Theme Definitions

A theme definition contains many options that guide a theme generator on how to dynamically generate theme resources. Options cover a variety of theme aspects, including:

• Font families and base font size.
• Color ramps for accent and other semantic use scenarios (e.g., success, danger).
• Default appearance kind when there are several control theme variations (e.g., outline, solid) available for a control type, such as for buttons, switches, edit controls, etc.
• Corner radii, lengths, paddings, and margins.

Theme Definition Options

Theme definitions are represented by the ThemeDefinition class, which has a wide variety of properties for directing theme generator output.

General Options

Font Options

Color Ramp Options

Color ramp name properties should be set to Hue enumeration value names.

Menu Control Options

Switch Control Options

ScrollBar Options

Other Control Options

Custom Theme Generators

The default theme generator implementation fully generates theme resources for all supported theme variants. Sometimes you may wish to further customize the default output of specific resource values for each theme variant. In those cases, creation of a custom ThemeGenerator-based class is possible. An instance of the custom generator class can be assigned to the ThemeDefinition.Generator property.

See the Theme Generator topic for detail on how to create and install custom theme generator logic, and when it is appropriate to do so.

Creating Derived Classes

It's perfectly fine to create a new instance of the ThemeDefinition class and set its various properties before passing the theme definition to a ModernTheme, as described in the Getting Started topic.

<Application ...
	xmlns:actipro="http://schemas.actiprosoftware.com/avaloniaui"
	xmlns:generation="using:ActiproSoftware.UI.Avalonia.Themes.Generation">
	<Application.Styles>

		<actipro:ModernTheme>
			<actipro:ModernTheme.Definition>
				<generation:ThemeDefinition UseAccentedSwitches="True" AccentColorRampName="Indigo" />
			</actipro:ModernTheme.Definition>
		</actipro:ModernTheme>

	</Application.Styles>
</Application>

If you configure multiple properties on the theme definition, or if you wish to swap in alternate theme definitions at runtime, you may wish to consider creating a custom class that inherits ThemeDefinition and sets all of the properties in the constructor.

Here is a custom MyThemeDefinition class that demonstrates this concept:

public class MyThemeDefinition : ThemeDefinition {

	public MyThemeDefinition() {
		UseAccentedSwitch = true;
		AccentColorRampName = Hue.Indigo.ToString();
	}

}

And here is how a MyThemeDefinition instance can be used:

<Application ... xmlns:actipro="http://schemas.actiprosoftware.com/avaloniaui">
	<Application.Styles>

		<actipro:ModernTheme>
			<actipro:ModernTheme.Definition>
				<local:MyThemeDefinition />
			</actipro:ModernTheme.Definition>
		</actipro:ModernTheme>

	</Application.Styles>
</Application>

Changing Theme Definitions

Actipro's themes include light and dark theme variants in the same theme. Therefore, toggling between light and dark modes is simply a factor of updating the Application.RequestedThemeVariant property as described in the Getting Started topic, which does not require an alternate theme definition to be used.

If your application would like to support a different theme appearance in general (e.g., different colors, font size, spacing), that is where creating alternate theme definitions is required.

Let's assume you have created two ThemeDefinition-based classes named MyThemeDefinition and MySecondThemeDefinition. MyThemeDefinition could have been initialized with code as in the previous section.

Here is a custom MySecondThemeDefinition class that provides an alternate theme appearance with orange accents:

public class MySecondThemeDefinition : ThemeDefinition {

	public MySecondThemeDefinition() {
		AccentColorRampName = Hue.Orange.ToString();
	}

}

The following example shows how the ModernTheme.Definition property can be updated at runtime to a new theme definition, which will immediately update the application appearance.

if (ModernTheme.TryGetCurrent(out var theme))
	theme.Definition = new MySecondThemeDefinition();