MahApps.Metro

MahApps.Styles.Page is three setters and no template, and it is the one style on this site you have to apply by hand — Styles/Controls.xaml does not make it implicit.

<Page x:Class="MetroDemo.Navigation.InterestingPage"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      Title="Interesting Page"
      Style="{DynamicResource MahApps.Styles.Page}">

    <StackPanel>
        <TextBlock>Sorry, nothing is here.</TextBlock>
    </StackPanel>
</Page>

Property	Set to
`Background`	`MahApps.Brushes.ThemeBackground`
`Foreground`	`MahApps.Brushes.ThemeForeground`
`TextElement.FontSize`	`MahApps.Font.Size.Content`

Those three will look familiar: they are exactly what the MetroWindow style hands down to everything inside it — see Text. The Page style exists because a page does not get them.

A Frame is a wall

A Page is hosted by a Frame, whether directly or inside a MetroNavigationWindow, and a Frame is a boundary for property value inheritance. Foreground and TextElement.FontSize set on the window stop there; the page starts again from WPF's own defaults.

It is a boundary for resource lookup as well. A ResourceDictionary merged into an element above the frame does not reach the page inside it — a DynamicResource in the page resolves from Application.Resources instead.

A page with and without the style, on a dark surface

Both frames above sit on the same dark surface. The left page has no style, so it has no background and keeps WPF's near-black default text — invisible against it. The right one is the same page with MahApps.Styles.Page, which gives it the theme background and the theme foreground.

Under the light base theme the difference is easy to miss: WPF's default font size is 12 and MahApps.Font.Size.Content is also 12, and WPF's default foreground is black where MahApps.Brushes.ThemeForeground is near-black. Only the background differs, and against a light window even that hardly shows.

Switch to a dark theme, or put the page on any dark surface, and an unstyled page becomes unreadable. That is the case the style is for, and it is why applying it is worth the line even when the light theme looks fine without it.

Applying it everywhere

Since the style is keyed rather than implicit, every page needs the attribute. One implicit style in App.xaml, after the MahApps dictionaries, saves repeating it:

<Style BasedOn="{StaticResource MahApps.Styles.Page}" TargetType="{x:Type Page}" />

There is nothing in the style that makes this unsafe — it sets no template and touches no layout, so an implicit Page style has none of the reach an implicit TextBlock style would.

MetroNavigationWindow is the window that hosts pages, and Text explains where the same three values come from for everything that is not behind a frame.

A Frame is a wall

Applying it everywhere

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