Variable font support

[hansmbakker]

Description

I would like to consume variable fonts in .NET MAUI.

Public API Changes

It would be nice to have an overload of the current font loading API that takes a dictionary of variation settings to define labeled combinations.

var variationSettingsA = new Dictionary<string, double>()
{
    { "wght", 700d},
    { "ital", 0d }
};

var variationSettingsB = new Dictionary<string, double>()
{
    { "wght", 300d},
    { "ital", 1d }
};

builder.ConfigureFonts(
            fonts =>
            {
                fonts.AddFont(filename: "myVariableFont.otf", label: "FontVariationA", variationSettings: variationSettingsA);
                fonts.AddFont(filename: "myVariableFont.otf", label: "FontVariationB", variationSettings: variationSettingsB);
            });

Intended Use-Case

One of the things this is needed for, is to use the Material Symbols, which are shipped as variable fonts. Besides these Material Symbols, supporting variable fonts allows app developers to have more flexibility with their typography in general.

⚠️ Note: the fixed fonts elsewhere in the linked repo are the legacy Material Icons, not the newer Material Symbols I want to use

[hansmbakker]

The manual workaround for this now seems to be using the mutator tool from fontTools.

[ghost]

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