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Video.cpp
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#include "Video.h"
#include "EmuState.h"
Video::Video() {
}
void Video::drawLine() {
int line = emuState.videoLine;
if (line < 0 || line >= VIDEO_HEIGHT)
return;
bool vActive = line >= 16 && line < 216;
// Render text
uint8_t lineText[1024];
{
bool mode80 = (emuState.videoCtrl & VCTRL_80_COLUMNS) != 0;
bool tramPage = (emuState.videoCtrl & VCTRL_TRAM_PAGE) != 0;
bool remapBorder = (emuState.videoCtrl & VCTRL_REMAP_BORDER_CHAR) != 0;
unsigned idx = 1024 - 32;
for (int i = 0; i < VIDEO_WIDTH; i++) {
// Draw text character
unsigned addr = 0;
if (vActive && idx < 640) {
int row = (line - 16) / 8;
if (mode80) {
int column = (i - 32) / 8;
addr = row * 80 + column;
} else {
int column = ((i / 2) - 16) / 8;
addr = row * 40 + column;
}
} else {
if (remapBorder) {
addr = mode80 ? 0x7FF : 0x3FF;
} else {
addr = 0;
}
}
if (!mode80) {
addr = (addr & 0x3FF) | (tramPage ? 0x400 : 0);
}
uint8_t ch = emuState.screenRam[addr];
uint8_t color = emuState.colorRam[addr];
uint8_t charBm = emuState.charRam[ch * 8 + (line & 7)];
lineText[idx] = (charBm & (1 << (7 - ((mode80 ? i : (i / 2)) & 7)))) ? (color >> 4) : (color & 0xF);
idx = (idx + 1) & 1023;
}
}
// Render bitmap/tile layer
uint8_t lineGfx[512];
if (vActive) {
int bmline = line - 16;
switch (emuState.videoCtrl & VCTRL_MODE_MASK) {
case VCTRL_MODE_BITMAP: {
// Bitmap mode 1bpp
for (int i = 0; i < 320; i++) {
int row = bmline / 8;
int column = i / 8;
uint8_t col = emuState.videoRam[0x2000 + row * 40 + column];
uint8_t bm = emuState.videoRam[0x0000 + bmline * 40 + column];
uint8_t color = (bm & (1 << (7 - (i & 7)))) ? (col >> 4) : (col & 0xF);
lineGfx[i] = (1 << 4) | color;
}
break;
}
case VCTRL_MODE_BITMAP_4BPP: {
// Bitmap mode 4bpp
for (int i = 0; i < 80; i++) {
uint8_t col = emuState.videoRam[bmline * 80 + i];
lineGfx[i * 4 + 0] = (1 << 4) | (col >> 4);
lineGfx[i * 4 + 1] = (1 << 4) | (col >> 4);
lineGfx[i * 4 + 2] = (1 << 4) | (col & 0xF);
lineGfx[i * 4 + 3] = (1 << 4) | (col & 0xF);
}
break;
}
case VCTRL_MODE_TILEMAP: {
// Tile mode
unsigned idx = (-(emuState.videoScrX & 7)) & 511;
unsigned tileLine = (bmline + emuState.videoScrY) & 255;
unsigned row = (tileLine >> 3) & 31;
unsigned col = emuState.videoScrX >> 3;
for (int i = 0; i < 41; i++) {
// Tilemap is 64x32 (2 bytes per entry)
// Fetch tilemap entry
uint8_t entryL = emuState.videoRam[(row << 7) | (col << 1)];
uint8_t entryH = emuState.videoRam[(row << 7) | (col << 1) | 1];
unsigned tileIdx = ((entryH & 1) << 8) | entryL;
bool hFlip = (entryH & (1 << 1)) != 0;
bool vFlip = (entryH & (1 << 2)) != 0;
uint8_t attr = entryH & 0x70;
unsigned patOffs = (tileIdx << 5) | ((tileLine & 7) << 2);
