[write-fonts] Add RemapVariationIndices trait

After compiling an ItemVariationStore, we need to remap any existing
indices into that structure, in any place that they exist.

This trait encapsulates that behaviour.

It is currently only implemented by GPOS, but only because I'm not very
familiar with its use elsewhere, and I want to make sure this works.

write-fonts/src/tables/gpos.rs

@@ -7,9 +7,13 @@ include!("../../generated/generated_gpos.rs");
 use std::collections::HashSet;
 
 //use super::layout::value_record::ValueRecord;
-use super::layout::{
-    ChainedSequenceContext, ClassDef, CoverageTable, DeviceOrVariationIndex, FeatureList,
-    FeatureVariations, Lookup, LookupList, LookupSubtable, LookupType, ScriptList, SequenceContext,
+use super::{
+    layout::{
+        ChainedSequenceContext, ClassDef, CoverageTable, DeviceOrVariationIndex, FeatureList,
+        FeatureVariations, Lookup, LookupList, LookupSubtable, LookupType, ScriptList,
+        SequenceContext,
+    },
+    variations::ivs_builder::{RemapVariationIndices, VariationIndexRemapping},
 };
 
 #[cfg(test)]
@@ -199,6 +203,199 @@ impl MarkArray {
     }
 }
 
+impl RemapVariationIndices for ValueRecord {
+    fn remap_variation_indices(&mut self, key_map: &VariationIndexRemapping) {
+        for table in [
+            self.x_placement_device.as_mut(),
+            self.y_placement_device.as_mut(),
+            self.x_advance_device.as_mut(),
+            self.y_advance_device.as_mut(),
+        ]
+        .into_iter()
+        .flatten()
+        {
+            table.remap_variation_indices(key_map)
+        }
+    }
+}
+
+impl RemapVariationIndices for DeviceOrVariationIndex {
+    fn remap_variation_indices(&mut self, key_map: &VariationIndexRemapping) {
+        if let DeviceOrVariationIndex::PendingVariationIndex(table) = self {
+            *self = key_map.get(table.delta_set_id).unwrap().into();
+        }
+    }
+}
+
+impl RemapVariationIndices for AnchorTable {
+    fn remap_variation_indices(&mut self, key_map: &VariationIndexRemapping) {
+        if let AnchorTable::Format3(table) = self {
+            table
+                .x_device
+                .as_mut()
+                .into_iter()
+                .chain(table.y_device.as_mut())
+                .for_each(|x| x.remap_variation_indices(key_map))
+        }
+    }
+}
+
+impl RemapVariationIndices for Gpos {
+    fn remap_variation_indices(&mut self, key_map: &VariationIndexRemapping) {
+        self.lookup_list.as_mut().remap_variation_indices(key_map)
+    }
+}
+
+impl RemapVariationIndices for PositionLookupList {
+    fn remap_variation_indices(&mut self, key_map: &VariationIndexRemapping) {
+        for lookup in &mut self.lookups {
+            lookup.remap_variation_indices(key_map)
+        }
+    }
+}
+
+impl RemapVariationIndices for PositionLookup {
+    fn remap_variation_indices(&mut self, key_map: &VariationIndexRemapping) {
+        match self {
+            PositionLookup::Single(lookup) => lookup.remap_variation_indices(key_map),
+            PositionLookup::Pair(lookup) => lookup.remap_variation_indices(key_map),
+            PositionLookup::Cursive(lookup) => lookup.remap_variation_indices(key_map),
+            PositionLookup::MarkToBase(lookup) => lookup.remap_variation_indices(key_map),
+            PositionLookup::MarkToLig(lookup) => lookup.remap_variation_indices(key_map),
+            PositionLookup::MarkToMark(lookup) => lookup.remap_variation_indices(key_map),
+
+            // don't contain any metrics directly
+            PositionLookup::Contextual(_)
+            | PositionLookup::ChainContextual(_)
+            | PositionLookup::Extension(_) => (),
+        }
+    }
+}
+
+impl<T: RemapVariationIndices> RemapVariationIndices for Lookup<T> {
+    fn remap_variation_indices(&mut self, key_map: &VariationIndexRemapping) {
+        for subtable in &mut self.subtables {
+            subtable.remap_variation_indices(key_map)
+        }
+    }
+}
+
+impl RemapVariationIndices for SinglePos {
+    fn remap_variation_indices(&mut self, key_map: &VariationIndexRemapping) {
+        match self {
+            SinglePos::Format1(table) => table.remap_variation_indices(key_map),
+            SinglePos::Format2(table) => table.remap_variation_indices(key_map),
+        }
+    }
+}
+
+impl RemapVariationIndices for SinglePosFormat1 {
+    fn remap_variation_indices(&mut self, key_map: &VariationIndexRemapping) {
+        self.value_record.remap_variation_indices(key_map);
+    }
+}
+
+impl RemapVariationIndices for SinglePosFormat2 {
