89 lines
1.8 KiB
C
89 lines
1.8 KiB
C
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/*
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This demo sets up two DLLs (Display List Lists) of
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16 slots each.
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By swapping between the two DLLs each frame, one DLL can
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be written while the other is displayed.
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*/
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#include "atari7800.h"
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#include <string.h>
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#include <stdlib.h>
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#include "dll.h"
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//#link "dll.c"
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//#link "chr_font.s"
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//#link "generic8x16.s"
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#define NUMSPRITES 16
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byte xpos[NUMSPRITES];
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byte ypos[NUMSPRITES];
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char* hello = "\2\4\6\0\220\222\102";
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// draw a text string randomly into the background
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void draw_background() {
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byte x = rand();
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byte y = rand();
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if (dll_bytesleft(y/SLOTHEIGHT) > 20) {
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dll_add_string(hello, x, y, DL_WP(7,0));
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dll_swap();
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dll_copy();
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dll_save();
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}
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}
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void main() {
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byte i;
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byte y = 0;
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dll_setup();
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// activate DMA
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MARIA.CHARBASE = 0x80;
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MARIA.P0C1 = 0x8f;
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MARIA.P0C2 = 0x4f;
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MARIA.P0C3 = 0x1f;
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MARIA.P1C1 = 0x34;
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MARIA.P1C2 = 0x28;
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MARIA.P1C3 = 0x1f;
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MARIA.BACKGRND = 0;
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MARIA.CTRL = CTRL_DMA_ON | CTRL_DBLBYTE | CTRL_160AB;
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// set background sprites and save to buffer
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dll_clear();
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draw_background();
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// set up sprite positions randomly
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for (i=0; i<NUMSPRITES; i++) {
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xpos[i] = rand();
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ypos[i] = rand();
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}
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// frame loop
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while (1) {
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// wait for vsync to end
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while ((MARIA.MSTAT & MSTAT_VBLANK) == 0) ;
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// swap buffers and restore background
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dll_swap();
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dll_restore();
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// draw new background sprite?
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// after 32 bytes, the display slots fill up
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if ((rand() & 255) == 0) {
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draw_background();
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}
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// draw forgeground sprites
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for (i=0; i<NUMSPRITES; i++) {
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dll_add_sprite(0xa06c, xpos[i], ypos[i], DL_WP(4,1));
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xpos[i] += rand() & 3;
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ypos[i] += rand() & 3;
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}
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// wait for vsync to start
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while ((MARIA.MSTAT & MSTAT_VBLANK) != 0) ;
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y++;
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}
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}
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