spans now good (other than direction) + refactor

src/render/primitive.rs

@@ -0,0 +1,27 @@
+use crate::Color;
+
+pub use super::data::PrimitiveInstance;
+
+#[derive(Default)]
+pub struct Primitives {
+    pub instances: Vec<PrimitiveInstance>,
+    pub data: Vec<u32>,
+}
+
+/// NOTE: Self must have at least u32 alignment
+pub trait PrimitiveData: bytemuck::Pod {
+    const DISCRIM: u32;
+}
+
+#[repr(C)]
+#[derive(Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
+pub struct RoundedRectData {
+    pub color: Color<u8>,
+    pub radius: f32,
+    pub thickness: f32,
+    pub inner_radius: f32,
+}
+
+impl PrimitiveData for RoundedRectData {
+    const DISCRIM: u32 = 0;
+}