Trouble wrapping OpenGL in object-oriented way - c++

Question

I'm not very experience with the OpenGL library so I'm having trouble understanding why when I move some initialization code to a class or a function, GL stops drawing onto the screen. Some research indicates that the library is "global" or state-based rather than object based?
Anyway, here is some code that works
GLuint vertexArrayBuffer;
glGenVertexArrays(1, &vertexArrayBuffer);
glBindBuffer(GL_ARRAY_BUFFER, vertexArrayBuffer);
// VBO is ready to accept vertex data
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
glBindVertexArray(0);
while(!screen.isClosed()) {
// Give the screen a background color
screen.paint(0.0f, 0.0f, 0.5f, 1.0f);
glBindBuffer(GL_ARRAY_BUFFER, vertexArrayBuffer);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);
glDrawArrays(GL_TRIANGLES, 0, 3);
glDisableVertexAttribArray(0);
// Switch to display buffer after drawing all of the above
screen.swapBuffers();
This is all enclosed in the main function, with not much programming structure. The output is a nice white triangle onto a blueish background.
This is the issue here, taking the exact code prior to the event loop and wrapping it into a function:
GLuint initVertexArray(vertex vertices[]) {
// Create file descriptor for the VBO for use as reference to gl vertex functions
GLuint vertexArrayBuffer;
glGenVertexArrays(1, &vertexArrayBuffer);
glBindBuffer(GL_ARRAY_BUFFER, vertexArrayBuffer);
// VBO is ready to accept vertex data
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
glBindVertexArray(0);
return vertexArrayBuffer;
}
and calling it GLuint vertexArrayBuffer = initVertexArray(vertices); in the main function, produces no output of any kind, no errors either, just the same blueish background.

Answer 1

Have you checked what sizeof(vertices) is returning. In this case vertices[] will decay into a pointer so I would imagine that sizeof(vertices) is sizeof(vertex*).
Try passing the size of the array alongside it like so:
GLuint initVertexArray(vertex vertices[], const unsigned int size);
Then you would use it like so:
glBufferData(GL_ARRAY_BUFFER, size, vertices, GL_STATIC_DRAW);
instead of:
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
You would then call it in the same scope as you declared your vertices array:
vertex vertices[100];
// sizeof(vertices) here will give the actual size of the vertices array
// eg: sizeof(vertex) * 100 instead of just giving sizeof(vertex*)
GLuint vertexArrayBuffer = initVertexArray(vertices, sizeof(vertices));