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https://github.com/libretro/bk-emulator.git
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59 lines
1.6 KiB
C
59 lines
1.6 KiB
C
#include "defines.h"
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unsigned char req_page[512], req_palette[512];
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unsigned char param_change_line;
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unsigned char change_req;
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int upper_porch = 0; /* Default */
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int lower_porch = 3; /* Default */
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static unsigned char active_palette, active_page;
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static unsigned char half_frame = 0;
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#define LINES_TOTAL (256+upper_porch+lower_porch)
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/* Returns the scan line number that is supposedly being displayed "now".
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* Each half frame is TICK_RATE/50 long and consists of 128 lines.
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*/
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static unsigned current_scan_line() {
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unsigned nframes = ticks/half_frame_delay;
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unsigned frame_ticks = ticks - half_frame_delay * nframes;
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unsigned line = frame_ticks / scan_line_duration;
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if (line < upper_porch) return 0;
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line -= upper_porch;
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if (line < 256) return line; else return 256;
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}
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void scr_param_change(int pal, int buf) {
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int cur = current_scan_line();
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unsigned int i;
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for (i = param_change_line; i < cur; i++) {
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req_palette[2 * i + half_frame] = active_palette;
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req_page[2 * i + half_frame] = active_page;
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}
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active_palette = pal;
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active_page = buf;
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param_change_line = cur;
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change_req = 3; /* For 2 half-frames */
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fprintf(stderr, "l=%d\n", cur);
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}
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void scr_common_init() {
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active_palette = bkmodel ? 15 : 0;
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scan_line_duration = TICK_RATE/(LINES_TOTAL*50);
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}
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/*
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* Just before a half frame ends, fill up the buffer and palette
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* requests to the end with the current values.
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*/
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void scr_sync() {
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unsigned int i;
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for (i = param_change_line; i < 256; i++) {
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req_palette[2 * i + half_frame] = active_palette;
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req_page[2 * i + half_frame] = active_page;
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}
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half_frame ^= 1;
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param_change_line = 0;
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}
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