36 lines
1.6 KiB
C++
36 lines
1.6 KiB
C++
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// Feasibility check: can we intercept EPFramebuffer::setBuffers to capture the
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// framebuffer's backing QImages? setBuffers is called from the epaper platform
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// plugin (libepaper) into libqsgepaper — a cross-DSO call, so unlike swapBuffers
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// it should be interposable via LD_PRELOAD. If this fires and reports real image
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// dimensions + a pixel pointer, the direct-framebuffer ink pipeline is viable.
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//
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// ABI: std::tuple<QImage,QImage> is non-trivially-copyable, so it's passed by
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// reference (a pointer); QImage* is a pointer. So three pointer args after this.
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#include <QImage>
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#include <tuple>
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#include <dlfcn.h>
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#include <cstdio>
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extern "C" void _ZN13EPFramebuffer10setBuffersESt5tupleIJ6QImageS1_EEPS1_(
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void *self, void *tuplePtr, void *imgPtr)
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{
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static void (*real)(void *, void *, void *) = nullptr;
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if (!real)
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real = (void (*)(void *, void *, void *))dlsym(
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RTLD_NEXT, "_ZN13EPFramebuffer10setBuffersESt5tupleIJ6QImageS1_EEPS1_");
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auto *t = reinterpret_cast<std::tuple<QImage, QImage> *>(tuplePtr);
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QImage *c = reinterpret_cast<QImage *>(imgPtr);
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const QImage &a = std::get<0>(*t);
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const QImage &b = std::get<1>(*t);
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fprintf(stderr,
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"SETBUFFERS self=%p | A=%dx%d fmt=%d bytesPerLine=%d cbits=%p | "
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"B=%dx%d fmt=%d | C=%p %dx%d\n",
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self, a.width(), a.height(), int(a.format()), a.bytesPerLine(),
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(const void *)a.constBits(), b.width(), b.height(), int(b.format()),
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(void *)c, c ? c->width() : -1, c ? c->height() : -1);
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if (real) real(self, tuplePtr, imgPtr);
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}
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