261 lines
8 KiB
C
Executable file
261 lines
8 KiB
C
Executable file
#include <dos.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include "video.h"
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#include "tiles.h"
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#include "egamap.h"
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/*** T I L E S ***/
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// Tiles are 16x16 bitmaps, stored as arrays of words.
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// Each tile has 4 or 5 planes (depending on whether it is a tile or sprite)
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// which are stored adjacant to each other; ie. a 16-word array of blue,
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// followed by a 16-word array of green, etc.
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// Tiles in RAM are stored byte-swapped to aid in fast bit-shifting, and must
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// be byte-swapped before being written to video memory.
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// Because bit-shifting operations happen on little-endian words:
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// 01234567 89ABCDEF << 3 => 34567XXX BCDEF012
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// which is wrong. So instead we do:
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// 89ABCDEF 01234567 << 3 => BCDEFXXX 3456789A byteswap => 3456789A BCDEFXXX
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void tile_init() {
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setLogicalWidth(PAGE_STRIDE >> 1);
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}
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void blitTile(unsigned int offsetFrom, unsigned int offsetTo) {
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int y;
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for (y = 0; y < 16; y ++) {
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VID[offsetTo] = VID[offsetFrom ++];
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VID[offsetTo + 1] = VID[offsetFrom ++];
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offsetTo += PAGE_STRIDE;
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}
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}
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void blitSolidBlock(unsigned int offsetTo, unsigned char color) {
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int y;
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setPlaneColor(color);
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for (y = 0; y < 16; y ++) {
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VID[offsetTo] = 0xff;
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VID[offsetTo + 1] = 0xff;
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offsetTo += PAGE_STRIDE;
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}
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}
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void blit32x32(unsigned int offsetFrom, unsigned int offsetTo) {
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int y;
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for (y = 0; y < 32; y ++) {
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VID[offsetTo] = VID[offsetFrom ++];
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VID[offsetTo + 1] = VID[offsetFrom ++];
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VID[offsetTo + 2] = VID[offsetFrom ++];
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VID[offsetTo + 3] = VID[offsetFrom ++];
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offsetTo += PAGE_STRIDE;
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}
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}
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#define D_NOTHING 0x80
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#define D_BGTILE 0x81
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#define isBufIndex(d) (!((d) & 0x80))
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#define nextBufferIndex(i) ((i + 1) % NUM_BUFFERS)
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TiledScreen_t screen = { 0, 0, 0, 0, { OFF_PAGE1, OFF_PAGE2 }, 0, 0, NULL, NULL,
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0, 0, 0, 0, 0 };
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void loadTiles(unsigned int tilesOffset, unsigned int far *memTiles) {
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screen.tilesOffset = tilesOffset;
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screen.memTiles = memTiles;
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}
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void loadMap(unsigned char *map, unsigned int w, unsigned int h) {
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screen.map = map;
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screen.w = w;
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screen.h = h;
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memset(screen.dirty, D_BGTILE, PAGE_TILES_COUNT * 2);
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}
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int prepareBuffer(int pageX, int pageY) {
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unsigned char *dirty = &screen.dirty[screen.currentPage][pageX + (pageY * PAGE_TILES_W)];
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int i;
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if (!isBufIndex(*dirty)) {
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unsigned int startX = screen.scrollX >> 4;
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unsigned int startY = screen.scrollY >> 4;
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unsigned char tile = screen.map[startX + pageX + ((startY + pageY) * screen.w)];
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unsigned char ibuffer = screen.nextBuffer;
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screen.nextBuffer = nextBufferIndex(ibuffer);
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*dirty = ibuffer;
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if ((tile & 0xf0) == 0xf0) {
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unsigned int val = (tile & 0x01) ? 0xffff : 0x0000;
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for (i = 0; i < 16; i ++) {
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screen.buffer[ibuffer][i] = val;
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}
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val = (tile & 0x02) ? 0xffff : 0x0000;
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for (i = 16; i < 32; i ++) {
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screen.buffer[ibuffer][i] = val;
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}
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val = (tile & 0x04) ? 0xffff : 0x0000;
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for (i = 32; i < 48; i ++) {
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screen.buffer[ibuffer][i] = val;
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}
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val = (tile & 0x08) ? 0xffff : 0x0000;
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for (i = 48; i < 64; i ++) {
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screen.buffer[ibuffer][i] = val;
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}
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} else {
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for (i = 0; i < BUF_WSIZE; i ++) {
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screen.buffer[ibuffer][i] = (&screen.memTiles[tile * BUF_WSIZE])[i];
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}
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}
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screen.bufferOffset[ibuffer] = screen.pageOffset[screen.currentPage]
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+ (pageX << 1) + (pageY * PAGE_STRIDE * 16);
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}
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return *dirty;
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}
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void drawSpriteToBuf(unsigned int far *sprite, int pageX, int pageY, int shift, int yStart) {
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unsigned int *buf;
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unsigned int far *mask;
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unsigned int maskval;
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int y, h, plane;
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if (pageX < 0 || pageY < 0 ||
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pageX >= PAGE_TILES_W || pageY >= PAGE_TILES_H ||
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shift >= 16 || shift <= -16 ||
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yStart <= -16 || yStart >= 16) {
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return;
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}
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buf = screen.buffer[prepareBuffer(pageX, pageY)];
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if (yStart < 0) {
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sprite = &sprite[-yStart];
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h = yStart + 16;
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} else {
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buf = &buf[yStart];
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h = 16 - yStart;
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}
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mask = &sprite[BUF_WSTRIDE * 4];
