[librsvg: 3/4] Parse writing-mode values from the CSS Writing Modes 3 specification

[Marge Bot <marge-bot src gnome org>]

commit 25834ec93af1238aafdde29414d09427e5b2bc2c
Author: Federico Mena Quintero <federico gnome org>
Date:   Fri Sep 24 18:49:08 2021 -0500

    Parse writing-mode values from the CSS Writing Modes 3 specification
    
    The values lr, lr-tb, rl, rl-tb, tb, tb-rl are made obsolete in SVG2,
    and replaced with horizontal-tb, vertical-rl, vertical-lr.
    
    The old values are computed into the new ones per
    https://www.w3.org/TR/css-writing-modes-3/#block-flow
    
    Regretfully this commit adds another case to the make_property! macro,
    as I'd like to use the "identifiers" machinery here, but specify a
    custom compute() implementation.
    
    Part-of: <https://gitlab.gnome.org/GNOME/librsvg/-/merge_requests/597>

 src/property_defs.rs   | 46 ++++++++++++++++++++++++++++++++++------------
 src/property_macros.rs | 27 ++++++++++++++++++++++++++-
 src/text.rs            | 15 +++++++--------
 3 files changed, 67 insertions(+), 21 deletions(-)
---
diff --git a/src/property_defs.rs b/src/property_defs.rs
index b1407712..6eb8c713 100644
--- a/src/property_defs.rs
+++ b/src/property_defs.rs
@@ -1029,28 +1029,50 @@ make_property!(
 make_property!(
     /// `writing-mode` property.
     ///
-    /// https://www.w3.org/TR/SVG/text.html#WritingModeProperty
-    ///
     /// https://www.w3.org/TR/css-writing-modes-3/#block-flow
+    /// https://svgwg.org/svg2-draft/text.html#WritingModeProperty
+    /// https://www.w3.org/TR/SVG/text.html#WritingModeProperty
     ///
     /// See the comments in the SVG2 spec for how the SVG1.1 values must be translated
     /// into CSS Writing Modes 3 values.
     WritingMode,
-    default: LrTb,
-    inherits_automatically: true,
+    default: HorizontalTb,
+    identifiers: {
+        "horizontal-tb" => HorizontalTb,
+        "vertical-rl" => VerticalRl,
+        "vertical-lr" => VerticalLr,
+        "lr" => Lr,
+        "lr-tb" => LrTb,
+        "rl" => Rl,
+        "rl-tb" => RlTb,
+        "tb" => Tb,
+        "tb-rl" => TbRl,
+    },
+    property_impl: {
+        impl Property for WritingMode {
+            fn inherits_automatically() -> bool {
+                true
+            }
 
-    identifiers:
-    "lr" => Lr,
-    "lr-tb" => LrTb,
-    "rl" => Rl,
-    "rl-tb" => RlTb,
-    "tb" => Tb,
-    "tb-rl" => TbRl,
+            fn compute(&self, _v: &ComputedValues) -> Self {
+                use WritingMode::*;
+
+                // Translate SVG1.1 compatibility values to SVG2 / CSS Writing Modes 3.
+                match *self {
+                    Lr | LrTb | Rl | RlTb => HorizontalTb,
+                    Tb | TbRl => VerticalRl,
+                    _ => *self,
+                }
+            }
+        }
+    }
 );
 
 impl WritingMode {
     pub fn is_horizontal(self) -> bool {
-        !matches!(self, WritingMode::Tb | WritingMode::TbRl)
+        use WritingMode::*;
+
+        matches!(self, HorizontalTb | Lr | LrTb | Rl | RlTb)
     }
 }
 
diff --git a/src/property_macros.rs b/src/property_macros.rs
index bb3fea85..28aa61e4 100644
--- a/src/property_macros.rs
+++ b/src/property_macros.rs
@@ -134,6 +134,32 @@ macro_rules! make_property {
         }
     };
 
+    ($(#[$attr:meta])*
+     $name: ident,
+     default: $default: ident,
+     identifiers: { $($str_prop: expr => $variant: ident,)+ },
+     property_impl: { $prop: item }
+    ) => {
+        $(#[$attr])*
+        #[derive(Debug, Copy, Clone, PartialEq)]
+        #[repr(C)]
+        pub enum $name {
+            $($variant),+
+        }
+
+        impl_default!($name, $name::$default);
+        $prop
+
+        impl crate::parsers::Parse for $name {
+            fn parse<'i>(parser: &mut ::cssparser::Parser<'i, '_>) -> Result<$name, 
crate::error::ParseError<'i>> {
+                Ok(parse_identifiers!(
+                    parser,
+                    $($str_prop => $name::$variant,)+
+                )?)
+            }
+        }
+    };
+
     ($(#[$attr:meta])*
      $name: ident,
      default: $default: expr,
@@ -183,7 +209,6 @@ macro_rules! make_property {
         $parse
     };
 
-    // pending - only BaselineShift
     ($(#[$attr:meta])*
      $name: ident,
      default: $default: expr,
diff --git a/src/text.rs b/src/text.rs
index ee612ed4..46baef3b 100644
--- a/src/text.rs
+++ b/src/text.rs
@@ -812,22 +812,21 @@ impl From<Direction> for pango::Alignment {
 
 impl From<WritingMode> for pango::Direction {
     fn from(m: WritingMode) -> pango::Direction {
+        use WritingMode::*;
         match m {
-            WritingMode::LrTb | WritingMode::Lr | WritingMode::Tb | WritingMode::TbRl => {
-                pango::Direction::Ltr
-            }
-            WritingMode::RlTb | WritingMode::Rl => pango::Direction::Rtl,
+            HorizontalTb | VerticalRl | VerticalLr | LrTb | Lr | Tb | TbRl => pango::Direction::Ltr,
+            RlTb | Rl => pango::Direction::Rtl,
         }
     }
 }
 
 impl From<WritingMode> for pango::Gravity {
     fn from(m: WritingMode) -> pango::Gravity {
+        use WritingMode::*;
         match m {
-            WritingMode::Tb | WritingMode::TbRl => pango::Gravity::East,
-            WritingMode::LrTb | WritingMode::Lr | WritingMode::RlTb | WritingMode::Rl => {
-                pango::Gravity::South
-            }
+            HorizontalTb | LrTb | Lr | RlTb | Rl => pango::Gravity::South,
+            VerticalRl | Tb | TbRl => pango::Gravity::East,
+            VerticalLr => pango::Gravity::West,
         }
     }
 }