style: Add page-size parsing to Servo

Differential Revision: https://phabricator.services.mozilla.com/D102360

components/style/values/specified/page.rs

@@ -0,0 +1,48 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Specified @page at-rule properties
+
+use crate::parser::{Parse, ParserContext};
+use crate::values::generics;
+use crate::values::generics::size::Size2D;
+use crate::values::specified::length::NonNegativeLength;
+use cssparser::Parser;
+use style_traits::ParseError;
+
+pub use generics::page::Orientation;
+pub use generics::page::PaperSize;
+/// Specified value of the @page size descriptor
+pub type PageSize = generics::page::PageSize<Size2D<NonNegativeLength>>;
+
+impl Parse for PageSize {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        // Try to parse as <page-size> [ <orientation> ]
+        if let Ok(paper_size) = input.try_parse(PaperSize::parse) {
+            if let Ok(orientation) = input.try_parse(Orientation::parse) {
+                return Ok(PageSize::PaperSizeAndOrientation(paper_size, orientation));
+            }
+            return Ok(PageSize::PaperSize(paper_size));
+        }
+        // Try to parse as <orientation> [ <page-size> ]
+        if let Ok(orientation) = input.try_parse(Orientation::parse) {
+            if let Ok(paper_size) = input.try_parse(PaperSize::parse) {
+                return Ok(PageSize::PaperSizeAndOrientation(paper_size, orientation));
+            }
+            return Ok(PageSize::Orientation(orientation));
+        }
+        // Try to parse dimensions
+        if let Ok(size) =
+            input.try_parse(|i| Size2D::parse_with(context, i, NonNegativeLength::parse))
+        {
+            return Ok(PageSize::Size(size));
+        }
+        // auto value
+        input.expect_ident_matching("auto")?;
+        Ok(PageSize::Auto)
+    }
+}