Sets the stacks initial size to depth elements
Pops a matrix from the stack and sets it as top matrix. Also returns a reference to the new top matrix.
Pushes the top matrix on the stack and keeps a copy as the new top matrix
Pushes the top matrix on the stack and sets matrix as the new top matrix.
Sets the top matrix
If the stack is too small to hold more items, space for realloc_interval more elements will be allocated
The top matrix, the one you work with
A matrix stack similiar to OpenGLs glPushMatrix/glPopMatrix