File-New-Project/EarTrumpet · error · NotImplementedException

BrushValueParser: '{value}'

Error message

BrushValueParser: '{value}'

What it means

BrushValueParser.Parse resolves a WPF theme brush from a compact markup string (e.g. "Theme=Transparent", "Flyout:Theme=Transparent, HighContrast=Window"). In HighContrast mode it tries, in order, the keys "" (default), "HighContrast", "Theme", "Light"; if none of those keys is present in the chosen scope map it throws NotImplementedException. The throw means the theme value provides no usable color for the active HighContrast state.

Source

Thrown at EarTrumpet/UI/Themes/BrushValueParser.cs:100

                    if (map.ContainsKey(""))
                    {
                        colorName = map[""];
                    }
                    else if (map.ContainsKey("HighContrast"))
                    {
                        colorName = map["HighContrast"];
                    }
                    else if (map.ContainsKey("Theme"))
                    {
                        colorName = map["Theme"].Replace("{Theme}", "Light");
                    }
                    else if (map.ContainsKey("Light"))
                    {
                        colorName = map["Light"];
                    }
                    else
                    {
                        throw new NotImplementedException($"BrushValueParser: '{value}'");
                    }
                }
                else
                {
                    if (map.ContainsKey(""))
                    {
                        colorName = map[""];
                    }
                    else if (map.ContainsKey("Theme"))
                    {
                        colorName = map["Theme"].Replace("{Theme}", isLight ? "Light" : "Dark");
                    }
                    else if (map.ContainsKey("Light") && isLight)
                    {
                        colorName = map["Light"];
                    }
                    else if (map.ContainsKey("Dark") && !isLight)
                    {

View on GitHub (pinned to aa894e51c2)

Solutions

1. Add a default "" entry or a "HighContrast=" entry to the offending brush value so the high-contrast branch resolves.
2. Provide a "Theme=" entry (it is substituted as Light in HC) if you want one value to cover HC.
3. Audit all BrushValueParser markup strings for coverage across "", HighContrast, Theme, Light, Dark.
4. Test theme loading with High Contrast enabled.

Example fix

// before (XAML/theme markup): "Header:Dark=AccentColor"
// after: "Header:Dark=AccentColor, HighContrast=WindowColor"
//   or simply: "AccentColor"  (default key covers all modes)

// validate a brush value covers high contrast before parsing
bool CoversHighContrast(Dictionary<string,string> map)
    => map.ContainsKey("") || map.ContainsKey("HighContrast") || map.ContainsKey("Theme") || map.ContainsKey("Light");

try { return BrushValueParser.Parse(element, value); } catch (Exception ex) { Trace.WriteLine($"{ex.Message} inner={ex.InnerException?.Message}"); return FallbackBrush; }

When it happens

Trigger: SystemParameters.HighContrast is true and a theme brush value contains only a "Dark=..." entry (or a scope that lacks ""/"HighContrast"/"Theme"/"Light"), so the high-contrast branch falls through to the throw.

Common situations: A theme author added a new brush with only a Dark variant; a scoped value ("Header:Dark=...") was added without a high-contrast fallback; high-contrast testing was skipped.

Related errors

• bad number of /
• BrushValueParser Error: '{value}' {element}
• Rule type not found

AI-assisted analysis of File-New-Project/EarTrumpet@aa894e51c2 (2026-08-13). Data as JSON: /api/errors/c510eca810989562. Report an issue: GitHub.