Implement window_get_x, window_get_y, window_set_position for desktop

[cobaltgit]

This should make the screen shake at the very end of Undertale's genocide route work, will need testing to confirm

[cobaltgit]

This won't work on GLFW2, SDL 1.2 or the web backend

[Un1q32]

make them static functions + function pointers in the runner struct, since these functions should be optional.

[cobaltgit]

That's what it should be doing, the builtins check if the runner and function pointer isn't a nullptr before proceeding, otherwise the logic is skipped and it just returns whatever

[cobaltgit]

Ok this should do it

[cobaltgit]

Ok done that

[Un1q32]

Can you make a test game that runs in 640x480 and moves exactly 640 pixels horizontally and 480 vertically so I can test that hidpi is working correctly.

[cobaltgit]

Hold up