从回调函数检索数据

Question

Were I to set a callback function in GLFW, let's say

glfwSetCursorPosCallback(window, mouse);

the most obvious way to retrieve the cursor position would be

vec2 m;

void mouse (GLFWwindow* window, GLdouble x, GLdouble y)
{
    m = vec2 (x, y);
}

However, I would prefer to do so without using a global variable. Can it be done?

Answer 1

You can associate a user pointer to a GLFWindow . See glfwSetWindowUserPointer .

the pointer can be retrieved at an time form the GLFWWindow object by glfwGetWindowUserPointer

struct MyWindowData
{
  GLdouble x;
  GLdouble y;
}

Associate a pointer to windowData , to the window :

MyWindowData windowData;

glfwSetWindowUserPointer( window, &windowData );
glfwSetCursorPosCallback( window, mouse );

Get the pointer form the window and Cast the pointer of type void* to MyWindowData * (Sadly you have to do the cast).

void mouse(GLFWwindow* window, GLdouble x, GLdouble y)
{
   MyWindowData *dataPtr = (MyWindowData*)glfwGetWindowUserPointer( window ); 
   dataPtr->x = x;
   dataPtr->y = y; 
}