- in Firefox, scrollbar would appear => adding overflow: hidden fixes this issue
- when the canvas has the focus, Chrome draws a very small blue outline, setting it to none fixes this issue
Without tabindex, the canvas element is not focusable in the DOM, so pongasoft/emscripten-glfw's focus/blur listeners on the canvas
never fire. This means glfwSetWindowFocusCallback is never called etc.
Ref: https://github.com/pongasoft/emscripten-glfw/issues/29