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if (shift < 0) {
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shift = -shift;
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for (plane = 0; plane < 4; plane ++) {
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for (y = 0; y < h; y ++) {
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maskval = mask[y] << shift;
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buf[y] = (buf[y] & ~maskval) | ((sprite[y] << shift) & maskval);
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}
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sprite += BUF_WSTRIDE;
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buf += BUF_WSTRIDE;
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}
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} else {
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for (plane = 0; plane < 4; plane ++) {
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for (y = 0; y < h; y ++) {
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maskval = mask[y] >> shift;
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buf[y] = (buf[y] & ~maskval) | ((sprite[y] >> shift) & maskval);
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}
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sprite += BUF_WSTRIDE;
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buf += BUF_WSTRIDE;
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}
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}
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}
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void drawSprite(unsigned int far *sprite, int x, int y) {
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int pageX = (int)(x - (screen.scrollX & 0xfff0)) >> 4;
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int pageY = (int)(y - (screen.scrollY & 0xfff0)) >> 4;
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int pageOffsetX = x & 0x0f;
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int pageOffsetY = y & 0x0f;
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drawSpriteToBuf(sprite, pageX, pageY, pageOffsetX, pageOffsetY);
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drawSpriteToBuf(sprite, pageX + 1, pageY, pageOffsetX - 16, pageOffsetY);
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drawSpriteToBuf(sprite, pageX, pageY + 1, pageOffsetX, pageOffsetY - 16);
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drawSpriteToBuf(sprite, pageX + 1, pageY + 1, pageOffsetX - 16, pageOffsetY - 16);
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}
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void scroll(int newX, int newY) {
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newX = min(max(newX, 0), (screen.w << 4) - 320);
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newY = min(max(newY, 0), (screen.h << 4) - 200);
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if ((screen.scrollX & 0xfff0) != (newX & 0xfff0) ||
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(screen.scrollY & 0xfff0) != (newY & 0xfff0)) {
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int mapX, mapY;
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unsigned char page;
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for (page = 0; page < 2; page ++) {
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int mapOffsetOld = (screen.scrollX >> 4) + ((screen.scrollY >> 4) * screen.w);
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int mapOffsetNew = (newX >> 4) + ((newY >> 4) * screen.w);
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unsigned char *dirty = screen.dirty[page];
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for (mapY = 0; mapY < PAGE_TILES_H; mapY ++) {
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for (mapX = 0; mapX < PAGE_TILES_W; mapX ++) {
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if (*dirty != D_NOTHING ||
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screen.map[mapOffsetOld + mapX] != screen.map[mapOffsetNew + mapX]) {
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*dirty = D_BGTILE;
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}
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dirty ++;
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}
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mapOffsetNew += screen.w;
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mapOffsetOld += screen.w;
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}
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}
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}
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screen.scrollX = newX;
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screen.scrollY = newY;
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}
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void drawScreen() {
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unsigned int startX = screen.scrollX >> 4;
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unsigned int startY = screen.scrollY >> 4;
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unsigned int offsetX = screen.scrollX - (startX << 4);
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unsigned int offsetY = screen.scrollY - (startY << 4);
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unsigned int drawOffset = screen.pageOffset[screen.currentPage];
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unsigned int scrollOffset = drawOffset + (offsetX >> 3) + (offsetY * PAGE_STRIDE);
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unsigned char *dirty = screen.dirty[screen.currentPage];
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unsigned int x, y, di, plane, bmp;
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setAllPlanes();
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setWriteMode(1);
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di = 0;
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for (y = startY; y < startY + PAGE_TILES_H; y ++) {
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for (x = startX; x < startX + PAGE_TILES_W; x ++) {
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if (dirty[di++] == D_BGTILE) {
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char tile = screen.map[x + (y * screen.w)];
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if ((tile & 0xf0) != 0xf0) {
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blitTile(screen.tilesOffset + (tile << 5), drawOffset);
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}
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}
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drawOffset += 2;
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}
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drawOffset += PAGE_STRIDE * 15;
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}
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setWriteMode(0);
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for(plane = 0; plane < 4; plane ++) {
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setPlane(plane);
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for (di = screen.firstBuffer; di != screen.nextBuffer; di = nextBufferIndex(di)) {
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drawOffset = screen.bufferOffset[di] >> 1;
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for (y = 0; y < 16; y ++) {
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bmp = screen.buffer[di][y + (BUF_WSTRIDE * plane)];
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WVID[drawOffset] = (bmp << 8) | (bmp >> 8);
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drawOffset += PAGE_STRIDE >> 1;
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}
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}
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}
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setAllPlanes();
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di = 0;
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drawOffset = screen.pageOffset[screen.currentPage];
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for (y = startY; y < startY + PAGE_TILES_H; y ++) {
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for (x = startX; x < startX + PAGE_TILES_W; x ++) {
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if (dirty[di++] == D_BGTILE) {
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char tile = screen.map[x + (y * screen.w)];
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if ((tile & 0xf0) == 0xf0) {
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blitSolidBlock(drawOffset, tile & 0x0f);
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}
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}
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drawOffset += 2;
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}
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drawOffset += PAGE_STRIDE * 15;
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}
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setDisplayOffset(scrollOffset);
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setHorizontalPan(screen.scrollX & 0x07);
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screen.currentPage ^= 1;
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screen.firstBuffer = screen.nextBuffer;
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for (di = 0; di < PAGE_TILES_COUNT; di ++) {
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dirty[di] = isBufIndex(dirty[di]) ? D_BGTILE : D_NOTHING;
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}
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}
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