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feat: implement unified IFormattable on Color, HslColor, and HsvColor #20919

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29bbc7a
fix: correct HslColor.ToString() prefix from hsva to hsla
NathanDrake2406 Mar 18, 2026
0b0dd03
feat: implement unified IFormattable on Color, HslColor, and HsvColor
NathanDrake2406 Mar 18, 2026
b87198d
Merge branch 'master' into feat/color-tostring-formats
NathanDrake2406 Mar 19, 2026
be9bb8d
Merge branch 'master' into feat/color-tostring-formats
jmacato Apr 3, 2026
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70 changes: 70 additions & 0 deletions src/Avalonia.Base/Media/Color.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,9 @@ namespace Avalonia.Media
public
#endif
readonly struct Color : IEquatable<Color>
#if !BUILDTASK
, IFormattable
#endif
{
private const double byteToDouble = 1.0 / 255;

Expand Down Expand Up @@ -461,6 +464,73 @@ internal void ToString(System.Text.StringBuilder builder)
}
}

#if !BUILDTASK
/// <summary>
/// Returns a formatted string representation of the color.
/// </summary>
/// <param name="format">
/// The format specifier. All color types support all specifiers via auto-conversion.
/// Uppercase includes alpha, lowercase excludes it. <c>%</c> suffix = percent mode:
/// <list type="bullet">
/// <item><c>null</c> or <c>""</c> — Default (known name or <c>#aarrggbb</c>)</item>
/// <item><c>"X"</c> — XAML hex with alpha: <c>#AARRGGBB</c></item>
/// <item><c>"x"</c> — Hex without alpha: <c>#RRGGBB</c></item>
/// <item><c>"H"</c> — HTML hex with alpha: <c>#RRGGBBAA</c></item>
/// <item><c>"R"</c> — CSS rgba absolute: <c>rgba(r, g, b, a)</c></item>
/// <item><c>"r"</c> — CSS rgb absolute: <c>rgb(r, g, b)</c></item>
/// <item><c>"R%"</c> — CSS rgba percent: <c>rgba(r%, g%, b%, a%)</c></item>
/// <item><c>"r%"</c> — CSS rgb percent: <c>rgb(r%, g%, b%)</c></item>
/// <item><c>"L"/"l"/"L%"/"l%"</c> — CSS hsl/hsla (auto-converts to HSL)</item>
/// <item><c>"V"/"v"/"V%"/"v%"</c> — CSS hsv/hsva (auto-converts to HSV)</item>
/// </list>
/// <para><c>"C"</c> and <c>"A"</c> are reserved for future complex format strings.</para>
/// </param>
/// <param name="formatProvider">Ignored. Color formatting is culture-invariant.</param>
/// <returns>The formatted string representation.</returns>
/// <exception cref="FormatException">Thrown when <paramref name="format"/> is not recognized.</exception>
public string ToString(string? format, IFormatProvider? formatProvider)
{
if (string.IsNullOrEmpty(format))
{
return ToString();
}

return format switch
{
"X" => $"#{A:X2}{R:X2}{G:X2}{B:X2}",
"x" => $"#{R:X2}{G:X2}{B:X2}",
"H" => $"#{R:X2}{G:X2}{B:X2}{A:X2}",

"R" => string.Format(CultureInfo.InvariantCulture, "rgba({0}, {1}, {2}, {3:F2})", R, G, B, A * byteToDouble),
"r" => string.Format(CultureInfo.InvariantCulture, "rgb({0}, {1}, {2})", R, G, B),
"R%" => FormatRgbaPercent(),
"r%" => FormatRgbPercent(),

"L" or "l" or "L%" or "l%" => ToHsl().ToString(format, formatProvider),
"V" or "v" or "V%" or "v%" => ToHsv().ToString(format, formatProvider),

_ => throw new FormatException($"Format string '{format}' is not supported.")
};
}

private string FormatRgbaPercent()
{
int rPct = (int)Math.Round(R * byteToDouble * 100.0);
int gPct = (int)Math.Round(G * byteToDouble * 100.0);
int bPct = (int)Math.Round(B * byteToDouble * 100.0);
int aPct = (int)Math.Round(A * byteToDouble * 100.0);
return string.Format(CultureInfo.InvariantCulture, "rgba({0}%, {1}%, {2}%, {3}%)", rPct, gPct, bPct, aPct);
}

private string FormatRgbPercent()
{
int rPct = (int)Math.Round(R * byteToDouble * 100.0);
int gPct = (int)Math.Round(G * byteToDouble * 100.0);
int bPct = (int)Math.Round(B * byteToDouble * 100.0);
return string.Format(CultureInfo.InvariantCulture, "rgb({0}%, {1}%, {2}%)", rPct, gPct, bPct);
}
#endif

