Thin recording bridge and canvas draw seams

src/legacy_canvas_draw_merge_services.h

@@ -276,6 +276,28 @@ template <typename ModesT>
     };
 }
 
+template <typename PlaneTransform, typename DrawPlane>
+[[nodiscard]] inline auto make_legacy_canvas_draw_merge_background_checkerboard_plane(
+    glm::mat4 proj,
+    glm::mat4 camera,
+    float layer_scale,
+    PlaneTransform plane_transform,
+    DrawPlane draw_plane)
+{
+    return [proj, camera, layer_scale, plane_transform, draw_plane](int plane_index) {
+        auto checkerboard_uniforms = LegacyCanvasDrawMergeCheckerboardUniforms {
+            .mvp = proj * camera *
+                glm::scale(glm::vec3(layer_scale)) *
+                plane_transform[plane_index] *
+                glm::translate(glm::vec3(0, 0, -1.f)),
+            .colorize = false,
+        };
+
+        setup_legacy_canvas_draw_merge_checkerboard_shader(checkerboard_uniforms);
+        draw_plane();
+    };
+}
+
 struct LegacyCanvasDrawMergeSmaskFacesExecution {
     std::function<void()> set_active_texture_unit;
     std::function<void()> enable_blend;