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<?php
namespace GameBoy;
class LcdController
{
//Actual scan line...
public $actualScanLine = 0;
protected $core;
//Is the emulated LCD controller on?
public $LCDisOn = false;
//Should we trigger an interrupt if LY==LYC?
public $LYCMatchTriggerSTAT = false;
//The scan line mode (for lines 1-144 it's 2-3-0, for 145-154 it's 1)
public $modeSTAT = 0;
//Should we trigger an interrupt if in mode 0?
public $mode0TriggerSTAT = false;
//Should we trigger an interrupt if in mode 1?
public $mode1TriggerSTAT = false;
//Should we trigger an interrupt if in mode 2?
public $mode2TriggerSTAT = false;
//Tracker for STAT triggering.
public $STATTracker = 0;
public function __construct($core)
{
$this->core = $core;
}
public function matchLYC()
{
// LY - LYC Compare
// If LY==LCY
if ($this->core->memory[0xFF44] == $this->core->memory[0xFF45]) {
$this->core->memory[0xFF41] |= 0x04; // set STAT bit 2: LY-LYC coincidence flag
if ($this->LYCMatchTriggerSTAT) {
$this->core->memory[0xFF0F] |= 0x2; // set IF bit 1
}
} else {
$this->core->memory[0xFF41] &= 0xFB; // reset STAT bit 2 (LY!=LYC)
}
}
public function notifyScanline()
{
if ($this->actualScanLine == 0) {
$this->core->windowSourceLine = 0;
}
// determine the left edge of the window (160 if window is inactive)
$windowLeft = ($this->core->gfxWindowDisplay && $this->core->memory[0xFF4A] <= $this->actualScanLine) ? min(160, $this->core->memory[0xFF4B] - 7) : 160;
// step 1: background+window
$skippedAnything = $this->core->drawBackgroundForLine($this->actualScanLine, $windowLeft, 0);
// At this point, the high (alpha) byte in the frameBuffer is 0xff for colors 1,2,3 and
// 0x00 for color 0. Foreground sprites draw on all colors, background sprites draw on
// top of color 0 only.
// step 2: sprites
$this->core->drawSpritesForLine($this->actualScanLine);
// step 3: prio tiles+window
if ($skippedAnything) {
$this->core->drawBackgroundForLine($this->actualScanLine, $windowLeft, 0x80);
}
if ($windowLeft < 160) {
++$this->core->windowSourceLine;
}
}
/**
* Scan Line and STAT Mode Control
* @param int $line Memory Scanline
*/
public function scanLine($line)
{
//When turned off = Do nothing!
if ($this->LCDisOn) {
if ($line < 143) {
//We're on a normal scan line:
if ($this->core->LCDTicks < 20) {
$this->scanLineMode2(); // mode2: 80 cycles
} elseif ($this->core->LCDTicks < 63) {
$this->scanLineMode3(); // mode3: 172 cycles
} elseif ($this->core->LCDTicks < 114) {
$this->scanLineMode0(); // mode0: 204 cycles
} else {
//We're on a new scan line:
$this->core->LCDTicks -= 114;
$this->actualScanLine = ++$this->core->memory[0xFF44];
$this->matchLYC();
if ($this->STATTracker != 2) {
if ($this->core->hdmaRunning && !$this->core->halt && $this->LCDisOn) {
$this->core->performHdma(); //H-Blank DMA
}
if ($this->mode0TriggerSTAT) {
$this->core->memory[0xFF0F] |= 0x2; // set IF bit 1
}
}
$this->STATTracker = 0;
$this->scanLineMode2(); // mode2: 80 cycles
if ($this->core->LCDTicks >= 114) {
//We need to skip 1 or more scan lines:
$this->core->notifyScanline();