/// <summary>
/// Returns the integer representation of the color.
/// </summary>
Expand Down
85 changes: 84 additions & 1 deletion src/Avalonia.Base/Media/HslColor.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,9 @@ namespace Avalonia.Media
public
#endif
readonly struct HslColor : IEquatable<HslColor>
#if !BUILDTASK
, IFormattable
#endif
{
/// <summary>
/// Initializes a new instance of the <see cref="HslColor"/> struct.
Expand Down Expand Up @@ -177,6 +180,86 @@ public HsvColor ToHsv()
return HslColor.ToHsv(H, S, L, A);
}

#if !BUILDTASK
/// <summary>
/// Returns a formatted string representation of the HSL color.
/// </summary>
/// <param name="format">
/// The format specifier. All color types support all specifiers via auto-conversion.
/// Uppercase includes alpha, lowercase excludes it. <c>%</c> suffix = percent mode.
/// <list type="bullet">
/// <item><c>null</c> or <c>""</c> — Default (full-precision <c>hsla(h, s, l, a)</c>)</item>
/// <item><c>"X"</c> — XAML hex: <c>#AARRGGBB</c></item>
/// <item><c>"x"</c> — Hex: <c>#RRGGBB</c></item>
/// <item><c>"H"</c> — HTML hex: <c>#RRGGBBAA</c></item>
/// <item><c>"R"/"r"/"R%"/"r%"</c> — CSS rgb/rgba (auto-converts to RGB)</item>
/// <item><c>"L"</c> — CSS hsla: <c>hsla(h, s%, l%, a)</c></item>
/// <item><c>"l"</c> — CSS hsl: <c>hsl(h, s%, l%)</c></item>
/// <item><c>"L%"</c> — All percent: <c>hsla(h%, s%, l%, a%)</c></item>
/// <item><c>"l%"</c> — All percent: <c>hsl(h%, s%, l%)</c></item>
/// <item><c>"V"/"v"/"V%"/"v%"</c> — CSS hsv/hsva (auto-converts to HSV)</item>
/// </list>
/// <para><c>"C"</c> and <c>"A"</c> are reserved for future complex format strings.</para>
/// </param>
/// <param name="formatProvider">Ignored. Color formatting is culture-invariant.</param>
/// <returns>The formatted string representation.</returns>
/// <exception cref="FormatException">Thrown when <paramref name="format"/> is not recognized.</exception>
public string ToString(string? format, IFormatProvider? formatProvider)
{
if (string.IsNullOrEmpty(format))
{
return ToString();
}

return format switch
{
"X" or "x" or "H" or "R" or "r" or "R%" or "r%" => ToRgb().ToString(format, formatProvider),

"L" => FormatHsla(),
"l" => FormatHsl(),
"L%" => FormatHslaPercent(),
"l%" => FormatHslPercent(),

"V" or "v" or "V%" or "v%" => ToHsv().ToString(format, formatProvider),

_ => throw new FormatException($"Format string '{format}' is not supported.")
};
}

private string FormatHsla()
{
int hDeg = (int)Math.Round(H);
int sPct = (int)Math.Round(S * 100.0);
int lPct = (int)Math.Round(L * 100.0);
return string.Format(CultureInfo.InvariantCulture, "hsla({0}, {1}%, {2}%, {3:F2})", hDeg, sPct, lPct, A);
}

private string FormatHsl()
{
int hDeg = (int)Math.Round(H);
int sPct = (int)Math.Round(S * 100.0);
int lPct = (int)Math.Round(L * 100.0);
return string.Format(CultureInfo.InvariantCulture, "hsl({0}, {1}%, {2}%)", hDeg, sPct, lPct);
}

private string FormatHslaPercent()
{
int hPct = (int)Math.Round(H / 360.0 * 100.0);
int sPct = (int)Math.Round(S * 100.0);
int lPct = (int)Math.Round(L * 100.0);
int aPct = (int)Math.Round(A * 100.0);
return string.Format(CultureInfo.InvariantCulture, "hsla({0}%, {1}%, {2}%, {3}%)", hPct, sPct, lPct, aPct);
}

private string FormatHslPercent()
{
int hPct = (int)Math.Round(H / 360.0 * 100.0);
int sPct = (int)Math.Round(S * 100.0);
int lPct = (int)Math.Round(L * 100.0);
return string.Format(CultureInfo.InvariantCulture, "hsl({0}%, {1}%, {2}%)", hPct, sPct, lPct);
}
#endif

