Move coord convert to go invert Y

[JiepengTan]

The goal is to migrate the coordinate transformation from C++ to Go and unify the implementation approach （Invert Y）

1. spx_sprite_mgr.cpp: 9 conversions

• Position, velocity, and anchor point set/get methods
• Collision detection points

2. spx_physic_mgr.cpp: 6 conversions

• Raycast input/output
• Shape queries

3. spx_scene_mgr.cpp: 5 conversions

• Position/pivot setup when rendering sprites and creating static sprites

4. spx_draw_tiles.cpp/h: 8 conversions

• All tilemap coordinate operations go through the flip_y() function

5. spx_debug_mgr.cpp: 4 conversions

• Debug drawing functions (circles, rectangles, lines)

6. spx_input_mgr.cpp: 1 conversion

• Mouse position retrieval

7. spx_path_finder.cpp: 2 conversions

• Pathfinding input/output

Conversion Patterns

• Input parameter conversion: pos.y = -pos.y or GdVec2(pos.x, -pos.y)
• Return value conversion: return GdVec2(val.x, -val.y)
• Helper function: flip_y() (used in spx_draw_tiles)

[gemini-code-assist]

Summary of Changes

Hello @JiepengTan, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request focuses on migrating coordinate transformation logic from C++ to Go, aiming for a unified implementation across the SPX project. The changes involve inverting the Y-axis in various managers to ensure consistency in coordinate handling. This refactoring impacts sprite management, physics, scene management, tile drawing, debugging, input handling, and pathfinding, leading to a more maintainable and coherent codebase.

Highlights

• Coordinate Transformation Migration: The primary goal of this pull request is to migrate coordinate transformations from C++ to Go, unifying the implementation approach by inverting the Y-axis.
• File Modifications: Several files were modified to implement the coordinate transformation, including spx_sprite_mgr.cpp, spx_physic_mgr.cpp, spx_scene_mgr.cpp, spx_draw_tiles.cpp/h, spx_debug_mgr.cpp, spx_input_mgr.cpp, and spx_path_finder.cpp.
• Conversion Patterns: The conversion patterns include input parameter conversion (e.g., pos.y = -pos.y), return value conversion (e.g., return GdVec2(val.x, -val.y)), and the use of a helper function flip_y() in spx_draw_tiles.
• Coordinate Inversion Removal: Coordinate inversion is removed from debug draw functions in SpxDebugMgr, tile placement and retrieval in SpxDrawTiles, mouse position retrieval in SpxInputMgr, and pathfinding input/output in SpxPathFinder.

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[gemini-code-assist]

Code Review

This pull request effectively moves the Y-coordinate inversion logic from C++ to Go, simplifying the C++ side of the FFI. The changes are consistently applied across multiple manager classes, including sprite, physics, scene, and input management, by removing all instances of y-coordinate flipping. This aligns perfectly with the stated goal of unifying the coordinate transformation approach. Additionally, a new comprehensive guide for the AI assistant, CLAUDE.md, is introduced. My review includes a suggestion to improve the reusability of this new documentation file.

[xgopilot]

Code Review Summary

Clean refactoring that successfully removes Y-axis coordinate conversions from C++ layer. The changes are consistent and maintain code correctness. However, critical security and performance issues require attention before merging.

🔴 Critical Issues

1. Integer Overflow in Float-to-Int Conversion

• Location: modules/spx/spx_utils.h:9-11 (used throughout collision/physics code)
• Issue: spx_float_to_int() can overflow when coordinate values exceed ±922,337,203,685
• Impact: Undefined behavior, incorrect calculations, potential exploits
• CWE-190: Integer Overflow or Wraparound
• Fix: Add bounds checking before multiplication

2. Missing Null Pointer Validation

• Location: modules/spx/spx_camera_mgr.cpp:78-86
• Issue: get_global_camera_rect() doesn't validate viewport pointer before dereferencing
• Impact: Crash/DoS during scene transitions
• CWE-476: NULL Pointer Dereference
• Fix: Add ERR_FAIL_NULL_V(vp, Rect2()) check

⚠️ Performance Concerns

3. Redundant Coordinate Conversions in Nested Loops

• Location: modules/spx/spx_sprite_mgr.cpp:920-921, 997-998
• Issue: _to_image_coord() called twice per pixel in collision detection (O(n²) calls)
• Impact: For 100×100 overlap = 20,000 function calls with allocations
• Fix: Pre-compute transform parameters and use incremental arithmetic

4. Unnecessary Vector2 Allocations

• Location: modules/spx/spx_sprite_mgr.cpp:870-872
• Issue: 3 Vector2 allocations per _to_image_coord() call
• Impact: 6N allocations for pixel collision checks
• Fix: Reuse xpos and modify in-place

📝 Documentation Issues

5. Missing Architectural Documentation

• Issue: No comments explaining that coordinate conversion moved from C++ to Go
• Impact: Future maintainers won't understand the design change
• Fix: Add comments to key functions like get_position(), set_velocity(), etc.

6. Undocumented FFI Boundary

• Location: platform/web/js/engine/gdspx.util.js
• Issue: No documentation on coordinate system conventions at Go/JS/C++ boundaries
• Fix: Add JSDoc comments explaining Y-axis handling

✅ Positive Aspects

• Consistent removal of Y-axis inversions across all modules
• Clean separation of concerns (conversion logic now in Go layer)
• No breaking changes to internal C++ logic
• Good use of object pooling patterns

Recommendations

1. Before Merge: Fix critical security issues (#1, #2)
2. High Priority: Optimize collision detection performance (#3, #4)
3. Should Have: Add architectural documentation (#5, #6)
4. Consider: Add unit tests in Go layer to verify Y-axis inversion correctness

[JiepengTan]

#187 需要在合并后 修改，里面涉及到了 y 的变动