mirror of
https://github.com/sehugg/8bitworkshop.git
synced 2024-11-23 06:32:11 +00:00
121 lines
2.4 KiB
C
121 lines
2.4 KiB
C
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#include <string.h>
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#include "scrolling.h"
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sbyte scroll_fine_x;
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sbyte scroll_fine_y;
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byte origin_x;
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byte origin_y;
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byte* hidbuf;
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byte* visbuf;
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byte colorbuf[COLS*ROWS];
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byte swap_needed;
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//
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void scroll_swap(void) {
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byte* tmp;
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// set VIC bank address
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VIC.addr = (VIC.addr & 0xf) | (((word)hidbuf >> 8) << 2);
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// swap hidden and visible buffers
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tmp = hidbuf;
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hidbuf = visbuf;
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visbuf = tmp;
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}
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void scroll_copy(void) {
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// copy temp buf to color ram
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memcpy(COLOR_RAM, colorbuf, COLS*ROWS);
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// copy visible buffer to hidden buffer
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memcpy(hidbuf, visbuf, COLS*ROWS);
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}
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void scroll_update(void) {
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VIC.ctrl1 = (VIC.ctrl1 & 0xf8) | scroll_fine_y;
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VIC.ctrl2 = (VIC.ctrl2 & 0xf8) | scroll_fine_x;
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if (swap_needed) {
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scroll_swap();
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scroll_copy();
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swap_needed = 0;
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}
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}
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void scroll_left(void) {
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memcpy(hidbuf, hidbuf+1, COLS*ROWS-1);
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memcpy(colorbuf, colorbuf+1, COLS*ROWS-1);
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++origin_x;
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scroll_draw_column(COLS-1);
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swap_needed = true;
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}
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void scroll_up(void) {
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memcpy(hidbuf, hidbuf+COLS, COLS*(ROWS-1));
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memcpy(colorbuf, colorbuf+COLS, COLS*(ROWS-1));
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++origin_y;
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scroll_draw_row(ROWS-1);
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swap_needed = true;
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}
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void scroll_right(void) {
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memmove(hidbuf+1, hidbuf, COLS*ROWS-1);
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memmove(colorbuf+1, colorbuf, COLS*ROWS-1);
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--origin_x;
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scroll_draw_column(0);
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swap_needed = true;
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}
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void scroll_down(void) {
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memmove(hidbuf+COLS, hidbuf, COLS*(ROWS-1));
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memmove(colorbuf+COLS, colorbuf, COLS*(ROWS-1));
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--origin_y;
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scroll_draw_row(0);
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swap_needed = true;
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}
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void scroll_horiz(sbyte delta_x) {
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scroll_fine_x += delta_x;
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while (scroll_fine_x < 0) {
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scroll_fine_x += 8;
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scroll_left();
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}
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while (scroll_fine_x >= 8) {
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scroll_fine_x -= 8;
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scroll_right();
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}
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}
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void scroll_vert(sbyte delta_y) {
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scroll_fine_y += delta_y;
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while (scroll_fine_y < 0) {
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scroll_fine_y += 8;
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scroll_up();
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}
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while (scroll_fine_y >= 8) {
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scroll_fine_y -= 8;
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scroll_down();
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}
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}
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void scroll_setup(void) {
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scroll_fine_x = scroll_fine_y = 0;
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origin_x = origin_y = 0x80;
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swap_needed = true;
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// get screen buffer addresses
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hidbuf = (byte*) 0x8000;
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visbuf = (byte*) 0x8400;
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// copy existing text to screen 0
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memcpy(hidbuf, (byte*)0x400, COLS*ROWS);
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// copy screen 1 to screen 0
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memcpy(visbuf, hidbuf, COLS*ROWS);
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// set VIC bank ($4000-$7FFF)
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// https://www.c64-wiki.com/wiki/VIC_bank
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CIA2.pra = 0x01;
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VIC.ctrl1 &= ~0x08; // 24 lines
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VIC.ctrl2 &= ~0x08; // 38 columns
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}
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