymax;
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if (y2 < ymin) y2 = ymin;
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if (y2 > ymax) y2 = ymax;
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if (y2 <= y1)
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return out;
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out.canvas_origin_y = (uint32_t)(y1 - ymin);
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out.source_skip_y = raw_y1 < (uint32_t)ymin
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? (uint32_t)ymin - raw_y1 : 0u;
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out.source_height = (uint32_t)(y2 - y1);
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out.offset_y = ((y1 + y2) - (centre * 2)) / 2;
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out.valid = 1;
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return out;
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}
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/* Return the vertical position of a GP1(07h) display range relative to the
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* broadcast centre. Positive values move the scanout down. The limits and
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* centres are the PS1 PAL/NTSC active regions documented by psx-spx. */
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static inline int psx_display_vertical_offset(int pal, uint32_t raw_y1,
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uint32_t raw_y2)
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{
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PsxDisplayVerticalLayout layout = psx_display_vertical_layout(
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pal, raw_y1, raw_y2);
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return layout.valid ? layout.offset_y : 0;
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}
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#endif
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