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LibWeb: Add a CSSPixelFraction class to allow comparison of fractions

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This class will allow us to compare the ratio of two `CSSPixels` values
losslessly.

Not only that, but an operation like `a * (b / c)` should no longer
be lossy, since the operation can be carried out as `(a * b) / c`
implicitly instead.
This commit is contained in:
Zaggy1024 2023-08-26 16:59:20 -05:00 • committed by Alexander Kalenik
parent 0fb571c1c2
commit 8cd1f65507
Notes: sideshowbarker 2024-07-17 01:46:00 +09:00
1 changed files with 90 additions and 10 deletions
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100
Userland/Libraries/LibWeb/PixelUnits.h
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@ -51,6 +51,8 @@ constexpr DevicePixels operator/(DevicePixels left, T right) { return left.value
template<Integral T>
constexpr DevicePixels operator%(DevicePixels left, T right) { return left.value() % right; }
class CSSPixelFraction;
/// CSSPixels: A position or length in CSS "reference pixels", independent of zoom or screen DPI.
/// See https://www.w3.org/TR/css-values-3/#reference-pixel
class CSSPixels {
@ -192,16 +194,10 @@ public:
return from_raw(int_value);
}
constexpr CSSPixels operator*(CSSPixelFraction const& other) const;
constexpr CSSPixels operator/(CSSPixels const& other) const
{
i64 mult = raw_value();
mult <<= fractional_bits;
mult /= other.raw_value();
int int_value = AK::clamp_to_int(mult);
return from_raw(int_value);
}
constexpr CSSPixelFraction operator/(CSSPixels const& other) const;
constexpr CSSPixels operator/(CSSPixelFraction const& other) const;
constexpr CSSPixels& operator+=(CSSPixels const& other)
{
@ -218,9 +214,14 @@ public:
*this = *this * other;
return *this;
}
constexpr CSSPixels& operator*=(CSSPixelFraction const& other)
{
*this = *this * other;
return *this;
}
constexpr CSSPixels& operator/=(CSSPixels const& other)
{
*this = *this / other;
*this = *this * other;
return *this;
}
@ -278,6 +279,85 @@ constexpr CSSPixels operator*(unsigned long left, CSSPixels right) { return righ
inline float operator*(float left, CSSPixels right) { return right.to_float() * left; }
inline double operator*(double left, CSSPixels right) { return right.to_double() * left; }
class CSSPixelFraction {
public:
constexpr CSSPixelFraction(CSSPixels numerator, CSSPixels denominator)
: m_numerator(numerator)
, m_denominator(denominator)
{
}
constexpr CSSPixelFraction(CSSPixels value)
: m_numerator(value)
, m_denominator(1)
{
}
template<Signed I>
constexpr CSSPixelFraction(I numerator, I denominator = 1)
: m_numerator(numerator)
, m_denominator(denominator)
{
}
constexpr operator CSSPixels() const
{
i64 wide_value = m_numerator.raw_value();
wide_value <<= CSSPixels::fractional_bits;
wide_value /= m_denominator.raw_value();
return CSSPixels::from_raw(AK::clamp_to_int(wide_value));
}
constexpr int operator<=>(CSSPixelFraction const& other) const
{
auto left = static_cast<i64>(m_numerator.raw_value()) * other.m_denominator.raw_value();
auto right = static_cast<i64>(other.m_numerator.raw_value()) * m_denominator.raw_value();
if (left > right)
return 1;
if (left < right)
return -1;
return 0;
}
template<Signed I>
constexpr int operator<=>(I const& other) const
{
return *this <=> CSSPixelFraction(other);
}
constexpr CSSPixels numerator() const { return m_numerator; }
constexpr CSSPixels denominator() const { return m_denominator; }
float to_float() const { return CSSPixels(*this).to_float(); }
double to_double() const { return CSSPixels(*this).to_double(); }
int to_int() const { return CSSPixels(*this).to_int(); }
bool might_be_saturated() const { return CSSPixels(*this).might_be_saturated(); }
private:
CSSPixels m_numerator;
CSSPixels m_denominator;
};
constexpr CSSPixels CSSPixels::operator*(CSSPixelFraction const& other) const
{
i64 wide_value = raw_value();
wide_value *= other.numerator().raw_value();
wide_value /= other.denominator().raw_value();
return CSSPixels::from_raw(AK::clamp_to_int(wide_value));
}
constexpr CSSPixelFraction CSSPixels::operator/(CSSPixels const& other) const
{
return CSSPixelFraction(*this, other);
}
constexpr CSSPixels CSSPixels::operator/(CSSPixelFraction const& other) const
{
i64 wide_value = raw_value();
wide_value *= other.denominator().raw_value();
wide_value /= other.numerator().raw_value();
return CSSPixels::from_raw(AK::clamp_to_int(wide_value));
}
constexpr CSSPixels operator/(CSSPixels left, int right) { return left / CSSPixels(right); }
constexpr CSSPixels operator/(CSSPixels left, unsigned long right) { return left / CSSPixels(right); }
inline float operator/(CSSPixels left, float right) { return left.to_float() / right; }