initial mask impl

src/render/primitive.rs

@@ -2,7 +2,10 @@ use std::ops::{Deref, DerefMut};
 
 use crate::{
     layout::{Color, UiRegion},
-    render::{ArrBuf, data::PrimitiveInstance},
+    render::{
+        ArrBuf,
+        data::{MaskIdx, PrimitiveInstance},
+    },
     util::Id,
 };
 use bytemuck::Pod;
@@ -95,19 +98,30 @@ macro_rules! primitives {
     (@count $t:tt) => { 1 };
 }
 
+pub struct PrimitiveInst<P> {
+    pub id: Id,
+    pub primitive: P,
+    pub region: UiRegion,
+    pub mask_idx: MaskIdx,
+}
+
 impl Primitives {
     pub fn write<P: Primitive>(
         &mut self,
         layer: usize,
-        id: Id,
-        data: P,
-        region: UiRegion,
+        PrimitiveInst {
+            id,
+            primitive,
+            region,
+            mask_idx,
+        }: PrimitiveInst<P>,
     ) -> PrimitiveHandle {
         let vec = P::vec(&mut self.data);
-        let i = vec.add(data);
+        let i = vec.add(primitive);
         let inst = PrimitiveInstance {
             region,
             idx: i as u32,
+            mask_idx,
             binding: P::BINDING,
         };
         let inst_i = if let Some(i) = self.free.pop() {
@@ -138,9 +152,10 @@ impl Primitives {
         })
     }
 
-    pub fn free(&mut self, h: &PrimitiveHandle) {
+    pub fn free(&mut self, h: &PrimitiveHandle) -> MaskIdx {
         self.data.free(h.binding, h.data_idx);
         self.free.push(h.inst_idx);
+        self.instances[h.inst_idx].mask_idx
     }
 
     pub fn data(&self) -> &PrimitiveData {