118 lines
2.6 KiB
C
118 lines
2.6 KiB
C
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#include "common.h"
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//#link "common.c"
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#include <cbm_petscii_charmap.h>
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sbyte scroll_fine_x = 0;
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sbyte scroll_fine_y = 0;
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byte* scrnbuf[2]; // screen buffer(s)
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byte hidbuf = 0;
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void scroll_update_regs() {
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SET_SCROLL_X(scroll_fine_x);
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SET_SCROLL_Y(scroll_fine_y);
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}
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void scroll_swap() {
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// swap hidden and visible buffers
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hidbuf ^= 1;
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// wait for end of frame and update registers
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wait_vblank();
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scroll_update_regs();
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SET_VIC_SCREEN(hidbuf ? 0x8000 : 0x8400);
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}
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void scroll_left() {
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memcpy(scrnbuf[hidbuf], scrnbuf[hidbuf^1]+1, COLS*ROWS-1);
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scroll_swap();
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}
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void scroll_right() {
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memcpy(scrnbuf[hidbuf]+1, scrnbuf[hidbuf^1], COLS*ROWS-1);
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scroll_swap();
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}
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void scroll_up() {
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memcpy(scrnbuf[hidbuf], scrnbuf[hidbuf^1]+COLS, COLS*(ROWS-1));
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scroll_swap();
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}
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void scroll_down() {
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memcpy(scrnbuf[hidbuf]+COLS, scrnbuf[hidbuf^1], COLS*(ROWS-1));
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scroll_swap();
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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() {
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// get screen buffer addresses
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scrnbuf[0] = (byte*) 0x8000;
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scrnbuf[1] = (byte*) 0x8400;
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// copy existing text to screen 0
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memcpy(scrnbuf[0], (byte*)0x400, COLS*ROWS);
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// copy screen 1 to screen 0
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memcpy(scrnbuf[1], scrnbuf[0], COLS*ROWS);
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// set VIC bank
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// https://www.c64-wiki.com/wiki/VIC_bank
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SET_VIC_BANK(0x8000);
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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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void main(void) {
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clrscr();
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printf("\n\n\n Hello World!");
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printf("\n\n\n This is how we scroll");
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printf("\n\n\n And now we have two buffers");
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printf("\n\n\n And can go in any direction");
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printf("\n\n\n But we are not incremental");
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printf("\n\n\n And have to pause to scroll and copy");
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scroll_setup();
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VIC.bordercolor = COLOR_GRAY1;
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// install the joystick driver
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joy_install (joy_static_stddrv);
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// infinite loop
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while (1) {
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// get joystick bits
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char joy = joy_read(0);
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// move sprite based on arrow keys
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if (JOY_LEFT(joy)) scroll_horiz(-1);
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if (JOY_UP(joy)) scroll_vert(-1);
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if (JOY_RIGHT(joy)) scroll_horiz(1);
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if (JOY_DOWN(joy)) scroll_vert(1);
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// update regs
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waitvsync();
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scroll_update_regs();
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}
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}
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