Reading Systems with
a CSS viewport should support the EPUB 3 CSS Profile [ContentDocs301] for rendering annotations.
In addition, even when a Reading System does have
a CSS Viewport, it is likely to render content in a manner that differs from typical HTML5 User Agents (e.g., paginating content rather than providing a infinitely scrolling surface).
' If it has
a CSS Viewport, it must support visual rendering of XHTML Content Documents as defined in EPUB Style Sheets — Reading System Conformance [ContentDocs301].
Reading Systems with
a CSS Viewport must support OpenType [OpenType] and WOFF [WOFF] fonts embedded using the @font - face rule.
During Media Overlays playback, Reading Systems with
a CSS Viewport should add the class names given by the metadata properties active - class and playback - active - class to the appropriate elements in the EPUB Content Document.
While the CSS display property can be used to control the visual rendering of EPUB Navigation Documents in Reading Systems with
CSS Viewports, not all Reading Systems provide such an interface.
Not exact matches
iBooks for iOS has a bug of not recalculating
viewport size (and therefore
viewport - relative distances too) when changing orientation after a page with such
CSS has been already rendered.
For both XHTML and SVG Content Documents, the dimension (
viewport / viewbox) expressions define the
CSS initial containing block (ICB) expressed in
CSS Pixels [
CSS].
If only the [SVG] viewBox attribute is present, the coordinate system it defines is mapped to the
Viewport, keeping the aspect ratio, thereby establishing the initial containing block (ICB) in pixels [
CSS Snapshot].
While the display property [
CSS Snapshot] can be used to control the visual rendering of EPUB Navigation Documents in Reading Systems with
Viewports, not all Reading Systems provide such an interface.
Apple designed the Safari Technology Preview to test features that may be introduced into future release versions of Safari.Safari Technology Preview release 20 includes bug fixes and updates for Visual
Viewport, Touch Bar, JavaScript, Web API, Security,
CSS, Pointer Lock, Web Inspector, WebCrypto API, and more.The Safari Technology Preview update is available through the Software Update mechanism in the Mac App Store to anyone who has downloaded the browser.