Function format_float

src/fl/stl/stdio.h:282–344

Format floating point with specified precision

// Format floating point with specified precision
inline fl::string format_float(float value, int precision) FL_NOEXCEPT {
    if (precision < 0) {
        // Default precision - use sstream's default behavior
        sstream stream;
        stream << value;
        return stream.str();
    }
    
    // Simple precision formatting
    // This is a basic implementation - could be enhanced
    if (precision == 0) {
        int int_part = static_cast<int>(value + 0.5f); // Round
        sstream stream;
        stream << int_part;
        return stream.str();
    }
    
    // For non-zero precision, use basic rounding
    int multiplier = 1;
    for (int i = 0; i < precision; ++i) {
        multiplier *= 10;
    }

    // Handle rounding correctly for both positive and negative numbers
    float scaled_float = value * multiplier;
    int scaled;
    if (scaled_float >= 0) {
        scaled = static_cast<int>(scaled_float + 0.5f);
    } else {
        scaled = static_cast<int>(scaled_float - 0.5f);
    }

    int int_part = scaled / multiplier;
    int frac_part = scaled % multiplier;

    // For negative numbers, frac_part will be negative, so take absolute value
    if (frac_part < 0) {
        frac_part = -frac_part;
    }

    sstream stream;
    // Preserve sign for values like -0.5 that round to int_part=0 (printed
    // without sign by the integer write below).
    if (value < 0 && int_part == 0) {
        stream << "-";
    }
    stream << int_part;
    stream << ".";

    // Emit exactly `precision` fractional digits, zero-padded on the left.
    // The previous implementation stopped padding once temp_multiplier dropped
    // to 1, which produced "0.0"/"1.0" instead of "0.00"/"1.00" for any
    // integer-valued input. It also omitted the digits entirely when
    // frac_part == 0.
    int temp_multiplier = multiplier / 10;
    while (temp_multiplier > 0) {
        int digit = (frac_part / temp_multiplier) % 10;
        stream << static_cast<char>('0' + digit);