feat(layouts): support exporting layouts with multiple top cells (#425)

substrate/src/context.rs

@@ -569,7 +569,28 @@ impl<PDK: Pdk> PdkContext<PDK> {
         let layer_ctx = self.layer_ctx.read().unwrap();
         let db_units = PDK::LAYOUT_DB_UNITS.to_f64().unwrap();
         GdsExporter::with_units(
-            cell.raw.clone(),
+            vec![cell.raw.clone()],
+            &layer_ctx,
+            GdsUnits::new(db_units / 1e-6, db_units),
+        )
+        .export()
+        .map_err(LayoutError::from)?
+        .save(path)
+        .map_err(GdsExportError::from)
+        .map_err(LayoutError::from)?;
+        Ok(())
+    }
+
+    /// Writes a set of layout cells to a GDS file.
+    pub fn write_layout_all(
+        &self,
+        cells: impl IntoIterator<Item = Arc<RawCell>>,
+        path: impl AsRef<Path>,
+    ) -> Result<()> {
+        let layer_ctx = self.layer_ctx.read().unwrap();
+        let db_units = PDK::LAYOUT_DB_UNITS.to_f64().unwrap();
+        GdsExporter::with_units(
+            cells.into_iter().collect::<Vec<_>>(),
             &layer_ctx,
             GdsUnits::new(db_units / 1e-6, db_units),
         )

substrate/src/layout/gds.rs

@@ -45,7 +45,7 @@ new_key_type! {
 ///
 /// Takes a [`RawCell`] and converts it to a [`gds::GdsLibrary`].
 pub struct GdsExporter<'a> {
-    cell: Arc<RawCell>,
+    cells: Vec<Arc<RawCell>>,
     layers: &'a LayerContext,
     cell_db: Names<CellId>,
     gds: gds::GdsLibrary,
@@ -56,9 +56,9 @@ impl<'a> GdsExporter<'a> {
     ///
     /// Requires the cell to be exported and a [`LayerContext`] for mapping Substrate layers to GDS
     /// layers.
-    pub fn new(cell: Arc<RawCell>, layers: &'a LayerContext) -> Self {
+    pub fn new(cells: Vec<Arc<RawCell>>, layers: &'a LayerContext) -> Self {
         Self {
-            cell,
+            cells,
             layers,
             cell_db: Default::default(),
             gds: gds::GdsLibrary::new("TOP"),
@@ -69,9 +69,9 @@ impl<'a> GdsExporter<'a> {
     ///
     /// Requires the cell to be exported and a [`LayerContext`] for mapping Substrate layers to GDS
     /// layers.
-    pub fn with_units(cell: Arc<RawCell>, layers: &'a LayerContext, units: GdsUnits) -> Self {
+    pub fn with_units(cells: Vec<Arc<RawCell>>, layers: &'a LayerContext, units: GdsUnits) -> Self {
         Self {
-            cell,
+            cells,
             layers,
             cell_db: Default::default(),
             gds: gds::GdsLibrary::with_units("TOP", units),
@@ -80,7 +80,9 @@ impl<'a> GdsExporter<'a> {
 
     /// Exports the contents of `self` as a [`gds::GdsLibrary`].
     pub fn export(mut self) -> GdsExportResult<gds::GdsLibrary> {
-        self.cell.clone().export(&mut self)?;
+        for cell in self.cells.clone() {
+            cell.clone().export(&mut self)?;
+        }
         Ok(self.gds)
     }
 

substrate/src/layout/mod.rs

@@ -153,7 +153,7 @@ impl<T: ExportsLayoutData> Cell<T> {
     }
 
     /// The raw layout geometry contained by this cell.
-    pub fn raw(&self) -> &RawCell {
+    pub fn raw(&self) -> &Arc<RawCell> {
         &self.raw
     }
 }

tests/src/layout.rs

@@ -171,6 +171,29 @@ fn cell_builder_supports_bbox() {
     assert_eq!(cell.bbox(), Some(Rect::from_sides(-10, -1110, 2200, 210)));
 }
 
+#[test]
+fn export_multi_top_layout() {
+    let test_name = "export_multi_top_layout";
+
+    let block1 = BufferNxM::new(5, 10, 6);
+    let block2 = BufferNxM::new(5, 10, 6);
+    let block3 = BufferNxM::new(8, 12, 4);
+
+    let ctx = PdkContext::new(ExamplePdkA);
+    let block1 = ctx.generate_layout(block1);
+    let block2 = ctx.generate_layout(block2);
+    let block3 = ctx.generate_layout(block3);
+    ctx.write_layout_all(
+        [
+            block1.cell().raw().clone(),
+            block2.cell().raw().clone(),
+            block3.cell().raw().clone(),
+        ],
+        get_path(test_name, "layout.gds"),
+    )
+    .expect("failed to write layout");
+}
+
 #[test]
 fn grid_tiler_works_with_various_spans() {
     let test_name = "grid_tiler_works_with_various_spans";