Collision between a player and a solid block C++ SDL2

Question

I am trying to implement a collision between a player and a solid e.g. a solid box.

bool Collision::Checkcollision(const SDL_Rect &A, const SDL_Rect &B)
{
    return A.y + A.h >= B.y &&
    A.y <= B.y + B.h &&
    A.x <= B.x + B.w &&
    A.x + A.w >= B.x;
}

if (CKeyboard::Get()->GetKey(SDL_SCANCODE_DOWN))
        {
             Vel.y += 1.0f;
        }
        if (CKeyboard::Get()->GetKey(SDL_SCANCODE_RIGHT))
        {
            Vel.x += 1.0f;
        }
        if (CKeyboard::Get()->GetKey(SDL_SCANCODE_UP))
        {
            Vel.y -= 1.0f;
        }
        if (CKeyboard::Get()->GetKey(SDL_SCANCODE_LEFT))
        {
            Vel.x -= 1.0f;
        }
        Position = Position + Vel.GetNormalized();
        SDL_Rect r1 = Sprite->Get_Rect();
        SDL_Rect r2 = Sprite1->Get_Rect();
        if (Collision::Get()->Checkcollision(r1,r2))
        {

            if (Vel.x < 1.f)
            {
                Position.x = Position.x - 1;
                Vel.x = 0;
            }
            if (Vel.x > 0.f)
            {
                Position.x = Position.x + 1;
                Vel.x = 0;
            }
            if (Vel.y < 1.f)
            {
                Position.y = Position.y - 1;
                Vel.y = 0;
            }
            if (Vel.y > 0.f)
            {
                Position.y= Position.y + 1;
                Vel.y = 0;
            }
        }

The problem is I still can move through the box if i keep pressing a key. So the question is what is the best way to implement collision in SDL? Thank you in advance

Answer 1

Create a new rect and initialize it with the dimensions of of your player(you named it Sprite) and make the new rect move with your player and check if the collision box of the player Colides with the solid object(Sprite1) and. Check out lazyfoo´s tutorial: https://lazyfoo.net/tutorials/SDL/27_collision_detection/index.php

    SDL_Rect r2 = Sprite1->GetRect();
    if (CKeyboard::Get()->GetKey(SDL_SCANCODE_LEFT))
    {
        Vel.x -= 1.0f;
    }
    else if (CKeyboard::Get()->GetKey(SDL_SCANCODE_RIGHT))
    {
        Vel.x += 1.0f;
    }

    Position.x += Vel.x;
    Collisionbox.x = Position.x;

    if (Collision::Get()->Checkcollision(Collisionbox, r2))
    {
        Position.x -= Vel.x;
        Collisionbox.x = Position.x;
    }

    if (CKeyboard::Get()->GetKey(SDL_SCANCODE_UP))
    {
        Vel.y -= 1.0f;
    }
    else if (CKeyboard::Get()->GetKey(SDL_SCANCODE_DOWN))
    {
        Vel.y += 1.0f;
        Vel.y += 1.0f;
    }

    Position.y += Vel.y;
    Collisionbox.y = Position.y;

    if (Collision::Get()->Checkcollision(Collisionbox, r2))
    {
        Position.y -= Vel.y;
        Collisionbox.y = Position.y;
    }

I didn't test the code but it should work. If you'll still have trouble check out lazyfoo's tutorial about collision as I said :P.

I hope this helps