82 lines
2.0 KiB
C
82 lines
2.0 KiB
C
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/*
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Demo of split screen effect.
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We position sprite 0 at the desired scanline, and when it
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collides with the background, a flag in the PPU is set.
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The split() function waits for this flag, then changes the
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X scroll register in the PPU.
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*/
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#include "neslib.h"
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#include <string.h>
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// vertical mirroring (horizontal scroling)
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#define NES_MIRRORING 1
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// link the pattern table into CHR ROM
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//#link "chr_generic.s"
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// function to write a string into the name table
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// adr = start address in name table
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// str = pointer to string
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void put_str(unsigned int adr, const char *str) {
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vram_adr(adr); // set PPU read/write address
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vram_write(str, strlen(str)); // write bytes to PPU
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}
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// function to scroll window up and down until end
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void scroll_demo() {
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int x = 0; // x scroll position
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int dx = 1; // x scroll direction
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// infinite loop
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while (1) {
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// set scroll register
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// waits for NMI, which means no frame-skip?
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split(x, 0);
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// update x variable
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x += dx;
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// change direction when hitting either edge of scroll area
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if (x >= 479) dx = -1;
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if (x == 0) dx = 1;
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}
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}
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// main function, run after console reset
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void main(void) {
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// set palette colors
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pal_col(0,0x00);
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pal_col(1,0x04);
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pal_col(2,0x20);
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pal_col(3,0x30);
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pal_col(5,0x14);
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pal_col(6,0x24);
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pal_col(7,0x34);
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// write text to name table
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put_str(NTADR_A(7,0), "Nametable A, Line 0");
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put_str(NTADR_A(7,1), "Nametable A, Line 1");
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put_str(NTADR_A(7,2), "Nametable A, Line 2");
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vram_adr(NTADR_A(0,3));
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vram_fill(5, 32);
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put_str(NTADR_A(2,4), "Nametable A, Line 4");
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put_str(NTADR_A(2,15),"Nametable A, Line 15");
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put_str(NTADR_A(2,27),"Nametable A, Line 27");
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put_str(NTADR_B(2,4), "Nametable B, Line 4");
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put_str(NTADR_B(2,15),"Nametable B, Line 15");
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put_str(NTADR_B(2,27),"Nametable B, Line 27");
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// set attributes
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vram_adr(0x23c0);
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vram_fill(0x55, 8);
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// set sprite 0
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oam_clear();
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oam_spr(1, 30, 0xa0, 0, 0);
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// enable PPU rendering (turn on screen)
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ppu_on_all();
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// scroll window back and forth
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scroll_demo();
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}
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