/// <inheritdoc/>
public override string ToString()
{
Expand All @@ -193,7 +276,7 @@ public override string ToString()
// hsla(230, 1.0, 0.5, 1.0)
//

sb.Append("hsva(");
sb.Append("hsla(");
sb.Append(H.ToString(CultureInfo.InvariantCulture));
sb.Append(", ");
sb.Append(S.ToString(CultureInfo.InvariantCulture));
Expand Down
83 changes: 83 additions & 0 deletions src/Avalonia.Base/Media/HsvColor.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,9 @@ namespace Avalonia.Media
public
#endif
readonly struct HsvColor : IEquatable<HsvColor>
#if !BUILDTASK
, IFormattable
#endif
{
/// <summary>
/// Initializes a new instance of the <see cref="HsvColor"/> struct.
Expand Down Expand Up @@ -207,6 +210,86 @@ public HslColor ToHsl()
return HsvColor.ToHsl(H, S, V, A);
}

#if !BUILDTASK
/// <summary>
/// Returns a formatted string representation of the HSV color.
/// </summary>
/// <param name="format">
/// The format specifier. All color types support all specifiers via auto-conversion.
/// Uppercase includes alpha, lowercase excludes it. <c>%</c> suffix = percent mode.
/// <list type="bullet">
/// <item><c>null</c> or <c>""</c> — Default (full-precision <c>hsva(h, s, v, a)</c>)</item>
/// <item><c>"X"</c> — XAML hex: <c>#AARRGGBB</c></item>
/// <item><c>"x"</c> — Hex: <c>#RRGGBB</c></item>
/// <item><c>"H"</c> — HTML hex: <c>#RRGGBBAA</c></item>
/// <item><c>"R"/"r"/"R%"/"r%"</c> — CSS rgb/rgba (auto-converts to RGB)</item>
/// <item><c>"L"/"l"/"L%"/"l%"</c> — CSS hsl/hsla (auto-converts to HSL)</item>
/// <item><c>"V"</c> — CSS hsva: <c>hsva(h, s%, v%, a)</c></item>
/// <item><c>"v"</c> — CSS hsv: <c>hsv(h, s%, v%)</c></item>
/// <item><c>"V%"</c> — All percent: <c>hsva(h%, s%, v%, a%)</c></item>
/// <item><c>"v%"</c> — All percent: <c>hsv(h%, s%, v%)</c></item>
/// </list>
/// <para><c>"C"</c> and <c>"A"</c> are reserved for future complex format strings.</para>
/// </param>
/// <param name="formatProvider">Ignored. Color formatting is culture-invariant.</param>
/// <returns>The formatted string representation.</returns>
/// <exception cref="FormatException">Thrown when <paramref name="format"/> is not recognized.</exception>
public string ToString(string? format, IFormatProvider? formatProvider)
{
if (string.IsNullOrEmpty(format))
{
return ToString();
}

return format switch
{
"X" or "x" or "H" or "R" or "r" or "R%" or "r%" => ToRgb().ToString(format, formatProvider),

"L" or "l" or "L%" or "l%" => ToHsl().ToString(format, formatProvider),

"V" => FormatHsva(),
"v" => FormatHsv(),
"V%" => FormatHsvaPercent(),
"v%" => FormatHsvPercent(),

_ => throw new FormatException($"Format string '{format}' is not supported.")
};
}

private string FormatHsva()
{
int hDeg = (int)Math.Round(H);
int sPct = (int)Math.Round(S * 100.0);
int vPct = (int)Math.Round(V * 100.0);
return string.Format(CultureInfo.InvariantCulture, "hsva({0}, {1}%, {2}%, {3:F2})", hDeg, sPct, vPct, A);
}

private string FormatHsv()
{
int hDeg = (int)Math.Round(H);
int sPct = (int)Math.Round(S * 100.0);
int vPct = (int)Math.Round(V * 100.0);
return string.Format(CultureInfo.InvariantCulture, "hsv({0}, {1}%, {2}%)", hDeg, sPct, vPct);
}

private string FormatHsvaPercent()
{
int hPct = (int)Math.Round(H / 360.0 * 100.0);
int sPct = (int)Math.Round(S * 100.0);
int vPct = (int)Math.Round(V * 100.0);
int aPct = (int)Math.Round(A * 100.0);
return string.Format(CultureInfo.InvariantCulture, "hsva({0}%, {1}%, {2}%, {3}%)", hPct, sPct, vPct, aPct);
}

private string FormatHsvPercent()
{
int hPct = (int)Math.Round(H / 360.0 * 100.0);
int sPct = (int)Math.Round(S * 100.0);
int vPct = (int)Math.Round(V * 100.0);
return string.Format(CultureInfo.InvariantCulture, "hsv({0}%, {1}%, {2}%)", hPct, sPct, vPct);
}
#endif

/// <inheritdoc/>
public override string ToString()
{
Expand Down
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