+    fn remap_variation_indices(&mut self, key_map: &VariationIndexRemapping) {
+        for rec in &mut self.value_records {
+            rec.remap_variation_indices(key_map);
+        }
+    }
+}
+
+impl RemapVariationIndices for PairPosFormat1 {
+    fn remap_variation_indices(&mut self, key_map: &VariationIndexRemapping) {
+        for pairset in &mut self.pair_sets {
+            for pairrec in &mut pairset.pair_value_records {
+                pairrec.value_record1.remap_variation_indices(key_map);
+                pairrec.value_record2.remap_variation_indices(key_map);
+            }
+        }
+    }
+}
+
+impl RemapVariationIndices for PairPosFormat2 {
+    fn remap_variation_indices(&mut self, key_map: &VariationIndexRemapping) {
+        for class1rec in &mut self.class1_records {
+            for class2rec in &mut class1rec.class2_records {
+                class2rec.value_record1.remap_variation_indices(key_map);
+                class2rec.value_record2.remap_variation_indices(key_map);
+            }
+        }
+    }
+}
+
+impl RemapVariationIndices for PairPos {
+    fn remap_variation_indices(&mut self, key_map: &VariationIndexRemapping) {
+        match self {
+            PairPos::Format1(table) => table.remap_variation_indices(key_map),
+            PairPos::Format2(table) => table.remap_variation_indices(key_map),
+        }
+    }
+}
+
+impl RemapVariationIndices for MarkBasePosFormat1 {
+    fn remap_variation_indices(&mut self, key_map: &VariationIndexRemapping) {
+        self.mark_array.as_mut().remap_variation_indices(key_map);
+        for rec in &mut self.base_array.as_mut().base_records {
+            for anchor in &mut rec.base_anchors {
+                if let Some(anchor) = anchor.as_mut() {
+                    anchor.remap_variation_indices(key_map);
+                }
+            }
+        }
+    }
+}
+
+impl RemapVariationIndices for MarkMarkPosFormat1 {
+    fn remap_variation_indices(&mut self, key_map: &VariationIndexRemapping) {
+        self.mark1_array.as_mut().remap_variation_indices(key_map);
+        for rec in &mut self.mark2_array.as_mut().mark2_records {
+            for anchor in &mut rec.mark2_anchors {
+                if let Some(anchor) = anchor.as_mut() {
+                    anchor.remap_variation_indices(key_map);
+                }
+            }
+        }
+    }
+}
+
+impl RemapVariationIndices for MarkLigPosFormat1 {
+    fn remap_variation_indices(&mut self, key_map: &VariationIndexRemapping) {
+        self.mark_array.as_mut().remap_variation_indices(key_map);
+        for lig in &mut self.ligature_array.as_mut().ligature_attaches {
+            for rec in &mut lig.component_records {
+                for anchor in &mut rec.ligature_anchors {
+                    if let Some(anchor) = anchor.as_mut() {
+                        anchor.remap_variation_indices(key_map);
+                    }
+                }
+            }
+        }
+    }
+}
+
+impl RemapVariationIndices for CursivePosFormat1 {
+    fn remap_variation_indices(&mut self, key_map: &VariationIndexRemapping) {
+        for rec in &mut self.entry_exit_record {
+            for anchor in [rec.entry_anchor.as_mut(), rec.exit_anchor.as_mut()]
+                .into_iter()
+                .flatten()
+            {
+                anchor.remap_variation_indices(key_map);
+            }
+        }
+    }
+}
+
+impl RemapVariationIndices for MarkArray {
+    fn remap_variation_indices(&mut self, key_map: &VariationIndexRemapping) {
+        for rec in &mut self.mark_records {
+            rec.mark_anchor.remap_variation_indices(key_map);
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
 

write-fonts/src/tables/variations/ivs_builder.rs

@@ -42,6 +42,20 @@ pub struct VariationIndexRemapping {
     map: HashMap<TemporaryDeltaSetId, VariationIndex>,
 }
 
+/// Remapping temporary delta set identifiers to the final values.
+///
+/// This is called after the [`ItemVariationStore`] has been built, at which
+/// point any table containing a delta set index needs to be updated to point
+/// to the final value.
+///
+/// This trait should be implemented by any table that contains delta set indices,
+/// as well as for any of table containing such a table, which should recursively
+/// call it on the relevant subtables.
+pub trait RemapVariationIndices {
+    /// Remap any `TemporaryDeltaSetId`s to their final `VariationIndex` values
+    fn remap_variation_indices(&mut self, key_map: &VariationIndexRemapping);
+}
+
 /// Always sorted, so we can ensure equality
 ///
 /// Each tuple is (region index, delta value)