[oden] Writable Textures and re-work TS API

Now we return Texture objects to make things a little bit more
type-safe, at the cost of a small allocation (I hope!)

src/script/graphics.rs

@@ -40,7 +40,15 @@ pub enum GraphicsCommand {
     Print(PrintCommand),
     Sprite(SpriteCommand),
     CreateTexture(CreateTextureCommand),
+    CreateWritableTexture {
+        id: u32,
+        width: u32,
+        height: u32,
+        label: Option<String>,
+    },
     UseTexture(u32),
+    WriteToTexture(u32),
+    WriteToScreen,
     EndFrame,
 }
 
@@ -109,6 +117,31 @@ impl GraphicsImpl {
     fn use_texture(&self, id: u32) {
         let _ = self.sender.send(GraphicsCommand::UseTexture(id));
     }
+
+    fn create_writable_texture(
+        &self,
+        width: u32,
+        height: u32,
+        label: Option<String>,
+    ) -> Result<u32> {
+        let id = self.next_texture_id.fetch_add(1, Ordering::SeqCst);
+        let _ = self.sender.send(GraphicsCommand::CreateWritableTexture {
+            id,
+            width,
+            height,
+            label,
+        });
+
+        Ok(id)
+    }
+
+    fn write_to_screen(&self) {
+        let _ = self.sender.send(GraphicsCommand::WriteToScreen);
+    }
+
+    fn write_to_texture(&self, id: u32) {
+        let _ = self.sender.send(GraphicsCommand::WriteToTexture(id));
+    }
 }
 
 pub struct GraphicsAPI {
@@ -168,6 +201,32 @@ impl GraphicsAPI {
                 )?,
             )?;
         }
+        {
+            let gfx = gfx.clone();
+            builder.export(
+                "create_writable_texture",
+                ctx.new_fn(
+                    move |_: &ContextRef, width: u32, height: u32, label: Option<String>| {
+                        gfx.create_writable_texture(width, height, label)
+                    },
+                )?,
+            )?;
+        }
+        {
+            let gfx = gfx.clone();
+            builder.export(
+                "write_to_screen",
+                ctx.new_fn(move |_: &ContextRef| gfx.write_to_screen())?,
+            )?;
+        }
+        {
+            let gfx = gfx.clone();
+            builder.export(
+                "write_to_texture",
+                ctx.new_fn(move |_: &ContextRef, id: u32| gfx.write_to_texture(id))?,
+            )?;
+        }
+
         builder.build("graphics-core")?;
         Ok(GraphicsAPI { gfx })
     }