posts/universal_vector2_pt1/

[utterances-bot]

Making a Universal Vector2 Type in C++ - Part 1: Library User Perspective | File Descriptor Two

The Interoperability Problem
When using multiple libraries in your project, a quite frequent source of annoyance is trying to share their fundamental types, such as a two dimensional vector, quaternion, euler angle, etc. In each library, you can find various names for exactly the same concept.
Consider a hypothetical game development scenario: you could be using Box2D for physics (which has b2Vec2), raylib for graphics (which has Vector2). Despite that two types represent exactly the same thing, they cannot be used interchangeably. This forces you to copy one object into another, every time you wish to pass data and convert between them. Since these conversions are needed quite frequently, constantly operating on copies can become

https://peter0x44.github.io/posts/universal_vector2_pt1/

[FedericoMansutti]

was trying to implement this but i'm having issues:

struct Vec2 {
    float x, y;
    Vec2() : x(0.0f), y(0.0f) {}

    Vec2(float x, float y) : x(x), y(y) {}

    Vec2(const b2Vec2& b2vec2) : x(b2vec2.x), y(b2vec2.y){}
    Vec2(const Vector2& vector2) : x(vector2.x), y(vector2.y){}
    
    // Conversion operators for different libraries
    operator b2Vec2() const {
        return b2Vec2{x,y};
    }
    operator Vector2() const {
        return Vector2{x, y};
    }
};

I added an extra costructor in order to make C style arrays and it works, there is however one other issue:

Vec2 vertices[polygon.count];

for (int i = 0; i < polygon.count; i++) {
    Vec2 world_vertex = b2TransformPoint(transform, polygon.vertices[i]);
    vertices[i] = {world_vertex.x, world_vertex.y};
}
DrawLineStrip(vertices, polygon.count, BLUE);

then this won't compile with the following error

[build] C:/Users/mansu/Documents/GameDev/Raylib/Purifier/src/systems/rendering_system.cpp:46:9: error: no matching function for call to 'DrawLineStrip'
[build] 46 | DrawLineStrip(vertices, polygon.count, BLUE);
[build] | ^~~~~
[build] C:/Users/mansu/Documents/GameDev/Raylib/Purifier/external/raylib-src/src\raylib.h:1252:12: note: candidate function not viable: no known conversion from 'Vec2[polygon.count]' to 'const Vector2 *' for 1st argument
do you have any idea how to fix this?

[Peter0x44]

Hmm, that's an interesting and tricky problem I did not consider.
Although it is not seamless, casting the pointer to a Vector2* should work for this case of calling raylib.

Vec2 vertices[polygon.count];

for (int i = 0; i < polygon.count; i++) {
    Vec2 world_vertex = b2TransformPoint(transform, polygon.vertices[i]);
    vertices[i] = {world_vertex.x, world_vertex.y};
}

DrawLineStrip(reinterpret_cast<Vector2*>(vertices), polygon.count, BLUE);

If I figure something better than this, I will edit the post to include it.