Implicit vector conversion in ImGui (ImVec <--> glm::vec) - glm-math

Question

I am trying to get the implicit conversion between ImGui's (ImVec) and glm's (glm::vec) vector types working.
In here I read, that I have to change the following lines in the imconfig.h file:
#define IM_VEC2_CLASS_EXTRA \
constexpr ImVec2(const MyVec2& f) : x(f.x), y(f.y) {} \
operator MyVec2() const { return MyVec2(x,y); }
#define IM_VEC4_CLASS_EXTRA \
constexpr ImVec4(const MyVec4& f) : x(f.x), y(f.y), z(f.z), w(f.w) {} \
operator MyVec4() const { return MyVec4(x,y,z,w); }
The first line makes sense to me, but I don't see the point of the second making a new constructor for MyVec.
Since I really have no idea what is going on here, I just tried to replace MyVecN with either glm::vecN or vecN, but neither works.
Also I don't get why there are these backslashes, I guess they're to comment out? Either way, I removed them, and it still didn't work.
The compiler ends up throwing tons of errors so I don't know where the problem is.

Answer 1

You have to defined/include your struct before including imgui:
// define glm::vecN or include it from another file
namespace glm
{
struct vec2
{
float x, y;
vec2(float x, float y) : x(x), y(y) {};
};
struct vec4
{
float x, y, z, w;
vec4(float x, float y, float z, float w) : x(x), y(y), z(z), w(w) {};
};
}
// define extra conversion here before including imgui, don't do it in the imconfig.h
#define IM_VEC2_CLASS_EXTRA \
constexpr ImVec2(glm::vec2& f) : x(f.x), y(f.y) {} \
operator glm::vec2() const { return glm::vec2(x, y); }
#define IM_VEC4_CLASS_EXTRA \
constexpr ImVec4(const glm::vec4& f) : x(f.x), y(f.y), z(f.z), w(f.w) {} \
operator glm::vec4() const { return glm::vec4(x,y,z,w); }
#include "imgui/imgui.h"
And the backslashes \ are just line breaks in the #define, to specify a continuous definition