In gfxapi I .preventDefault() the wheel event if (either the window is full screen, or the mouse is in the window client area) and the user code tells that it handled the scroll event. This allows code that don't use wheel events to not interfere with browser behavior, and code that does use wheel events will get those when the mouse is scrolled on top of the canvas. This gives a scroll behavior similar to like when you have a textbox in html page with scrollbar and the html page itself also has a scrollbar, and you can choose which one to scroll by moving the mouse.

I am not sure how feasible that is to implement in glfw?