note transform/style invariant in Encoding docs

linebender · Feb 13, 2024 · 595ef62 · 595ef62
1 parent 5c298da
commit 595ef62
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diff --git a/crates/encoding/src/encoding.rs b/crates/encoding/src/encoding.rs
@@ -16,6 +16,11 @@ use {
 };
 
 /// Encoded data streams for a scene.
+///
+/// # Invariants
+///
+/// * At least one transform and style must be encoded before any path data
+/// or draw object.
 #[derive(Clone, Default)]
 pub struct Encoding {
     /// The path tag stream.

diff --git a/shader/flatten.wgsl b/shader/flatten.wgsl
@@ -478,6 +478,8 @@ fn compute_tag_monoid(ix: u32) -> PathTagData {
     var tag_byte = (tag_word >> shift) & 0xffu;
     // We no longer encode an initial transform and style so these
     // are off by one.
+    // Note: an alternative would be to adjust config.transform_base and
+    // config.style_base.
     tm.trans_ix -= 1u;
     tm.style_ix -= STYLE_SIZE_IN_WORDS;
     return PathTagData(tag_byte, tm);