pxcoord is calculated from some other uniform variables, 0,0 is the lower left corner, the upper left corner is 1920,1080 simply edit the shader and rerun you might want to replace the shader string ...

You can also use glutin (a pure Rust alternative to GLFW), but the API is a bit different, so following the tutorials might not be as straight-forward. You might be tempted to use glium instead of raw ...