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Theming, localization and accessibility

Themes​

The package ships two themes, each with light and dark palettes. Include one of them in App.axaml.

ThemeDescription
Default.axamlA neutral, rounded, borderless look with its own palette. It does not depend on the host's Avalonia theme.
Fluent.axamlMaps the same keys onto FluentTheme resources such as SystemAccentColor and ControlCornerRadius, so the viewer follows the host's accent, theme variant and any Fluent resource the application overrides.
<Application.Styles>
    <FluentTheme />
    <StyleInclude Source="avares://Avalonia.Controls.PdfViewer/Themes/Fluent.axaml" />
</Application.Styles>

Both themes use the same control template, which only references Pdf* resources. The viewer therefore renders fully under SimpleTheme or a custom application theme as long as one of the two theme files is included.

Override theme brushes​

Override the Pdf* resources in App.axaml to match your application. The keys resolve per theme variant, so an override can supply light and dark values through a ResourceDictionary.ThemeDictionaries block.

<Application.Resources>
    <SolidColorBrush x:Key="PdfBackground" Color="#252526" />
    <SolidColorBrush x:Key="PdfErrorForeground" Color="#F48771" />
    <SolidColorBrush x:Key="PdfToolbarBackground" Color="#2D2D30" />
    <SolidColorBrush x:Key="PdfToolbarIconColor" Color="#CCCCCC" />
    <SolidColorBrush x:Key="PdfToolbarTextColor" Color="#E0E0E0" />
    <SolidColorBrush x:Key="PdfToolbarHoverBackground" Color="#3E3E42" />
    <SolidColorBrush x:Key="PdfToolbarBorderColor" Color="#555555" />
    <SolidColorBrush x:Key="PdfToolbarSeparatorColor" Color="#444444" />
    <SolidColorBrush x:Key="PdfMenuIconColor" Color="#AAAAAA" />

    <!-- Chrome the viewer builds in code -->
    <SolidColorBrush x:Key="PdfThumbnailBackground" Color="#2E2E2E" />
    <SolidColorBrush x:Key="PdfThumbnailSelectedBorder" Color="#4A9EDF" />
    <SolidColorBrush x:Key="PdfThumbnailLabelColor" Color="#B0B0B0" />
    <SolidColorBrush x:Key="PdfPagePlaceholderBackground" Color="#2A2A2A" />
    <SolidColorBrush x:Key="PdfDestructiveColor" Color="#FF6B6B" />

    <!-- Highlights and edit adorners drawn on the page -->
    <SolidColorBrush x:Key="PdfTextSelectionHighlight" Color="#5033A0FF" />
    <SolidColorBrush x:Key="PdfSearchHighlight" Color="#66FFEB3B" />
    <SolidColorBrush x:Key="PdfSearchHighlightActive" Color="#99FF9800" />
    <SolidColorBrush x:Key="PdfAdornerAccent" Color="#33A0FF" />
    <SolidColorBrush x:Key="PdfAdornerHandleBackground" Color="White" />
    <SolidColorBrush x:Key="PdfLinkHoverColor" Color="#DCA0A0A0" />
</Application.Resources>

SidebarSelectionBrush on the control overrides PdfThumbnailSelectedBorder for one viewer.

Pseudo-classes​

The viewer exposes its states as pseudo-classes for use in style selectors.

Pseudo-classState
:has-documentA document is open.
:loadingA document is loading.
:errorErrorMessage is set.
:read-onlyIsReadOnly is true.
:annotatingA tool is active.
:sidebar-openThe sidebar is expanded.
:mobileThe compact mobile layout is in use.
:narrowThe control is narrower than 640 DIPs, such as a phone in portrait. The search field collapses to an icon.
:search-openThe search field is open.
:text-selectedText is selected.
:shape-selectedAn annotation is selected.
:form-field-focusedA form field has focus.
:editing-textThe inline text editor is open.
<Style Selector="pdf|PdfViewer:read-only">
    <Setter Property="Opacity" Value="0.9" />
</Style>

Custom templates​

The template parts are declared with [TemplatePart] attributes on PdfViewer. Only PART_ScrollViewer and PART_PagesContainer are required. Every other part is optional, and its feature is absent when a custom template leaves it out.

To build your own theme, copy Default.axaml from the package, change the values and include the template the same way.

Localization​

Every text the viewer shows comes from PdfViewerStrings: tooltips, menu entries, dialog text, sidebar labels, placeholders and error messages. Assign an instance with your translations to Strings. Properties you leave out keep the English default.

Viewer.Strings = new PdfViewerStrings
{
    Highlight = "Surligner",
    SearchPlaceholder = "Rechercher...",
    PageCountFormat = "sur {0}",
    Loading = "Chargement...",
};

Properties ending in Format are string.Format patterns and must keep their {0} placeholder, for example PageCountFormat ("of {0}") and PageLabelFormat ("Page {0}").

Set Strings before loading a document. The toolbar updates immediately on a change, but context menus, the Stamp dropdown and thumbnail labels only pick up new strings when they are next built. The zoom percentage is formatted with the current culture.

Accessibility​

  • Toolbar and sidebar buttons expose their tooltip as AutomationProperties.Name, so a screen reader announces "Highlight" or "Zoom" rather than the control type.
  • The control reports as a document region, named from the document title (or file name) and the current page. Set AutomationProperties.Name on the PdfViewer to override this.
  • Hidden overlays (password, go-to-page, custom zoom) are out of the tab order.
  • Form fields are reachable with Tab and show a focus ring. See Forms.

Page content is rendered as a bitmap, so the PDF's text is not exposed to assistive technology as elements. If you need it, read it with GetPageTextAsync and present it in your own accessible surface.

See also​

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