add pos to compositor layers

compositor.cm

@@ -107,6 +107,10 @@ function compile_node(node, ctx, parent_target, parent_size) {
     owns_target = true
     target_size = parent_size || ctx.screen_size
     target = allocate_target(ctx, target_size, node.name || 'effect_island')
+  } else if (node.pos) {
+    owns_target = true
+    target_size = parent_size || ctx.screen_size
+    target = allocate_target(ctx, target_size, node.name || 'translated_target')
   }
   
   // Handle clear for target owners
@@ -189,7 +193,8 @@ function compile_group(node, ctx, target, target_size, parent_target, parent_siz
         source: target,
         source_size: target_size,
         dest_size: parent_size,
-        presentation: presentation
+        presentation: presentation,
+        pos: node.pos
       })
     } else {
       ctx.passes.push({
@@ -199,7 +204,8 @@ function compile_group(node, ctx, target, target_size, parent_target, parent_siz
         source_size: target_size,
         dest_size: parent_size,
         presentation: presentation,
-        blend: blend
+        blend: blend,
+        pos: node.pos
       })
     }
   }
@@ -261,7 +267,8 @@ function compile_renderer_layer(node, ctx, target, target_size, parent_target, p
       source_size: layer_size,
       dest_size: parent_size,
       presentation: presentation,
-      blend: blend
+      blend: blend,
+      pos: node.pos
     })
   }
   
@@ -606,6 +613,10 @@ function execute_pass(pass, renderers, backend, resolve_target) {
       var source = resolve_target(pass.source)
       var dest = resolve_target(pass.dest)
       var rect = compositor.calculate_presentation_rect(pass.source_size, pass.dest_size, pass.presentation)
+      if (pass.pos) {
+        rect.x += (pass.pos.x || 0)
+        rect.y += (pass.pos.y || 0)
+      }
       var filter = pass.presentation == 'integer_scale' ? 'nearest' : 'linear'
       commands.push({
         cmd: 'blit',
@@ -619,6 +630,10 @@ function execute_pass(pass, renderers, backend, resolve_target) {
     case 'blit_to_screen':
       var source = resolve_target(pass.source)
       var rect = compositor.calculate_presentation_rect(pass.source_size, pass.dest_size, pass.presentation)
+      if (pass.pos) {
+        rect.x += (pass.pos.x || 0)
+        rect.y += (pass.pos.y || 0)
+      }
       var filter = pass.presentation == 'integer_scale' ? 'nearest' : 'linear'
       commands.push({
         cmd: 'blit',