SuperImposedFrame.cc

Go to the documentation of this file.

#include "SuperImposedFrame.hh"
 
#include "LineScalers.hh"
 
#include "inplace_buffer.hh"
 
#include <algorithm>
#include <cstdint>
 
namespace openmsx {
 
using Pixel = uint32_t;
 
void SuperImposedFrame::init(
        const FrameSource* top_, const FrameSource* bottom_)
{
        top = top_;
        bottom = bottom_;
        setHeight(std::max(top->getHeight(), bottom->getHeight()));
}
 
unsigned SuperImposedFrame::getLineWidth(unsigned line) const
{
        unsigned tNum = (getHeight() == top   ->getHeight()) ? line : line / 2;
        unsigned bNum = (getHeight() == bottom->getHeight()) ? line : line / 2;
        unsigned tWidth = top   ->getLineWidth(tNum);
        unsigned bWidth = bottom->getLineWidth(bNum);
        return std::max(tWidth, bWidth);
}
 
std::span<const FrameSource::Pixel> SuperImposedFrame::getUnscaledLine(
        unsigned line, std::span<Pixel> helpBuf) const
{
        unsigned tNum = (getHeight() == top   ->getHeight()) ? line : line / 2;
        unsigned bNum = (getHeight() == bottom->getHeight()) ? line : line / 2;
        unsigned tWidth = top   ->getLineWidth(tNum);
        unsigned bWidth = bottom->getLineWidth(bNum);
        auto width = std::min(std::max<size_t>(tWidth, bWidth), // as wide as the widest source
                              helpBuf.size()); // but no wider than the output buffer
 
        auto tBuf = helpBuf.subspan(0, width);
        inplace_buffer<Pixel, 1280> bBuf(uninitialized_tag{}, width);
        auto tLine = top   ->getLine(narrow<int>(tNum), tBuf);
        auto bLine = bottom->getLine(narrow<int>(bNum), bBuf);
 
        alphaBlendLines(tLine, bLine, tBuf); // possibly tLine == tBuf
        return tBuf;
}
 
} // namespace openmsx