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Fix line semantics.

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This commit is contained in:
Thomas Harte 2023-01-27 11:57:40 -05:00
parent d42b6df570
commit 75ad4cdb67
1 changed files with 46 additions and 29 deletions
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75
Components/9918/Implementation/YamahaCommands.hpp
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@ -25,9 +25,19 @@ struct Vector {
v[offset] = (v[offset] & ~(mask << shift)) | (value << shift);
}
template <int offset> void add(int amount) {
v[offset] += amount;
if constexpr (offset == 1) {
v[offset] &= 0x3ff;
} else {
v[offset] &= 0x1ff;
}
}
Vector & operator += (const Vector &rhs) {
v[0] += rhs.v[0];
v[1] += rhs.v[1];
add<0>(rhs.v[0]);
add<1>(rhs.v[1]);
return *this;
}
};
@ -79,50 +89,57 @@ namespace Commands {
struct Line: public Command {
public:
Line(CommandContext &context) : Command(context) {
// Set up Bresenham constants.
if(abs(context.size.v[0]) > abs(context.size.v[1])) {
major_.v[0] = context.size.v[0] < 0 ? -1 : 1;
minor_.v[1] = context.size.v[1] < 0 ? -1 : 1;
major_.v[1] = minor_.v[0] = 0;
// context.destination = start position;
// context.size.v[0] = long side dots;
// context.size.v[1] = short side dots;
// context.arguments => direction
position_ = abs(context.size.v[1]);
duration_ = abs(context.size.v[0]);
} else {
major_.v[1] = context.size.v[1] < 0 ? -1 : 1;
minor_.v[0] = context.size.v[0] < 0 ? -1 : 1;
major_.v[0] = minor_.v[1] = 0;
position_ = abs(context.size.v[0]);
duration_ = abs(context.size.v[1]);
}
numerator_ = position_ << 1;
denominator_ = duration_ << 1;
cycles = 0;
access = AccessType::PlotPoint;
location = context.destination;
position_ = context.size.v[1];
numerator_ = position_ << 1;
denominator_ = context.size.v[0] << 1;
cycles = 32;
access = AccessType::PlotPoint;
}
bool done() final {
return !duration_;
return !context.size.v[0];
}
void advance() final {
--duration_;
--context.size.v[0];
cycles = 88;
location += major_;
// b0: 1 => long direction is y;
// 0 => long direction is x.
//
// b2: 1 => x direction is left;
// 0 => x direction is right.
//
// b3: 1 => y direction is up;
// 0 => y direction is down.
if(context.arguments & 0x1) {
location.add<1>(context.arguments & 0x8 ? -1 : 1);
} else {
location.add<0>(context.arguments & 0x4 ? -1 : 1);
}
position_ -= numerator_;
if(position_ < 0) {
cycles += 32;
location += minor_;
position_ += denominator_;
cycles += 32;
if(context.arguments & 0x1) {
location.add<0>(context.arguments & 0x4 ? -1 : 1);
} else {
location.add<1>(context.arguments & 0x8 ? -1 : 1);
}
}
}
private:
int position_, numerator_, denominator_, duration_;
Vector major_, minor_;
};
/// Implements the PSET command, which plots a single pixel.