if (vFlip)
patOffs ^= (7 << 2);
// Next column
col = (col + 1) & 63;
for (int n = 0; n < 4; n++) {
int m = n;
if (hFlip)
m ^= 3;
uint8_t data = emuState.videoRam[patOffs + m];
if (!hFlip) {
uint8_t val = data >> 4;
val |= (attr & ((val == 0) ? 0x30 : 0x70));
lineGfx[idx++] = val;
idx &= 511;
}
{
uint8_t val = data & 0xF;
val |= (attr & ((val == 0) ? 0x30 : 0x70));
lineGfx[idx++] = val;
idx &= 511;
}
if (hFlip) {
uint8_t val = data >> 4;
val |= (attr & ((val == 0) ? 0x30 : 0x70));
lineGfx[idx++] = val;
idx &= 511;
}
}
}
break;
}
default: {
for (int i = 0; i < 320; i++) {
lineGfx[i] = 0;
}
break;
}
}
// Render sprites
if ((emuState.videoCtrl & (1 << 3)) != 0) {
for (int i = 0; i < 64; i++) {
unsigned sprAttr = emuState.videoSprAttr[i];
// Check if sprite enabled
bool enabled = (sprAttr & (1 << 7)) != 0;
if (!enabled)
continue;
// Check if sprite is visible on this line
bool h16 = (sprAttr & (1 << 3)) != 0;
int sprLine = (bmline - emuState.videoSprY[i]) & 0xFF;
if (sprLine >= (h16 ? 16 : 8))
continue;
int sprX = emuState.videoSprX[i];
unsigned tileIdx = emuState.videoSprIdx[i];
bool hFlip = (sprAttr & (1 << 1)) != 0;
bool vFlip = (sprAttr & (1 << 2)) != 0;
uint8_t palette = sprAttr & 0x30;
bool priority = (sprAttr & (1 << 6)) != 0;
unsigned idx = sprX;
if (vFlip)
sprLine ^= (h16 ? 15 : 7);
tileIdx ^= (sprLine >> 3);
unsigned patOffs = (tileIdx << 5) | ((sprLine & 7) << 2);
for (int n = 0; n < 4; n++) {
int m = n;
if (hFlip)
m ^= 3;
uint8_t data = emuState.videoRam[patOffs + m];
if (!hFlip) {
if (priority || (lineGfx[idx] & (1 << 6)) == 0) {
unsigned colIdx = (data >> 4);
if (colIdx != 0)
lineGfx[idx] = colIdx | palette;
}
idx++;
idx &= 511;
}
if (priority || (lineGfx[idx] & (1 << 6)) == 0) {
unsigned colIdx = (data & 0xF);
if (colIdx != 0)
lineGfx[idx] = colIdx | palette;
}
idx++;
idx &= 511;
if (hFlip) {
if (priority || (lineGfx[idx] & (1 << 6)) == 0) {
unsigned colIdx = (data >> 4);
if (colIdx != 0)
lineGfx[idx] = colIdx | palette;
}
idx++;
idx &= 511;
}
}
}
}
}
// Compose layers
{
uint16_t *pd = &screen[line * VIDEO_WIDTH];
unsigned idx = 1024 - 32;
for (int i = 0; i < VIDEO_WIDTH; i++) {
bool active = idx < 640 && vActive;
bool textPriority = (emuState.videoCtrl & VCTRL_TEXT_PRIORITY) != 0;
bool textEnable = (emuState.videoCtrl & VCTRL_TEXT_ENABLE) != 0;
uint8_t colIdx = 0;
if (!active) {
if (textEnable)
colIdx = lineText[idx];
} else {
if (textEnable)
colIdx = lineText[idx];
if (textEnable && !textPriority)
colIdx = lineText[idx];
if (!textEnable || textPriority || (lineGfx[idx / 2] & 0xF) != 0)
colIdx = lineGfx[idx / 2];
if (textEnable && textPriority && (lineText[idx] & 0xF) != 0)
colIdx = lineText[idx];
}
pd[i] = emuState.videoPalette[colIdx & 0x3F];
idx = (idx + 1) & 1023;
}
}
}