// Feasibility check: can we intercept EPFramebuffer::setBuffers to capture the
// framebuffer's backing QImages? setBuffers is called from the epaper platform
// plugin (libepaper) into libqsgepaper — a cross-DSO call, so unlike swapBuffers
// it should be interposable via LD_PRELOAD. If this fires and reports real image
// dimensions + a pixel pointer, the direct-framebuffer ink pipeline is viable.
//
// ABI: std::tuple<QImage,QImage> is non-trivially-copyable, so it's passed by
// reference (a pointer); QImage* is a pointer. So three pointer args after this.

#include <QImage>
#include <tuple>
#include <dlfcn.h>
#include <cstdio>

extern "C" void _ZN13EPFramebuffer10setBuffersESt5tupleIJ6QImageS1_EEPS1_(
    void *self, void *tuplePtr, void *imgPtr)
{
    static void (*real)(void *, void *, void *) = nullptr;
    if (!real)
        real = (void (*)(void *, void *, void *))dlsym(
            RTLD_NEXT, "_ZN13EPFramebuffer10setBuffersESt5tupleIJ6QImageS1_EEPS1_");

    auto *t = reinterpret_cast<std::tuple<QImage, QImage> *>(tuplePtr);
    QImage *c = reinterpret_cast<QImage *>(imgPtr);
    const QImage &a = std::get<0>(*t);
    const QImage &b = std::get<1>(*t);
    fprintf(stderr,
            "SETBUFFERS self=%p | A=%dx%d fmt=%d bytesPerLine=%d cbits=%p | "
            "B=%dx%d fmt=%d | C=%p %dx%d\n",
            self, a.width(), a.height(), int(a.format()), a.bytesPerLine(),
            (const void *)a.constBits(), b.width(), b.height(), int(b.format()),
            (void *)c, c ? c->width() : -1, c ? c->height() : -1);

    if (real) real(self, tuplePtr, imgPtr);
}