Function linearAngleToEndpoints

src/core/ThemeManager.cpp:146–159

Convert a CSS-convention angle (0deg = bottom→top, 90deg = left→right, 180deg = top→bottom, 270deg = right→left) to a 0–1 normalised (x1, y1, x2, y2) endpoint pair that covers a unit square. Used by both brush() (mapping onto a real QRect) and cssFragment() (emitting normalised stylesheet coords). Extracted so the two paths stay in lock-step — a future bug in one would otherwise produce subtle m

// mismatches between the painted gradient and the stylesheet-emitted
// preview.
void linearAngleToEndpoints(qreal angleDeg,
                            qreal& x1, qreal& y1, qreal& x2, qreal& y2)
{
    const qreal rad = qDegreesToRadians(angleDeg);
    // Half-diagonal of the unit square — guarantees the gradient line
    // reaches the corners regardless of angle.  sqrt(2)/2 ≈ 0.7071.
    constexpr qreal kHalfDiagonal = 0.7071067811865476;
    const qreal dx = std::sin(rad);
    const qreal dy = -std::cos(rad);  // CSS Y axis is inverted vs screen
    x1 = 0.5 - dx * kHalfDiagonal;
    y1 = 0.5 - dy * kHalfDiagonal;
    x2 = 0.5 + dx * kHalfDiagonal;
    y2 = 0.5 + dy * kHalfDiagonal;
}

// Emit a Qt stylesheet gradient fragment for the given gradient.
QString gradientCssFragment(const ThemeGradient& g)