Created
September 13, 2023 18:19
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QPointF hash function
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| namespace std { | |
| template<> struct hash<QPointF> | |
| { | |
| size_t operator()(const QPointF &point, size_t seed) const | |
| { | |
| size_t x = static_cast<size_t>(point.x()); | |
| size_t y = static_cast<size_t>(point.y()); | |
| size_t half_qreal = sizeof(qreal) / 2; | |
| size_t half_bits = half_qreal*8; | |
| size_t half1s = pow(2, half_qreal*8)-1; | |
| size_t swappedX = (x & half1s) << half_bits | (x & (half1s << half_bits)) >> half_bits; | |
| return (swappedX | y) ^ seed; | |
| } | |
| }; | |
| } |
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From Marc Mutz' presentation on Qt Container changes between Qt 5 and Qt 6, 20230913.
He asked us to implement a qHash function for hashing QPointF, which meets all the requirements for QHash.
Note that this is a bit odd because it does not make the assumption that qreal is a 64 bit type, since this can be altered when compiling Qt using the -qreal option.