$this->scanLine($this->actualScanLine); //Scan Line and STAT Mode Control
}
}
} elseif ($line == 143) {
//We're on the last visible scan line of the LCD screen:
if ($this->core->LCDTicks < 20) {
$this->scanLineMode2(); // mode2: 80 cycles
} elseif ($this->core->LCDTicks < 63) {
$this->scanLineMode3(); // mode3: 172 cycles
} elseif ($this->core->LCDTicks < 114) {
$this->scanLineMode0(); // mode0: 204 cycles
} else {
//Starting V-Blank:
//Just finished the last visible scan line:
$this->core->LCDTicks -= 114;
$this->actualScanLine = ++$this->core->memory[0xFF44];
$this->matchLYC();
if ($this->mode1TriggerSTAT) {
$this->core->memory[0xFF0F] |= 0x2; // set IF bit 1
}
if ($this->STATTracker != 2) {
if ($this->core->hdmaRunning && !$this->core->halt && $this->LCDisOn) {
$this->core->performHdma(); //H-Blank DMA
}
if ($this->mode0TriggerSTAT) {
$this->core->memory[0xFF0F] |= 0x2; // set IF bit 1
}
}
$this->STATTracker = 0;
$this->modeSTAT = 1;
$this->core->memory[0xFF0F] |= 0x1; // set IF flag 0
//LCD off takes at least 2 frames.
if ($this->core->drewBlank > 0) {
--$this->core->drewBlank;
}
if ($this->core->LCDTicks >= 114) {
//We need to skip 1 or more scan lines:
$this->scanLine($this->actualScanLine); //Scan Line and STAT Mode Control
}
}
} elseif ($line < 153) {
//In VBlank
if ($this->core->LCDTicks >= 114) {
//We're on a new scan line:
$this->core->LCDTicks -= 114;
$this->actualScanLine = ++$this->core->memory[0xFF44];
$this->matchLYC();
if ($this->core->LCDTicks >= 114) {
//We need to skip 1 or more scan lines:
$this->scanLine($this->actualScanLine); //Scan Line and STAT Mode Control
}
}
} else {
//VBlank Ending (We're on the last actual scan line)
if ($this->core->memory[0xFF44] == 153) {
$this->core->memory[0xFF44] = 0; //LY register resets to 0 early.
$this->matchLYC(); //LY==LYC Test is early here (Fixes specific one-line glitches (example: Kirby2 intro)).
}
if ($this->core->LCDTicks >= 114) {
//We reset back to the beginning:
$this->core->LCDTicks -= 114;
$this->actualScanLine = 0;
$this->scanLineMode2(); // mode2: 80 cycles
if ($this->core->LCDTicks >= 114) {
//We need to skip 1 or more scan lines:
$this->scanLine($this->actualScanLine); //Scan Line and STAT Mode Control
}
}
}
}
}
public function scanLineMode0()
{
// H-Blank
if ($this->modeSTAT != 0) {
if ($this->core->hdmaRunning && !$this->core->halt && $this->LCDisOn) {
$this->performHdma(); //H-Blank DMA
}
if ($this->mode0TriggerSTAT || ($this->mode2TriggerSTAT && $this->STATTracker == 0)) {
$this->core->memory[0xFF0F] |= 0x2; // if STAT bit 3 -> set IF bit1
}
$this->notifyScanline();
$this->STATTracker = 2;
$this->modeSTAT = 0;
}
}
public function scanLineMode2()
{
// OAM in use
if ($this->modeSTAT != 2) {
if ($this->mode2TriggerSTAT) {
$this->core->memory[0xFF0F] |= 0x2; // set IF bit 1
}
$this->STATTracker = 1;
$this->modeSTAT = 2;
}
}
public function scanLineMode3()
{
// OAM in use
if ($this->modeSTAT != 3) {
if ($this->mode2TriggerSTAT && $this->STATTracker == 0) {
$this->core->memory[0xFF0F] |= 0x2; // set IF bit 1
}
$this->STATTracker = 1;
$this->modeSTAT = 3;
}
}
}
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