Epple-II/src/video.cpp

/*
    epple2
    Copyright (C) 2008 by Chris Mosher <chris@mosher.mine.nu>

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY, without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "video.h"
#include "e2const.h"
#include "videoaddressing.h"
#include "videomode.h"
#include "addressbus.h"
#include "picturegenerator.h"
#include "textcharacters.h"


static const int FLASH_HALF_PERIOD = E2Const::AVG_CPU_HZ/4; // 2 Hz period = 4 Hz half-period


Video::Video(VideoMode& mode, AddressBus& addressBus, PictureGenerator& picgen, TextCharacters& textRows):
	mode(mode), addressBus(addressBus), picgen(picgen), textRows(textRows)
{
	VideoAddressing::buildLUT(TEXT_BASE_1,TEXT_LEN,lutTEXT[0]);
	VideoAddressing::buildLUT(TEXT_BASE_2,TEXT_LEN,lutTEXT[1]);
	VideoAddressing::buildLUT(HRES_BASE_1,HRES_LEN,lutHRES[0]);
	VideoAddressing::buildLUT(HRES_BASE_2,HRES_LEN,lutHRES[1]);
}

Video::~Video()
{
}

void Video::powerOn()
{
	this->t = 0;
	this->flash = false;
	this->cflash = 0;
}

void Video::tick()
{
	const unsigned char data = getDataByte();
	const unsigned char rowToPlot = getRowToPlot(data);

	this->picgen.tick(this->t,rowToPlot);

	updateFlash();

	++this->t;

	if (this->t >= E2Const::BYTES_PER_FIELD)
	{
		this->t = 0;
	}
}

void Video::updateFlash()
{
	++this->cflash;
	if (this->cflash >= FLASH_HALF_PERIOD)
	{
		this->flash = !this->flash;
		this->cflash = 0;
	}
}

unsigned char Video::getDataByte()
{
	// TODO should fix the mixed-mode scanning during VBL (see U.A.][, p. 5-13)

	std::vector<unsigned short>& lut = 
	(this->mode.isDisplayingText(this->t) || !this->mode.isHiRes())
	?
		this->lutTEXT[this->mode.getPage()]
	:
		this->lutHRES[this->mode.getPage()];

	return this->addressBus.read(lut[this->t]);
}

unsigned char Video::getRowToPlot(unsigned char d)
{
	if (this->mode.isDisplayingText(this->t))
	{
		const bool inverse = inverseChar(d);
		const int y = this->t / E2Const::BYTES_PER_ROW;
		d = this->textRows.get(((d & 0x3F) << 3) | (y & 0x07));
		if (inverse)
		{
			d = ~d & 0x7F;
		}
	}
	return d;
}

bool Video::inverseChar(const unsigned char d)
{
	bool inverse;

	const int cs = (d >> 6) & 3;
	if (cs == 0)
	{
		inverse = true;
	}
	else if (cs == 1)
	{
		inverse = this->flash;
	}
	else
	{
		inverse = false;
	}

	return inverse;
}