SDLSnow.cc

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#include "SDLSnow.hh"
#include "SDLOutputSurface.hh"
#include "Display.hh"
#include "build-info.hh"
#include "checked_cast.hh"
#include "enumerate.hh"
#include "random.hh"
#include <cstdint>
 
namespace openmsx {
 
template<std::unsigned_integral Pixel>
SDLSnow<Pixel>::SDLSnow(OutputSurface& output, Display& display_)
        : Layer(COVER_FULL, Z_BACKGROUND)
        , display(display_)
{
        // Precalc gray values for noise
        for (auto [i, g] : enumerate(gray)) {
                g = Pixel(output.mapRGB255(gl::ivec3(int(i))));
        }
}
 
template<std::unsigned_integral Pixel>
void SDLSnow<Pixel>::paint(OutputSurface& output_)
{
        auto& generator = global_urng(); // fast (non-cryptographic) random numbers
        std::uniform_int_distribution<int> distribution(0, 255);
 
        auto& output = checked_cast<SDLOutputSurface&>(output_);
        {
                auto pixelAccess = output.getDirectPixelAccess();
                auto [width, height] = output.getLogicalSize();
                for (int y = 0; y < height; y += 2) {
                        auto p0 = pixelAccess.getLine<Pixel>(y + 0).subspan(0, width);
                        for (int x = 0; x < width; x += 2) {
                                p0[x + 0] = p0[x + 1] = gray[distribution(generator)];
                        }
                        auto p1 = pixelAccess.getLine<Pixel>(y + 1).subspan(0, width);
                        ranges::copy(p0, p1);
                }
        }
        output.flushFrameBuffer();
 
        display.repaintDelayed(100 * 1000); // 10fps
}
 
// Force template instantiation.
#if HAVE_16BPP
template class SDLSnow<uint16_t>;
#endif
#if HAVE_32BPP
template class SDLSnow<uint32_t>;
#endif
 
} // namespace openmsx