Extract menu, stylus, and canvas draw helpers

src/legacy_canvas_draw_merge_services.h

@@ -130,6 +130,14 @@ struct LegacyCanvasDrawMergeLayerPathExecution {
     std::function<void(int, float)> draw_frame;
 };
 
+struct LegacyCanvasDrawLayerVisit {
+    size_t layer_index = 0;
+    int plane_index = 0;
+    int z = 0;
+    int first_frame = 0;
+    int last_frame = 0;
+};
+
 struct LegacyCanvasDrawMergeTemporaryCompositeExecution {
     std::function<void()> setup;
     std::function<void()> bind_samplers;
@@ -671,6 +679,39 @@ inline void execute_legacy_canvas_draw_merge_layer_path(
     execution.draw_debug_outline();
 }
 
+template <typename PlanOnionRange, typename ShouldDrawPlane, typename VisitLayerPlane, typename LogOnionRangeFailure>
+inline void execute_legacy_canvas_draw_layer_traversal(
+    size_t layer_count,
+    PlanOnionRange&& plan_onion_range,
+    ShouldDrawPlane&& should_draw_plane,
+    VisitLayerPlane&& visit_layer_plane,
+    LogOnionRangeFailure&& log_onion_range_failure)
+{
+    for (size_t i = 0; i < layer_count; ++i) {
+        const auto layer_index = i;
+        const auto onion_range_result = plan_onion_range(layer_index);
+        if (!onion_range_result) {
+            log_onion_range_failure(onion_range_result.status().message);
+            continue;
+        }
+
+        const auto onion_range = onion_range_result.value();
+        for (int plane_index = 0; plane_index < 6; ++plane_index) {
+            if (!should_draw_plane(layer_index, plane_index, onion_range.first_frame, onion_range.last_frame)) {
+                continue;
+            }
+
+            visit_layer_plane(LegacyCanvasDrawLayerVisit {
+                .layer_index = layer_index,
+                .plane_index = plane_index,
+                .z = static_cast<int>(layer_count - i),
+                .first_frame = onion_range.first_frame,
+                .last_frame = onion_range.last_frame,
+            }, onion_range);
+        }
+    }
+}
+
 inline void execute_legacy_canvas_draw_merge_temporary_composite(
     const LegacyCanvasDrawMergeTemporaryCompositeExecution& execution)
 {