Add a scene field to render target IDs to reduce the chance of misuse

content/src/render_target.rs

@@ -11,4 +11,7 @@
 //! Render targets.
 
 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
-pub struct RenderTargetId(pub u32);
+pub struct RenderTargetId {
+    pub scene: u32,
+    pub render_target: u32,
+}

renderer/src/gpu/renderer.rs

@@ -472,12 +472,12 @@ where
     fn declare_render_target(&mut self,
                              render_target_id: RenderTargetId,
                              location: TextureLocation) {
-        while self.render_targets.len() < render_target_id.0 as usize + 1 {
+        while self.render_targets.len() < render_target_id.render_target as usize + 1 {
             self.render_targets.push(RenderTargetInfo {
                 location: TextureLocation { page: TexturePageId(!0), rect: RectI::default() },
             });
         }
-        let mut render_target = &mut self.render_targets[render_target_id.0 as usize];
+        let mut render_target = &mut self.render_targets[render_target_id.render_target as usize];
         debug_assert_eq!(render_target.location.page, TexturePageId(!0));
         render_target.location = location;
     }
@@ -1078,7 +1078,7 @@ where
     }
 
     fn render_target_location(&self, render_target_id: RenderTargetId) -> TextureLocation {
-        self.render_targets[render_target_id.0 as usize].location
+        self.render_targets[render_target_id.render_target as usize].location
     }
 
     fn texture_page_framebuffer(&self, id: TexturePageId) -> &D::Framebuffer {

renderer/src/paint.rs

@@ -11,7 +11,7 @@
 use crate::allocator::{AllocationMode, TextureAllocator};
 use crate::gpu_data::{RenderCommand, TextureLocation, TextureMetadataEntry, TexturePageDescriptor};
 use crate::gpu_data::{TexturePageId, TileBatchTexture};
-use crate::scene::RenderTarget;
+use crate::scene::{RenderTarget, SceneId};
 use hashbrown::HashMap;
 use pathfinder_color::ColorU;
 use pathfinder_content::effects::{Filter, PatternFilter};
@@ -37,6 +37,7 @@ pub struct Palette {
     pub(crate) paints: Vec<Paint>,
     pub(crate) render_targets: Vec<RenderTarget>,
     cache: HashMap<Paint, PaintId>,
+    scene_id: SceneId,
 }
 
 #[derive(Clone, PartialEq, Eq, Hash, Debug)]
@@ -84,8 +85,8 @@ impl Debug for PaintContents {
 
 impl Palette {
     #[inline]
-    pub fn new() -> Palette {
-        Palette { paints: vec![], render_targets: vec![], cache: HashMap::new() }
+    pub fn new(scene_id: SceneId) -> Palette {
+        Palette { paints: vec![], render_targets: vec![], cache: HashMap::new(), scene_id }
     }
 }
 
@@ -336,9 +337,9 @@ impl Palette {
     }
 
     pub fn push_render_target(&mut self, render_target: RenderTarget) -> RenderTargetId {
-        let id = RenderTargetId(self.render_targets.len() as u32);
+        let id = self.render_targets.len() as u32;
         self.render_targets.push(render_target);
-        id
+        RenderTargetId { scene: self.scene_id.0, render_target: id }
     }
 
     pub fn build_paint_info(&self, render_transform: Transform2F) -> PaintInfo {
@@ -377,8 +378,8 @@ impl Palette {
                         let location;
                         match *pattern.source() {
                             PatternSource::RenderTarget { id: render_target_id, .. } => {
-                                location =
-                                    render_target_metadata[render_target_id.0 as usize].location;
+                                let index = render_target_id.render_target as usize;
+                                location = render_target_metadata[index].location;
                             }
                             PatternSource::Image(ref image) => {
                                 // TODO(pcwalton): We should be able to use tile cleverness to
@@ -510,7 +511,7 @@ impl Palette {
             RenderCommand::AllocateTexturePages(texture_page_descriptors),
         ];
         for (index, metadata) in render_target_metadata.iter().enumerate() {
-            let id = RenderTargetId(index as u32);
+            let id = RenderTargetId { scene: self.scene_id.0, render_target: index as u32 };
             render_commands.push(RenderCommand::DeclareRenderTarget {
                 id,
                 location: metadata.location,

renderer/src/scene.rs

@@ -24,6 +24,9 @@ use pathfinder_geometry::rect::RectF;
 use pathfinder_geometry::transform2d::Transform2F;
 use pathfinder_geometry::vector::{Vector2I, vec2f};
 use std::collections::HashMap;
+use std::sync::atomic::{AtomicUsize, Ordering};
+
+static NEXT_SCENE_ID: AtomicUsize = AtomicUsize::new(0);
 
 #[derive(Clone)]
 pub struct Scene {
@@ -33,18 +36,24 @@ pub struct Scene {
     palette: Palette,
     bounds: RectF,
     view_box: RectF,
+    id: SceneId,
 }
 
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct SceneId(pub u32);
+
 impl Scene {
     #[inline]
     pub fn new() -> Scene {
+        let scene_id = SceneId(NEXT_SCENE_ID.fetch_add(1, Ordering::Relaxed) as u32);
         Scene {
             display_list: vec![],
             paths: vec![],
             clip_paths: vec![],
-            palette: Palette::new(),
+            palette: Palette::new(scene_id),
             bounds: RectF::default(),
             view_box: RectF::default(),
+            id: scene_id,
         }
     }
 
@@ -94,7 +103,10 @@ impl Scene {
                                                              .render_targets
                                                              .into_iter()
                                                              .enumerate() {
-            let old_render_target_id = RenderTargetId(old_render_target_index as u32);
+            let old_render_target_id = RenderTargetId {
+                scene: scene.id.0,
+                render_target: old_render_target_index as u32,
+            };
             let new_render_target_id = self.palette.push_render_target(render_target);
             render_target_mapping.insert(old_render_target_id, new_render_target_id);
         }